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Merge pull request #36 from rust-console/lokathor

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Much improved Quirks chapter, some Concepts work
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13
.travis.yml
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@ -9,6 +9,7 @@ rust:
before_script:
- rustup component add rust-src
- rustup component add clippy
- (test -x $HOME/.cargo/bin/cargo-install-update || cargo install cargo-update)
- (test -x $HOME/.cargo/bin/cargo-xbuild || cargo install cargo-xbuild)
- (test -x $HOME/.cargo/bin/cargo-make || cargo install cargo-make)
@ -27,9 +28,15 @@ script:
- export PATH="$PATH:/opt/devkitpro/devkitARM/bin"
- export PATH="$PATH:/opt/devkitpro/tools/bin"
- cd ..
# Test the lib and then compile all examples with `cargo make`
- cargo test --lib && cargo test --lib --release
- cargo make
# Run all verificaions, both debug and release
- cargo clippy
- cargo clippy --release
- cargo test --no-fail-fast --lib
- cargo test --no-fail-fast --lib --release
- cargo test --no-fail-fast --tests
- cargo test --no-fail-fast --tests --release
# Let cargo make take over the rest
- cargo make build-all
# Test build the book so that a failed book build kills this run
- cd book && mdbook build

5
Cargo.toml
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@ -12,8 +12,13 @@ license = "Apache-2.0"
publish = false
[dependencies]
typenum = "1.10"
gba-proc-macro = "0.2.1"
#[dev-dependencies]
#quickcheck="0.7"
# TODO: F
[profile.release]
lto = true
panic = "abort"

11
Makefile.toml
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@ -55,12 +55,15 @@ fn main() -> std::io::Result<()> {
'''
]
[tasks.build]
dependencies = ["build-examples-debug", "build-examples-release", "pack-roms"]
[tasks.test]
command = "cargo"
args = ["test", "--lib"]
[tasks.justrelease]
dependencies = ["build-examples-release", "pack-roms"]
[tasks.build-all]
dependencies = ["build-examples-debug", "build-examples-release", "pack-roms"]
[tasks.default]
alias = "build"
alias = "build-all"

115
book/src-bak/ch01/hello1.md
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@ -1,115 +0,0 @@
## A basic hello1 explanation
So, what just happened? Even if you're used to Rust that might look pretty
strange. We'll go over most of the little parts right here, and then bigger
parts will get their own sections.
```rust
#![feature(start)]
```
This enables the [start
feature](https://doc.rust-lang.org/beta/unstable-book/language-features/start.html),
which you would normally be able to read about in the unstable book, except that
the book tells you nothing at all except to look at the [tracking
issue](https://github.com/rust-lang/rust/issues/29633).
Basically, a GBA game is even more low-level than the _normal_ amount of
low-level that you get from Rust, so we have to tell the compiler to account for
that by specifying a `#[start]`, and we need this feature on to do that.
```rust
#![no_std]
```
There's no standard library available on the GBA, so we'll have to live a core
only life.
```rust
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
loop {}
}
```
This sets our [panic
handler](https://doc.rust-lang.org/nightly/nomicon/panic-handler.html).
Basically, if we somehow trigger a panic, this is where the program goes.
However, right now we don't know how to get any sort of message out to the user
so... we do nothing at all. We _can't even return_ from here, so we just sit in
an infinite loop. The player will have to reset the universe from the outside.
```rust
#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
```
This is our `#[start]`. We call it `main`, but it's not like a `main` that you'd
see in a Rust program. It's _more like_ the sort of `main` that you'd see in a C
program, but it's still **not** that either. If you compile a `#[start]` program
for a target with an OS such as `arm-none-eabi-nm` you can open up the debug
info and see that your result will have the symbol for the C `main` along side
the symbol for the start `main` that we write here. Our start `main` is just its
own unique thing, and the inputs and outputs have to be like that because that's
how `#[start]` is specified to work in Rust.
If you think about it for a moment you'll probably realize that, those inputs
and outputs are totally useless to us on a GBA. There's no OS on the GBA to call
our program, and there's no place for our program to "return to" when it's done.
Side note: if you want to learn more about stuff "before main gets called" you
can watch a great [CppCon talk](https://www.youtube.com/watch?v=dOfucXtyEsU) by
Matt Godbolt (yes, that Godbolt) where he delves into quite a bit of it. The
talk doesn't really apply to the GBA, but it's pretty good.
```rust
unsafe {
```
I hope you're all set for some `unsafe`, because there's a lot of it to be had.
```rust
(0x04000000 as *mut u16).write_volatile(0x0403);
```
Sure!
```rust
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
```
Ah, of course.
```rust
loop {}
}
}
```
And, as mentioned above, there's no place for a GBA program to "return to", so
we can't ever let `main` try to return there. Instead, we go into an infinite
`loop` that does nothing. The fact that this doesn't ever return an `isize`
value doesn't seem to bother Rust, because I guess we're at least not returning
any other type of thing instead.
Fun fact: unlike in C++, an infinite loop with no side effects isn't Undefined
Behavior for us rustaceans... _semantically_. In truth LLVM has a [known
bug](https://github.com/rust-lang/rust/issues/28728) in this area, so we won't
actually be relying on empty loops in any future programs.
## All Those Magic Numbers
Alright, I cheated quite a bit in the middle there. The program works, but I
didn't really tell you why because I didn't really tell you what any of those
magic numbers mean or do.
* `0x04000000` is the address of an IO Register called the Display Control.
* `0x06000000` is the start of Video RAM.
So we write some magic to the display control register once, then we write some
other magic to three magic locations in the Video RAM. Somehow that shows three
dots. Gotta read on to find out why!

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@ -1,132 +0,0 @@
# hello2
Okay so let's have a look again:
`hello1`
```rust
#![feature(start)]
#![no_std]
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
loop {}
}
#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
unsafe {
(0x04000000 as *mut u16).write_volatile(0x0403);
(0x06000000 as *mut u16).offset(120 + 80 * 240).write_volatile(0x001F);
(0x06000000 as *mut u16).offset(136 + 80 * 240).write_volatile(0x03E0);
(0x06000000 as *mut u16).offset(120 + 96 * 240).write_volatile(0x7C00);
loop {}
}
}
```
Now let's clean this up so that it's clearer what's going on.
First we'll label that display control stuff, including using the `VolatilePtr`
type from the volatile explanation:
```rust
pub const DISPCNT: VolatilePtr<u16> = VolatilePtr(0x04000000 as *mut u16);
pub const MODE3: u16 = 3;
pub const BG2: u16 = 0b100_0000_0000;
```
Next we make some const values for the actual pixel drawing
```rust
pub const VRAM: usize = 0x06000000;
pub const SCREEN_WIDTH: isize = 240;
```
Note that VRAM has to be interpreted in different ways depending on mode, so we
just leave it as `usize` and we'll cast it into the right form closer to the
actual use.
Next we want a small helper function for putting together a color value.
Happily, this one can even be declared as a `const` function. At the time of
writing, we've got the "minimal const fn" support in nightly. It really is quite
limited, but I'm happy to let rustc and LLVM pre-compute as much as they can
when it comes to the GBA's tiny CPU.
```rust
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
blue << 10 | green << 5 | red
}
```
Finally, we'll make a function for drawing a pixel in Mode 3. Even though it's
just a one-liner, having the "important parts" be labeled as function arguments
usually helps you think about it a lot better.
```rust
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
VolatilePtr(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write(color);
}
```
So now we've got this:
`hello2`
```rust
#![feature(start)]
#![no_std]
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
loop {}
}
#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
unsafe {
DISPCNT.write(MODE3 | BG2);
mode3_pixel(120, 80, rgb16(31, 0, 0));
mode3_pixel(136, 80, rgb16(0, 31, 0));
mode3_pixel(120, 96, rgb16(0, 0, 31));
loop {}
}
}
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct VolatilePtr<T>(pub *mut T);
impl<T> VolatilePtr<T> {
pub unsafe fn read(&self) -> T {
core::ptr::read_volatile(self.0)
}
pub unsafe fn write(&self, data: T) {
core::ptr::write_volatile(self.0, data);
}
pub unsafe fn offset(self, count: isize) -> Self {
VolatilePtr(self.0.wrapping_offset(count))
}
}
pub const DISPCNT: VolatilePtr<u16> = VolatilePtr(0x04000000 as *mut u16);
pub const MODE3: u16 = 3;
pub const BG2: u16 = 0b100_0000_0000;
pub const VRAM: usize = 0x06000000;
pub const SCREEN_WIDTH: isize = 240;
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
blue << 10 | green << 5 | red
}
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
VolatilePtr(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write(color);
}
```
Exact same program that we started with, but much easier to read.
Of course, in the full `gba` crate that this book is a part of we have these and
other elements all labeled and sorted out for you (not identically, but
similarly). Still, for educational purposes it's often best to do it yourself at
least once.

10
book/src-bak/ch01/index.md
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@ -1,10 +0,0 @@
# Ch 1: Hello GBA
Traditionally a person writes a "hello, world" program so that they can test
that their development environment is setup properly and to just get a feel for
using the tools involved. To get an idea of what a small part of a source file
will look like. All that stuff.
Normally, you write a program that prints "hello, world" to the terminal. The
GBA has no terminal, but it does have a screen, so instead we're going to draw
three dots to the screen.

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book/src-bak/ch01/volatile.md
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@ -1,70 +0,0 @@
# Volatile
Before we focus on what the numbers mean, first let's ask ourselves: Why are we
doing _volatile_ writes? You've probably never used that keywords before at all.
What _is_ volatile anyway?
Well, the optimizer is pretty aggressive, and so it'll skip reads and writes
when it thinks can. Like if you write to a pointer once, and then again a moment
later, and it didn't see any other reads in between, it'll think that it can
just skip doing that first write since it'll get overwritten anyway. Sometimes
that's correct, but sometimes it's not.
Marking a read or write as _volatile_ tells the compiler that it really must do
that action, and in the exact order that we wrote it out. It says that there
might even be special hardware side effects going on that the compiler isn't
aware of. In this case, the write to the display control register sets a video
mode, and the writes to the Video RAM set pixels that will show up on the
screen.
Similar to "atomic" operations you might have heard about, all volatile
operations are enforced to happen in the exact order that you specify them, but
only relative to other volatile operations. So something like
```rust
c.write_volatile(5);
a += b;
d.write_volatile(7);
```
might end up changing `a` either before or after the change to `c` (since the
value of `a` doesn't affect the write to `c`), but the write to `d` will
_always_ happen after the write to `c`, even though the compiler doesn't see any
direct data dependency there.
If you ever go on to use volatile stuff on other platforms it's important to
note that volatile doesn't make things thread-safe, you still need atomic for
that. However, the GBA doesn't have threads, so we don't have to worry about
those sorts of thread safety concerns (there's interrupts, but that's another
matter).
## Volatile by default
Of course, writing out `volatile_write` every time is more than we wanna do.
There's clarity and then there's excessive. This is a chance to write our first
[newtype](https://doc.rust-lang.org/1.0.0/style/features/types/newtype.html).
Basically a type that's got the exact same binary representation as some other
type, but new methods and trait implementations.
We want a `*mut T` that's volatile by default, and also when we offset it...
well the verdict is slightly unclear on how `offset` vs `wrapping_offset` work
when you're using pointers that you made up out of nowhere. I've asked the
experts and they genuinely weren't sure, so we'll make an `offset` method that
does a `wrapping_offset` just to be careful.
```rust
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct VolatilePtr<T>(pub *mut T);
impl<T> VolatilePtr<T> {
pub unsafe fn read(&self) -> T {
core::ptr::read_volatile(self.0)
}
pub unsafe fn write(&self, data: T) {
core::ptr::write_volatile(self.0, data);
}
pub unsafe fn offset(self, count: isize) -> Self {
VolatilePtr(self.0.wrapping_offset(count))
}
}
```

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book/src-bak/ch02/index.md
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@ -1,22 +0,0 @@
# Ch 2: User Input
It's all well and good to draw three pixels, but they don't do anything yet. We
want them to do something, and for that we need to get some input from the user.
The GBA, as I'm sure you know, has an arrow pad, A and B, L and R, Start and
Select. That's a little more than the NES/GB/CGB had, and a little less than the
SNES had. As you can guess, we get key state info from an IO register.
Also, we will need a way to keep the program from running "too fast". On a
modern computer or console you do this with vsync info from the GPU and Monitor,
and on the GBA we'll be using vsync info from an IO register that tracks what
the display hardware is doing.
As a way to apply our knowledge We'll make a simple "light cycle" game where
your dot leaves a trail behind them and you die if you go off the screen or if
you touch your own trail. We just make a copy of `hello2.rs` named
`light_cycle.rs` and then fill it in as we go through the chapter. Normally you
might not place the entire program into a single source file, particularly as it
grows over time, but since these are small examples it's much better to have
them be completely self contained than it is to have them be "properly
organized" for the long term.

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# GBA Memory Mapping
The [GBA Memory Map](http://problemkaputt.de/gbatek.htm#gbamemorymap) has
several memory portions to it, each with their own little differences. Most of
the memory has pre-determined use according to the hardware, but there is also
space for games to use as a scratch pad in whatever way the game sees fit.
The memory ranges listed here are _inclusive_, so they end with a lot of F's
and E's.
We've talked about volatile memory before, but just as a reminder I'll say that
all of the memory we'll talk about here should be accessed using volatile with
two exceptions:
1) Work RAM (both internal and external) can be used normally, and if the
compiler is able to totally elide some reads and writes that's okay.
2) However, if you set aside any space in Work RAM where an interrupt will
communicate with the main program then that specific location will have to
keep using volatile access, since the compiler never knows when an interrupt
will actually happen.
## BIOS / System ROM
* `0x0` to `0x3FFF` (16k)
This is special memory for the BIOS. It is "read-only", but even then it's only
accessible when the program counter is pointing into the BIOS region. At all
other times you get a [garbage
value](http://problemkaputt.de/gbatek.htm#gbaunpredictablethings) back when you
try to read out of the BIOS.
## External Work RAM / EWRAM
* `0x2000000` to `0x203FFFF` (256k)
This is a big pile of space, the use of which is up to each game. However, the
external work ram has only a 16-bit bus (if you read/write a 32-bit value it
silently breaks it up into two 16-bit operations) and also 2 wait cycles (extra
CPU cycles that you have to expend _per 16-bit bus use_).
It's most helpful to think of EWRAM as slower, distant memory, similar to the
"heap" in a normal application. You can take the time to go store something
within EWRAM, or to load it out of EWRAM, but if you've got several operations
to do in a row and you're worried about time you should pull that value into
local memory, work on your local copy, and then push it back out to EWRAM.
## Internal Work RAM / IWRAM
* `0x3000000` to `0x3007FFF` (32k)
This is a smaller pile of space, but it has a 32-bit bus and no wait.
By default, `0x3007F00` to `0x3007FFF` is reserved for interrupt and BIOS use.
The rest of it is totally up to you. The user's stack space starts at
`0x3007F00` and proceeds _down_ from there. For best results you should probably
start at `0x3000000` and then go upwards. Under normal use it's unlikely that
the two memory regions will crash into each other.
## IO Registers
* `0x4000000` to `0x40003FE`
We've touched upon a few of these so far, and we'll get to more later. At the
moment it is enough to say that, as you might have guessed, all of them live in
this region. Each individual register is a `u16` or `u32` and they control all
sorts of things. We'll actually be talking about some more of them in this very
chapter, because that's how we'll control some of the background and object
stuff.
## Palette RAM / PALRAM
* `0x5000000` to `0x50003FF` (1k)
Palette RAM has a 16-bit bus, which isn't really a problem because it
conceptually just holds `u16` values. There's no automatic wait state, but if
you try to access the same location that the display controller is accessing you
get bumped by 1 cycle. Since the display controller can use the palette ram any
number of times per scanline it's basically impossible to predict if you'll have
to do a wait or not during VDraw. During VBlank you won't have any wait of
course.
PALRAM is among the memory where there's weirdness if you try to write just one
byte: if you try to write just 1 byte, it writes that byte into _both_ parts of
the larger 16-bit location. This doesn't really affect us much with PALRAM,
because palette values are all supposed to be `u16` anyway.
The palette memory actually contains not one, but _two_ sets of palettes. First
there's 256 entries for the background palette data (starting at `0x5000000`),
and then there's 256 entries for object palette data (starting at `0x5000200`).
The GBA also has two modes for palette access: 8-bits-per-pixel (8bpp) and
4-bits-per-pixel (4bpp).
* In 8bpp mode an 8-bit palette index value within a background or sprite
simply indexes directly into the 256 slots for that type of thing.
* In 4bpp mode a 4-bit palette index value within a background or sprite
specifies an index within a particular "palbank" (16 palette entries each),
and then a _separate_ setting outside of the graphical data determines which
palbank is to be used for that background or object (the screen entry data for
backgrounds, and the object attributes for objects).
### Transparency
When a pixel within a background or object specifies index 0 as its palette
entry it is treated as a transparent pixel. This means that in 8bpp mode there's
only 255 actual color options (0 being transparent), and in 4bpp mode there's
only 15 actual color options available within each palbank (the 0th entry of
_each_ palbank is transparent).
Individual backgrounds, and individual objects, each determine if they're 4bpp
or 8bpp separately, so a given overall palette slot might map to a used color in
8bpp and an unused/transparent color in 4bpp. If you're a palette wizard.
Palette slot 0 of the overall background palette is used to determine the
"backdrop" color. That's the color you see if no background or object ends up
being rendered within a given pixel.
Since display mode 3 and display mode 5 don't use the palette, they cannot
benefit from transparency.
## Video RAM / VRAM
* `0x6000000` to `0x6017FFF` (96k)
We've used this before! VRAM has a 16-bit bus and no wait. However, the same as
with PALRAM, the "you might have to wait if the display controller is looking at
it" rule applies here.
Unfortunately there's not much more exact detail that can be given about VRAM.
The use of the memory depends on the video mode that you're using.
One general detail of note is that you can't write individual bytes to any part
of VRAM. Depending on mode and location, you'll either get your bytes doubled
into both the upper and lower parts of the 16-bit location targeted, or you
won't even affect the memory. This usually isn't a big deal, except in two
situations:
* In Mode 4, if you want to change just 1 pixel, you'll have to be very careful
to read the old `u16`, overwrite just the byte you wanted to change, and then
write that back.
* In any display mode, avoid using `memcopy` to place things into VRAM.
It's written to be byte oriented, and only does 32-bit transfers under select
conditions. The rest of the time it'll copy one byte at a time and you'll get
either garbage or nothing at all.
## Object Attribute Memory / OAM
* `0x7000000` to `0x70003FF` (1k)
The Object Attribute Memory has a 32-bit bus and no default wait, but suffers
from the "you might have to wait if the display controller is looking at it"
rule. You cannot write individual bytes to OAM at all, but that's not really a
problem because all the fields of the data types within OAM are either `i16` or
`u16` anyway.
Object attribute memory is the wildest yet: it conceptually contains two types
of things, but they're _interlaced_ with each other all the way through.
Now, [GBATEK](http://problemkaputt.de/gbatek.htm#lcdobjoamattributes) and
[CowByte](https://www.cs.rit.edu/~tjh8300/CowBite/CowBiteSpec.htm#OAM%20(sprites))
doesn't quite give names to the two data types here.
[TONC](https://www.coranac.com/tonc/text/regobj.htm#sec-oam) calls them
`OBJ_ATTR` and `OBJ_AFFINE`, but we'll be giving them names fitting with the
Rust naming convention. Just know that if you try to talk about it with others
they might not be using the same names. In Rust terms their layout would look
like this:
```rust
#[repr(C)]
pub struct ObjectAttributes {
attr0: u16,
attr1: u16,
attr2: u16,
filler: i16,
}
#[repr(C)]
pub struct AffineMatrix {
filler0: [u16; 3],
pa: i16,
filler1: [u16; 3],
pb: i16,
filler2: [u16; 3],
pc: i16,
filler3: [u16; 3],
pd: i16,
}
```
(Note: the `#[repr(C)]` part just means that Rust must lay out the data exactly
in the order we specify, which otherwise it is not required to do).
So, we've got 1024 bytes in OAM and each `ObjectAttributes` value is 8 bytes, so
naturally we can support up to 128 objects.
_At the same time_, we've got 1024 bytes in OAM and each `AffineMatrix` is 32
bytes, so we can have 32 of them.
But, as I said, these things are all _interlaced_ with each other. See how
there's "filler" fields in each struct? If we imagine the OAM as being just an
array of one type or the other, indexes 0/1/2/3 of the `ObjectAttributes` array
would line up with index 0 of the `AffineMatrix` array. It's kinda weird, but
that's just how it works. When we setup functions to read and write these values
we'll have to be careful with how we do it. We probably _won't_ want to use
those representations above, at least not with the `AffineMatrix` type, because
they're quite wasteful if you want to store just object attributes or just
affine matrices.
## Game Pak ROM / Flash ROM
* `0x8000000` to `0x9FFFFFF` (wait 0)
* `0xA000000` to `0xBFFFFFF` (wait 1)
* `0xC000000` to `0xDFFFFFF` (wait 2)
* Max of 32Mb
These portions of the memory are less fixed, because they depend on the precise
details of the game pak you've inserted into the GBA. In general, they connect
to the game pak ROM and/or Flash memory, using a 16-bit bus. The ROM is
read-only, but the Flash memory (if any) allows writes.
The game pak ROM is listed as being in three sections, but it's actually the
same memory being effectively mirrored into three different locations. The
mirror that you choose to access the game pak through affects which wait state
setting it uses (configured via IO register of course). Unfortunately, the
details come down more to the game pak hardware that you load your game onto
than anything else, so there's not much I can say right here. We'll eventually
talk about it more later when I'm forced to do the boring thing and just cover
all the IO registers that aren't covered anywhere else.
One thing of note is the way that the 16-bit bus affects us: the instructions to
execute are coming through the same bus as the rest of the game data, so we want
them to be as compact as possible. The ARM chip in the GBA supports two
different instruction sets, "thumb" and "non-thumb". The thumb mode instructions
are 16-bit, so they can each be loaded one at a time, and the non-thumb
instructions are 32-bit, so we're at a penalty if we execute them directly out
of the game pak. However, some things will demand that we use non-thumb code, so
we'll have to deal with that eventually. It's possible to switch between modes,
but it's a pain to keep track of what mode you're in because there's not
currently support for it in Rust itself (perhaps some day). So we'll stick with
thumb code as much as we possibly can, that's why our target profile for our
builds starts with `thumbv4`.
## Game Pak SRAM
* `0xE000000` to `0xE00FFFF` (64k)
The game pak SRAM has an 8-bit bus. Why did Pokémon always take so long to save?
Saving the whole game one byte at a time is why. The SRAM also has some amount
of wait, but as with the ROM, the details depend on your game pak hardware (and
also as with ROM, you can adjust the settings with an IO register, should you
need to).
One thing to note about the SRAM is that the GBA has a Direct Memory Access
(DMA) feature that can be used for bulk memory movements in some cases, but the
DMA _cannot_ access the SRAM region. You really are stuck reading and writing
one byte at a time when you're using the SRAM.

16
book/src/00-introduction/05-help_and_resources.md
View file

@ -26,9 +26,19 @@ available while you're debugging problems.
## Information Resources
Ketsuban and I didn't magically learn this all from nowhere, we read various
technical manuals and guides ourselves and then distilled the knowledge (usually
oriented towards C and C++) into this book for Rust.
First, if I fail to describe something related to Rust, you can always try
checking in [The Rust
Reference](https://doc.rust-lang.org/nightly/reference/introduction.html) to see
if they cover it. You can mostly ignore that big scary red banner at the top,
things are a lot better documented than they make it sound.
If you need help trying to fiddle your math down as hard as you can, there are
resources such as the [Bit Twiddling
Hacks](https://graphics.stanford.edu/~seander/bithacks.html) page.
As to GBA related lore, Ketsuban and I didn't magically learn this all from
nowhere, we read various technical manuals and guides ourselves and then
distilled those works oriented around C and C++ into a book for Rust.
We have personally used some or all of the following:

11
book/src/01-quirks/01-no_std.md
View file

@ -89,10 +89,6 @@ the standard library types to be used "for free" once it was set up, or just a
custom allocator that's GBA specific if Rust's global allocator style isn't a
good fit for the GBA (I honestly haven't looked into it).
## LLVM Intrinsics
TODO: explain that we'll occasionally have to provide some intrinsics.
## Bare Metal Panic
TODO: expand this
@ -114,3 +110,10 @@ TODO: expand this
* Sending the message also automatically zeroes the output buffer.
* View the output within the "Tools" menu, "View Logs...". Note that the Fatal
message, if any doesn't get logged.
TODO: this will probably fail without a `__clzsi2` implementation, which is a
good seg for the next section
## LLVM Intrinsics
TODO: explain that we'll occasionally have to provide some intrinsics.

551
book/src/01-quirks/02-fixed_only.md
View file

@ -1,13 +1,548 @@
# Fixed Only
In addition to not having the standard library available, we don't even have a
floating point unit available! We can't do floating point math in hardware! We
could still do floating point math as software computations if we wanted, but
that's a slow, slow thing to do.
In addition to not having much of the standard library available, we don't even
have a floating point unit available! We can't do floating point math in
hardware! We _could_ still do floating point math as pure software computations
if we wanted, but that's a slow, slow thing to do.
Instead let's learn about another way to have fractional values called "Fixed
Point"
Are there faster ways? It's the same answer as always: "Yes, but not without a
tradeoff."
## Fixed Point
The faster way is to represent fractional values using a system called a [Fixed
Point Representation](https://en.wikipedia.org/wiki/Fixed-point_arithmetic).
What do we trade away? Numeric range.
TODO: describe fixed point, make some types, do the impls, all that.
* Floating point math stores bits for base value and for exponent all according
to a single [well defined](https://en.wikipedia.org/wiki/IEEE_754) standard
for how such a complicated thing works.
* Fixed point math takes a normal integer (either signed or unsigned) and then
just "mentally associates" it (so to speak) with a fractional value for its
"units". If you have 3 and it's in units of 1/2, then you have 3/2, or 1.5
using decimal notation. If your number is 256 and it's in units of 1/256th
then the value is 1.0 in decimal notation.
Floating point math requires dedicated hardware to perform quickly, but it can
"trade" precision when it needs to represent extremely large or small values.
Fixed point math is just integral math, which our GBA is reasonably good at, but
because your number is associated with a fixed fraction your results can get out
of range very easily.
## Representing A Fixed Point Value
So we want to associate our numbers with a mental note of what units they're in:
* [PhantomData](https://doc.rust-lang.org/core/marker/struct.PhantomData.html)
is a type that tells the compiler "please remember this extra type info" when
you add it as a field to a struct. It goes away at compile time, so it's
perfect for us to use as space for a note to ourselves without causing runtime
overhead.
* The [typenum](https://crates.io/crates/typenum) crate is the best way to
represent a number within a type in Rust. Since our values on the GBA are
always specified as a number of fractional bits to count the number as, we can
put `typenum` types such as `U8` or `U14` into our `PhantomData` to keep track
of what's going on.
Now, those of you who know me, or perhaps just know my reputation, will of
course _immediately_ question what happened to the real Lokathor. I do not care
for most crates, and I particularly don't care for using a crate in teaching
situations. However, `typenum` has a number of factors on its side that let me
suggest it in this situation:
* It's version 1.10 with a total of 21 versions and nearly 700k downloads, so we
can expect that the major troubles have been shaken out and that it will remain
fairly stable for quite some time to come.
* It has no further dependencies that it's going to drag into the compilation.
* It happens all at compile time, so it's not clogging up our actual game with
any nonsense.
* The (interesting) subject of "how do you do math inside Rust's trait system?" is
totally separate from the concern that we're trying to focus on here.
Therefore, we will consider it acceptable to use this crate.
Now the `typenum` crate defines a whole lot, but we'll focus down to just a
single type at the moment:
[UInt](https://docs.rs/typenum/1.10.0/typenum/uint/struct.UInt.html) is a
type-level unsigned value. It's like `u8` or `u16`, but while they're types that
then have values, each `UInt` construction statically equates to a specific
value. Like how the `()` type only has one value, which is also called `()`. In
this case, you wrap up `UInt` around smaller `UInt` values and a `B1` or `B0`
value to build up the binary number that you want at the type level.
In other words, instead of writing
```rust
let six = 0b110;
```
We write
```rust
type U6 = UInt<UInt<UInt<UTerm, B1>, B1>, B0>;
```
Wild, I know. If you look into the `typenum` crate you can do math and stuff
with these type level numbers, and we will a little bit below, but to start off
we _just_ need to store one in some `PhantomData`.
### A struct For Fixed Point
Our actual type for a fixed point value looks like this:
```rust
use core::marker::PhantomData;
use typenum::marker_traits::Unsigned;
/// Fixed point `T` value with `F` fractional bits.
#[derive(Debug, Copy, Clone, Default, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct Fx<T, F: Unsigned> {
bits: T,
_phantom: PhantomData<F>,
}
```
This says that `Fx<T,F>` is a generic type that holds some base number type `T`
and a `F` type that's marking off how many fractional bits we're using. We only
want people giving unsigned type-level values for the `PhantomData` type, so we
use the trait bound `F: Unsigned`.
We use
[repr(transparent)](https://github.com/rust-lang/rfcs/blob/master/text/1758-repr-transparent.md)
here to ensure that `Fx` will always be treated just like the base type in the
final program (in terms of bit pattern and ABI).
If you go and check, this is _basically_ how the existing general purpose crates
for fixed point math represent their numbers. They're a little fancier about it
because they have to cover every case, and we only have to cover our GBA case.
That's quite a bit to type though. We probably want to make a few type aliases
for things to be easier to look at. Unfortunately there's [no standard
notation](https://en.wikipedia.org/wiki/Fixed-point_arithmetic#Notation) for how
you write a fixed point type. We also have to limit ourselves to what's valid
for use in a Rust type too. I like the `fx` thing, so we'll use that for signed
and then `fxu` if we need an unsigned value.
```rust
/// Alias for an `i16` fixed point value with 8 fractional bits.
pub type fx8_8 = Fx<i16,U8>;
```
Rust will complain about having `non_camel_case_types`, and you can shut that
warning up by putting an `#[allow(non_camel_case_types)]` attribute on the type
alias directly, or you can use `#![allow(non_camel_case_types)]` at the very top
of the module to shut up that warning for the whole module (which is what I
did).
## Constructing A Fixed Point Value
So how do we actually _make_ one of these values? Well, we can always just wrap or unwrap any value in our `Fx` type:
```rust
impl<T, F: Unsigned> Fx<T, F> {
/// Uses the provided value directly.
pub fn from_raw(r: T) -> Self {
Fx {
num: r,
phantom: PhantomData,
}
}
/// Unwraps the inner value.
pub fn into_raw(self) -> T {
self.num
}
}
```
I'd like to use the `From` trait of course, but it was giving me some trouble, i
think because of the orphan rule. Oh well.
If we want to be particular to the fact that these are supposed to be
_numbers_... that gets tricky. Rust is actually quite bad at being generic about
number types. You can use the [num](https://crates.io/crates/num) crate, or you
can just use a macro and invoke it once per type. Guess what we're gonna do.
```rust
macro_rules! fixed_point_methods {
($t:ident) => {
impl<F: Unsigned> Fx<$t, F> {
/// Gives the smallest positive non-zero value.
pub fn precision() -> Self {
Fx {
num: 1,
phantom: PhantomData,
}
}
/// Makes a value with the integer part shifted into place.
pub fn from_int_part(i: $t) -> Self {
Fx {
num: i << F::U8,
phantom: PhantomData,
}
}
}
};
}
fixed_point_methods! {u8}
fixed_point_methods! {i8}
fixed_point_methods! {i16}
fixed_point_methods! {u16}
fixed_point_methods! {i32}
fixed_point_methods! {u32}
```
Now _you'd think_ that those can be `const`, but at the moment you can't have a
`const` function with a bound on any trait other than `Sized`, so they have to
be normal functions.
Also, we're doing something a little interesting there with `from_int_part`. We
can take our `F` type and get its constant value. There's other associated
constants if we want it in other types, and also non-const methods if you wanted
that for some reason (maybe passing it as a closure function? dunno).
## Casting Base Values
Next, once we have a value in one base type we will need to be able to move it
into another base type. Unfortunately this means we gotta use the `as` operator,
which requires a concrete source type and a concrete destination type. There's
no easy way for us to make it generic here.
We could let the user use `into_raw`, cast, and then do `from_raw`, but that's
error prone because they might change the fractional bit count accidentally.
This means that we have to write a function that does the casting while
perfectly preserving the fractional bit quantity. If we wrote one function for
each conversion it'd be like 30 different possible casts (6 base types that we
support, and then 5 possible target types). Instead, we'll write it just once in
a way that takes a closure, and let the user pass a closure that does the cast.
The compiler should merge it all together quite nicely for us once optimizations
kick in.
This code goes outside the macro. I want to avoid too much code in the macro if
we can, it's a little easier to cope with I think.
```rust
/// Casts the base type, keeping the fractional bit quantity the same.
pub fn cast_inner<Z, C: Fn(T) -> Z>(self, op: C) -> Fx<Z, F> {
Fx {
num: op(self.num),
phantom: PhantomData,
}
}
```
It's horrible and ugly, but Rust is just bad at numbers sometimes.
## Adjusting Fractional Part
In addition to the base value we might want to change our fractional bit
quantity. This is actually easier that it sounds, but it also requires us to be
tricky with the generics. We can actually use some typenum type level operators
here.
This code goes inside the macro: we need to be able to use the left shift and
right shift, which is easiest when we just use the macro's `$t` as our type. We
could alternately put a similar function outside the macro and be generic on `T`
having the left and right shift operators by using a `where` clause. As much as
I'd like to avoid too much code being generated by macro, I'd _even more_ like
to avoid generic code with huge and complicated trait bounds. It comes down to
style, and you gotta decide for yourself.
```rust
/// Changes the fractional bit quantity, keeping the base type the same.
pub fn adjust_fractional_bits<Y: Unsigned + IsEqual<F, Output = False>>(self) -> Fx<$t, Y> {
let leftward_movement: i32 = Y::to_i32() - F::to_i32();
Fx {
num: if leftward_movement > 0 {
self.num << leftward_movement
} else {
self.num >> (-leftward_movement)
},
phantom: PhantomData,
}
}
```
There's a few things at work. First, we introduce `Y` as the target number of
fractional bits, and we _also_ limit it that the target bits quantity can't be
the same as we already have using a type-level operator. If it's the same as we
started with, why are you doing the cast at all?
Now, once we're sure that the current bits and target bits aren't the same, we
compute `target - start`, and call this our "leftward movement". Example: if
we're targeting 8 bits and we're at 4 bits, we do 8-4 and get +4 as our leftward
movement. If the leftward_movement is positive we naturally shift our current
value to the left. If it's not positive then it _must_ be negative because we
eliminated 0 as a possibility using the type-level operator, so we shift to the
right by the negative value.
## Addition, Subtraction, Shifting, Negative, Comparisons
From here on we're getting help from [this blog
post](https://spin.atomicobject.com/2012/03/15/simple-fixed-point-math/) by [Job
Vranish](https://spin.atomicobject.com/author/vranish/), so thank them if you
learn something.
I might have given away the game a bit with those `derive` traits on our fixed
point type. For a fair number of operations you can use the normal form of the
op on the inner bits as long as the fractional parts have the same quantity.
This includes equality and ordering (which we derived) as well as addition,
subtraction, and bit shifting (which we need to do ourselves).
This code can go outside the macro, with sufficient trait bounds.
```rust
impl<T: Add<Output = T>, F: Unsigned> Add for Fx<T, F> {
type Output = Self;
fn add(self, rhs: Fx<T, F>) -> Self::Output {
Fx {
num: self.num + rhs.num,
phantom: PhantomData,
}
}
}
```
The bound on `T` makes it so that `Fx<T, F>` can be added any time that `T` can
be added to its own type with itself as the output. We can use the exact same
pattern for `Sub`, `Shl`, `Shr`, and `Neg`. With enough trait bounds, we can do
anything!
```rust
impl<T: Sub<Output = T>, F: Unsigned> Sub for Fx<T, F> {
type Output = Self;
fn sub(self, rhs: Fx<T, F>) -> Self::Output {
Fx {
num: self.num - rhs.num,
phantom: PhantomData,
}
}
}
impl<T: Shl<u32, Output = T>, F: Unsigned> Shl<u32> for Fx<T, F> {
type Output = Self;
fn shl(self, rhs: u32) -> Self::Output {
Fx {
num: self.num << rhs,
phantom: PhantomData,
}
}
}
impl<T: Shr<u32, Output = T>, F: Unsigned> Shr<u32> for Fx<T, F> {
type Output = Self;
fn shr(self, rhs: u32) -> Self::Output {
Fx {
num: self.num >> rhs,
phantom: PhantomData,
}
}
}
impl<T: Neg<Output = T>, F: Unsigned> Neg for Fx<T, F> {
type Output = Self;
fn neg(self) -> Self::Output {
Fx {
num: -self.num,
phantom: PhantomData,
}
}
}
```
Unfortunately, for `Shl` and `Shr` to have as much coverage on our type as it
does on the base type (allowing just about any right hand side) we'd have to do
another macro, but I think just `u32` is fine. We can always add more later if
we need.
We could also implement `BitAnd`, `BitOr`, `BitXor`, and `Not`, but they don't
seem relevent to our fixed point math use, and this section is getting long
already. Just use the same general patterns if you want to add it in your own
programs. Shockingly, `Rem` also works directly if you want it, though I don't
forsee us needing floating point remainder. Also, the GBA can't do hardware
division or remainder, and we'll have to work around that below when we
implement `Div` (which maybe we don't need, but it's complex enough I should
show it instead of letting people guess).
**Note:** In addition to the various `Op` traits, there's also `OpAssign`
variants. Each `OpAssign` is the same as `Op`, but takes `&mut self` instead of
`self` and then modifies in place instead of producing a fresh value. In other
words, if you want both `+` and `+=` you'll need to do the `AddAssign` trait
too. It's not the worst thing to just write `a = a+b`, so I won't bother with
showing all that here. It's pretty easy to figure out for yourself if you want.
## Multiplication
This is where things get more interesting. When we have two numbers `A` and `B`
they really stand for `(a*f)` and `(b*f)`. If we write `A*B` then we're really
writing `(a*f)*(b*f)`, which can be rewritten as `(a*b)*2f`, and now it's
obvious that we have one more `f` than we wanted to have. We have to do the
multiply of the inner value and then divide out the `f`. We divide by `1 <<
bit_count`, so if we have 8 fractional bits we'll divide by 256.
The catch is that, when we do the multiply we're _extremely_ likely to overflow
our base type with that multiplication step. Then we do that divide, and now our
result is basically nonsense. We can avoid this to some extent by casting up to
a higher bit type, doing the multiplication and division at higher precision,
and then casting back down. We want as much precision as possible without being
too inefficient, so we'll always cast up to 32-bit (on a 64-bit machine you'd
cast up to 64-bit instead).
Naturally, any signed value has to be cast up to `i32` and any unsigned value
has to be cast up to `u32`, so we'll have to handle those separately.
Also, instead of doing an _actual_ divide we can right-shift by the correct
number of bits to achieve the same effect. _Except_ when we have a signed value
that's negative, because actual division truncates towards zero and
right-shifting truncates towards negative infinity. We can get around _this_ by
flipping the sign, doing the shift, and flipping the sign again (which sounds
silly but it's so much faster than doing an actual division).
Also, again signed values can be annoying, because if the value _just happens_
to be `i32::MIN` then when you negate it you'll have... _still_ a negative
value. I'm not 100% on this, but I think the correct thing to do at that point
is to give `$t::MIN` as out output num value.
Did you get all that? Good, because this is involves casting, we will need to
implement it three times, which calls for another macro.
```rust
macro_rules! fixed_point_signed_multiply {
($t:ident) => {
impl<F: Unsigned> Mul for Fx<$t, F> {
type Output = Self;
fn mul(self, rhs: Fx<$t, F>) -> Self::Output {
let pre_shift = (self.num as i32).wrapping_mul(rhs.num as i32);
if pre_shift < 0 {
if pre_shift == core::i32::MIN {
Fx {
num: core::$t::MIN,
phantom: PhantomData,
}
} else {
Fx {
num: (-((-pre_shift) >> F::U8)) as $t,
phantom: PhantomData,
}
}
} else {
Fx {
num: (pre_shift >> F::U8) as $t,
phantom: PhantomData,
}
}
}
}
};
}
fixed_point_signed_multiply! {i8}
fixed_point_signed_multiply! {i16}
fixed_point_signed_multiply! {i32}
macro_rules! fixed_point_unsigned_multiply {
($t:ident) => {
impl<F: Unsigned> Mul for Fx<$t, F> {
type Output = Self;
fn mul(self, rhs: Fx<$t, F>) -> Self::Output {
Fx {
num: ((self.num as u32).wrapping_mul(rhs.num as u32) >> F::U8) as $t,
phantom: PhantomData,
}
}
}
};
}
fixed_point_unsigned_multiply! {u8}
fixed_point_unsigned_multiply! {u16}
fixed_point_unsigned_multiply! {u32}
```
## Division
Division is similar to multiplication, but reversed. Which makes sense. This
time `A/B` gives `(a*f)/(b*f)` which is `a/b`, one _less_ `f` than we were
after.
As with the multiplication version of things, we have to up-cast our inner value
as much a we can before doing the math, to allow for the most precision
possible.
The snag here is that the GBA has no division or remainder. Instead, the GBA has
a BIOS function you can call to do `i32/i32` division.
This is a potential problem for us though. If we have some unsigned value, we
need it to fit within the positive space of an `i32` _after the multiply_ so
that we can cast it to `i32`, call the BIOS function that only works on `i32`
values, and cast it back to its actual type.
* If you have a u8 you're always okay, even with 8 floating bits.
* If you have a u16 you're okay even with a maximum value up to 15 floating
bits, but having a maximum value and 16 floating bits makes it break.
* If you have a u32 you're probably going to be in trouble all the time.
So... ugh, there's not much we can do about this. For now we'll just have to
suffer some.
// TODO: find a numerics book that tells us how to do `u32/u32` divisions.
```rust
macro_rules! fixed_point_signed_division {
($t:ident) => {
impl<F: Unsigned> Div for Fx<$t, F> {
type Output = Self;
fn div(self, rhs: Fx<$t, F>) -> Self::Output {
let mul_output: i32 = (self.num as i32).wrapping_mul(1 << F::U8);
let divide_result: i32 = crate::bios::div(mul_output, rhs.num as i32);
Fx {
num: divide_result as $t,
phantom: PhantomData,
}
}
}
};
}
fixed_point_signed_division! {i8}
fixed_point_signed_division! {i16}
fixed_point_signed_division! {i32}
macro_rules! fixed_point_unsigned_division {
($t:ident) => {
impl<F: Unsigned> Div for Fx<$t, F> {
type Output = Self;
fn div(self, rhs: Fx<$t, F>) -> Self::Output {
let mul_output: i32 = (self.num as i32).wrapping_mul(1 << F::U8);
let divide_result: i32 = crate::bios::div(mul_output, rhs.num as i32);
Fx {
num: divide_result as $t,
phantom: PhantomData,
}
}
}
};
}
fixed_point_unsigned_division! {u8}
fixed_point_unsigned_division! {u16}
fixed_point_unsigned_division! {u32}
```
## Trigonometry
TODO: look up tables! arcbits!
## Just Using A Crate
If, after seeing all that, and seeing that I still didn't even cover every
possible trait impl that you might want for all the possible types... if after
all that you feel too intimidated, then I'll cave a bit on your behalf and
suggest to you that the [fixed](https://crates.io/crates/fixed) crate seems to
be the best crate available for fixed point math.
_I have not tested its use on the GBA myself_.
It's just my recommendation from looking at the docs of the various options
available, if you really wanted to just have a crate for it.

138
book/src/01-quirks/04-newtype.md
View file

@ -1,5 +1,8 @@
# Newtype
TODO: we've already used newtype twice by now (fixed point values and volatile
addresses), so we need to adjust how we start this section.
There's a great Zero Cost abstraction that we'll be using a lot that you might
not already be familiar with: we're talking about the "Newtype Pattern"!
@ -27,32 +30,19 @@ cost at compile time.
pub struct PixelColor(u16);
```
TODO: we've already talked about repr(transparent) by now
Ah, except that, as I'm sure you remember from [The
Rustonomicon](https://doc.rust-lang.org/nomicon/other-reprs.html#reprtransparent)
(and from [the
RFC](https://github.com/rust-lang/rfcs/blob/master/text/1758-repr-transparent.md)
too, of course), if we have a single field struct that's sometimes different
from having just the bare value, so we should be using `#[repr(transparent)]`
with our newtypes.
(and from the RFC too, of course), if we have a single field struct that's
sometimes different from having just the bare value, so we should be using
`#[repr(transparent)]` with our newtypes.
```rust
#[repr(transparent)]
pub struct PixelColor(u16);
```
Ah, and of course we'll need to make it so you can unwrap the value:
```rust
#[repr(transparent)]
pub struct PixelColor(u16);
impl From<PixelColor> for u16 {
fn from(color: PixelColor) -> u16 {
color.0
}
}
```
And then we'll need to do that same thing for _every other newtype we want_.
Except there's only two tiny parts that actually differ between newtype
@ -62,7 +52,12 @@ a job for a macro to me!
## Making It A Macro
The most basic version of the macro we want goes like this:
If you're going to do much with macros you should definitely read through [The
Little Book of Rust
Macros](https://danielkeep.github.io/tlborm/book/index.html), but we won't be
doing too much so you can just follow along here a bit if you like.
The most basic version of a newtype macro starts like this:
```rust
#[macro_export]
@ -74,8 +69,39 @@ macro_rules! newtype {
}
```
Except we also want to be able to add attributes (which includes doc comments),
so we upgrade our macro a bit:
The `#[macro_export]` makes it exported by the current module (like `pub`
kinda), and then we have one expansion option that takes an identifier, a `,`,
and then a second identifier. The new name is the outer type we'll be using, and
the old name is the inner type that's being wrapped. You'd use our new macro
something like this:
```rust
newtype! {PixelColorCurly, u16}
newtype!(PixelColorParens, u16);
newtype![PixelColorBrackets, u16];
```
Note that you can invoke the macro with the outermost grouping as any of `()`,
`[]`, or `{}`. It makes no particular difference to the macro. Also, that space
in the first version is kinda to show off that you can put white space in
between the macro name and the grouping if you want. The difference is mostly
style, but there are some rules and considerations here:
* If you use curly braces then you _must not_ put a `;` after the invocation.
* If you use parentheses or brackets then you _must_ put the `;` at the end.
* Rustfmt cares which you use and formats accordingly:
* Curly brace macro use mostly gets treated like a code block.
* Parentheses macro use mostly gets treated like a function call.
* Bracket macro use mostly gets treated like an array declaration.
## Upgrade That Macro!
We also want to be able to add `derive` stuff and doc comments to our newtype.
Within the context of `macro_rules!` definitions these are called "meta". Since
we can have any number of them we wrap it all up in a "zero or more" matcher.
Then our macro looks like this:
```rust
#[macro_export]
@ -88,52 +114,44 @@ macro_rules! newtype {
}
```
And we want to automatically add the ability to turn the wrapper type back into
the wrapped type.
So now we can write
```rust
#[macro_export]
macro_rules! newtype {
($(#[$attr:meta])* $new_name:ident, $old_name:ident) => {
$(#[$attr])*
#[repr(transparent)]
pub struct $new_name($old_name);
impl From<$new_name> for $old_name {
fn from(x: $new_name) -> $old_name {
x.0
}
}
};
newtype! {
/// Color on the GBA gives 5 bits for each channel, the highest bit is ignored.
#[derive(Debug, Clone, Copy)]
PixelColor, u16
}
```
That seems like enough for all of our examples, so we'll stop there. We could
add more things:
* Making the `From` impl being optional. We'd have to make the newtype
invocation be more complicated somehow, the user puts ", no-unwrap" after the
inner type declaration or something, or something like that.
* Allowing for more precise visibility controls on the wrapping type and on the
inner field. This would add a lot of line noise, so we'll just always have our
newtypes be `pub`.
* Allowing for generic newtypes, which might sound silly but that we'll actually
see an example of soon enough. To do this you might _think_ that we can change
the `:ident` declarations to `:ty`, but since we're declaring a fresh type not
using an existing type we have to accept it as an `:ident`. The way you get
around this is with a proc-macro, which is a lot more powerful but which also
requires that you write the proc-macro in an entirely other crate that gets
compiled first. We don't need that much power, so for our examples we'll go
with the macro_rules version and just do it by hand in the few cases where we
need a generic newtype.
* Allowing for `Deref` and `DerefMut`, which usually defeats the point of doing
the newtype, but maybe sometimes it's the right thing, so if you were going
for the full industrial strength version with a proc-macro and all you might
want to make that part of your optional add-ons as well the same way you might
want optional `From`. You'd probably want `From` to be "on by default" and
`Deref`/`DerefMut` to be "off by default", but whatever.
And that's about all we'll need for the examples.
**As a reminder:** remember that `macro_rules` macros have to appear _before_
they're invoked in your source, so the `newtype` macro will always have to be at
the very top of your file, or if you put it in a module within your project
you'll need to declare the module before anything that uses it.
## Potential Homework
If you wanted to keep going and get really fancy with it, you could potentially
add a lot more:
* Make a `pub const fn new() -> Self` method that outputs the base value in a
const way. Combine this with builder style "setter" methods that are also
const and you can get the compiler to do quite a bit of the value building
work at compile time.
* Making the macro optionally emit a `From` impl to unwrap it back into the base
type.
* Allow for visibility modifiers to be applied to the inner field and the newly
generated type.
* Allowing for generic newtypes. You already saw the need for this once in the
volatile section. Unfortunately, this particular part gets really tricky if
you're using `macro_rules!`, so you might need to move up to a full
`proc_macro`. Having a `proc_macro` isn't bad except that they have to be
defined in a crate of their own and they're compiled before use. You can't
ever use them in the crate that defines them, so we won't be using them in any
of our single file examples.
* Allowing for optional `Deref` and `DerefMut` of the inner value. This takes
away most all the safety aspect of doing the newtype, but there may be times
for it. As an example, you could make a newtype with a different form of
Display impl that you want to otherwise treat as the base type in all places.

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# Constant Assertions
Have you ever wanted to assert things _even before runtime_? We all have, of
course. Particularly when the runtime machine is a poor little GBA, we'd like to
have the machine doing the compile handle as much checking as possible.
Enter the [static assertions](https://docs.rs/static_assertions/) crate, which
provides a way to let you assert on a `const` expression.
This is an amazing crate that you should definitely use when you can.
It's written by [Nikolai Vazquez](https://github.com/nvzqz), and they kindly
wrote up a [blog
post](https://nikolaivazquez.com/posts/programming/rust-static-assertions/) that
explains the thinking behind it.
However, I promised that each example would be single file, and I also promised
to explain what's going on as we go, so we'll briefly touch upon giving an
explanation here.
## How We Const Assert
Alright, as it stands (2018-12-15), we can't use `if` in a `const` context.
Since we can't use `if`, we can't use a normal `assert!`. Some day it will be
possible, and a failed assert at compile time will be a compile error and a
failed assert at run time will be a panic and we'll have a nice unified
programming experience. We can add runtime-only assertions by being a little
tricky with the compiler.
If we write
```rust
const ASSERT: usize = 0 - 1;
```
that gives a warning, since the math would underflow. We can upgrade that
warning to a hard error:
```rust
#[deny(const_err)]
const ASSERT: usize = 0 - 1;
```
And to make our construction reusable we can enable the
[underscore_const_names](https://github.com/rust-lang/rust/issues/54912) feature
in our program (or library) and then give each such const an underscore for a
name.
```rust
#![feature(underscore_const_names)]
#[deny(const_err)]
const _: usize = 0 - 1;
```
Now we wrap this in a macro where we give a `bool` expression as input. We
negate the bool then cast it to a `usize`, meaning that `true` negates into
`false`, which becomes `0usize`, and then there's no underflow error. Or if the
input was `false`, it negates into `true`, then becomes `1usize`, and then the
underflow error fires.
```rust
macro_rules! const_assert {
($condition:expr) => {
#[deny(const_err)]
#[allow(dead_code)]
const ASSERT: usize = 0 - !$condition as usize;
}
}
```
Technically, written like this, the expression can be anything with a
`core::ops::Not` implementation that can also be `as` cast into `usize`. That's
`bool`, but also basically all the other number types. Since we want to ensure
that we get proper looking type errors when things go wrong, we can use
`($condition && true)` to enforce that we get a `bool` (thanks to `Talchas` for
that particular suggestion).
```rust
macro_rules! const_assert {
($condition:expr) => {
#[deny(const_err)]
#[allow(dead_code)]
const _: usize = 0 - !($condition && true) as usize;
}
}
```
## Asserting Something
As an example of how we might use a `const_assert`, we'll do a demo with colors.
There's a red, blue, and green channel. We store colors in a `u16` with 5 bits
for each channel.
```rust
newtype! {
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
Color, u16
}
```
And when we're building a color, we're passing in `u16` values, but they could
be using more than just 5 bits of space. We want to make sure that each channel
is 31 or less, so we can make a color builder that does a `const_assert!` on the
value of each channel.
```rust
macro_rules! rgb {
($r:expr, $g:expr, $b:expr) => {
{
const_assert!($r <= 31);
const_assert!($g <= 31);
const_assert!($b <= 31);
Color($b << 10 | $g << 5 | $r)
}
}
}
```
And then we can declare some colors
```rust
const RED: Color = rgb!(31, 0, 0);
const BLUE: Color = rgb!(31, 500, 0);
```
The second one is clearly out of bounds and it fires an error just like we
wanted.

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# Broad Concepts
The GameBoy Advance sits in a middle place between the chthonic game consoles of
the ancient past and the "small PC in a funny case" consoles of the modern age.
On the one hand, yeah, you're gonna find a few strange conventions as you learn
all the ropes.
On the other, at least we're writing in Rust at all, and not having to do all
the assembly by hand.
This chapter for "concepts" has a section for each part of the GBA's hardware
memory map, going by increasing order of base address value. The sections try to
explain as much as possible while sticking to just the concerns you might have
regarding that part of the memory map.
For an assessment of how to wrangle all three parts of the video system (PALRAM,
VRAM, and OAM), along with the correct IO registers, into something that shows a
picture, you'll want the Video chapter.
Similarly, the "IO Registers" part of the GBA actually controls how you interact
with every single bit of hardware connected to the GBA. A full description of
everything is obviously too much for just one section of the book. Instead you
get an overview of general IO register rules and advice. Each particular
register is described in the appropriate sections of either the Video or
Non-Video chapters.
## Bus Size
TODO: describe this
## Minimum Write Size
TODO: talk about parts where you can't write one byte at a time
## Volatile or Not?
TODO: discuss what memory should be used volatile style and what can be used normal style.

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# BIOS
* **Address Span:** `0x0` to `0x3FFF` (16k)
The [BIOS](https://en.wikipedia.org/wiki/BIOS) of the GBA is a small read-only
portion of memory at the very base of the address space. However, it is also
hardware protected against reading, so if you try to read from BIOS memory when
the program counter isn't pointed into the BIOS (eg: any time code _you_ write
is executing) then you get [basically garbage
data](https://problemkaputt.de/gbatek.htm#gbaunpredictablethings) back.
So we're not going to spend time here talking about what bits to read or write
within BIOS memory like we do with the other sections. Instead we're going to
spend time talking about [inline
assembly](https://doc.rust-lang.org/unstable-book/language-features/asm.html)
([tracking issue](https://github.com/rust-lang/rust/issues/29722)) and then use
it to call the [GBA BIOS
Functions](https://problemkaputt.de/gbatek.htm#biosfunctions).
Note that BIOS calls have _more overhead than normal function calls_, so don't
go using them all over the place if you don't have to. They're also usually
written more to be compact in terms of code than for raw speed, so you actually
can out speed them in some cases. Between the increased overhead and not being
as speed optimized, you can sometimes do a faster job without calling the BIOS
at all. (TODO: investigate more about what parts of the BIOS we could
potentially offer faster alternatives for.)
I'd like to take a moment to thank [Marc Brinkmann](https://github.com/mbr)
(with contributions from [Oliver Schneider](https://github.com/oli-obk) and
[Philipp Oppermann](https://github.com/phil-opp)) for writing [this blog
post](http://embed.rs/articles/2016/arm-inline-assembly-rust/). It's at least
ten times the tutorial quality as the `asm` entry in the Unstable Book has. In
fairness to the Unstable Book, the actual spec of how inline ASM works in rust
is "basically what clang does", and that's specified as "basically what GCC
does", and that's basically/shockingly not specified much at all despite GCC
being like 30 years old.
So let's be slow and pedantic about this process.
## Inline ASM
**Fair Warning:** Inline asm is one of the least stable parts of Rust overall,
and if you write bad things you can trigger internal compiler errors and panics
and crashes and make LLVM choke and die without explanation. If you write some
inline asm and then suddenly your program suddenly stops compiling without
explanation, try commenting out that whole inline asm use and see if it's
causing the problem. Double check that you've written every single part of the
asm call absolutely correctly, etc, etc.
**Bonus Warning:** The general information that follows regarding the asm macro
is consistent from system to system, but specific information about register
names, register quantities, asm instruction argument ordering, and so on is
specific to ARM on the GBA. If you're programming for any other device you'll
need to carefully investigate that before you begin.
Now then, with those out of the way, the inline asm docs describe an asm call as
looking like this:
```rust
asm!(assembly template
: output operands
: input operands
: clobbers
: options
);
```
And once you stick a lot of stuff in there it can _absolutely_ be hard to
remember the ordering of the elements. So we'll start with a code block that
has some comments thrown in on each line:
```rust
asm!(/* ASM */ TODO
:/* OUT */ TODO
:/* INP */ TODO
:/* CLO */ TODO
:/* OPT */
);
```
Now we have to decide what we're gonna write. Obviously we're going to do some
instructions, but those instructions use registers, and how are we gonna talk
about them? We've got two choices.
1) We can pick each and every register used by specifying exact register names.
In THUMB mode we have 8 registers available, named `r0` through `r7`. If you
switch into 32-bit mode there's additional registers that are also available.
2) We can specify slots for registers we need and let LLVM decide. In this style
you name your slots `$0`, `$1` and so on. Slot numbers are assigned first to
all specified outputs, then to all specified inputs, in the order that you
list them.
In the case of the GBA BIOS, each BIOS function has pre-designated input and
output registers, so we will use the first style. If you use inline ASM in other
parts of your code you're free to use the second style.
### Assembly
This is just one big string literal. You write out one instruction per line, and
excess whitespace is ignored. You can also do comments within your assembly
using `;` to start a comment that goes until the end of the line.
Assembly convention doesn't consider it unreasonable to comment potentially as
much as _every single line_ of asm that you write when you're getting used to
things. Or even if you are used to things. This is cryptic stuff, there's a
reason we avoid writing in it as much as possible.
Remember that our Rust code is in 16-bit mode. You _can_ switch to 32-bit mode
within your asm as long as you switch back by the time the block ends. Otherwise
you'll have a bad time.
### Outputs
A comma separated list. Each entry looks like
* `"constraint" (binding)`
An output constraint starts with a symbol:
* `=` for write only
* `+` for reads and writes
* `&` for for "early clobber", meaning that you'll write to this at some point
before all input values have been read. It prevents this register from being
assigned to an input register.
Followed by _either_ the letter `r` (if you want LLVM to pick the register to
use) or curly braces around a specific register (if you want to pick).
* The binding can be any single 32-bit or smaller value.
* If your binding has bit pattern requirements ("must be non-zero", etc) you are
responsible for upholding that.
* If your binding type will try to `Drop` later then you are responsible for it
being in a fit state to do that.
* The binding must be either a mutable binding or a binding that was
pre-declared but not yet assigned.
Anything else is UB.
### Inputs
This is a similar comma separated list.
* `"constraint" (binding)`
An input constraint doesn't have the symbol prefix, you just pick either `r` or
a named register with curly braces around it.
* An input binding must be a single 32-bit or smaller value.
* An input binding _should_ be a type that is `Copy` but this is not an absolute
requirement. Having the input be read is semantically similar to using
`core::ptr::read(&binding)` and forgetting the value when you're done.
### Clobbers
Sometimes your asm will touch registers other than the ones declared for input
and output.
Clobbers are declared as a comma separated list of string literals naming
specific registers. You don't use curly braces with clobbers.
LLVM _needs_ to know this information. It can move things around to keep your
data safe, but only if you tell it what's about to happen.
Failure to define all of your clobbers can cause UB.
### Options
There's only one option we'd care to specify. That option is "volatile".
Just like with a function call, LLVM will skip a block of asm if it doesn't see
that any outputs from the asm were used later on. Nearly every single BIOS call
(other than the math operations) will need to be marked as "volatile".
### BIOS ASM
* Inputs are always `r0`, `r1`, `r2`, and/or `r3`, depending on function.
* Outputs are always zero or more of `r0`, `r1`, and `r3`.
* Any of the output registers that aren't actually used should be marked as
clobbered.
* All other registers are unaffected.
All of the GBA BIOS calls are performed using the
[swi](http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0068b/BABFCEEG.html)
instruction, combined with a value depending on what BIOS function you're trying
to invoke. If you're in 16-bit code you use the value directly, and if you're in
32-bit mode you shift the value up by 16 bits first.
### Example BIOS Function: Division
For our example we'll use the division function, because GBATEK gives very clear
instructions on how each register is used with that one:
```txt
Signed Division, r0/r1.
r0 signed 32bit Number
r1 signed 32bit Denom
Return:
r0 Number DIV Denom ;signed
r1 Number MOD Denom ;signed
r3 ABS (Number DIV Denom) ;unsigned
For example, incoming -1234, 10 should return -123, -4, +123.
The function usually gets caught in an endless loop upon division by zero.
```
The math folks tell me that the `r1` value should be properly called the
"remainder" not the "modulus". We'll go with that for our function, doesn't hurt
to use the correct names. Our Rust function has an assert against dividing by
`0`, then we name some bindings _without_ giving them a value, we make the asm
call, and then return what we got.
```rust
pub fn div_rem(numerator: i32, denominator: i32) -> (i32, i32) {
assert!(denominator != 0);
let div_out: i32;
let rem_out: i32;
unsafe {
asm!(/* ASM */ "swi 0x06"
:/* OUT */ "={r0}"(div_out), "={r1}"(rem_out)
:/* INP */ "{r0}"(numerator), "{r1}"(denominator)
:/* CLO */ "r3"
:/* OPT */
);
}
(div_out, rem_out)
}
```
I _hope_ this all makes sense by now.
## Specific BIOS Functions
For a full list of all the specific BIOS functions and their use you should
check the `gba::bios` module within the `gba` crate. There's just so many of
them that enumerating them all here wouldn't serve much purpose.
Which is not to say that we'll never cover any BIOS functions in this book!
Instead, we'll simply mention them when whenever they're relevent to the task at
hand (such as controlling sound or waiting for vblank).
//TODO: list/name all BIOS functions as well as what they relate to elsewhere.

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# Work RAM
## External Work RAM (EWRAM)
* **Address Span:** `0x2000000` to `0x203FFFF` (256k)
This is a big pile of space, the use of which is up to each game. However, the
external work ram has only a 16-bit bus (if you read/write a 32-bit value it
silently breaks it up into two 16-bit operations) and also 2 wait cycles (extra
CPU cycles that you have to expend _per 16-bit bus use_).
It's most helpful to think of EWRAM as slower, distant memory, similar to the
"heap" in a normal application. You can take the time to go store something
within EWRAM, or to load it out of EWRAM, but if you've got several operations
to do in a row and you're worried about time you should pull that value into
local memory, work on your local copy, and then push it back out to EWRAM.
## Internal Work RAM (IWRAM)
* **Address Span:** `0x3000000` to `0x3007FFF` (32k)
This is a smaller pile of space, but it has a 32-bit bus and no wait.
By default, `0x3007F00` to `0x3007FFF` is reserved for interrupt and BIOS use.
The rest of it is mostly up to you. The user's stack space starts at `0x3007F00`
and proceeds _down_ from there. For best results you should probably start at
`0x3000000` and then go upwards. Under normal use it's unlikely that the two
memory regions will crash into each other.

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# IO Registers
* **Address Span:** `0x400_0000` to `0x400_03FE`

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# Palette RAM
# Palette RAM (PALRAM)
* **Address Span:** `0x500_0000` to `0x500_03FF` (1k)
Palette RAM has a 16-bit bus, which isn't really a problem because it
conceptually just holds `u16` values. There's no automatic wait state, but if
you try to access the same location that the display controller is accessing you
get bumped by 1 cycle. Since the display controller can use the palette ram any
number of times per scanline it's basically impossible to predict if you'll have
to do a wait or not during VDraw. During VBlank you won't have any wait of
course.
PALRAM is among the memory where there's weirdness if you try to write just one
byte: if you try to write just 1 byte, it writes that byte into _both_ parts of
the larger 16-bit location. This doesn't really affect us much with PALRAM,
because palette values are all supposed to be `u16` anyway.
The palette memory actually contains not one, but _two_ sets of palettes. First
there's 256 entries for the background palette data (starting at `0x5000000`),
and then there's 256 entries for object palette data (starting at `0x5000200`).
The GBA also has two modes for palette access: 8-bits-per-pixel (8bpp) and
4-bits-per-pixel (4bpp).
* In 8bpp mode an 8-bit palette index value within a background or sprite
simply indexes directly into the 256 slots for that type of thing.
* In 4bpp mode a 4-bit palette index value within a background or sprite
specifies an index within a particular "palbank" (16 palette entries each),
and then a _separate_ setting outside of the graphical data determines which
palbank is to be used for that background or object (the screen entry data for
backgrounds, and the object attributes for objects).
### Transparency
When a pixel within a background or object specifies index 0 as its palette
entry it is treated as a transparent pixel. This means that in 8bpp mode there's
only 255 actual color options (0 being transparent), and in 4bpp mode there's
only 15 actual color options available within each palbank (the 0th entry of
_each_ palbank is transparent).
Individual backgrounds, and individual objects, each determine if they're 4bpp
or 8bpp separately, so a given overall palette slot might map to a used color in
8bpp and an unused/transparent color in 4bpp. If you're a palette wizard.
Palette slot 0 of the overall background palette is used to determine the
"backdrop" color. That's the color you see if no background or object ends up
being rendered within a given pixel.
Since display mode 3 and display mode 5 don't use the palette, they cannot
benefit from transparency.

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# Video RAM
# Video RAM (VRAM)
* **Address Span:** `0x600_0000` to `0x601_7FFF` (96k)
We've used this before! VRAM has a 16-bit bus and no wait. However, the same as
with PALRAM, the "you might have to wait if the display controller is looking at
it" rule applies here.
Unfortunately there's not much more exact detail that can be given about VRAM.
The use of the memory depends on the video mode that you're using.
One general detail of note is that you can't write individual bytes to any part
of VRAM. Depending on mode and location, you'll either get your bytes doubled
into both the upper and lower parts of the 16-bit location targeted, or you
won't even affect the memory. This usually isn't a big deal, except in two
situations:
* In Mode 4, if you want to change just 1 pixel, you'll have to be very careful
to read the old `u16`, overwrite just the byte you wanted to change, and then
write that back.
* In any display mode, avoid using `memcopy` to place things into VRAM.
It's written to be byte oriented, and only does 32-bit transfers under select
conditions. The rest of the time it'll copy one byte at a time and you'll get
either garbage or nothing at all.

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# Object Attribute Memory
# Object Attribute Memory (OAM)
* **Address Span:** `0x700_0000` to `0x700_03FF` (1k)
The Object Attribute Memory has a 32-bit bus and no default wait, but suffers
from the "you might have to wait if the display controller is looking at it"
rule. You cannot write individual bytes to OAM at all, but that's not really a
problem because all the fields of the data types within OAM are either `i16` or
`u16` anyway.
Object attribute memory is the wildest yet: it conceptually contains two types
of things, but they're _interlaced_ with each other all the way through.
Now, [GBATEK](http://problemkaputt.de/gbatek.htm#lcdobjoamattributes) and
[CowByte](https://www.cs.rit.edu/~tjh8300/CowBite/CowBiteSpec.htm#OAM%20(sprites))
doesn't quite give names to the two data types here.
[TONC](https://www.coranac.com/tonc/text/regobj.htm#sec-oam) calls them
`OBJ_ATTR` and `OBJ_AFFINE`, but we'll be giving them names fitting with the
Rust naming convention. Just know that if you try to talk about it with others
they might not be using the same names. In Rust terms their layout would look
like this:
```rust
#[repr(C)]
pub struct ObjectAttributes {
attr0: u16,
attr1: u16,
attr2: u16,
filler: i16,
}
#[repr(C)]
pub struct AffineMatrix {
filler0: [u16; 3],
pa: i16,
filler1: [u16; 3],
pb: i16,
filler2: [u16; 3],
pc: i16,
filler3: [u16; 3],
pd: i16,
}
```
(Note: the `#[repr(C)]` part just means that Rust must lay out the data exactly
in the order we specify, which otherwise it is not required to do).
So, we've got 1024 bytes in OAM and each `ObjectAttributes` value is 8 bytes, so
naturally we can support up to 128 objects.
_At the same time_, we've got 1024 bytes in OAM and each `AffineMatrix` is 32
bytes, so we can have 32 of them.
But, as I said, these things are all _interlaced_ with each other. See how
there's "filler" fields in each struct? If we imagine the OAM as being just an
array of one type or the other, indexes 0/1/2/3 of the `ObjectAttributes` array
would line up with index 0 of the `AffineMatrix` array. It's kinda weird, but
that's just how it works. When we setup functions to read and write these values
we'll have to be careful with how we do it. We probably _won't_ want to use
those representations above, at least not with the `AffineMatrix` type, because
they're quite wasteful if you want to store just object attributes or just
affine matrices.

15
book/src/02-concepts/08-rom.md
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@ -1 +1,14 @@
# Game Pak ROM / Flash ROM
# Game Pak ROM / Flash ROM (ROM)
* **Address Span (Wait State 0):** `0x800_0000` to `0x9FF_FFFF`
* **Address Span (Wait State 1):** `0xA00_0000` to `0xBFF_FFFF`
* **Address Span (Wait State 2):** `0xC00_0000` to `0xDFF_FFFF`
The game's ROM data is a single set of data that's up to 32 megabytes in size.
However, that data is mirrored to three different locations in the address
space. Depending on which part of the address space you use, it can affect the
memory timings involved.
TODO: describe `WAITCNT` here, we won't get a better chance at it.
TODO: discuss THUMB vs ARM code and why THUMB is so much faster (because ROM is a 16-bit bus)

17
book/src/02-concepts/09-sram.md
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@ -1 +1,16 @@
# Save RAM
# Save RAM (SRAM)
* **Address Span:** `0xE00_0000` to `0xE00FFFF` (64k)
The actual amount of SRAM available depends on your game pak, and the 64k figure
is simply the maximum possible. A particular game pak might have less, and an
emulator will likely let you have all 64k if you want.
As with other portions of the address space, SRAM has some number of wait cycles
per use. As with ROM, you can change the wait cycle settings via the `WAITCNT`
register if the defaults don't work well for your game pak. See the ROM section
for full details of how the `WAITCNT` register works.
The game pak SRAM also has only an 8-bit bus, so have fun with that.
The GBA Direct Memory Access (DMA) unit cannot access SRAM.

8
book/src/03-video/00-index.md
View file

@ -1 +1,9 @@
# Video
GBA Video starts with an IO register called the "Display Control Register", and
then spirals out from there. You generally have to use Palette RAM (PALRAM),
Video RAM (VRAM), Object Attribute Memory (OAM), as well as any number of other
IO registers.
They all have to work together just right, and there's a lot going on when you
first try doing it, so try to take it very slowly as you're learning each step.

20
book/src/04-non-video/00-index.md
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@ -1 +1,21 @@
# Non-Video
Besides video effects the GBA still has an okay amount of stuff going on.
Obviously you'll want to know how to read the user's button inputs. That can
almost go without saying, except that I said it.
Each other part can be handled in about any order you like.
Using interrupts is perhaps one of the hardest things for us as Rust programmers
due to quirks in our compilation process. Our code all gets compiled to 16-bit
THUMB instructions, and we don't have a way to mark a function to be compiled
using 32-bit ASM instructions instead. However, an interrupt handler _must_ be
written in 32-bit ASM instructions for it to work. That means that we have to
write our interrupt handler in 32-bit ASM by hand. We'll do it, but I don't
think we'll be too happy about it.
The Link Cable related stuff is also probably a little harder to test than
anything else. Just because link cable emulation isn't always the best, and or
you need two GBAs with two flash carts and the cable for hardware testing.
Still, we'll try to go over it eventually.

4
book/src/04-non-video/01-buttons.md
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@ -1 +1,5 @@
# Buttons
It's all well and good to just show a picture, even to show an animation, but if
we want a game we have to let the user interact with something.

1
book/src/04-non-video/06-link_cable.md Normal file
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@ -0,0 +1 @@
# Link Cable

1
book/src/04-non-video/06-network.md
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@ -1 +0,0 @@
# Network

3
book/src/SUMMARY.md
View file

@ -12,6 +12,7 @@
* [Fixed Only](01-quirks/02-fixed_only.md)
* [Volatile Destination](01-quirks/03-volatile_destination.md)
* [Newtype](01-quirks/04-newtype.md)
* [Const Asserts](01-quirks/05-const_asserts.md)
* [Concepts](02-concepts/00-index.md)
* [CPU](02-concepts/01-cpu.md)
* [BIOS](02-concepts/02-bios.md)
@ -31,7 +32,7 @@
* [Direct Memory Access](04-non-video/03-dma.md)
* [Sound](04-non-video/04-sound.md)
* [Interrupts](04-non-video/05-interrupts.md)
* [Network](04-non-video/06-network.md)
* [Link Cable](04-non-video/06-link_cable.md)
* [Game Pak](04-non-video/07-game_pak.md)
* [Examples](05-examples/00-index.md)
* [hello_magic](05-examples/01-hello_magic.md)

2
examples/bg_demo.rs
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@ -1,5 +1,5 @@
#![feature(start)]
#![no_std]
#![feature(start)]
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {

96
examples/hello_world.rs
View file

@ -1,22 +1,37 @@
#![feature(start)]
#![no_std]
#![feature(start)]
#![feature(underscore_const_names)]
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
loop {}
#[macro_export]
macro_rules! newtype {
($(#[$attr:meta])* $new_name:ident, $old_name:ident) => {
$(#[$attr])*
#[repr(transparent)]
pub struct $new_name($old_name);
};
}
#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
unsafe {
DISPCNT.write(MODE3 | BG2);
mode3_pixel(120, 80, rgb16(31, 0, 0));
mode3_pixel(136, 80, rgb16(0, 31, 0));
mode3_pixel(120, 96, rgb16(0, 0, 31));
loop {}
}
#[macro_export]
macro_rules! const_assert {
($condition:expr) => {
#[deny(const_err)]
#[allow(dead_code)]
const _: usize = 0 - !$condition as usize;
};
}
/// Constructs an RGB value with a `const_assert!` that the input is in range.
#[macro_export]
macro_rules! const_rgb {
($r:expr, $g:expr, $b:expr) => {{
const_assert!($r <= 31);
const_assert!($g <= 31);
const_assert!($b <= 31);
Color::new($r, $g, $b)
}};
}
// TODO: kill this
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct VolatilePtr<T>(pub *mut T);
@ -32,17 +47,50 @@ impl<T> VolatilePtr<T> {
}
}
pub const DISPCNT: VolatilePtr<u16> = VolatilePtr(0x04000000 as *mut u16);
pub const MODE3: u16 = 3;
pub const BG2: u16 = 0b100_0000_0000;
pub const VRAM: usize = 0x06000000;
pub const SCREEN_WIDTH: isize = 240;
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
blue << 10 | green << 5 | red
newtype! {
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
Color, u16
}
pub unsafe fn mode3_pixel(col: isize, row: isize, color: u16) {
VolatilePtr(VRAM as *mut u16).offset(col + row * SCREEN_WIDTH).write(color);
impl Color {
/// Combines the Red, Blue, and Green provided into a single color value.
pub const fn new(red: u16, green: u16, blue: u16) -> Color {
Color(blue << 10 | green << 5 | red)
}
}
newtype! {
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
DisplayControlSetting, u16
}
pub const DISPLAY_CONTROL: VolatilePtr<DisplayControlSetting> = VolatilePtr(0x0400_0000 as *mut DisplayControlSetting);
pub const JUST_MODE3: DisplayControlSetting = DisplayControlSetting(3);
pub const JUST_BG2: DisplayControlSetting = DisplayControlSetting(0b100_0000_0000);
pub const JUST_MODE3_AND_BG2: DisplayControlSetting = DisplayControlSetting(JUST_MODE3.0 | JUST_BG2.0);
pub struct Mode3;
impl Mode3 {
const SCREEN_WIDTH: isize = 240;
const PIXELS: VolatilePtr<Color> = VolatilePtr(0x600_0000 as *mut Color);
pub unsafe fn draw_pixel_unchecked(col: isize, row: isize, color: Color) {
Self::PIXELS.offset(col + row * Self::SCREEN_WIDTH).write(color);
}
}
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
loop {}
}
#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
unsafe {
DISPLAY_CONTROL.write(JUST_MODE3_AND_BG2);
Mode3::draw_pixel_unchecked(120, 80, const_rgb!(31, 0, 0));
Mode3::draw_pixel_unchecked(136, 80, const_rgb!(0, 31, 0));
Mode3::draw_pixel_unchecked(120, 96, const_rgb!(0, 0, 31));
loop {}
}
}

2
examples/light_cycle.rs
View file

@ -1,5 +1,5 @@
#![feature(start)]
#![no_std]
#![feature(start)]
#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {

517
src/bios.rs Normal file
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@ -0,0 +1,517 @@
//! This module contains wrappers for all GBA BIOS function calls.
//!
//! A GBA BIOS call has significantly more overhead than a normal function call,
//! so think carefully before using them too much.
//!
//! The actual content of each function here is generally a single inline asm
//! instruction to invoke the correct BIOS function (`swi x`, with `x` being
//! whatever value is necessary for that function). Some functions also perform
//! necessary checks to save you from yourself, such as not dividing by zero.
//TODO: ALL functions in this module should have `if cfg!(test)` blocks. The
//functions that never return must panic, the functions that return nothing
//should just do so, and the math functions should just return the correct math
//I guess.
/// (`swi 0x00`) SoftReset the device.
///
/// This function does not ever return.
///
/// Instead, it clears the top `0x200` bytes of IWRAM (containing stacks, and
/// BIOS IRQ vector/flags), re-initializes the system, supervisor, and irq stack
/// pointers (new values listed below), sets `r0` through `r12`, `LR_svc`,
/// `SPSR_svc`, `LR_irq`, and `SPSR_irq` to zero, and enters system mode. The
/// return address is loaded into `r14` and then the function jumps there with
/// `bx r14`.
///
/// * sp_svc: `0x300_7FE0`
/// * sp_irq: `0x300_7FA0`
/// * sp_sys: `0x300_7F00`
/// * Zero-filled Area: `0x300_7E00` to `0x300_7FFF`
/// * Return Address: Depends on the 8-bit flag value at `0x300_7FFA`. In either
/// case execution proceeds in ARM mode.
/// * zero flag: `0x800_0000` (ROM), which for our builds means that the
/// `crt0` program to execute (just like with a fresh boot), and then
/// control passes into `main` and so on.
/// * non-zero flag: `0x200_0000` (RAM), This is where a multiboot image would
/// go if you were doing a multiboot thing. However, this project doesn't
/// support multiboot at the moment. You'd need an entirely different build
/// pipeline because there's differences in header format and things like
/// that. Perhaps someday, but probably not even then. Submit the PR for it
/// if you like!
///
/// ## Safety
///
/// This functions isn't ever unsafe to the current iteration of the program.
/// However, because not all memory is fully cleared you theoretically could
/// threaten the _next_ iteration of the program that runs. I'm _fairly_
/// convinced that you can't actually use this to force purely safe code to
/// perform UB, but such a scenario might exist.
#[inline(always)]
pub unsafe fn soft_reset() -> ! {
asm!(/* ASM */ "swi 0x00"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
core::hint::unreachable_unchecked()
}
/// (`swi 0x01`) RegisterRamReset.
///
/// Clears the portions of memory given by the `flags` value, sets the Display
/// Control Register to `0x80` (forced blank and nothing else), then returns.
///
/// * Flag bits:
/// 0) Clears the 256k of EWRAM (don't use if this is where your function call
/// will return to!)
/// 1) Clears the 32k of IWRAM _excluding_ the last `0x200` bytes (see also:
/// the `soft_reset` function)
/// 2) Clears all Palette data
/// 3) Clears all VRAM
/// 4) Clears all OAM (reminder: a zeroed object isn't disabled!)
/// 5) Reset SIO registers (resets them to general purpose mode)
/// 6) Reset Sound registers
/// 7) Reset all IO registers _other than_ SIO and Sound
///
/// **Bug:** The LSB of `SIODATA32` is always zeroed, even if bit 5 was not
/// enabled. This is sadly a bug in the design of the GBA itself.
///
/// ## Safety
///
/// It is generally a safe operation to suddenly clear any part of the GBA's
/// memory, except in the case that you were executing out of EWRAM and clear
/// that. If you do then you return to nothing and have a bad time.
#[inline(always)]
pub unsafe fn register_ram_reset(flags: u8) {
asm!(/* ASM */ "swi 0x01"
:/* OUT */ // none
:/* INP */ "{r0}"(flags)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
//TODO(lokathor): newtype this flag business.
/// (`swi 0x02`) Halts the CPU until an interrupt occurs.
///
/// Components _other than_ the CPU continue to function. Halt mode ends when
/// any enabled interrupt triggers.
#[inline(always)]
pub fn halt() {
unsafe {
asm!(/* ASM */ "swi 0x02"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
/// (`swi 0x03`) Stops the CPU as well as most other components.
///
/// Stop mode must be stopped by an interrupt, but can _only_ be stopped by a
/// Keypad, Game Pak, or General-Purpose-SIO interrupt.
///
/// Before going into stop mode you should manually disable video and sound (or
/// they will continue to consume power), and you should also disable any other
/// optional externals such as rumble and infra-red.
#[inline(always)]
pub fn stop() {
unsafe {
asm!(/* ASM */ "swi 0x03"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
/// (`swi 0x04`) "IntrWait", similar to halt but with more options.
///
/// * The first argument controls if you want to ignore all current flags and
/// wait until a new flag is set.
/// * The second argument is what flags you're waiting on (same format as the
/// IE/IF registers).
///
/// If you're trying to handle more than one interrupt at once this has less
/// overhead than calling `halt` over and over.
///
/// When using this routing your interrupt handler MUST update the BIOS
/// Interrupt Flags `0x300_7FF8` in addition to the usual interrupt
/// acknowledgement.
#[inline(always)]
pub fn interrupt_wait(ignore_current_flags: bool, target_flags: u16) {
unsafe {
asm!(/* ASM */ "swi 0x04"
:/* OUT */ // none
:/* INP */ "{r0}"(ignore_current_flags), "{r1}"(target_flags)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
//TODO(lokathor): newtype this flag business.
/// (`swi 0x05`) "VBlankIntrWait", VBlank Interrupt Wait.
///
/// This is as per `interrupt_wait(true, 1)` (aka "wait for a new vblank"). You
/// must follow the same guidelines that `interrupt_wait` outlines.
#[inline(always)]
pub fn vblank_interrupt_wait() {
unsafe {
asm!(/* ASM */ "swi 0x04"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ "r0", "r1" // both set to 1 by the routine
:/* OPT */ "volatile"
);
}
}
/// (`swi 0x06`) Software Division and Remainder.
///
/// ## Panics
///
/// If the denominator is 0.
#[inline(always)]
pub fn div_rem(numerator: i32, denominator: i32) -> (i32, i32) {
assert!(denominator != 0);
if cfg!(test) {
(numerator / denominator, numerator % denominator)
} else {
let div_out: i32;
let rem_out: i32;
unsafe {
asm!(/* ASM */ "swi 0x06"
:/* OUT */ "={r0}"(div_out), "={r1}"(rem_out)
:/* INP */ "{r0}"(numerator), "{r1}"(denominator)
:/* CLO */ "r3"
:/* OPT */
);
}
(div_out, rem_out)
}
}
/// As `div_rem`, keeping only the `div` output.
#[inline(always)]
pub fn div(numerator: i32, denominator: i32) -> i32 {
div_rem(numerator, denominator).0
}
/// As `div_rem`, keeping only the `rem` output.
#[inline(always)]
pub fn rem(numerator: i32, denominator: i32) -> i32 {
div_rem(numerator, denominator).1
}
// (`swi 0x07`): We deliberately don't implement this one. It's the same as DIV
// but with reversed arguments, so it just runs 3 cycles slower as it does the
// swap.
/// (`swi 0x08`) Integer square root.
///
/// If you want more fractional precision, you can shift your input to the left
/// by `2n` bits to get `n` more bits of fractional precision in your output.
#[inline(always)]
pub fn sqrt(val: u32) -> u16 {
let out: u16;
unsafe {
asm!(/* ASM */ "swi 0x08"
:/* OUT */ "={r0}"(out)
:/* INP */ "{r0}"(val)
:/* CLO */ "r1", "r3"
:/* OPT */
);
}
out
}
/// (`swi 0x09`) Gives the arctangent of `theta`.
///
/// The input format is 1 bit for sign, 1 bit for integral part, 14 bits for
/// fractional part.
///
/// Accuracy suffers if `theta` is less than `-pi/4` or greater than `pi/4`.
#[inline(always)]
pub fn atan(theta: i16) -> i16 {
let out: i16;
unsafe {
asm!(/* ASM */ "swi 0x09"
:/* OUT */ "={r0}"(out)
:/* INP */ "{r0}"(theta)
:/* CLO */ "r1", "r3"
:/* OPT */
);
}
out
}
/// (`swi 0x0A`) Gives the atan2 of `y` over `x`.
///
/// The output `theta` value maps into the range `[0, 2pi)`, or `0 .. 2pi` if
/// you prefer Rust's range notation.
///
/// `y` and `x` use the same format as with `atan`: 1 bit for sign, 1 bit for
/// integral, 14 bits for fractional.
#[inline(always)]
pub fn atan2(y: i16, x: i16) -> u16 {
let out: u16;
unsafe {
asm!(/* ASM */ "swi 0x0A"
:/* OUT */ "={r0}"(out)
:/* INP */ "{r0}"(x), "{r1}"(y)
:/* CLO */ "r3"
:/* OPT */
);
}
out
}
/// (`swi 0x0B`) "CpuSet", `u16` memory copy.
///
/// * `count` is the number of `u16` values to copy (20 bits or less)
/// * `fixed_source` argument, if true, turns this copying routine into a
/// filling routine.
///
/// ## Safety
///
/// * Both pointers must be aligned
#[inline(always)]
pub unsafe fn cpu_set16(src: *const u16, dest: *mut u16, count: u32, fixed_source: bool) {
let control = count + ((fixed_source as u32) << 24);
asm!(/* ASM */ "swi 0x0B"
:/* OUT */ // none
:/* INP */ "{r0}"(src), "{r1}"(dest), "{r2}"(control)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
/// (`swi 0x0B`) "CpuSet", `u32` memory copy/fill.
///
/// * `count` is the number of `u32` values to copy (20 bits or less)
/// * `fixed_source` argument, if true, turns this copying routine into a
/// filling routine.
///
/// ## Safety
///
/// * Both pointers must be aligned
#[inline(always)]
pub unsafe fn cpu_set32(src: *const u32, dest: *mut u32, count: u32, fixed_source: bool) {
let control = count + ((fixed_source as u32) << 24) + (1 << 26);
asm!(/* ASM */ "swi 0x0B"
:/* OUT */ // none
:/* INP */ "{r0}"(src), "{r1}"(dest), "{r2}"(control)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
/// (`swi 0x0C`) "CpuFastSet", copies memory in 32 byte chunks.
///
/// * The `count` value is the number of `u32` values to transfer (20 bits or
/// less), and it's rounded up to the nearest multiple of 8 words.
/// * The `fixed_source` argument, if true, turns this copying routine into a
/// filling routine.
///
/// ## Safety
///
/// * Both pointers must be aligned
#[inline(always)]
pub unsafe fn cpu_fast_set(src: *const u32, dest: *mut u32, count: u32, fixed_source: bool) {
let control = count + ((fixed_source as u32) << 24);
asm!(/* ASM */ "swi 0x0C"
:/* OUT */ // none
:/* INP */ "{r0}"(src), "{r1}"(dest), "{r2}"(control)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
/// (`swi 0x0C`) "GetBiosChecksum" (Undocumented)
///
/// Though we usually don't cover undocumented functionality, this one can make
/// it into the crate.
///
/// The function computes the checksum of the BIOS data. You should get either
/// `0xBAAE_187F` (GBA / GBA SP) or `0xBAAE_1880` (DS in GBA mode). If you get
/// some other value I guess you're probably running on an emulator that just
/// broke the fourth wall.
pub fn get_bios_checksum() -> u32 {
let out: u32;
unsafe {
asm!(/* ASM */ "swi 0x0D"
:/* OUT */ "={r0}"(out)
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ // none
);
}
out
}
// TODO: these things will require that we build special structs
//BgAffineSet
//ObjAffineSet
//BitUnPack
//LZ77UnCompReadNormalWrite8bit
//LZ77UnCompReadNormalWrite16bit
//HuffUnCompReadNormal
//RLUnCompReadNormalWrite8bit
//Diff8bitUnFilterWrite8bit
//Diff8bitUnFilterWrite16bit
//Diff16bitUnFilter
/// (`swi 0x19`) "SoundBias", adjusts the volume level to a new level.
///
/// This increases or decreases the current level of the `SOUNDBIAS` register
/// (with short delays) until at the new target level. The upper bits of the
/// register are unaffected.
///
/// The final sound level setting will be `level` * `0x200`.
pub fn sound_bias(level: u32) {
unsafe {
asm!(/* ASM */ "swi 0x19"
:/* OUT */ // none
:/* INP */ "{r0}"(level)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
//SoundDriverInit
/// (`swi 0x1B`) "SoundDriverMode", sets the sound driver operation mode.
///
/// The `mode` input uses the following flags and bits:
///
/// * Bits 0-6: Reverb value
/// * Bit 7: Reverb Enable
/// * Bits 8-11: Simultaneously-produced channel count (default=8)
/// * Bits 12-15: Master Volume (1-15, default=15)
/// * Bits 16-19: Playback Frequency Index (see below, default=4)
/// * Bits 20-23: "Final number of D/A converter bits (8-11 = 9-6bits, def. 9=8bits)" TODO: what the hek?
/// * Bits 24 and up: Not used
///
/// The frequency index selects a frequency from the following array:
/// * 0: 5734
/// * 1: 7884
/// * 2: 10512
/// * 3: 13379
/// * 4: 15768
/// * 5: 18157
/// * 6: 21024
/// * 7: 26758
/// * 8: 31536
/// * 9: 36314
/// * 10: 40137
/// * 11: 42048
pub fn sound_driver_mode(mode: u32) {
unsafe {
asm!(/* ASM */ "swi 0x1B"
:/* OUT */ // none
:/* INP */ "{r0}"(mode)
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
//TODO(lokathor): newtype this mode business.
/// (`swi 0x1C`) "SoundDriverMain", main of the sound driver
///
/// You should call `SoundDriverVSync` immediately after the vblank interrupt
/// fires.
///
/// "After that, this routine is called after BG and OBJ processing is
/// executed." --what?
#[inline(always)]
pub fn sound_driver_main() {
unsafe {
asm!(/* ASM */ "swi 0x1C"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
/// (`swi 0x1D`) "SoundDriverVSync", resets the sound DMA.
///
/// The timing is critical, so you should call this _immediately_ after the
/// vblank interrupt (every 1/60th of a second).
#[inline(always)]
pub fn sound_driver_vsync() {
unsafe {
asm!(/* ASM */ "swi 0x1D"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
/// (`swi 0x1E`) "SoundChannelClear", clears the direct sound channels and stops
/// the sound.
///
/// "This function may not operate properly when the library which expands the
/// sound driver feature is combined afterwards. In this case, do not use it."
/// --what?
#[inline(always)]
pub fn sound_channel_clear() {
unsafe {
asm!(/* ASM */ "swi 0x1E"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
//MidiKey2Freq
//MultiBoot
/// (`swi 0x28`) "SoundDriverVSyncOff", disables sound
///
/// If you can't use vblank interrupts to ensure that `sound_driver_vsync` is
/// called every 1/60th of a second for any reason you must use this function to
/// stop sound DMA. Otherwise the DMA will overrun its buffer and cause random
/// noise.
#[inline(always)]
pub fn sound_driver_vsync_off() {
unsafe {
asm!(/* ASM */ "swi 0x28"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}
/// (`swi 0x29`) "SoundDriverVSyncOn", enables sound that was stopped by
/// `sound_driver_vsync_off`.
///
/// Restarts sound DMA system. After restarting the sound you must have a vblank
/// interrupt followed by a `sound_driver_vsync` within 2/60th of a second.
#[inline(always)]
pub fn sound_driver_vsync_on() {
unsafe {
asm!(/* ASM */ "swi 0x29"
:/* OUT */ // none
:/* INP */ // none
:/* CLO */ // none
:/* OPT */ "volatile"
);
}
}

77
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#![allow(missing_docs)]
//! The module to provide "builtin" functions that LLVM expects.
//!
//! You shouldn't need to call anything in here yourself, it just has to be in
//! the translation unit and LLVM will find it.
#[no_mangle]
#[cfg(any(target_pointer_width = "16", target_pointer_width = "32", target_pointer_width = "64"))]
pub extern "C" fn __clzsi2(mut x: usize) -> usize {
// TODO: const this? Requires const if
let mut y: usize;
let mut n: usize = {
#[cfg(target_pointer_width = "64")]
{
64
}
#[cfg(target_pointer_width = "32")]
{
32
}
#[cfg(target_pointer_width = "16")]
{
16
}
};
#[cfg(target_pointer_width = "64")]
{
y = x >> 32;
if y != 0 {
n -= 32;
x = y;
}
}
#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
{
y = x >> 16;
if y != 0 {
n -= 16;
x = y;
}
}
y = x >> 8;
if y != 0 {
n -= 8;
x = y;
}
y = x >> 4;
if y != 0 {
n -= 4;
x = y;
}
y = x >> 2;
if y != 0 {
n -= 2;
x = y;
}
y = x >> 1;
if y != 0 {
n - 2
} else {
n - x
}
}
#[test]
fn __clzsi2_test() {
let mut i = 1 << 63;
while i > 0 {
assert_eq!(__clzsi2(i), i.leading_zeros() as usize);
i >>= 1;
}
}
// TODO: add some shims
// #[no_mangle] extern "aapcs" fn __aeabi_uidiv(num: u32: denom: u32) -> u32
// #[no_mangle] extern "aapcs" fn __aeabi_idiv(num: i32: denom: i32) -> u32

310
src/core_extras.rs
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@ -1,39 +1,301 @@
//! Things that I wish were in core, but aren't.
/// A simple wrapper for any `*mut T` to adjust the basic operations.
//TODO(Lokathor): reorganize as gba::core_extras::fixed_point and gba::core_extras::volatile ?
use core::{cmp::Ordering, iter::FusedIterator, marker::PhantomData, num::NonZeroUsize};
/// Abstracts the use of a volatile hardware address.
///
/// Read and Write are made to be volatile. Offset is made to be
/// wrapping_offset. This makes it much easier to correctly work with IO
/// Registers and all display related memory on the GBA.
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
/// If you're trying to do anything other than abstract a volatile hardware
/// device then you _do not want to use this type_. Use one of the many other
/// smart pointer types.
///
/// A volatile address doesn't store a value in the normal way: It maps to some
/// real hardware _other than_ RAM, and that hardware might have any sort of
/// strange rules. The specifics of reading and writing depend on the hardware
/// being mapped. For example, a particular address might be read only (ignoring
/// writes), write only (returning some arbitrary value if you read it),
/// "normal" read write (where you read back what you wrote), or some complex
/// read-write situation where writes have an effect but you _don't_ read back
/// what you wrote.
///
/// As you imagine it can be very unsafe. The design of this type is set up so
/// that _creation_ is unsafe, and _use_ is safe. This gives an optimal
/// experience, since you'll use memory locations a lot more often than you try
/// to name them, on average.
///
/// `VolAddress` is _not_ a thread safe type. If your device is multi-threaded
/// then you must arrange for synchronization in some other way. A `VolAddress`
/// _can_ be used to share data between an interrupt running on a core and a
/// thread running on that core as long as all access of that location is
/// volatile (if you're using the `asm!` macro add the "volatile" option, if
/// you're linking in ASM with the linker that's effectively volatile since the
/// compiler doesn't get a chance to mess with it).
///
/// # Safety
///
/// In order for values of this type to operate correctly they must follow quite
/// a few safety limits:
///
/// * The declared address must be non-null (it uses the `NonNull` optimization
/// for better iteration results). This shouldn't be a big problem, since
/// hardware can't really live at the null address.
/// * The declared address must be aligned for the declared type of `T`.
/// * The declared address must _always_ read as something that's a valid bit
/// pattern for `T`. Don't pick any enums or things like that if your hardware
/// doesn't back it up. If there's _any_ doubt at all, you must instead read
/// or write an unsigned int of the correct bit size and then parse the bits
/// by hand.
/// * The declared address must be a part of the address space that Rust's
/// allocator and/or stack frames will never use. If you're not sure, please
/// re-read the hardware specs of your device and its memory map until you
/// know.
///
/// The exact points of UB are if the address is ever 0, or if you ever `read`
/// or `write` with the invalid pointer. For example, if you offset to some
/// crazy (non-zero) value and then never use it that won't be an immediate
/// trigger of UB.
#[derive(Debug)]
#[repr(transparent)]
pub struct VolatilePtr<T>(pub *mut T);
impl<T> core::fmt::Pointer for VolatilePtr<T> {
/// Formats exactly like the inner `*mut T`.
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
write!(f, "{:p}", self.0)
pub struct VolAddress<T> {
address: NonZeroUsize,
marker: PhantomData<*mut T>,
}
// Note(Lokathor): We have to hand implement all these traits because if we use
// `derive` then they only get derived if the inner `T` has the trait. However,
// since we're acting like a pointer to `T`, the capability we offer isn't
// affected by whatever type `T` ends up being.
impl<T> Clone for VolAddress<T> {
fn clone(&self) -> Self {
*self
}
}
impl<T> Copy for VolAddress<T> {}
impl<T> PartialEq for VolAddress<T> {
fn eq(&self, other: &Self) -> bool {
self.address == other.address
}
}
impl<T> Eq for VolAddress<T> {}
impl<T> PartialOrd for VolAddress<T> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.address.cmp(&other.address))
}
}
impl<T> Ord for VolAddress<T> {
fn cmp(&self, other: &Self) -> Ordering {
self.address.cmp(&other.address)
}
}
impl<T> VolatilePtr<T> {
/// Performs a `read_volatile`.
pub unsafe fn read(&self) -> T {
self.0.read_volatile()
impl<T> VolAddress<T> {
/// Constructs a new address.
///
/// # Safety
///
/// You must follow the standard safety rules as outlined in the type docs.
pub const unsafe fn new_unchecked(address: usize) -> Self {
VolAddress {
address: NonZeroUsize::new_unchecked(address),
marker: PhantomData,
}
}
/// Performs a `write_volatile`.
pub unsafe fn write(&self, data: T) {
self.0.write_volatile(data);
/// Casts the type of `T` into type `Z`.
///
/// # Safety
///
/// You must follow the standard safety rules as outlined in the type docs.
pub const unsafe fn cast<Z>(self) -> VolAddress<Z> {
VolAddress {
address: self.address,
marker: PhantomData,
}
}
/// Performs a `wrapping_offset`.
pub fn offset(self, count: isize) -> Self {
VolatilePtr(self.0.wrapping_offset(count))
/// Offsets the address by `offset` slots (like `pointer::wrapping_offset`).
///
/// # Safety
///
/// You must follow the standard safety rules as outlined in the type docs.
pub unsafe fn offset(self, offset: isize) -> Self {
// TODO: const this
VolAddress {
address: NonZeroUsize::new_unchecked(self.address.get().wrapping_add(offset as usize * core::mem::size_of::<T>())),
marker: PhantomData,
}
}
/// Performs a cast into some new pointer type.
pub fn cast<Z>(self) -> VolatilePtr<Z> {
VolatilePtr(self.0 as *mut Z)
/// Checks that the current target type of this address is aligned at this
/// address value.
///
/// Technically it's a safety violation to even make a `VolAddress` that isn't
/// aligned. However, I know you're gonna try doing the bad thing, and it's
/// better to give you a chance to call `is_aligned` and potentially back off
/// from the operation or throw a `debug_assert!` or something instead of
/// triggering UB. Eventually this will be `const fn`, which will potentially
/// let you spot errors without even having to run your program.
pub fn is_aligned(self) -> bool {
// TODO: const this
self.address.get() % core::mem::align_of::<T>() == 0
}
/// Makes an iterator starting here across the given number of slots.
///
/// # Safety
///
/// The normal safety rules must be correct for each address iterated over.
pub const unsafe fn iter_slots(self, slots: usize) -> VolAddressIter<T> {
VolAddressIter { vol_address: self, slots }
}
// non-const and never can be.
/// Reads a `Copy` value out of the address.
///
/// The `Copy` bound is actually supposed to be `!Drop`, but rust doesn't
/// allow negative trait bounds. If your type isn't `Copy` you can use the
/// `read_non_copy` fallback to do an unsafe read.
///
/// That said, I don't think that you legitimately have hardware that maps to
/// a Rust type with a `Drop` impl. If you do please tell me, I'm interested
/// to hear about it.
pub fn read(self) -> T
where
T: Copy,
{
unsafe { (self.address.get() as *mut T).read_volatile() }
}
/// Reads a value out of the address with no trait bound.
///
/// # Safety
///
/// This is _not_ a move, it forms a bit duplicate of the current address
/// value. If `T` has a `Drop` trait that does anything it is up to you to
/// ensure that repeated drops do not cause UB (such as a double free).
pub unsafe fn read_non_copy(self) -> T {
(self.address.get() as *mut T).read_volatile()
}
/// Writes a value to the address.
///
/// Semantically, the value is moved into the `VolAddress` and then forgotten,
/// so if `T` has a `Drop` impl then that will never get executed. This is
/// "safe" under Rust's safety rules, but could cause something unintended
/// (eg: a memory leak).
pub fn write(self, val: T) {
unsafe { (self.address.get() as *mut T).write_volatile(val) }
}
}
/// An iterator that produces a series of `VolAddress` values.
#[derive(Debug)]
pub struct VolAddressIter<T> {
vol_address: VolAddress<T>,
slots: usize,
}
impl<T> Clone for VolAddressIter<T> {
fn clone(&self) -> Self {
VolAddressIter {
vol_address: self.vol_address,
slots: self.slots,
}
}
}
impl<T> PartialEq for VolAddressIter<T> {
fn eq(&self, other: &Self) -> bool {
self.vol_address == other.vol_address && self.slots == other.slots
}
}
impl<T> Eq for VolAddressIter<T> {}
impl<T> Iterator for VolAddressIter<T> {
type Item = VolAddress<T>;
fn next(&mut self) -> Option<Self::Item> {
if self.slots > 0 {
let out = self.vol_address;
unsafe {
self.slots -= 1;
self.vol_address = self.vol_address.offset(1);
}
Some(out)
} else {
None
}
}
}
impl<T> FusedIterator for VolAddressIter<T> {}
/// This type is like `VolAddress`, but for when you have a block of values all
/// in a row.
///
/// This is similar to the idea of an array or a slice, but called a "block"
/// because you could _also_ construct a `[VolAddress]`, and we want to avoid
/// any accidental confusion.
#[derive(Debug)]
pub struct VolAddressBlock<T> {
vol_address: VolAddress<T>,
slots: usize,
}
impl<T> Clone for VolAddressBlock<T> {
fn clone(&self) -> Self {
VolAddressBlock {
vol_address: self.vol_address,
slots: self.slots,
}
}
}
impl<T> PartialEq for VolAddressBlock<T> {
fn eq(&self, other: &Self) -> bool {
self.vol_address == other.vol_address && self.slots == other.slots
}
}
impl<T> Eq for VolAddressBlock<T> {}
impl<T> VolAddressBlock<T> {
/// Constructs a new `VolAddressBlock`.
///
/// # Safety
///
/// The given `VolAddress` must be valid when offset by each of `0 .. slots`
pub const unsafe fn new_unchecked(vol_address: VolAddress<T>, slots: usize) -> Self {
VolAddressBlock { vol_address, slots }
}
/// Gives an iterator over this block's slots.
pub const fn iter(self) -> VolAddressIter<T> {
VolAddressIter {
vol_address: self.vol_address,
slots: self.slots,
}
}
/// Unchecked indexing into the block.
///
/// # Safety
///
/// The slot given must be in bounds.
pub unsafe fn index_unchecked(self, slot: usize) -> VolAddress<T> {
// TODO: const this
self.vol_address.offset(slot as isize)
}
/// Checked "indexing" style access of the block, giving either a `VolAddress` or a panic.
pub fn index(self, slot: usize) -> VolAddress<T> {
if slot < self.slots {
unsafe { self.vol_address.offset(slot as isize) }
} else {
panic!("Index Requested: {} >= Bound: {}", slot, self.slots)
}
}
/// Checked "getting" style access of the block, giving an Option value.
pub fn get(self, slot: usize) -> Option<VolAddress<T>> {
if slot < self.slots {
unsafe { Some(self.vol_address.offset(slot as isize)) }
} else {
None
}
}
}

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#![allow(non_camel_case_types)]
//! Module for fixed point math types and operations.
use core::{
marker::PhantomData,
ops::{Add, Div, Mul, Neg, Shl, Shr, Sub},
};
use typenum::{consts::False, marker_traits::Unsigned, type_operators::IsEqual, U8};
/// Fixed point `T` value with `F` fractional bits.
#[derive(Debug, Copy, Clone, Default, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct Fx<T, F: Unsigned> {
num: T,
phantom: PhantomData<F>,
}
impl<T, F: Unsigned> Fx<T, F> {
/// Uses the provided value directly.
pub fn from_raw(r: T) -> Self {
Fx {
num: r,
phantom: PhantomData,
}
}
/// Unwraps the inner value.
pub fn into_raw(self) -> T {
self.num
}
/// Casts the base type, keeping the fractional bit quantity the same.
pub fn cast_inner<Z, C: Fn(T) -> Z>(self, op: C) -> Fx<Z, F> {
Fx {
num: op(self.num),
phantom: PhantomData,
}
}
}
impl<T: Add<Output = T>, F: Unsigned> Add for Fx<T, F> {
type Output = Self;
fn add(self, rhs: Fx<T, F>) -> Self::Output {
Fx {
num: self.num + rhs.num,
phantom: PhantomData,
}
}
}
impl<T: Sub<Output = T>, F: Unsigned> Sub for Fx<T, F> {
type Output = Self;
fn sub(self, rhs: Fx<T, F>) -> Self::Output {
Fx {
num: self.num - rhs.num,
phantom: PhantomData,
}
}
}
impl<T: Shl<u32, Output = T>, F: Unsigned> Shl<u32> for Fx<T, F> {
type Output = Self;
fn shl(self, rhs: u32) -> Self::Output {
Fx {
num: self.num << rhs,
phantom: PhantomData,
}
}
}
impl<T: Shr<u32, Output = T>, F: Unsigned> Shr<u32> for Fx<T, F> {
type Output = Self;
fn shr(self, rhs: u32) -> Self::Output {
Fx {
num: self.num >> rhs,
phantom: PhantomData,
}
}
}
impl<T: Neg<Output = T>, F: Unsigned> Neg for Fx<T, F> {
type Output = Self;
fn neg(self) -> Self::Output {
Fx {
num: -self.num,
phantom: PhantomData,
}
}
}
macro_rules! fixed_point_methods {
($t:ident) => {
impl<F: Unsigned> Fx<$t, F> {
/// Gives the smallest positive non-zero value.
pub fn precision() -> Self {
Fx {
num: 1,
phantom: PhantomData,
}
}
/// Makes a value with the integer part shifted into place.
pub fn from_int_part(i: $t) -> Self {
Fx {
num: i << F::U8,
phantom: PhantomData,
}
}
/// Changes the fractional bit quantity, keeping the base type the same.
pub fn adjust_fractional_bits<Y: Unsigned + IsEqual<F, Output = False>>(self) -> Fx<$t, Y> {
let leftward_movement: i32 = Y::to_i32() - F::to_i32();
Fx {
num: if leftward_movement > 0 {
self.num << leftward_movement
} else {
self.num >> (-leftward_movement)
},
phantom: PhantomData,
}
}
}
};
}
fixed_point_methods! {u8}
fixed_point_methods! {i8}
fixed_point_methods! {i16}
fixed_point_methods! {u16}
fixed_point_methods! {i32}
fixed_point_methods! {u32}
macro_rules! fixed_point_signed_multiply {
($t:ident) => {
impl<F: Unsigned> Mul for Fx<$t, F> {
type Output = Self;
#[allow(clippy::suspicious_arithmetic_impl)]
fn mul(self, rhs: Fx<$t, F>) -> Self::Output {
let pre_shift = (self.num as i32).wrapping_mul(rhs.num as i32);
if pre_shift < 0 {
if pre_shift == core::i32::MIN {
Fx {
num: core::$t::MIN,
phantom: PhantomData,
}
} else {
Fx {
num: (-((-pre_shift) >> F::U8)) as $t,
phantom: PhantomData,
}
}
} else {
Fx {
num: (pre_shift >> F::U8) as $t,
phantom: PhantomData,
}
}
}
}
};
}
fixed_point_signed_multiply! {i8}
fixed_point_signed_multiply! {i16}
fixed_point_signed_multiply! {i32}
macro_rules! fixed_point_unsigned_multiply {
($t:ident) => {
impl<F: Unsigned> Mul for Fx<$t, F> {
type Output = Self;
#[allow(clippy::suspicious_arithmetic_impl)]
fn mul(self, rhs: Fx<$t, F>) -> Self::Output {
Fx {
num: ((self.num as u32).wrapping_mul(rhs.num as u32) >> F::U8) as $t,
phantom: PhantomData,
}
}
}
};
}
fixed_point_unsigned_multiply! {u8}
fixed_point_unsigned_multiply! {u16}
fixed_point_unsigned_multiply! {u32}
macro_rules! fixed_point_signed_division {
($t:ident) => {
impl<F: Unsigned> Div for Fx<$t, F> {
type Output = Self;
#[allow(clippy::suspicious_arithmetic_impl)]
fn div(self, rhs: Fx<$t, F>) -> Self::Output {
let mul_output: i32 = (self.num as i32).wrapping_mul(1 << F::U8);
let divide_result: i32 = crate::bios::div(mul_output, rhs.num as i32);
Fx {
num: divide_result as $t,
phantom: PhantomData,
}
}
}
};
}
fixed_point_signed_division! {i8}
fixed_point_signed_division! {i16}
fixed_point_signed_division! {i32}
macro_rules! fixed_point_unsigned_division {
($t:ident) => {
impl<F: Unsigned> Div for Fx<$t, F> {
type Output = Self;
#[allow(clippy::suspicious_arithmetic_impl)]
fn div(self, rhs: Fx<$t, F>) -> Self::Output {
let mul_output: i32 = (self.num as i32).wrapping_mul(1 << F::U8);
let divide_result: i32 = crate::bios::div(mul_output, rhs.num as i32);
Fx {
num: divide_result as $t,
phantom: PhantomData,
}
}
}
};
}
fixed_point_unsigned_division! {u8}
fixed_point_unsigned_division! {u16}
fixed_point_unsigned_division! {u32}
/// Alias for an `i16` fixed point value with 8 fractional bits.
pub type fx8_8 = Fx<i16, U8>;
#[cfg(test)]
mod fixed_tests {
use super::*;
#[test]
fn test_add() {
use typenum::U4;
let one = Fx::<u16, U4>::from_int_part(1);
let two = Fx::<u16, U4>::from_int_part(2);
assert!(one + one == two)
}
#[test]
fn test_sub() {
use typenum::U4;
let one = Fx::<u16, U4>::from_int_part(1);
let two = Fx::<u16, U4>::from_int_part(2);
assert!(two - one == one)
}
#[test]
fn test_shl() {
use typenum::U4;
let one = Fx::<u16, U4>::from_int_part(1);
let two = Fx::<u16, U4>::from_int_part(2);
assert!(one << 1 == two)
}
#[test]
fn test_shr() {
use typenum::U4;
let one = Fx::<u16, U4>::from_int_part(1);
let two = Fx::<u16, U4>::from_int_part(2);
assert!(two >> 1 == one)
}
#[test]
fn test_neg() {
use typenum::U4;
let one = Fx::<i16, U4>::from_int_part(1);
let neg_one = Fx::<i16, U4>::from_int_part(-1);
assert!(-one == neg_one);
assert!(-(-one) == one);
}
#[test]
fn test_mul() {
use typenum::U4;
let half = Fx::<u16, U4>::from_int_part(1) >> 1;
let two = Fx::<u16, U4>::from_int_part(2);
let three = Fx::<u16, U4>::from_int_part(3);
let twelve = Fx::<u16, U4>::from_int_part(12);
assert!(two * three == twelve * half);
}
#[test]
fn test_div() {
use typenum::U4;
let two = Fx::<u16, U4>::from_int_part(2);
let six = Fx::<u16, U4>::from_int_part(6);
let twelve = Fx::<u16, U4>::from_int_part(12);
assert!(twelve / two == six);
}
}

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//! This module contains definitions and types for the IO Registers.
//!
//! ## Naming
//!
//! In the interest of making things easy to search for, all io register
//! constants are given the names used in the
//! [GBATEK](https://problemkaputt.de/gbatek.htm) technical description.
use super::*;
use gba_proc_macro::register_bit;
pub mod keypad;

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//! Allows access to the keypad.
use super::*;
/// The Key Input Register.
///
/// This register follows the "low-active" convention. If you want your code to
/// follow the "high-active" convention (hint: you probably do, it's far easier
/// to work with) then call `read_key_input()` rather than reading this register
/// directly. It will perform the necessary bit flip operation for you.
pub const KEYINPUT: VolAddress<u16> = unsafe { VolAddress::new_unchecked(0x400_0130) };
/// A "tribool" value helps us interpret the arrow pad.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(i32)]
#[allow(missing_docs)]
pub enum TriBool {
Minus = -1,
Neutral = 0,
Plus = 1,
}
newtype! {
/// Records a particular key press combination.
///
/// Methods here follow the "high-active" convention, where a bit is enabled
/// when it's part of the set.
#[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
KeyInput, u16
}
#[allow(missing_docs)]
impl KeyInput {
register_bit!(A_BIT, u16, 1, a_pressed);
register_bit!(B_BIT, u16, 1 << 1, b_pressed);
register_bit!(SELECT_BIT, u16, 1 << 2, select_pressed);
register_bit!(START_BIT, u16, 1 << 3, start_pressed);
register_bit!(RIGHT_BIT, u16, 1 << 4, right_pressed);
register_bit!(LEFT_BIT, u16, 1 << 5, left_pressed);
register_bit!(UP_BIT, u16, 1 << 6, up_pressed);
register_bit!(DOWN_BIT, u16, 1 << 7, down_pressed);
register_bit!(R_BIT, u16, 1 << 8, r_pressed);
register_bit!(L_BIT, u16, 1 << 9, l_pressed);
/// Takes the set difference between these keys and another set of keys.
pub fn difference(self, other: Self) -> Self {
KeyInput(self.0 ^ other.0)
}
/// Gives the arrow pad value as a tribool, with Plus being increased column
/// value (right).
pub fn column_direction(self) -> TriBool {
if self.right_pressed() {
TriBool::Plus
} else if self.left_pressed() {
TriBool::Minus
} else {
TriBool::Neutral
}
}
/// Gives the arrow pad value as a tribool, with Plus being increased row
/// value (down).
pub fn row_direction(self) -> TriBool {
if self.down_pressed() {
TriBool::Plus
} else if self.up_pressed() {
TriBool::Minus
} else {
TriBool::Neutral
}
}
}
/// Gets the current state of the keys
pub fn read_key_input() -> KeyInput {
// Note(Lokathor): The 10 used bits are "low when pressed" style, but the 6
// unused bits are always low, so we XOR with this mask to get a result where
// the only active bits are currently pressed keys.
KeyInput(KEYINPUT.read() ^ 0b0000_0011_1111_1111)
}
newtype! {
/// Allows configuration of when a keypad interrupt fires.
///
/// * The most important bit here is the `irq_enabled` bit, which determines
/// if an interrupt happens at all.
/// * The second most important bit is the `irq_logical_and` bit. If this bit
/// is set, _all_ the selected buttons are required to be set for the
/// interrupt to be fired (logical AND). If it's not set then _any_ of the
/// buttons selected can be pressed to fire the interrupt (logical OR).
/// * All other bits select a particular button to be required or not as part
/// of the interrupt firing.
///
/// NOTE: This _only_ configures the operation of when keypad interrupts can
/// fire. You must still set the `IME` to have interrupts at all, and you must
/// further set `IE` for keypad interrupts to be possible.
#[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
KeyInterruptSetting, u16
}
#[allow(missing_docs)]
impl KeyInterruptSetting {
register_bit!(A_BIT, u16, 1, a_pressed);
register_bit!(B_BIT, u16, 1 << 1, b_pressed);
register_bit!(SELECT_BIT, u16, 1 << 2, select_pressed);
register_bit!(START_BIT, u16, 1 << 3, start_pressed);
register_bit!(RIGHT_BIT, u16, 1 << 4, right_pressed);
register_bit!(LEFT_BIT, u16, 1 << 5, left_pressed);
register_bit!(UP_BIT, u16, 1 << 6, up_pressed);
register_bit!(DOWN_BIT, u16, 1 << 7, down_pressed);
register_bit!(R_BIT, u16, 1 << 8, r_pressed);
register_bit!(L_BIT, u16, 1 << 9, l_pressed);
//
register_bit!(IRQ_ENABLE_BIT, u16, 1 << 14, irq_enabled);
register_bit!(IRQ_AND_BIT, u16, 1 << 15, irq_logical_and);
}
/// Use this to configure when a keypad interrupt happens.
///
/// See the `KeyInterruptSetting` type for more.
pub const KEYCNT: VolAddress<KeyInterruptSetting> = unsafe { VolAddress::new_unchecked(0x400_0132) };

388
src/io_registers.rs
View file

@ -15,19 +15,20 @@
// TODO(lokathor): IO Register newtypes.
use gba_proc_macro::{newtype, register_bit};
use gba_proc_macro::register_bit;
use super::*;
/// LCD Control. Read/Write.
///
/// * [gbatek entry](http://problemkaputt.de/gbatek.htm#lcdiodisplaycontrol)
pub const DISPCNT: VolatilePtr<u16> = VolatilePtr(0x400_0000 as *mut u16);
pub const DISPCNT: VolAddress<DisplayControlSetting> = unsafe { VolAddress::new_unchecked(0x400_0000) };
newtype!(
/// A newtype over the various display control options that you have on a GBA.
#[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
DisplayControlSetting,
u16,
"A newtype over the various display control options that you have on a GBA."
u16
);
#[allow(missing_docs)]
@ -97,24 +98,19 @@ pub enum DisplayControlMode {
/// Assigns the given display control setting.
pub fn set_display_control(setting: DisplayControlSetting) {
unsafe {
DISPCNT.write(setting.0);
}
DISPCNT.write(setting);
}
/// Obtains the current display control setting.
pub fn display_control() -> DisplayControlSetting {
unsafe { DisplayControlSetting(DISPCNT.read()) }
DISPCNT.read()
}
/// General LCD Status (STAT,LYC)
pub const DISPSTAT: VolatilePtr<u16> = VolatilePtr(0x400_0004 as *mut u16);
/// Vertical Counter (LY)
pub const VCOUNT: VolatilePtr<u16> = VolatilePtr(0x400_0006 as *mut u16);
pub const VCOUNT: VolAddress<u16> = unsafe { VolAddress::new_unchecked(0x400_0006) };
/// Obtains the current VCount value.
pub fn vcount() -> u16 {
unsafe { VCOUNT.read() }
VCOUNT.read()
}
/// Performs a busy loop until VBlank starts.
@ -128,369 +124,3 @@ pub fn wait_until_vdraw() {
// TODO: make this the better version with BIOS and interrupts and such.
while vcount() >= SCREEN_HEIGHT as u16 {}
}
/// BG0 Control
pub const BG0CNT: VolatilePtr<u16> = VolatilePtr(0x400_0008 as *mut u16);
/// BG1 Control
pub const BG1CNT: VolatilePtr<u16> = VolatilePtr(0x400_000A as *mut u16);
/// BG2 Control
pub const BG2CNT: VolatilePtr<u16> = VolatilePtr(0x400_000C as *mut u16);
/// BG3 Control
pub const BG3CNT: VolatilePtr<u16> = VolatilePtr(0x400_000E as *mut u16);
/// BG0 X-Offset
pub const BG0HOFS: VolatilePtr<u16> = VolatilePtr(0x400_0010 as *mut u16);
/// BG0 Y-Offset
pub const BG0VOFS: VolatilePtr<u16> = VolatilePtr(0x400_0012 as *mut u16);
/// BG1 X-Offset
pub const BG1HOFS: VolatilePtr<u16> = VolatilePtr(0x400_0014 as *mut u16);
/// BG1 Y-Offset
pub const BG1VOFS: VolatilePtr<u16> = VolatilePtr(0x400_0016 as *mut u16);
/// BG2 X-Offset
pub const BG2HOFS: VolatilePtr<u16> = VolatilePtr(0x400_0018 as *mut u16);
/// BG2 Y-Offset
pub const BG2VOFS: VolatilePtr<u16> = VolatilePtr(0x400_001A as *mut u16);
/// BG3 X-Offset
pub const BG3HOFS: VolatilePtr<u16> = VolatilePtr(0x400_001C as *mut u16);
/// BG3 Y-Offset
pub const BG3VOFS: VolatilePtr<u16> = VolatilePtr(0x400_001E as *mut u16);
/// BG2 Rotation/Scaling Parameter A (dx)
pub const BG2PA: VolatilePtr<u16> = VolatilePtr(0x400_0020 as *mut u16);
/// BG2 Rotation/Scaling Parameter B (dmx)
pub const BG2PB: VolatilePtr<u16> = VolatilePtr(0x400_0022 as *mut u16);
/// BG2 Rotation/Scaling Parameter C (dy)
pub const BG2PC: VolatilePtr<u16> = VolatilePtr(0x400_0024 as *mut u16);
/// BG2 Rotation/Scaling Parameter D (dmy)
pub const BG2PD: VolatilePtr<u16> = VolatilePtr(0x400_0026 as *mut u16);
/// BG2 Reference Point X-Coordinate
pub const BG2X: VolatilePtr<u32> = VolatilePtr(0x400_0028 as *mut u32);
/// BG2 Reference Point Y-Coordinate
pub const BG2Y: VolatilePtr<u32> = VolatilePtr(0x400_002C as *mut u32);
/// BG3 Rotation/Scaling Parameter A (dx)
pub const BG3PA: VolatilePtr<u16> = VolatilePtr(0x400_0030 as *mut u16);
/// BG3 Rotation/Scaling Parameter B (dmx)
pub const BG3PB: VolatilePtr<u16> = VolatilePtr(0x400_0032 as *mut u16);
/// BG3 Rotation/Scaling Parameter C (dy)
pub const BG3PC: VolatilePtr<u16> = VolatilePtr(0x400_0034 as *mut u16);
/// BG3 Rotation/Scaling Parameter D (dmy)
pub const BG3PD: VolatilePtr<u16> = VolatilePtr(0x400_0036 as *mut u16);
/// BG3 Reference Point X-Coordinate
pub const BG3X: VolatilePtr<u32> = VolatilePtr(0x400_0038 as *mut u32);
/// BG3 Reference Point Y-Coordinate
pub const BG3Y: VolatilePtr<u32> = VolatilePtr(0x400_003C as *mut u32);
/// Window 0 Horizontal Dimensions
pub const WIN0H: VolatilePtr<u16> = VolatilePtr(0x400_0040 as *mut u16);
/// Window 1 Horizontal Dimensions
pub const WIN1H: VolatilePtr<u16> = VolatilePtr(0x400_0042 as *mut u16);
/// Window 0 Vertical Dimensions
pub const WIN0V: VolatilePtr<u16> = VolatilePtr(0x400_0044 as *mut u16);
/// Window 1 Vertical Dimensions
pub const WIN1V: VolatilePtr<u16> = VolatilePtr(0x400_0046 as *mut u16);
/// Inside of Window 0 and 1
pub const WININ: VolatilePtr<u16> = VolatilePtr(0x400_0048 as *mut u16);
/// Inside of OBJ Window & Outside of Windows
pub const WINOUT: VolatilePtr<u16> = VolatilePtr(0x400_004A as *mut u16);
/// Mosaic Size
pub const MOSAIC: VolatilePtr<u16> = VolatilePtr(0x400_004C as *mut u16);
/// Color Special Effects Selection
pub const BLDCNT: VolatilePtr<u16> = VolatilePtr(0x400_0050 as *mut u16);
/// Alpha Blending Coefficients
pub const BLDALPHA: VolatilePtr<u16> = VolatilePtr(0x400_0052 as *mut u16);
/// Brightness (Fade-In/Out) Coefficient
pub const BLDY: VolatilePtr<u16> = VolatilePtr(0x400_0054 as *mut u16);
/// Channel 1 Sweep register (NR10)
pub const UND1CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_0060 as *mut u16);
/// Channel 1 Duty/Length/Envelope (NR11, NR12)
pub const UND1CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_0062 as *mut u16);
/// Channel 1 Frequency/Control (NR13, NR14)
pub const UND1CNT_X: VolatilePtr<u16> = VolatilePtr(0x400_0064 as *mut u16);
/// Channel 2 Duty/Length/Envelope (NR21, NR22)
pub const UND2CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_0068 as *mut u16);
/// Channel 2 Frequency/Control (NR23, NR24)
pub const UND2CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_006C as *mut u16);
/// Channel 3 Stop/Wave RAM select (NR30)
pub const UND3CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_0070 as *mut u16);
/// Channel 3 Length/Volume (NR31, NR32)
pub const UND3CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_0072 as *mut u16);
/// Channel 3 Frequency/Control (NR33, NR34)
pub const UND3CNT_X: VolatilePtr<u16> = VolatilePtr(0x400_0074 as *mut u16);
/// Channel 4 Length/Envelope (NR41, NR42)
pub const UND4CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_0078 as *mut u16);
/// Channel 4 Frequency/Control (NR43, NR44)
pub const UND4CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_007C as *mut u16);
/// Control Stereo/Volume/Enable (NR50, NR51)
pub const UNDCNT_L: VolatilePtr<u16> = VolatilePtr(0x400_0080 as *mut u16);
/// Control Mixing/DMA Control
pub const UNDCNT_H: VolatilePtr<u16> = VolatilePtr(0x400_0082 as *mut u16);
/// Control Sound on/off (NR52)
pub const UNDCNT_X: VolatilePtr<u16> = VolatilePtr(0x400_0084 as *mut u16);
/// Sound PWM Control
pub const UNDBIAS: VolatilePtr<u16> = VolatilePtr(0x400_0088 as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM0_L: VolatilePtr<u16> = VolatilePtr(0x400_0090 as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM0_H: VolatilePtr<u16> = VolatilePtr(0x400_0092 as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM1_L: VolatilePtr<u16> = VolatilePtr(0x400_0094 as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM1_H: VolatilePtr<u16> = VolatilePtr(0x400_0096 as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM2_L: VolatilePtr<u16> = VolatilePtr(0x400_0098 as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM2_H: VolatilePtr<u16> = VolatilePtr(0x400_009A as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM3_L: VolatilePtr<u16> = VolatilePtr(0x400_009C as *mut u16);
/// Channel 3 Wave Pattern RAM (W/R)
pub const WAVE_RAM3_H: VolatilePtr<u16> = VolatilePtr(0x400_009E as *mut u16);
/// Channel A FIFO, Data 0-3
pub const FIFO_A: VolatilePtr<u32> = VolatilePtr(0x400_00A0 as *mut u32);
/// Channel B FIFO, Data 0-3
pub const FIFO_B: VolatilePtr<u32> = VolatilePtr(0x400_00A4 as *mut u32);
/// DMA 0 Source Address
pub const DMA0SAD: VolatilePtr<u32> = VolatilePtr(0x400_00B0 as *mut u32);
/// DMA 0 Destination Address
pub const DMA0DAD: VolatilePtr<u32> = VolatilePtr(0x400_00B4 as *mut u32);
/// DMA 0 Word Count
pub const DMA0CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_00B8 as *mut u16);
/// DMA 0 Control
pub const DMA0CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_00BA as *mut u16);
/// DMA 1 Source Address
pub const DMA1SAD: VolatilePtr<u32> = VolatilePtr(0x400_00BC as *mut u32);
/// DMA 1 Destination Address
pub const DMA1DAD: VolatilePtr<u32> = VolatilePtr(0x400_00C0 as *mut u32);
/// DMA 1 Word Count
pub const DMA1CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_00C4 as *mut u16);
/// DMA 1 Control
pub const DMA1CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_00C6 as *mut u16);
/// DMA 2 Source Address
pub const DMA2SAD: VolatilePtr<u32> = VolatilePtr(0x400_00C8 as *mut u32);
/// DMA 2 Destination Address
pub const DMA2DAD: VolatilePtr<u32> = VolatilePtr(0x400_00CC as *mut u32);
/// DMA 2 Word Count
pub const DMA2CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_00D0 as *mut u16);
/// DMA 2 Control
pub const DMA2CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_00D2 as *mut u16);
/// DMA 3 Source Address
pub const DMA3SAD: VolatilePtr<u32> = VolatilePtr(0x400_00D4 as *mut u32);
/// DMA 3 Destination Address
pub const DMA3DAD: VolatilePtr<u32> = VolatilePtr(0x400_00D8 as *mut u32);
/// DMA 3 Word Count
pub const DMA3CNT_L: VolatilePtr<u16> = VolatilePtr(0x400_00DC as *mut u16);
/// DMA 3 Control
pub const DMA3CNT_H: VolatilePtr<u16> = VolatilePtr(0x400_00DE as *mut u16);
/// Timer 0 Counter/Reload
pub const TM0D: VolatilePtr<u16> = VolatilePtr(0x400_0100 as *mut u16);
/// Timer 0 Control
pub const TM0CNT: VolatilePtr<u16> = VolatilePtr(0x400_0102 as *mut u16);
/// Timer 1 Counter/Reload
pub const TM1D: VolatilePtr<u16> = VolatilePtr(0x400_0104 as *mut u16);
/// Timer 1 Control
pub const TM1CNT: VolatilePtr<u16> = VolatilePtr(0x400_0106 as *mut u16);
/// Timer 2 Counter/Reload
pub const TM2D: VolatilePtr<u16> = VolatilePtr(0x400_0108 as *mut u16);
/// Timer 2 Control
pub const TM2CNT: VolatilePtr<u16> = VolatilePtr(0x400_010A as *mut u16);
/// Timer 3 Counter/Reload
pub const TM3D: VolatilePtr<u16> = VolatilePtr(0x400_010C as *mut u16);
/// Timer 3 Control
pub const TM3CNT: VolatilePtr<u16> = VolatilePtr(0x400_010E as *mut u16);
/// SIO Data (Normal-32bit Mode; shared with below)
pub const SIODATA32: VolatilePtr<u32> = VolatilePtr(0x400_0120 as *mut u32);
/// SIO Data 0 (Parent) (Multi-Player Mode)
pub const SIOMULTI0: VolatilePtr<u16> = VolatilePtr(0x400_0120 as *mut u16);
/// SIO Data 1 (1st Child) (Multi-Player Mode)
pub const SIOMULTI1: VolatilePtr<u16> = VolatilePtr(0x400_0122 as *mut u16);
/// SIO Data 2 (2nd Child) (Multi-Player Mode)
pub const SIOMULTI2: VolatilePtr<u16> = VolatilePtr(0x400_0124 as *mut u16);
/// SIO Data 3 (3rd Child) (Multi-Player Mode)
pub const SIOMULTI3: VolatilePtr<u16> = VolatilePtr(0x400_0126 as *mut u16);
/// SIO Control Register
pub const SIOCNT: VolatilePtr<u16> = VolatilePtr(0x400_0128 as *mut u16);
/// D SIO Data (Local of MultiPlayer; shared below)
pub const SIOMLT_SEN: VolatilePtr<u16> = VolatilePtr(0x400_012A as *mut u16);
/// SIO Data (Normal-8bit and UART Mode)
pub const SIODATA8: VolatilePtr<u16> = VolatilePtr(0x400_012A as *mut u16);
/// Key Status
pub const KEYINPUT: VolatilePtr<u16> = VolatilePtr(0x400_0130 as *mut u16);
/// A "tribool" value helps us interpret the arrow pad.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(i32)]
#[allow(missing_docs)]
pub enum TriBool {
Minus = -1,
Neutral = 0,
Plus = 1,
}
newtype!(KeyInputSetting, u16, "A newtype over the key input state of the GBA");
#[allow(missing_docs)]
impl KeyInputSetting {
register_bit!(A_BIT, u16, 1, a_pressed);
register_bit!(B_BIT, u16, 1 << 1, b_pressed);
register_bit!(SELECT_BIT, u16, 1 << 2, select_pressed);
register_bit!(START_BIT, u16, 1 << 3, start_pressed);
register_bit!(RIGHT_BIT, u16, 1 << 4, right_pressed);
register_bit!(LEFT_BIT, u16, 1 << 5, left_pressed);
register_bit!(UP_BIT, u16, 1 << 6, up_pressed);
register_bit!(DOWN_BIT, u16, 1 << 7, down_pressed);
register_bit!(R_BIT, u16, 1 << 8, r_pressed);
register_bit!(L_BIT, u16, 1 << 9, l_pressed);
/// Takes the difference between these keys and another set of keys.
pub fn difference(self, other: KeyInputSetting) -> KeyInputSetting {
KeyInputSetting(self.0 ^ other.0)
}
/// Gives the arrow pad value as a tribool, with Plus being increased column
/// value (right).
pub fn column_direction(self) -> TriBool {
if self.right_pressed() {
TriBool::Plus
} else if self.left_pressed() {
TriBool::Minus
} else {
TriBool::Neutral
}
}
/// Gives the arrow pad value as a tribool, with Plus being increased row
/// value (down).
pub fn row_direction(self) -> TriBool {
if self.down_pressed() {
TriBool::Plus
} else if self.up_pressed() {
TriBool::Minus
} else {
TriBool::Neutral
}
}
}
/// Gets the current state of the keys
pub fn key_input() -> KeyInputSetting {
// Note(Lokathor): The 10 used bits are "low when pressed" style, but the 6
// unused bits are always low, so we XOR with this mask to get a result where
// the only active bits are currently pressed keys.
unsafe { KeyInputSetting(KEYINPUT.read() ^ 0b0000_0011_1111_1111) }
}
/// Key Interrupt Control
pub const KEYCNT: VolatilePtr<u16> = VolatilePtr(0x400_0132 as *mut u16);
/// SIO Mode Select/General Purpose Data
pub const RCNT: VolatilePtr<u16> = VolatilePtr(0x400_0134 as *mut u16);
/// SIO JOY Bus Control
pub const JOYCNT: VolatilePtr<u16> = VolatilePtr(0x400_0140 as *mut u16);
/// SIO JOY Bus Receive Data
pub const JOY_RECV: VolatilePtr<u32> = VolatilePtr(0x400_0150 as *mut u32);
/// SIO JOY Bus Transmit Data
pub const JOY_TRANS: VolatilePtr<u32> = VolatilePtr(0x400_0154 as *mut u32);
/// SIO JOY Bus Receive Status
pub const JOYSTAT: VolatilePtr<u16> = VolatilePtr(0x400_0158 as *mut u16);
/// Interrupt Enable Register
pub const IE: VolatilePtr<u16> = VolatilePtr(0x400_0200 as *mut u16);
/// Interrupt Request Flags / IRQ Acknowledge
pub const IF: VolatilePtr<u16> = VolatilePtr(0x400_0202 as *mut u16);
/// Game Pak Waitstate Control
pub const WAITCNT: VolatilePtr<u16> = VolatilePtr(0x400_0204 as *mut u16);
/// Interrupt Master Enable Register
pub const IME: VolatilePtr<u16> = VolatilePtr(0x400_0208 as *mut u16);

249
src/lib.rs
View file

@ -1,12 +1,14 @@
#![cfg_attr(not(test), no_std)]
#![cfg_attr(not(test), feature(asm))]
#![feature(asm)]
#![feature(const_int_wrapping)]
#![feature(min_const_unsafe_fn)]
#![warn(missing_docs)]
#![allow(clippy::cast_lossless)]
#![deny(clippy::float_arithmetic)]
//! This crate helps you write GBA ROMs.
//!
//! # SAFETY POLICY
//! ## SAFETY POLICY
//!
//! Some parts of this crate are safe wrappers around unsafe operations. This is
//! good, and what you'd expect from a Rust crate.
@ -16,78 +18,211 @@
//!
//! **Do not** use this crate in programs that aren't running on the GBA. If you
//! do, it's a giant bag of Undefined Behavior.
//!
//! # TESTING POLICY
//!
//! It is the intent of the crate authors that as much of the crate as possible
//! be written so that you can use `cargo test` for at least some parts of your
//! code without everything exploding instantly. To that end, where possible we
//! attempt to use `cfg` flags to make things safe for `cargo test`. Hopefully
//! we got it all.
/// Assists in defining a newtype wrapper over some base type.
///
/// Note that rustdoc and derives are all the "meta" stuff, so you can write all
/// of your docs and derives in front of your newtype in the same way you would
/// for a normal struct. Then the inner type to be wrapped it name.
///
/// The macro _assumes_ that you'll be using it to wrap zero safe numeric types,
/// so it automatically provides a `const fn` method for `new` that just wraps
/// `0`. If this is not desired you can add `, no frills` to the invocation.
///
/// Example:
/// ```
/// newtype! {
/// /// Records a particular key press combination.
/// #[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
/// KeyInput, u16
/// }
/// ```
#[macro_export]
macro_rules! newtype {
($(#[$attr:meta])* $new_name:ident, $old_name:ident) => {
$(#[$attr])*
#[repr(transparent)]
pub struct $new_name($old_name);
impl $new_name {
/// A `const` "zero value" constructor
pub const fn new() -> Self {
$new_name(0)
}
}
};
($(#[$attr:meta])* $new_name:ident, $old_name:ident, no frills) => {
$(#[$attr])*
#[repr(transparent)]
pub struct $new_name($old_name);
};
}
pub mod builtins;
pub mod fixed;
pub mod bios;
pub mod core_extras;
pub(crate) use crate::core_extras::*;
pub mod io_registers;
pub mod io;
pub mod video_ram;
pub(crate) use crate::video_ram::*;
/// Combines the Red, Blue, and Green provided into a single color value.
pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
blue << 10 | green << 5 | red
/// Performs unsigned divide and remainder, gives None if dividing by 0.
pub fn divrem_u32(numer: u32, denom: u32) -> Option<(u32, u32)> {
// TODO: const this? Requires const if
if denom == 0 {
None
} else {
Some(unsafe { divrem_u32_unchecked(numer, denom) })
}
}
/// BIOS Call: Div (GBA SWI 0x06).
/// Performs divide and remainder, no check for 0 division.
///
/// Gives just the DIV output of `numerator / denominator`.
/// # Safety
///
/// # Panics
///
/// If `denominator` is 0.
#[inline]
pub fn div(numerator: i32, denominator: i32) -> i32 {
div_modulus(numerator, denominator).0
/// If you call this with a denominator of 0 the result is implementation
/// defined (not literal UB) including but not limited to: an infinite loop,
/// panic on overflow, or incorrect output.
pub unsafe fn divrem_u32_unchecked(numer: u32, denom: u32) -> (u32, u32) {
// TODO: const this? Requires const if
if (numer >> 5) < denom {
divrem_u32_simple(numer, denom)
} else {
divrem_u32_non_restoring(numer, denom)
}
}
/// BIOS Call: Div (GBA SWI 0x06).
///
/// Gives just the MOD output of `numerator / denominator`.
///
/// # Panics
///
/// If `denominator` is 0.
#[inline]
pub fn modulus(numerator: i32, denominator: i32) -> i32 {
div_modulus(numerator, denominator).1
/// The simplest form of division. If N is too much larger than D this will be
/// extremely slow. If N is close enough to D then it will likely be faster than
/// the non_restoring form.
fn divrem_u32_simple(mut numer: u32, denom: u32) -> (u32, u32) {
// TODO: const this? Requires const if
let mut quot = 0;
while numer >= denom {
numer -= denom;
quot += 1;
}
(quot, numer)
}
/// BIOS Call: Div (GBA SWI 0x06).
///
/// Gives both the DIV and MOD output of `numerator / denominator`.
///
/// # Panics
///
/// If `denominator` is 0.
#[inline]
pub fn div_modulus(numerator: i32, denominator: i32) -> (i32, i32) {
assert!(denominator != 0);
#[cfg(not(test))]
{
let div_out: i32;
let mod_out: i32;
unsafe {
asm!(/* assembly template */ "swi 0x06"
:/* output operands */ "={r0}"(div_out), "={r1}"(mod_out)
:/* input operands */ "{r0}"(numerator), "{r1}"(denominator)
:/* clobbers */ "r3"
:/* options */
);
/// Takes a fixed quantity of time based on the bit width of the number (in this
/// case 32).
fn divrem_u32_non_restoring(numer: u32, denom: u32) -> (u32, u32) {
// TODO: const this? Requires const if
let mut r: i64 = numer as i64;
let d: i64 = (denom as i64) << 32;
let mut q: u32 = 0;
let mut i = 1 << 31;
while i > 0 {
if r >= 0 {
q |= i;
r = 2 * r - d;
} else {
r = 2 * r + d;
}
(div_out, mod_out)
i >>= 1;
}
q -= !q;
if r < 0 {
q -= 1;
r += d;
}
r >>= 32;
// TODO: remove this once we've done more checks here.
debug_assert!(r >= 0);
debug_assert!(r <= core::u32::MAX as i64);
(q, r as u32)
}
/// Performs signed divide and remainder, gives None if dividing by 0 or
/// computing `MIN/-1`
pub fn divrem_i32(numer: i32, denom: i32) -> Option<(i32, i32)> {
if denom == 0 || (numer == core::i32::MIN && denom == -1) {
None
} else {
Some(unsafe { divrem_i32_unchecked(numer, denom) })
}
}
/// Performs signed divide and remainder, no check for 0 division or `MIN/-1`.
///
/// # Safety
///
/// * If you call this with a denominator of 0 the result is implementation
/// defined (not literal UB) including but not limited to: an infinite loop,
/// panic on overflow, or incorrect output.
/// * If you call this with `MIN/-1` you'll get a panic in debug or just `MIN`
/// in release (which is incorrect), because of how twos-compliment works.
pub unsafe fn divrem_i32_unchecked(numer: i32, denom: i32) -> (i32, i32) {
// TODO: const this? Requires const if
let unsigned_numer = numer.abs() as u32;
let unsigned_denom = denom.abs() as u32;
let opposite_sign = (numer ^ denom) < 0;
let (udiv, urem) = if (numer >> 5) < denom {
divrem_u32_simple(unsigned_numer, unsigned_denom)
} else {
divrem_u32_non_restoring(unsigned_numer, unsigned_denom)
};
match (opposite_sign, numer < 0) {
(true, true) => (-(udiv as i32), -(urem as i32)),
(true, false) => (-(udiv as i32), urem as i32),
(false, true) => (udiv as i32, -(urem as i32)),
(false, false) => (udiv as i32, urem as i32),
}
}
/*
#[cfg(test)]
{
(numerator / denominator, numerator % denominator)
mod tests {
use super::*;
use quickcheck::quickcheck;
// We have an explicit property on the non_restoring division
quickcheck! {
fn divrem_u32_non_restoring_prop(num: u32, denom: u32) -> bool {
if denom > 0 {
divrem_u32_non_restoring(num, denom) == (num / denom, num % denom)
} else {
true
}
}
}
// We have an explicit property on the simple division
quickcheck! {
fn divrem_u32_simple_prop(num: u32, denom: u32) -> bool {
if denom > 0 {
divrem_u32_simple(num, denom) == (num / denom, num % denom)
} else {
true
}
}
}
// Test the u32 wrapper
quickcheck! {
fn divrem_u32_prop(num: u32, denom: u32) -> bool {
if denom > 0 {
divrem_u32(num, denom).unwrap() == (num / denom, num % denom)
} else {
divrem_u32(num, denom).is_none()
}
}
}
// test the i32 wrapper
quickcheck! {
fn divrem_i32_prop(num: i32, denom: i32) -> bool {
if denom == 0 || num == core::i32::MIN && denom == -1 {
divrem_i32(num, denom).is_none()
} else {
divrem_i32(num, denom).unwrap() == (num / denom, num % denom)
}
}
}
}
*/

8
src/macros.rs
View file

@ -1,8 +0,0 @@
//! Module for all macros.
//!
//! Macros are the only thing in Rust where declaration order matters, so we
//! place all of them here regardless of what they do so that the macros module
//! can appear at the "top" of the library and all other modules can see them
//! properly.
// no macros yet!

15
src/video_ram.rs
View file

@ -15,6 +15,8 @@
pub use super::*;
// TODO: kill all this too
/// The physical width in pixels of the GBA screen.
pub const SCREEN_WIDTH: isize = 240;
@ -28,6 +30,8 @@ pub const SCREEN_HEIGHT: isize = 160;
/// value as just being a `usize`.
pub const VRAM_BASE_ADDRESS: usize = 0x0600_0000;
const MODE3_VRAM: VolAddress<u16> = unsafe { VolAddress::new_unchecked(VRAM_BASE_ADDRESS) };
/// Draws a pixel to the screen while in Display Mode 3, with bounds checks.
///
/// # Panics
@ -51,7 +55,7 @@ pub fn mode3_draw_pixel(col: isize, row: isize, color: u16) {
/// * `col` must be in `0..SCREEN_WIDTH`
/// * `row` must be in `0..SCREEN_HEIGHT`
pub unsafe fn mode3_draw_pixel_unchecked(col: isize, row: isize, color: u16) {
VolatilePtr(VRAM_BASE_ADDRESS as *mut u16).offset(col + row * SCREEN_WIDTH).write(color);
MODE3_VRAM.offset(col + row * SCREEN_WIDTH).write(color);
}
/// Reads the given pixel of video memory according to Mode 3 placement.
@ -61,7 +65,7 @@ pub unsafe fn mode3_draw_pixel_unchecked(col: isize, row: isize, color: u16) {
/// If the location is out of bounds you get `None`.
pub fn mode3_read_pixel(col: isize, row: isize) -> Option<u16> {
if col >= 0 && col < SCREEN_WIDTH && row >= 0 && row < SCREEN_HEIGHT {
unsafe { Some(VolatilePtr(VRAM_BASE_ADDRESS as *mut u16).offset(col + row * SCREEN_WIDTH).read()) }
unsafe { Some(MODE3_VRAM.offset(col + row * SCREEN_WIDTH).read()) }
} else {
None
}
@ -72,9 +76,8 @@ pub unsafe fn mode3_clear_screen(color: u16) {
// TODO: use DMA?
let color = color as u32;
let bulk_color = color << 16 | color;
let mut ptr = VolatilePtr(VRAM_BASE_ADDRESS as *mut u32);
for _ in 0..(SCREEN_HEIGHT * SCREEN_WIDTH / 2) {
ptr.write(bulk_color);
ptr = ptr.offset(1);
let block: VolAddressBlock<u32> = VolAddressBlock::new_unchecked(MODE3_VRAM.cast::<u32>(), (SCREEN_HEIGHT * SCREEN_WIDTH / 2) as usize);
for b in block.iter() {
b.write(bulk_color);
}
}

12
todo_check.bat Normal file
View file

@ -0,0 +1,12 @@
@echo off
echo -------
echo -------
set Wildcard=*.rs
echo TODOS FOUND:
findstr -s -n -i -l "TODO" %Wildcard%
echo -------
echo -------