Make Rust standard library optional (WIP) (#342)

* Remove `std` dependency.

* Format code with `cargo fmt`.

examples/invaders/simple-invaders/src/collision.rs

@@ -2,17 +2,17 @@
 
 use crate::geo::{Point, Rect};
 use crate::{Bullet, Invaders, Laser, Player, Shield, COLS, GRID, ROWS};
-use std::collections::HashSet;
+use alloc::collections::BTreeSet;
 
 /// Store information about collisions (for debug mode).
 #[derive(Debug, Default)]
 pub(crate) struct Collision {
-    pub(crate) bullet_details: HashSet<BulletDetail>,
-    pub(crate) laser_details: HashSet<LaserDetail>,
+    pub(crate) bullet_details: BTreeSet<BulletDetail>,
+    pub(crate) laser_details: BTreeSet<LaserDetail>,
 }
 
 /// Information regarding collisions between bullets and invaders, lasers, or shields.
-#[derive(Debug, Eq, Hash, PartialEq)]
+#[derive(Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
 pub(crate) enum BulletDetail {
     /// A grid position (col, row) for an invader.
     Invader(usize, usize),
@@ -23,7 +23,7 @@ pub(crate) enum BulletDetail {
 }
 
 /// Information regarding collisions between lasers and shields or the player.
-#[derive(Debug, Eq, Hash, PartialEq)]
+#[derive(Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
 pub(crate) enum LaserDetail {
     /// A shield index.
     Shield(usize),

examples/invaders/simple-invaders/src/geo.rs

@@ -23,7 +23,7 @@ impl Point {
     }
 }
 
-impl std::ops::Add for Point {
+impl core::ops::Add for Point {
     type Output = Self;
 
     fn add(self, other: Self) -> Self {
@@ -31,7 +31,7 @@ impl std::ops::Add for Point {
     }
 }
 
-impl std::ops::Mul for Point {
+impl core::ops::Mul for Point {
     type Output = Self;
 
     fn mul(self, other: Self) -> Self {

examples/invaders/simple-invaders/src/lib.rs

@@ -4,16 +4,20 @@
 //! this in practice. That said, the game is fully functional, and it should not be too difficult
 //! to understand the code.
 
+#![no_std]
 #![deny(clippy::all)]
 #![forbid(unsafe_code)]
 
+extern crate alloc;
+use alloc::vec::Vec;
+
 use crate::collision::Collision;
 pub use crate::controls::{Controls, Direction};
 use crate::geo::Point;
 use crate::loader::{load_assets, Assets};
 use crate::sprites::{blit, Animation, Drawable, Frame, Sprite, SpriteRef};
+use core::time::Duration;
 use randomize::PCG32;
-use std::time::Duration;
 
 mod collision;
 mod controls;

examples/invaders/simple-invaders/src/loader.rs

@@ -1,6 +1,7 @@
-use std::collections::HashMap;
-use std::io::Cursor;
-use std::rc::Rc;
+use alloc::collections::BTreeMap;
+use alloc::rc::Rc;
+
+use alloc::vec::Vec;
 
 use crate::sprites::{CachedSprite, Frame};
 
@@ -8,11 +9,11 @@ use crate::sprites::{CachedSprite, Frame};
 #[derive(Debug)]
 pub(crate) struct Assets {
     // sounds: TODO
-    sprites: HashMap<Frame, CachedSprite>,
+    sprites: BTreeMap<Frame, CachedSprite>,
 }
 
 impl Assets {
-    pub(crate) fn sprites(&self) -> &HashMap<Frame, CachedSprite> {
+    pub(crate) fn sprites(&self) -> &BTreeMap<Frame, CachedSprite> {
         &self.sprites
     }
 }
@@ -21,7 +22,7 @@ impl Assets {
 pub(crate) fn load_assets() -> Assets {
     use Frame::*;
 
-    let mut sprites = HashMap::new();
+    let mut sprites = BTreeMap::new();
 
     sprites.insert(Blipjoy1, load_pcx(include_bytes!("assets/blipjoy1.pcx")));
     sprites.insert(Blipjoy2, load_pcx(include_bytes!("assets/blipjoy2.pcx")));
@@ -57,7 +58,7 @@ pub(crate) fn load_assets() -> Assets {
 
 /// Convert PCX data to raw pixels
 fn load_pcx(pcx: &[u8]) -> CachedSprite {
-    let mut reader = pcx::Reader::new(Cursor::new(pcx)).unwrap();
+    let mut reader = pcx::Reader::new(pcx).unwrap();
     let width = reader.width() as usize;
     let height = reader.height() as usize;
     let mut result = Vec::new();
@@ -113,6 +114,8 @@ fn load_pcx(pcx: &[u8]) -> CachedSprite {
 
 #[cfg(test)]
 mod tests {
+    use alloc::vec;
+
     use super::*;
 
     #[test]

examples/invaders/simple-invaders/src/sprites.rs

@@ -1,16 +1,17 @@
 use crate::loader::Assets;
 use crate::TIME_STEP;
 use crate::{Point, HEIGHT, WIDTH};
+use alloc::rc::Rc;
+use alloc::vec::Vec;
+use core::cmp::min;
+use core::time::Duration;
 use line_drawing::Bresenham;
-use std::cmp::min;
-use std::rc::Rc;
-use std::time::Duration;
 
 // This is the type stored in the `Assets` hash map
 pub(crate) type CachedSprite = (usize, usize, Rc<[u8]>);
 
 /// Frame identifier for managing animations.
-#[derive(Debug, Eq, Hash, PartialEq)]
+#[derive(Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
 pub(crate) enum Frame {
     Blipjoy1,
     Blipjoy2,