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Lokathor 2018-12-25 16:45:40 -07:00
parent 89def7331b
commit 0a6a089e70
1 changed files with 9 additions and 7 deletions
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16
src/palram.rs
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@ -1,9 +1,9 @@
//! Module that allows interacting with `PALRAM`. //! Module that allows interacting with palette memory, (`PALRAM`).
//! //!
//! The `PALRAM` is 256 `Color` values for Background use, and 256 `Color` //! The `PALRAM` contains 256 `Color` values for Background use, and 256 `Color`
//! values for Object use. //! values for Object use.
//! //!
//! Each type of `PALRAM` can be viewed as "8 bits per pixel" (8bpp), where //! Each block of `PALRAM` can be viewed as "8 bits per pixel" (8bpp), where
//! there's a single palette of 256 entries. It can also be viewed as "4 bits //! there's a single palette of 256 entries. It can also be viewed as "4 bits
//! per pixel" (4bpp), where there's 16 "palbank" entries that each have 16 //! per pixel" (4bpp), where there's 16 "palbank" entries that each have 16
//! slots. **Both** interpretations are correct, simultaneously. If you're a //! slots. **Both** interpretations are correct, simultaneously. If you're a
@ -50,18 +50,20 @@ pub fn index_palram_obj_8bpp(slot: u8) -> VolAddress<Color> {
unsafe { PALRAM_OBJ.index_unchecked(slot as usize) } unsafe { PALRAM_OBJ.index_unchecked(slot as usize) }
} }
/// Obtains the address of the specified 4bpp background palbank and slot. /// Obtains the address of the specified 4bpp background palbank and palslot.
/// ///
/// If `palbank` or `palslot` are out of bounds they'll wrap around. /// Accesses `palbank * 16 + palslot`, if this is out of bounds the computation
/// will wrap.
pub fn index_palram_bg_4bpp(palbank: u8, palslot: u8) -> VolAddress<Color> { pub fn index_palram_bg_4bpp(palbank: u8, palslot: u8) -> VolAddress<Color> {
// TODO: const this // TODO: const this
// Note(Lokathor): because of the `u8` limit we can't go out of bounds here. // Note(Lokathor): because of the `u8` limit we can't go out of bounds here.
unsafe { PALRAM_BG.index_unchecked(palbank.wrapping_mul(16).wrapping_add(palslot) as usize) } unsafe { PALRAM_BG.index_unchecked(palbank.wrapping_mul(16).wrapping_add(palslot) as usize) }
} }
/// Obtains the address of the specified 4bpp object palbank and slot. /// Obtains the address of the specified 4bpp object palbank and palslot.
/// ///
/// If `palbank` or `palslot` are out of bounds they'll wrap around. /// Accesses `palbank * 16 + palslot`, if this is out of bounds the computation
/// will wrap.
pub fn index_palram_obj_4bpp(palbank: u8, palslot: u8) -> VolAddress<Color> { pub fn index_palram_obj_4bpp(palbank: u8, palslot: u8) -> VolAddress<Color> {
// TODO: const this // TODO: const this
// Note(Lokathor): because of the `u8` limit we can't go out of bounds here. // Note(Lokathor): because of the `u8` limit we can't go out of bounds here.