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Make the tile references clearer

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This commit is contained in:
Gwilym Kuiper 2022-01-31 20:00:06 +00:00
parent bf10d9a5ff
commit a2c6c6a70c
1 changed files with 39 additions and 12 deletions
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51
agb/src/display/background.rs
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@ -53,6 +53,11 @@ pub struct TileSetReference {
#[derive(Debug)]
pub struct TileIndex(u16);
enum TileReference {
ReferenceCounted(u16, (u16, u16)),
Free(u16),
}
enum ArenaStorageItem<T> {
EndOfFreeList,
NextFree(usize),
@ -65,7 +70,7 @@ pub struct VRamManager<'a> {
free_pointer: Option<usize>,
tile_set_to_vram: HashMap<(u16, u16), u16>,
references: Vec<u16>,
references: Vec<TileReference>,
vram_free_pointer: Option<usize>,
}
@ -79,7 +84,7 @@ impl<'a> VRamManager<'a> {
free_pointer: None,
tile_set_to_vram: HashMap::new(),
references: vec![1],
references: vec![TileReference::Free(0)],
vram_free_pointer: None,
}
}
@ -134,20 +139,35 @@ impl<'a> VRamManager<'a> {
}
fn add_tile(&mut self, tile_set_ref: TileSetReference, tile: u16) -> TileIndex {
if let Some(&reference) = self.tile_set_to_vram.get(&(tile_set_ref.id, tile)) {
self.references[reference as usize] += 1;
let tile_ref = (tile_set_ref.id, tile);
if let Some(&reference) = self.tile_set_to_vram.get(&tile_ref) {
if let TileReference::ReferenceCounted(count, tile_ref) =
self.references[reference as usize]
{
self.references[reference as usize] =
TileReference::ReferenceCounted(count + 1, tile_ref);
} else {
panic!("Corrupted tile reference state");
}
return TileIndex(reference as u16);
}
let index_to_copy_into = if let Some(ptr) = self.vram_free_pointer.take() {
if self.references[ptr] != END_OF_FREE_LIST_MARKER {
self.vram_free_pointer = Some(self.references[ptr] as usize);
match self.references[ptr] {
TileReference::Free(next_free) => {
if next_free != END_OF_FREE_LIST_MARKER {
self.vram_free_pointer = Some(next_free as usize);
}
}
TileReference::ReferenceCounted(_, _) => panic!("Corrupted tile reference state"),
}
self.references[ptr] = 1;
self.references[ptr] = TileReference::ReferenceCounted(1, tile_ref);
ptr
} else {
self.references.push(1);
self.references
.push(TileReference::ReferenceCounted(1, tile_ref));
self.references.len() - 1
};
@ -179,16 +199,23 @@ impl<'a> VRamManager<'a> {
fn remove_tile(&mut self, tile_index: TileIndex) {
let index = tile_index.0 as usize;
self.references[index] -= 1;
if self.references[index] != 0 {
let (new_count, tile_ref) = match self.references[index] {
TileReference::ReferenceCounted(count, tile_ref) => {
self.references[index] = TileReference::ReferenceCounted(count - 1, tile_ref);
(count - 1, tile_ref)
}
_ => panic!("Corrupted tile reference state"),
};
if new_count != 0 {
return;
}
if let Some(ptr) = self.vram_free_pointer {
self.references[index] = ptr as u16;
self.references[index] = TileReference::Free(ptr as u16);
} else {
self.references[index] = END_OF_FREE_LIST_MARKER;
self.references[index] = TileReference::Free(END_OF_FREE_LIST_MARKER);
}
self.vram_free_pointer = Some(index);