From e6d47afa310699f928acd7a719307e41c33e8cd2 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Mon, 21 Mar 2022 22:58:16 +0000
Subject: [PATCH] Use a hash map rather than an array in vram manager

---
 agb/src/display/tiled/vram_manager.rs | 28 +++++++++++++--------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/agb/src/display/tiled/vram_manager.rs b/agb/src/display/tiled/vram_manager.rs
index bb93599..9db99db 100644
--- a/agb/src/display/tiled/vram_manager.rs
+++ b/agb/src/display/tiled/vram_manager.rs
@@ -1,12 +1,12 @@
 use core::{alloc::Layout, ptr::NonNull};
 
-use alloc::vec;
 use alloc::vec::Vec;
 
 use crate::{
     agb_alloc::{block_allocator::BlockAllocator, bump_allocator::StartEnd},
     display::palette16,
     dma::dma_copy16,
+    hash_map::HashMap,
     memory_mapped::MemoryMapped1DArray,
 };
 
@@ -61,7 +61,7 @@ impl<'a> TileSet<'a> {
     }
 
     fn num_tiles(&self) -> usize {
-        self.tiles.len() / self.format.tile_size()
+        self.tiles.len() / self.format.tile_size() * 4
     }
 }
 
@@ -104,18 +104,20 @@ pub struct VRamManager<'a> {
     generation: u16,
     free_pointer: Option<usize>,
 
-    tile_set_to_vram: Vec<Vec<Option<TileReference>>>,
+    tile_set_to_vram: HashMap<(u16, u16), TileReference>,
     reference_counts: Vec<(u16, Option<(TileSetReference, u16)>)>,
 }
 
 impl<'a> VRamManager<'a> {
     pub(crate) fn new() -> Self {
+        let tile_set_to_vram: HashMap<(u16, u16), TileReference> = HashMap::with_capacity(256);
+
         Self {
             tilesets: Vec::new(),
             generation: 0,
             free_pointer: None,
 
-            tile_set_to_vram: Default::default(),
+            tile_set_to_vram,
             reference_counts: Default::default(),
         }
     }
@@ -124,7 +126,6 @@ impl<'a> VRamManager<'a> {
         let generation = self.generation;
         self.generation = self.generation.wrapping_add(1);
 
-        let num_tiles = tileset.num_tiles();
         let tileset = ArenaStorageItem::Data(tileset, generation);
 
         let index = if let Some(ptr) = self.free_pointer.take() {
@@ -145,10 +146,6 @@ impl<'a> VRamManager<'a> {
             self.tilesets.len() - 1
         };
 
-        self.tile_set_to_vram
-            .resize(self.tilesets.len(), Default::default());
-        self.tile_set_to_vram[index] = vec![Default::default(); num_tiles];
-
         TileSetReference::new(index as u16, generation)
     }
 
@@ -185,10 +182,10 @@ impl<'a> VRamManager<'a> {
     }
 
     pub(crate) fn add_tile(&mut self, tile_set_ref: TileSetReference, tile: u16) -> TileIndex {
-        let reference = self.tile_set_to_vram[tile_set_ref.id as usize][tile as usize];
+        let reference = self.tile_set_to_vram.get(&(tile_set_ref.id, tile));
 
         if let Some(reference) = reference {
-            let index = Self::index_from_reference(reference);
+            let index = Self::index_from_reference(*reference);
             self.reference_counts[index].0 += 1;
             return TileIndex::new(index);
         }
@@ -210,7 +207,7 @@ impl<'a> VRamManager<'a> {
             panic!("Tile set ref must point to existing tile set");
         };
 
-        let tile_size_in_half_words = TileFormat::FourBpp.tile_size() / 2;
+        let tile_size_in_half_words = tile_slice.len() / 2;
 
         unsafe {
             dma_copy16(
@@ -224,7 +221,8 @@ impl<'a> VRamManager<'a> {
 
         let index = Self::index_from_reference(tile_reference);
 
-        self.tile_set_to_vram[tile_set_ref.id as usize][tile as usize] = Some(tile_reference);
+        self.tile_set_to_vram
+            .insert((tile_set_ref.id, tile), tile_reference);
 
         self.reference_counts
             .resize(self.reference_counts.len().max(index + 1), (0, None));
@@ -250,11 +248,11 @@ impl<'a> VRamManager<'a> {
 
         let tile_reference = Self::reference_from_index(tile_index);
         unsafe {
-            TILE_ALLOCATOR.dealloc(tile_reference.0.cast().as_ptr(), TILE_LAYOUT);
+            TILE_ALLOCATOR.dealloc_no_normalise(tile_reference.0.cast().as_ptr(), TILE_LAYOUT);
         }
 
         let tile_ref = self.reference_counts[index].1.unwrap();
-        self.tile_set_to_vram[tile_ref.0.id as usize][tile_ref.1 as usize] = None;
+        self.tile_set_to_vram.remove(&(tile_ref.0.id, tile_ref.1));
         self.reference_counts[index].1 = None;
     }