better order for RelBlockPos and slightly cleanup calculate_cached_mining_costs_index

2 files changed, 29 insertions, 15 deletions

diff --git a/azalea/src/pathfinder/rel_block_pos.rs b/azalea/src/pathfinder/rel_block_pos.rs
index b8e96041..65b61ffa 100644
--- a/azalea/src/pathfinder/rel_block_pos.rs
+++ b/azalea/src/pathfinder/rel_block_pos.rs
@@ -14,10 +14,12 @@ use azalea_core::position::BlockPos;
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 #[repr(C)]
 pub struct RelBlockPos {
-    pub x: i16,
-    pub z: i16,
     /// The actual non-relative Y coordinate of the block.
     pub y: i32,
+    /// The X coordinate of the block, relative to some origin.
+    pub x: i16,
+    /// The Y coordinate of the block, relative to some origin.
+    pub z: i16,
 }
 
 impl RelBlockPos {
diff --git a/azalea/src/pathfinder/world.rs b/azalea/src/pathfinder/world.rs
index 819e4254..a44af6b5 100644
--- a/azalea/src/pathfinder/world.rs
+++ b/azalea/src/pathfinder/world.rs
@@ -108,8 +108,11 @@ impl CachedWorld {
             cached_blocks: Default::default(),
             // this uses about 12mb of memory. it *really* helps though.
             cached_mining_costs: UnsafeCell::new(
-                vec![(RelBlockPos::new(i16::MAX, i32::MAX, i16::MAX), 0.); 2usize.pow(20)]
-                    .into_boxed_slice(),
+                vec![
+                    (RelBlockPos::new(i16::MAX, i32::MAX, i16::MAX), 0.);
+                    CACHED_MINING_COSTS_SIZE
+                ]
+                .into_boxed_slice(),
             ),
         }
     }
@@ -314,7 +317,7 @@ impl CachedWorld {
         let cached_mining_costs = unsafe { &mut *self.cached_mining_costs.get() };
         // 20 bits total:
         // 8 bits for x, 4 bits for y, 8 bits for z
-        let hash_index = Self::calculate_cached_mining_costs_index(pos);
+        let hash_index = calculate_cached_mining_costs_index(pos);
         let &(cached_pos, potential_cost) =
             unsafe { cached_mining_costs.get_unchecked(hash_index) };
         if cached_pos == pos {
@@ -329,16 +332,6 @@ impl CachedWorld {
         cost
     }
 
-    fn calculate_cached_mining_costs_index(pos: RelBlockPos) -> usize {
-        // 20 bits total:
-        // 8 bits for x, 8 bits for z, 4 bits for y
-        let hash_index = ((pos.x as usize & 0xff) << 12)
-            | ((pos.z as usize & 0xff) << 4)
-            | (pos.y as usize & 0xf);
-        debug_assert!(hash_index < 1048576);
-        hash_index
-    }
-
     fn uncached_cost_for_breaking_block(
         &self,
         pos: RelBlockPos,
@@ -526,6 +519,25 @@ impl CachedWorld {
     }
 }
 
+const CACHED_MINING_COSTS_SIZE: usize = 2usize.pow(20);
+fn calculate_cached_mining_costs_index(pos: RelBlockPos) -> usize {
+    // create a 20-bit index by taking the bottom bits from each axis
+
+    const X_BITS: usize = 8;
+    const Y_BITS: usize = 3;
+    const Z_BITS: usize = 8;
+
+    const X_MASK: usize = (1 << X_BITS) - 1;
+    const Y_MASK: usize = (1 << Y_BITS) - 1;
+    const Z_MASK: usize = (1 << Z_BITS) - 1;
+
+    let hash_index = ((pos.x as usize & X_MASK) << (Y_BITS + Z_BITS))
+        | ((pos.z as usize & Z_MASK) << Y_BITS)
+        | (pos.y as usize & Y_MASK);
+    debug_assert!(hash_index < CACHED_MINING_COSTS_SIZE);
+    hash_index
+}
+
 /// Whether our client could pass through this block.
 pub fn is_block_state_passable(block_state: BlockState) -> bool {
     // i already tried optimizing this by having it cache in an IntMap/FxHashMap but