From 42cb342749891d38e8207a09329be54740218d7e Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Wed, 10 May 2023 00:48:53 +0200
Subject: [PATCH] world/layer: avoid iproduct-based iterator in inner loop

iproduct iterators are fairly slow. As the iterator implementation is
now unused, it is removed as well.
---
 src/types.rs       | 14 --------------
 src/world/layer.rs | 30 +++++++++++++++++-------------
 2 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/src/types.rs b/src/types.rs
index 06e01f9..18045bb 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -73,20 +73,6 @@ impl LayerBlockCoords {
 #[derive(Debug, Clone, Copy, Default, Serialize, Deserialize)]
 pub struct LayerBlockArray<T>(pub [[T; BLOCKS_PER_CHUNK]; BLOCKS_PER_CHUNK]);
 
-impl<T> LayerBlockArray<T> {
-	pub fn keys() -> impl Iterator<Item = LayerBlockCoords> + Clone + Debug {
-		iproduct!(BlockZ::iter(), BlockX::iter()).map(|(z, x)| LayerBlockCoords { x, z })
-	}
-
-	pub fn values(&self) -> impl Iterator<Item = &T> + Clone + Debug {
-		Self::keys().map(|k| &self[k])
-	}
-
-	pub fn iter(&self) -> impl Iterator<Item = (LayerBlockCoords, &T)> + Clone + Debug {
-		Self::keys().map(|k| (k, &self[k]))
-	}
-}
-
 impl<T> Index<LayerBlockCoords> for LayerBlockArray<T> {
 	type Output = T;
 
diff --git a/src/world/layer.rs b/src/world/layer.rs
index 440c137..4b23f26 100644
--- a/src/world/layer.rs
+++ b/src/world/layer.rs
@@ -111,21 +111,25 @@ pub fn top_layer(chunk: &Chunk) -> Result<Option<LayerData>> {
 
 	for section in chunk.sections().rev() {
 		for y in BlockY::iter().rev() {
-			for xz in LayerBlockArray::<()>::keys() {
-				let mut entry = ret.entry(xz);
-				if entry.done() {
-					continue;
-				}
+			for z in BlockZ::iter() {
+				for x in BlockX::iter() {
+					let xz = LayerBlockCoords { x, z };
 
-				let coords = SectionBlockCoords { xz, y };
-				if !entry.fill(section, coords)? {
-					continue;
-				}
+					let mut entry = ret.entry(xz);
+					if entry.done() {
+						continue;
+					}
 
-				assert!(entry.done());
-				done += 1;
-				if done == N * N {
-					break;
+					let coords = SectionBlockCoords { xz, y };
+					if !entry.fill(section, coords)? {
+						continue;
+					}
+
+					assert!(entry.done());
+					done += 1;
+					if done == N * N {
+						break;
+					}
 				}
 			}
 		}