Introduce ChunkArray type

A generic array for per-chunk data, indexed by ChunkCoords.

Cargo.lock

@@ -90,6 +90,12 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "either"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcaabb2fef8c910e7f4c7ce9f67a1283a1715879a7c230ca9d6d1ae31f16d91"
+
 [[package]]
 name = "errno"
 version = "0.2.8"
@@ -170,6 +176,15 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.139"
@@ -190,6 +205,7 @@ dependencies = [
  "clap",
  "fastnbt",
  "flate2",
+ "itertools",
  "serde",
 ]
 

Cargo.toml

@@ -12,4 +12,5 @@ anyhow = "1.0.68"
 clap = { version = "4.1.4", features = ["derive"] }
 fastnbt = "2.3.2"
 flate2 = "1.0.25"
+itertools = "0.10.5"
 serde = "1.0.152"

src/io/region.rs

@@ -22,29 +22,19 @@ struct ChunkDesc {
 fn parse_header(header: &[u8; BLOCKSIZE]) -> HashMap<u32, ChunkDesc> {
 	let mut map = HashMap::new();
 
-	for z in 0..CHUNKS_PER_REGION {
+	for coords in ChunkArray::<()>::keys() {
-		for x in 0..CHUNKS_PER_REGION {
+		let chunk = &header[(4
-			let chunk =
+			* (usize::from(CHUNKS_PER_REGION) * usize::from(coords.z.0)
-				&header[(4 * (usize::from(CHUNKS_PER_REGION) * usize::from(z) + usize::from(x)))..];
+				+ usize::from(coords.x.0)))..];
 
-			let offset = u32::from(chunk[0]) << 16 | u32::from(chunk[1]) << 8 | u32::from(chunk[2]);
+		let offset = u32::from(chunk[0]) << 16 | u32::from(chunk[1]) << 8 | u32::from(chunk[2]);
-			if offset == 0 {
+		if offset == 0 {
-				continue;
+			continue;
-			}
-
-			let len = chunk[3];
-
-			map.insert(
-				offset,
-				ChunkDesc {
-					coords: ChunkCoords {
-						x: ChunkX(x),
-						z: ChunkZ(z),
-					},
-					len,
-				},
-			);
 		}
+
+		let len = chunk[3];
+
+		map.insert(offset, ChunkDesc { coords, len });
 	}
 
 	map
@@ -100,7 +90,7 @@ impl<R: Read + Seek> Region<R> {
 		};
 
 		let mut index = 1;
-		let mut seen = [[false; CHUNKS_PER_REGION as usize]; CHUNKS_PER_REGION as usize];
+		let mut seen = ChunkArray::<bool>::default();
 
 		while !chunk_map.is_empty() {
 			let Some(ChunkDesc { coords, len }) = chunk_map.remove(&index) else {
@@ -109,11 +99,10 @@ impl<R: Read + Seek> Region<R> {
 				continue;
 			};
 
-			let chunk_seen = &mut seen[coords.x.0 as usize][coords.z.0 as usize];
+			if seen[coords] {
-			if *chunk_seen {
 				bail!("Duplicate chunk");
 			}
-			*chunk_seen = true;
+			seen[coords] = true;
 
 			let mut buffer = vec![0; (len as usize) * BLOCKSIZE];
 			reader

src/types.rs

@@ -1,4 +1,9 @@
-use std::fmt::Debug;
+use std::{
+	fmt::Debug,
+	ops::{Index, IndexMut},
+};
+
+use itertools::iproduct;
 
 pub const CHUNKS_PER_REGION: u8 = 32;
 
@@ -22,3 +27,37 @@ impl Debug for ChunkCoords {
 		write!(f, "({}, {})", self.x.0, self.z.0)
 	}
 }
+
+#[derive(Debug, Clone, Copy, Default)]
+pub struct ChunkArray<T>(pub [[T; CHUNKS_PER_REGION as usize]; CHUNKS_PER_REGION as usize]);
+
+impl<T> ChunkArray<T> {
+	pub fn keys() -> impl Iterator<Item = ChunkCoords> {
+		iproduct!(0..CHUNKS_PER_REGION, 0..CHUNKS_PER_REGION).map(|(z, x)| ChunkCoords {
+			x: ChunkX(x),
+			z: ChunkZ(z),
+		})
+	}
+
+	pub fn values(&self) -> impl Iterator<Item = &T> {
+		Self::keys().map(|k| &self[k])
+	}
+
+	pub fn iter(&self) -> impl Iterator<Item = (ChunkCoords, &T)> {
+		Self::keys().map(|k| (k, &self[k]))
+	}
+}
+
+impl<T> Index<ChunkCoords> for ChunkArray<T> {
+	type Output = T;
+
+	fn index(&self, index: ChunkCoords) -> &Self::Output {
+		&self.0[index.z.0 as usize][index.x.0 as usize]
+	}
+}
+
+impl<T> IndexMut<ChunkCoords> for ChunkArray<T> {
+	fn index_mut(&mut self, index: ChunkCoords) -> &mut Self::Output {
+		&mut self.0[index.z.0 as usize][index.x.0 as usize]
+	}
+}