Add new regiondump implemention

Cargo.lock

@@ -190,6 +190,7 @@ dependencies = [
  "clap",
  "fastnbt",
  "flate2",
+ "serde",
 ]
 
 [[package]]

Cargo.toml

@@ -11,3 +11,4 @@ anyhow = "1.0.68"
 clap = { version = "4.1.4", features = ["derive"] }
 fastnbt = "2.3.2"
 flate2 = "1.0.25"
+serde = "1.0.152"

src/bin/regiondump.rs

@@ -0,0 +1,147 @@
+use std::{
+	collections::HashMap,
+	fs::File,
+	io::{prelude::*, SeekFrom},
+	path::PathBuf,
+};
+
+use anyhow::{bail, Context, Result};
+use clap::Parser;
+use flate2::read::ZlibDecoder;
+use serde::de::DeserializeOwned;
+
+const BLOCKSIZE: usize = 4096;
+const CHUNKS_PER_REGION: u8 = 32;
+
+/// A chunk X coordinate relative to a region
+#[derive(Debug, Clone, Copy)]
+pub struct ChunkX(pub u8);
+
+/// A chunk Z coordinate relative to a region
+#[derive(Debug, Clone, Copy)]
+pub struct ChunkZ(pub u8);
+
+#[derive(Debug)]
+struct ChunkDesc {
+	x: ChunkX,
+	z: ChunkZ,
+	len: u8,
+}
+
+fn parse_header(header: &[u8; BLOCKSIZE]) -> HashMap<u32, ChunkDesc> {
+	let mut map = HashMap::new();
+
+	for z in 0..CHUNKS_PER_REGION {
+		for x in 0..CHUNKS_PER_REGION {
+			let chunk =
+				&header[(4 * (usize::from(CHUNKS_PER_REGION) * usize::from(z) + usize::from(x)))..];
+
+			let offset = u32::from(chunk[0]) << 16 | u32::from(chunk[1]) << 8 | u32::from(chunk[2]);
+			if offset == 0 {
+				continue;
+			}
+
+			let len = chunk[3];
+
+			map.insert(
+				offset,
+				ChunkDesc {
+					x: ChunkX(x),
+					z: ChunkZ(z),
+					len,
+				},
+			);
+		}
+	}
+
+	map
+}
+
+fn decode_chunk<T>(buf: &[u8]) -> Result<T>
+where
+	T: DeserializeOwned,
+{
+	let (len_bytes, buf) = buf.split_at(4);
+	let len = u32::from_be_bytes(
+		len_bytes
+			.try_into()
+			.context("Failed to decode chunk size")?,
+	) as usize;
+
+	let buf = &buf[..len];
+	let (format, buf) = buf.split_at(1);
+	if format.get(0) != Some(&2) {
+		bail!("Unknown chunk format");
+	}
+
+	let mut decoder = ZlibDecoder::new(&buf[..]);
+	let mut decode_buffer = vec![];
+	decoder
+		.read_to_end(&mut decode_buffer)
+		.context("Failed to decompress chunk data")?;
+
+	fastnbt::from_bytes(&decode_buffer).context("Failed to decode NBT data")
+}
+
+fn foreach_chunk<R, T, F>(mut reader: R, mut f: F) -> Result<()>
+where
+	R: Read + Seek,
+	T: DeserializeOwned,
+	F: FnMut(ChunkX, ChunkZ, T),
+{
+	let chunk_map = {
+		let mut header = [0u8; BLOCKSIZE];
+		reader
+			.read_exact(&mut header)
+			.context("Failed to read region header")?;
+
+		parse_header(&header)
+	};
+
+	let mut index = 1;
+	let mut count = 0;
+	let mut seen = [[false; CHUNKS_PER_REGION as usize]; CHUNKS_PER_REGION as usize];
+
+	while count < chunk_map.len() {
+		let Some(&ChunkDesc { x, z, len }) = chunk_map.get(&index) else {
+			reader.seek(SeekFrom::Current(BLOCKSIZE as i64)).context("Failed to seek chunk data")?;
+			index += 1;
+			continue;
+		};
+
+		let chunk_seen = &mut seen[x.0 as usize][z.0 as usize];
+		if *chunk_seen {
+			bail!("Duplicate chunk");
+		}
+
+		*chunk_seen = true;
+		count += 1;
+
+		let mut buffer = vec![0; (len as usize) * BLOCKSIZE];
+		reader
+			.read_exact(&mut buffer[..])
+			.context("Failed to read chunk data")?;
+
+		f(x, z, decode_chunk(&buffer[..])?);
+
+		index += len as u32;
+	}
+
+	Ok(())
+}
+
+#[derive(Debug, Parser)]
+struct Args {
+	/// Filename to dump
+	file: PathBuf,
+}
+
+fn main() -> Result<()> {
+	let args = Args::parse();
+
+	let mut file = File::open(&args.file).context("Failed to open file")?;
+
+	foreach_chunk(&mut file, |x, z, value: fastnbt::Value| {
+		println!("Chunk({}, {}): {:#x?}", x.0, z.0, value);
+	})
+}