1 files changed, 133 insertions, 0 deletions
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..eb131dd
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,133 @@
+pub mod helper;
+
+use anyhow::{Result, anyhow};
+use helper::ReadExt;
+use std::{
+    env::args,
+    fs::File,
+    io::{BufReader, Cursor, Read, Seek, SeekFrom},
+};
+
+fn main() -> anyhow::Result<()> {
+    let mut file = BufReader::new(File::open(args().nth(1).unwrap())?);
+
+    let signature = file.read_cstr()?;
+    let file_version = file.read_u32_be()?;
+    let player_version = file.read_cstr()?;
+    let unity_version = file.read_cstr()?;
+    let size = file.read_u64_be()?;
+    let meta_comp_size = file.read_u32_be()?;
+    let meta_decomp_size = file.read_u32_be()?;
+    let flags = file.read_u32_be()?;
+
+    let meta_comp_scheme = CompressionScheme::from_flag_num((flags & 0x3f) as u8)
+        .ok_or(anyhow!("unknown block compression"))?;
+    let eof_meta = flags & 0x80 != 0;
+
+    eprintln!("signature={signature:?}");
+    eprintln!("file_version={file_version:?}");
+    eprintln!("player_version={player_version:?}");
+    eprintln!("unity_version={unity_version:?}");
+    eprintln!("size={size:?}");
+    eprintln!("meta_comp_size={meta_comp_size:?}");
+    eprintln!("meta_decomp_size={meta_decomp_size:?}");
+    eprintln!("flags={flags:?}");
+    eprintln!("meta_comp_scheme={meta_comp_scheme:?}");
+    eprintln!("eof_meta={eof_meta:?}");
+
+    let restore_position = if eof_meta {
+        let pos = file.stream_position()?;
+        file.seek(SeekFrom::End(-(meta_comp_size as i64)))?;
+        Some(pos)
+    } else {
+        None
+    };
+
+    let mut block = vec![0u8; meta_comp_size as usize];
+    file.read_exact(&mut block)?;
+
+    if let Some(pos) = restore_position {
+        file.seek(SeekFrom::Start(pos))?;
+    }
+
+    let block = meta_comp_scheme.decompress(block, meta_decomp_size as usize)?;
+    let mut block = Cursor::new(block);
+
+    let guid = block.read_u128_be()?;
+    eprintln!("guid={guid:032x}");
+
+    let num_blocks = block.read_u32_be()?;
+    eprintln!("num_blocks={num_blocks:?}");
+    let mut blocks = Vec::new();
+    for _ in 0..num_blocks {
+        let block_decomp_size = block.read_u32_be()?;
+        let block_comp_size = block.read_u32_be()?;
+        let block_flags = block.read_u16_be()?;
+        let block_comp_scheme = CompressionScheme::from_flag_num((block_flags & 0x3f) as u8)
+            .ok_or(anyhow!("unknown block compression"))?;
+        blocks.push((block_comp_size, block_decomp_size, block_comp_scheme))
+    }
+
+    let num_nodes = block.read_u32_be()?;
+    eprintln!("num_nodes={num_nodes:?}");
+    let mut nodes = Vec::new();
+    for _ in 0..num_nodes {
+        let offset = block.read_u64_be()?;
+        let size = block.read_u64_be()?;
+        let status = block.read_u32_be()?;
+        let name = block.read_cstr()?;
+        nodes.push((offset, size, status, name))
+    }
+
+    let mut all_blocks = Vec::new();
+    for (comp_size, decomp_size, comp_scheme) in blocks {
+        let mut comp_buf = vec![0u8; comp_size as usize];
+        file.read_exact(&mut comp_buf)?;
+        let decomp_buf = comp_scheme.decompress(comp_buf, decomp_size as usize)?;
+        assert_eq!(decomp_size, decomp_buf.len() as u32);
+        all_blocks.extend_from_slice(&decomp_buf);
+    }
+
+    eprintln!("{nodes:#?}");
+
+    Ok(())
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+enum CompressionScheme {
+    None,
+    LZMA,
+    LZ4,
+    LZ4HC,
+    LZHAM,
+}
+impl CompressionScheme {
+    pub fn from_flag_num(n: u8) -> Option<CompressionScheme> {
+        Some(match n & 0x3f {
+            0 => CompressionScheme::None,
+            1 => CompressionScheme::LZMA,
+            2 => CompressionScheme::LZ4,
+            3 => CompressionScheme::LZ4HC,
+            4 => CompressionScheme::LZHAM,
+            _ => return None,
+        })
+    }
+    pub fn decompress(&self, block: Vec<u8>, decomp_size: usize) -> Result<Vec<u8>> {
+        match self {
+            CompressionScheme::None => Ok(block),
+            CompressionScheme::LZMA => {
+                let mut r = lzma::Reader::from(Cursor::new(block))?;
+                let mut buf = Vec::new();
+                r.read_to_end(&mut buf)?;
+                Ok(buf)
+            }
+            // CompressionScheme::LZ4HC | CompressionScheme::LZ4 => {
+            //     Ok(lz4_flex::block::decompress(&block, decomp_size).context("lz4 decomp")?)
+            // }
+            CompressionScheme::LZ4HC | CompressionScheme::LZ4 => {
+                Ok(lz4::block::decompress(&block, Some(decomp_size as i32))?)
+            }
+            CompressionScheme::LZHAM => todo!(),
+        }
+    }
+}