Crate chd

Expand description

An implementation of the MAME CHD (Compressed Hunks of Data) format in pure Safe Rust, with support for CHD V1-5.

Supported Compression Codecs

chd-rs supports the following compression codecs.

None
Zlib/Zlib+/Zlib V5
CDZL (CD Zlib)
CDLZ (CD LZMA)
CDFL (CD FLAC)
FLAC (Raw FLAC)
LZMA (Raw LZMA)
Huffman (Huff)

AVHuff decompression is experimental and can be enabled with the avhuff feature.

Iterating over hunks

Because ChdHunk keeps a mutable reference to its owning ChdFile, direct iteration of hunks is not possible without Generic Associated Types. Instead, the hunk indices should be iterated over.

use std::fs::File;
use std::io::BufReader;
use chd::ChdFile;

let mut f = BufReader::new(File::open("file.chd")?);
let mut chd = ChdFile::open(&mut f, None)?;
let hunk_count = chd.header().hunk_count();
let hunk_size = chd.header().hunk_size();

// buffer to store uncompressed hunk data must be the same length as the hunk size.
let mut hunk_buf = vec![0u8; hunk_size as usize];
// buffer to store compressed data.
let mut cmp_buf = Vec::new();

for hunk_num in 0..hunk_count {
    let mut hunk = chd.hunk(hunk_num)?;
    hunk.read_hunk_in(&mut cmp_buf, &mut hunk_buf)?;
}

Metadata in a CHD file consists of a list of entries that contain offsets to the byte data of the metadata contents in the CHD file. The individual metadata entries can be iterated directly, but a reference to the source stream has to be provided to read the data.

use std::fs::File;
use std::io::BufReader;
use chd::ChdFile;

let mut f = BufReader::new(File::open("file.chd")?);
let mut chd = ChdFile::open(&mut f, None)?;
let entries = chd.metadata()?;
for entry in entries {
    let metadata = entry.read(&mut f)?;
}

chd-rs provides a helper to retrieve all metadata content at once for convenience.

use std::fs::File;
use std::io::BufReader;
use chd::ChdFile;
use chd::metadata::ChdMetadata;

let mut f = BufReader::new(File::open("file.chd")?);
let mut chd = ChdFile::open(&mut f, None)?;
let entries = chd.metadata()?;
let metadatas: Vec<ChdMetadata> = entries.try_into()?;