dxcontainer

Reads the part directory of a DXBC container, the file format Direct3D shader programs are stored in (Shader Model 4 to 6), and computes its digest.

let bytes = std::fs::read("shader.dxbc")?;
for part in dxcontainer::chunks(&bytes)? {
    println!("{}: {} bytes", String::from_utf8_lossy(&part.kind), part.data.len());
}
println!("digest: {:02x?}", dxcontainer::checksum(&bytes));

Run it with cargo run -p dxcontainer --example parts -- shader.dxbc; the source is examples/parts.rs. The crate documentation has a self-contained example with a hand-built container.

What it reads

A header (DXBC, a 16-byte digest, version 1, the container's size, the number of parts), the directory of the parts' offsets, then the parts one after another in the directory's order (each its four-character kind, its length and its bytes), the last ending where the container does. Shader Model 6 parts are not padded, so an offset need not be a multiple of 4. This layout holds for the 127 containers committed under dxbc-reader/tests/fixtures and dxil-reader/tests/fixtures: the tests read each to its exact end and check that checksum equals the digest it stores.

What it guarantees

The reader reads to the exact end and refuses, with an Error that names the byte, a part anywhere else (overlapping, or after a gap), a byte after the last part, a part kind twice, a size other than the container's and a version other than 1. The crate denies indexing and unchecked arithmetic at compile time, so untrusted bytes produce an Error, not a panic.

What it does not do

It does not verify the digest: the digest is not an authenticity check. checksum(bytes) computes it (MD5's block function over the bytes from 20 on, padded as the compiler pads it), for a caller that wants to compare; on all 127 committed fixtures it equals the stored digest. It does not interpret the parts; dxbc-reader (Shader Model 4 and 5) and dxil-reader (Shader Model 6) do.

Tests

cargo test -p dxcontainer: containers built by hand for each refusal, every truncation of one, and the committed fixtures of dxbc-reader and dxil-reader read to their end. No game files are needed.

License: GPL-3.0-or-later.