#parser #WebAssembly #wasm

wasmparser

A simple event-driven library for parsing WebAssembly binary files

108 releases (50 breaking)

✓ Uses Rust 2018 edition

0.51.1 Feb 7, 2020
0.50.0 Feb 5, 2020
0.45.0 Dec 17, 2019
0.42.1 Nov 18, 2019
0.7.2 Jul 7, 2017

#3 in WebAssembly

Download history 7412/week @ 2019-11-01 6810/week @ 2019-11-08 6648/week @ 2019-11-15 7005/week @ 2019-11-22 6956/week @ 2019-11-29 10251/week @ 2019-12-06 9897/week @ 2019-12-13 5195/week @ 2019-12-20 3832/week @ 2019-12-27 11162/week @ 2020-01-03 17355/week @ 2020-01-10 9707/week @ 2020-01-17 7565/week @ 2020-01-24 9501/week @ 2020-01-31 9243/week @ 2020-02-07

37,300 downloads per month
Used in 85 crates (29 directly)

Apache-2.0 WITH LLVM-exception

390KB
9K SLoC

The WebAssembly binary file decoder in Rust

A Bytecode Alliance project

CI crates.io link

The decoder library provides lightweight and fast decoding/parsing of WebAssembly binary files.

The other goal is minimal memory footprint. For this reason, there is no AST or IR of WebAssembly data.

See also its sibling at https://github.com/wasdk/wasmparser

Documentation

The documentation and examples can be found at the https://docs.rs/wasmparser/

Example

use wasmparser::WasmDecoder;
use wasmparser::Parser;
use wasmparser::ParserState;

fn get_name(bytes: &[u8]) -> &str {
  str::from_utf8(bytes).ok().unwrap()
}

fn main() {
  let ref buf: Vec<u8> = read_wasm_bytes();
  let mut parser = Parser::new(buf);
  loop {
    let state = parser.read();
    match *state {
        ParserState::BeginWasm { .. } => {
            println!("====== Module");
        }
        ParserState::ExportSectionEntry { field, ref kind, .. } => {
            println!("  Export {} {:?}", get_name(field), kind);
        }
        ParserState::ImportSectionEntry { module, field, .. } => {
            println!("  Import {}::{}", get_name(module), get_name(field))
        }
        ParserState::EndWasm => break,
        _ => ( /* println!(" Other {:?}", state) */ )
    }
  }
}

Fuzzing

To fuzz test wasmparser.rs, switch to a nightly Rust compiler and install cargo-fuzz:

cargo install cargo-fuzz

Then, from the root of the repository, run:

cargo fuzz run parse

If you want to use files as seeds for the fuzzer, add them to fuzz/corpus/parse/ and restart cargo-fuzz.

No runtime deps