zstddec

ZSTD (Zstandard) decoder for Web and Node.js, using WebAssembly.

Installation

npm install --save zstddec

API

import { ZSTDDecoder } from 'zstddec';

const decoder = new ZSTDDecoder();

await decoder.init();

const decompressedArray = decoder.decode( compressedArray, uncompressedSize );

Limitations: The decoder may fail with the error wasm function signature contains illegal type when the uncompressedSize is not known in advance and given to the decode() method. This is presumably a bug in the WASM bindings, which I am not yet sure how to fix.

Contributing

To build the project locally, run:

npm install
npm run dist

To test changes:

npm test

Building from source

Compiled from https://github.com/facebook/zstd/tree/dev/build/single_file_libs, with the following steps:

./create_single_file_decoder.sh

Note The current build is based on zstd v1.5.0. The binary sized increased following this version.

emcc zstddeclib.c -s EXPORTED_FUNCTIONS="['_ZSTD_decompress', '_ZSTD_findDecompressedSize', '_ZSTD_isError', '_malloc', '_free']"  -Wl,--no-entry -s WASM=1 -Oz -g0 -flto -s ALLOW_MEMORY_GROWTH=1 -s FILESYSTEM=0 -s STANDALONE_WASM=1 -DNDEBUG=1 -s PURE_WASI=0 -o zstddec.wasm
base64 -w 0 zstddec.wasm > zstddec.txt

Note The -w 0 argument is only for the base64 shipped on Linux systems -- on macOS this should be omitted.

The base64 string written to zstddec.txt is embedded as the wasm variable at the bottom of the source file. The rest of the file is written by hand, in order to avoid an additional JS wrapper generated by Emscripten.

License

JavaScript wrapper is provided under the MIT License, and the WASM ZSTD decoder is provided by Facebook under the BSD 3-Clause License.