title: Zstd description: WebAssembly wrapper for the Zstandard compression library outline: deep

@hpcc-js/wasm-zstd

This package provides a WebAssembly wrapper around the Zstandard library. This provides efficient compression and decompression of data.

Installation

::: code-group

npm install @hpcc-js/wasm-zstd

yarn add @hpcc-js/wasm-zstd

pnpm add @hpcc-js/wasm-zstd

:::

One-shot usage

import { Zstd } from "@hpcc-js/wasm-zstd";

const zstd = await Zstd.load();

//  Generate some "data"
const data = new Uint8Array(Array.from({ length: 100000 }, (_, i) => i % 256));

const compressed_data = zstd.compress(data);
const decompressed_data = zstd.decompress(compressed_data);

decompress() uses a fast path when the frame records its content size. Frames with unknown content size (streaming compressors, stdin, many network streams) automatically fall back to the safe streaming decoder—no output-size guessing is required.

Streaming compression

import { Zstd } from "@hpcc-js/wasm-zstd";

const zstd = await Zstd.load();
zstd.resetCompression(3);

const parts: Uint8Array[] = [];
parts.push(zstd.compressChunk(chunk1)); // may be empty while Zstd buffers input
parts.push(zstd.compressChunk(chunk2));
parts.push(zstd.compressEnd());

Streaming decompression

import { Zstd } from "@hpcc-js/wasm-zstd";

const zstd = await Zstd.load();
zstd.resetDecompression();

const parts: Uint8Array[] = [];
parts.push(zstd.decompressChunk(compressedChunk1)); // may be empty
parts.push(zstd.decompressChunk(compressedChunk2));
zstd.decompressEnd(); // throws if the final frame is truncated

Call decompressEnd() after the last chunk. Intermediate empty output is valid and does not mean the frame is complete. Corrupt or truncated input throws an Error that includes the operation name and Zstandard error name when available.

Workers

Use the default package entry from browser module workers or Node.js worker threads. The WASM payload is embedded in the bundled JavaScript, so there is no separate .wasm file to copy or URL to pass to Zstd.load().

Browser module worker

import { Zstd } from "@hpcc-js/wasm-zstd";

self.onmessage = async function (e: MessageEvent<Uint8Array>) {
  const zstd = await Zstd.load();
  const compressed = zstd.compress(e.data);
  const decompressed = zstd.decompress(compressed);

  self.postMessage(decompressed);
};

const worker = new Worker(new URL("./worker.ts", import.meta.url), {
  type: "module",
});

worker.onmessage = function (e: MessageEvent<Uint8Array>) {
  console.log(e.data);
};

worker.postMessage(data);

Node.js worker thread

import { parentPort } from "node:worker_threads";
import { Zstd } from "@hpcc-js/wasm-zstd";

parentPort?.on("message", async function (data) {
  const zstd = await Zstd.load();
  const compressed = zstd.compress(data);
  const decompressed = zstd.decompress(compressed);

  parentPort?.postMessage(decompressed);
});

import { Worker } from "node:worker_threads";

const worker = new Worker(new URL("./worker.js", import.meta.url));

worker.on("message", function (data: Uint8Array) {
  console.log(data);
});

worker.postMessage(data);

Singleton / serialization warning

Zstd.load() returns a singleton within the current JavaScript context. Compression and decompression contexts are stateful. Callers must serialize streaming operations on the shared instance—do not interleave concurrent streams on the same Zstd object. Prefer resetCompression() / resetDecompression() over the legacy reset() so one context is not cleared accidentally with the other.

Reference

• API Documentation