149 lines
4.1 KiB
Markdown
149 lines
4.1 KiB
Markdown
---
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title: Zstd
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description: WebAssembly wrapper for the Zstandard compression library
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outline: deep
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---
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# @hpcc-js/wasm-zstd
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<script setup>
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import ZstdDemo from "../../.vitepress/components/ZstdDemo.vue";
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</script>
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This package provides a WebAssembly wrapper around the [Zstandard](https://facebook.github.io/zstd/) library. This provides efficient compression and decompression of data.
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## Installation
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::: code-group
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```sh [npm]
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npm install @hpcc-js/wasm-zstd
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```
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```sh [yarn]
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yarn add @hpcc-js/wasm-zstd
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```
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```sh [pnpm]
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pnpm add @hpcc-js/wasm-zstd
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```
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:::
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## One-shot usage
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```typescript
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import { Zstd } from "@hpcc-js/wasm-zstd";
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const zstd = await Zstd.load();
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// Generate some "data"
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const data = new Uint8Array(Array.from({ length: 100000 }, (_, i) => i % 256));
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const compressed_data = zstd.compress(data);
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const decompressed_data = zstd.decompress(compressed_data);
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```
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## Try it
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<ZstdDemo />
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`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.
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## Streaming compression
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```typescript
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import { Zstd } from "@hpcc-js/wasm-zstd";
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const zstd = await Zstd.load();
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zstd.resetCompression(3);
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const parts: Uint8Array[] = [];
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parts.push(zstd.compressChunk(chunk1)); // may be empty while Zstd buffers input
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parts.push(zstd.compressChunk(chunk2));
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parts.push(zstd.compressEnd());
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```
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## Streaming decompression
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```typescript
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import { Zstd } from "@hpcc-js/wasm-zstd";
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const zstd = await Zstd.load();
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zstd.resetDecompression();
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const parts: Uint8Array[] = [];
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parts.push(zstd.decompressChunk(compressedChunk1)); // may be empty
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parts.push(zstd.decompressChunk(compressedChunk2));
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zstd.decompressEnd(); // throws if the final frame is truncated
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```
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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.
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## Workers
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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()`.
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### Browser module worker
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```typescript [worker.ts]
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import { Zstd } from "@hpcc-js/wasm-zstd";
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self.onmessage = async function (e: MessageEvent<Uint8Array>) {
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const zstd = await Zstd.load();
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const compressed = zstd.compress(e.data);
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const decompressed = zstd.decompress(compressed);
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self.postMessage(decompressed);
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};
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```
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```typescript [main.ts]
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const worker = new Worker(new URL("./worker.ts", import.meta.url), {
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type: "module",
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});
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worker.onmessage = function (e: MessageEvent<Uint8Array>) {
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console.log(e.data);
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};
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worker.postMessage(data);
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```
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### Node.js worker thread
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```javascript [worker.js]
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import { parentPort } from "node:worker_threads";
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import { Zstd } from "@hpcc-js/wasm-zstd";
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parentPort?.on("message", async function (data) {
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const zstd = await Zstd.load();
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const compressed = zstd.compress(data);
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const decompressed = zstd.decompress(compressed);
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parentPort?.postMessage(decompressed);
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});
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```
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```typescript [main.ts]
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import { Worker } from "node:worker_threads";
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const worker = new Worker(new URL("./worker.js", import.meta.url));
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worker.on("message", function (data: Uint8Array) {
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console.log(data);
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});
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worker.postMessage(data);
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```
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## Singleton / serialization warning
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`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.
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<!--@include: ../../docs/zstd/src/zstd/README.md-->
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## Reference
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- [API Documentation](https://hpcc-systems.github.io/hpcc-js-wasm/docs/zstd/src/zstd/classes/Zstd.html)
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