The Zstandard WASM library, provides a simplified wrapper around the Zstandard c++ library.

See Zstandard for more details.

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);

Methods

load()

static load(): Promise<Zstd>

Compiles and instantiates the raw wasm.

INFO

In general WebAssembly compilation is disallowed on the main thread if the buffer size is larger than 4KB, hence forcing load to be asynchronous;

Returns

Promise<Zstd>

A promise to an instance of the Zstd class.

---

unload()

static unload(): Promise<void>

Unloades the compiled wasm instance.

Returns

Promise<void>

---

version()

version(): string

Returns

string

The Zstd c++ version

---

reset()

reset(): void

Resets the internal compression/decompression state.

Returns

void

---

setCompressionLevel()

setCompressionLevel(level): void

Sets the compression level for streaming compression.

Parameters

level

number

Compression level (use minCLevel() to maxCLevel())

Returns

void

---

compress()

compress(data, compressionLevel?): Uint8Array

Parameters

data

Uint8Array

Data to be compressed

compressionLevel?

number = ...

Compression v Speed tradeoff, when omitted it will default to zstd.defaultCLevel() which is currently 3.

Returns

Uint8Array

Compressed data.

TIP

A note on compressionLevel: The library supports regular compression levels from 1 up o 22. Levels >= 20, should be used with caution, as they require more memory. The library also offers negative compression levels, which extend the range of speed vs. ratio preferences. The lower the level, the faster the speed (at the cost of compression).

---

compressChunk()

compressChunk(data): Uint8Array

Compresses a chunk of data in streaming mode. Call reset() before the first chunk, then compressChunk() for each chunk, and finally compressEnd().

Parameters

data

Uint8Array

Chunk of data to be compressed

Returns

Uint8Array

Compressed chunk data

---

compressEnd()

compressEnd(): Uint8Array

Finishes the streaming compression and returns any remaining compressed data.

Returns

Uint8Array

Final compressed data

---

decompress()

decompress(compressedData): Uint8Array

Parameters

compressedData

Uint8Array

Data to be compressed

Returns

Uint8Array

Uncompressed data.

---

decompressChunk()

decompressChunk(compressedData, outputSize): Uint8Array

Decompresses a chunk of data in streaming mode. Call reset() before the first chunk, then decompressChunk() for each chunk.

Parameters

compressedData

Uint8Array

Chunk of compressed data

outputSize

number

Expected output size for this chunk

Returns

Uint8Array

Decompressed chunk data

---

defaultCLevel()

defaultCLevel(): number

Returns

number

Default compression level (see notes above above).

---

minCLevel()

minCLevel(): number

Returns

number

---

maxCLevel()

maxCLevel(): number

Returns

number