@thi.ng/leb128 NPM

npm downloads

This project is part of the @thi.ng/umbrella monorepo.

About

WASM based Little Endian Base 128 varint encoding / decoding, supporting (u)int64 range (however for JS purposes only up to MAX_SAFE_INTEGER).

The WASM binary (~860 bytes) is embedded as base64 string in the TypeScript source to make it easier to use in both browser & node environments. The source code of the actual implementation (written in Zig) is included in /src/leb128.zig

All public functions throw an error if the WASM module could not be initialized.

References:

Status

STABLE - used in production

Search or submit any issues for this package

Installation

yarn add @thi.ng/leb128

ES module import:

<script type="module" src="https://cdn.skypack.dev/@thi.ng/leb128"></script>

Skypack documentation

For Node.js REPL:

# with flag only for < v16
node --experimental-repl-await

> const leb128 = await import("@thi.ng/leb128");

Package sizes (gzipped, pre-treeshake): ESM: 1.09 KB

Dependencies

API

Generated API docs

import * as leb from "@thi.ng/leb128";

// if WASM is unavailable, the encode/decode functions will throw an error
enc = leb.encodeULEB128(Number.MAX_SAFE_INTEGER);
// Uint8Array [ 255, 255, 255, 255, 255, 255, 255, 15 ]

// decoding returns tuple of [value, bytes consumed]
leb.decodeULEB128(enc);
// [ 9007199254740991, 8 ]

// encode signed int
enc = leb.encodeSLEB128(Number.MIN_SAFE_INTEGER)
// Uint8Array [ 129, 128, 128, 128, 128, 128, 128, 112 ]

leb.decodeSLEB128(enc)
// [ -9007199254740991, 8 ]

Building the binary

Requirements:

# install required tools
brew install zig binaryen

# first run native tests
zig test packages/leb128/src/leb128.zig
# Test 1/2 min safe integer...OK
# Test 2/2 max safe integer...OK
# All tests passed.

# build binary and regenerate src/binary.ts
yarn build:binary

# test TS/JS version
yarn test

Authors

Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-leb128,
  title = "@thi.ng/leb128",
  author = "Karsten Schmidt",
  note = "https://thi.ng/leb128",
  year = 2019
}

License

64bit bigint binary conversion integer typedarray typescript varint wasm webassembly zig ziglang

@thi.ng/checks @thi.ng/errors @thi.ng/transducers-binary

@everything-registry/sub-chunk-914 wasm-backporter stream-wasm-parser

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