xdelta3-wasm

Create efficiently compressed deltas (diffs) between any kinds of data, in the browser or Node.js!

This is a wrapper around the xdelta3 library, which has been compiled to WebAssembly with Emscripten and @rollup/plugin-wasm.

Usage

First, install the package:

yarn add xdelta3-wasm

Creating a delta

A delta is a result of an input and a source - the delta is calculated relative to the source data, and can be applied to the source to get the input data.

You can use any kind of data that can be represented as binary; for this example we'll use strings.

import { init, xd3_encode_memory, xd3_smatch_cfg } from "xdelta3-wasm";

await init();

const source = "Hello, world!";
const input = "Hello, world! This is a test. Hello, world!";

const textEncoder = new TextEncoder();
const sourceBytes = new Uint8Array(source.length);
textEncoder.encodeInto(source, sourceBytes);
const inputBytes = new Uint8Array(input.length);
textEncoder.encodeInto(input, inputBytes);

const delta = xd3_encode_memory(inputBytes, sourceBytes, 9999, xd3_smatch_cfg.DEFAULT);

console.log(delta);
// {
//   ret: 0,
//   str: 'SUCCESS',
//   output: Uint8Array(48) [
//     214, 195, 196,   0,   0,   1,  13,   0,  39,  43,
//       0,  30,   3,   1,  32,  84, 104, 105, 115,  32,
//     105, 115,  32,  97,  32, 116, 101, 115, 116,  46,
//      32,  72, 101, 108, 108, 111,  44,  32, 119, 111,
//     114, 108, 100,  33,  29,   1,  30,   0
//   ]
// }

Applying a delta

Once we have a delta, we can apply it to the source to get the input back. Continuing our previous example:

const orig = xd3_decode_memory(result.output, sourceBytes, 9999);
console.log(orig);
// {
//   ret: 0,
//   str: 'SUCCESS',
//   output: Uint8Array(43) [
//      72, 101, 108, 108, 111,  44,  32, 119, 111,
//     114, 108, 100,  33,  32,  84, 104, 105, 115,
//      32, 105, 115,  32,  97,  32, 116, 101, 115,
//     116,  46,  32,  72, 101, 108, 108, 111,  44,
//      32, 119, 111, 114, 108, 100,  33
//   ]
// }
console.log(new TextDecoder().decode(orig.output));
// Hello, world! This is a test. Hello, world!

Development

Building

To build the C components, you'll need to have the Emscripten SDK set up.

yarn make-native
yarn build

Testing

yarn test

Related

• xdelta-async-nodejs-addon: Asynchronous native addon for Node.js