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fast-asar

A faster implementation of Electron's ASAR archive format.

This is both a library and a CLI tool.

Installation

You can install fast-asar from NPM (or your preferred package manager):

npm install fast-asar

Usage

CLI

You can use the CLI tool to extract and create ASAR archives.

npx fast-asar help

Library

The library exports an Asar class, which can be used to read and write ASAR archives.

For example, to extract an ASAR archive to a directory:

import { Asar } from "fast-asar";
import { readFile } from "fs/promises";

const asarBytes = await readFile("./app.asar");

const asar = new Asar(asarBytes);

await asar.extract("./app-extracted");

For more information, see the API documentation.

Compatibility

This library can be run with Node.js and Bun.

Browser support is planned.

Benchmarks

The following benchmarks were run with hyperfine on a 2016 MacBook Pro with a 2.9 GHz Quad-Core Intel Core i7 processor and 16 GB of RAM.

Extract files

This benchmark extracts all files in the Replit Desktop app's app.asar file.

Command Mean [ms] Min [ms] Max [ms] Relative
./node_modules/.bin/asar extract test/ignore/app.asar test/ignore/app1 670.0 ± 52.6 614.6 739.4 1.54 ± 0.41
bun ./src/cli/index.ts extract test/ignore/app.asar test/ignore/app2 435.1 ± 110.9 373.7 632.3 1.00

Summary: fast-asar is 1.54 ± 0.41 times faster than @electron/asar.

To run this benchmark yourself, run bun run benchmark:extract.

Pack directories

This benchmark packs the src directory into an ASAR archive at test/ignore/src.asar.

Command Mean [ms] Min [ms] Max [ms] Relative
./node_modules/.bin/asar pack src test/ignore/src.asar 154.7 ± 45.3 123.4 231.7 1.93 ± 0.57
bun ./src/cli/index.ts pack src test/ignore/src.asar 80.0 ± 3.1 77.6 85.4 1.00

Summary: fast-asar is 1.93 ± 0.57 times faster than @electron/asar.

To run this benchmark yourself, run bun run benchmark:pack.

List files

This benchmark lists all files in the Replit Desktop app's app.asar file.

Command Mean [ms] Min [ms] Max [ms] Relative
./node_modules/.bin/asar list test/ignore/app.asar 136.0 ± 31.3 117.5 191.5 1.28 ± 0.30
bun ./src/cli/index.ts list test/ignore/app.asar 106.0 ± 5.9 101.3 116.2 1.00

Summary: fast-asar is 1.28 ± 0.30 times faster than @electron/asar.

To run this benchmark yourself, run bun run benchmark:list.

Contributing

Running tests

For the tests, you must have the Replit Desktop app's app.asar file in the test/ignore directory. You can get this file by installing the Replit Desktop app and copying the app.asar file from the installation directory.

Then, to run all tests:

bun pretest
bun test

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A faster implementation of Electron's ASAR archive format.

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