asar

Read and write Go library for Electron ASAR archives.

An ASAR file is an 8-byte Chromium pickle, a JSON index pickle, and concatenated uncompressed file bytes. Open returns io.SectionReader values over packed files. Pack and WriteArchive build the same layout, including shared offsets for identical contents and SHA-256 integrity blocks. Hashes are not verified on read.

Unpacked entries (unpacked: true) live in a sibling {archive}.unpacked directory. The reader records the flag; callers copy those files themselves.

Integration tests pack archives with @electron/asar 4.3.0 and read them back:

npm ci --prefix integration
go test -tags integration -race ./...

package main

import (
	"fmt"
	"io"
	"os"

	"golift.io/asar"
)

func main() {
	reader, err := asar.Open("app.asar")
	if err != nil {
		panic(err)
	}
	defer reader.Close()

	for _, file := range reader.Files {
		if !file.Packed() {
			continue
		}

		src, err := file.Open()
		if err != nil {
			panic(err)
		}

		fmt.Println(file.Name, file.Size)
		_, _ = io.Copy(os.Stdout, src)
	}
}