archives

A Go library for reading and browsing archive files in memory. Supports ZIP, TAR (with gzip, bzip2, xz compression), and Ruby gem formats.

Installation

go get github.com/git-pkgs/archives

Usage

package main

import (
	"fmt"
	"os"

	"github.com/git-pkgs/archives"
)

func main() {
	f, _ := os.Open("package.tar.gz")
	defer f.Close()

	reader, _ := archives.Open("package.tar.gz", f)
	defer reader.Close()

	// List all files
	files, _ := reader.List()
	for _, fi := range files {
		fmt.Println(fi.Path, fi.Size)
	}

	// List a specific directory
	dirFiles, _ := reader.ListDir("src")
	for _, fi := range dirFiles {
		fmt.Println(fi.Name, fi.IsDir)
	}

	// Extract a file
	rc, _ := reader.Extract("README.md")
	defer rc.Close()
	// read from rc...
}

Hashing

Open buffers the raw archive bytes in memory, so the reader can compute checksums of the original artifact without re-reading from the source. This is useful for verifying a downloaded package against the digest published by its registry.

reader, _ := archives.Open("rails-7.1.0.gem", f)
defer reader.Close()

sha, _ := reader.Hash(archives.SHA256)
fmt.Println(sha) // hex-encoded sha256 of the .gem file

// also available: archives.SHA512, archives.SHA1, archives.MD5

The hash is computed over the archive as it was passed to Open, not the decompressed contents. For nested formats like gems this means the outer .gem file, which is what rubygems.org publishes. If you already have the bytes in hand, OpenBytes skips the extra read:

reader, _ := archives.OpenBytes("pkg.tgz", data)

Prefix stripping

Some package formats wrap content in a directory (npm uses package/). OpenWithPrefix strips a path prefix from all entries:

reader, _ := archives.OpenWithPrefix("pkg.tgz", f, "package/")
// files are now accessible without the package/ prefix

Comparing versions

The diff subpackage compares two archives and produces unified diffs. It classifies each file as added, deleted, modified, or binary, and includes line-level diff output for text files.

import "github.com/git-pkgs/archives/diff"

result, _ := diff.Compare(oldReader, newReader)
for _, f := range result.Files {
	fmt.Printf("%s %s (+%d -%d)\n", f.Type, f.Path, f.LinesAdded, f.LinesDeleted)
	if f.Diff != "" {
		fmt.Println(f.Diff)
	}
}

Supported formats

• .zip, .jar, .whl, .nupkg, .egg (ZIP-based)
• .tar, .tar.gz, .tgz, .tar.bz2, .tar.xz
• .gem (Ruby gems with nested data.tar.gz)

License

MIT