zip

Go Advanced ZIP Library

This project is a highly optimized and advanced drop-in replacement for the Go standard library archive/zip.

It combines the stability of the standard library with the best open-source ZIP processing features available in the Go ecosystem into a single, powerful package.

Key Features

• Drop-in Compatibility: 100% compatible with the archive/zip API. You can safely replace your archive/zip imports with github.com/unxed/zip.

• High Performance: Uses the blazing-fast klauspost/compress library for DEFLATE and adds native Zstandard (ZSTD) support. Both reading and writing are heavily optimized with buffer pooling.

• Parallel Archiving & Extraction: A concurrent archiver and extractor (adapted from saracen/fastzip) processes multiple files in parallel, significantly speeding up operations on multi-core systems.

• Advanced Encryption:

  • WinZip AES (AE-2): Full support for reading and writing AES-encrypted archives (128, 192, and 256-bit).
  • Central Directory Encryption (CDE): Encrypt the archive's metadata (filenames, sizes, etc.), making the list of files completely invisible without the correct password.

• Broad Compression Support:

  • Built-in Deflate64 (Method 9) decoder, used by Windows for large files.
  • Support for BZIP2, LZMA, and PPMd decompression.

• In-Place Updates (Updater): Modify existing ZIP files by appending or overwriting entries without performing a full re-compression of the entire archive.

• Cross-Platform Metadata:

  • Unix: Automatic preservation and restoration of UID/GID, extended timestamps, symlinks, hardlinks, and special files (Devices, FIFOs).
  • Windows: Support for reading and writing NTFS Security Descriptors (ACLs), alongside physical pre-allocation to prevent file fragmentation on NTFS.

• Safe Extraction & Advanced Policies:

  • Path Traversal Defense: Automatic verification to block symlink directory traversal attacks (such as Zip Slip).
  • MOTW Sanitization: Automatically sanitizes Zone.Identifier (Mark of the Web) streams during extraction.
  • Granular Controls: Options for safe atomic writes (SafeWrites), path component stripping (StripComponents), zero-block sparse extraction (Sparse), file-timestamp touching/skipping (NoTimes), and partial file cleanup on errors (KeepBroken).

• Legacy Codepage Auto-Detection: Includes the advanced heuristic algorithm from 7-zip and far2l to automatically fix "mojibake" (garbled text) in filenames from legacy archives created on different operating systems.

• Multi-Volume Support: Transparently read split ZIP archives (e.g., archive.z01, archive.z02, ..., archive.zip).

Usage

1. Standard Drop-in Usage

Simply replace the import path. All existing code for archive/zip will work.

import "github.com/unxed/zip"

// Use exactly like the standard library
r, err := zip.OpenReader("archive.zip")
if err != nil {
	log.Fatal(err)
}
defer r.Close()
// ...

2. High-Speed Multithreaded Archiving

The Archiver provides a high-level API for creating archives from a directory structure concurrently.

package main

import (
	"context"
	"log"
	"os"
	"path/filepath"

	"github.com/unxed/zip"
)

func main() {
	sourceDir := "/path/to/source"

	w, err := os.Create("archive.zip")
	if err != nil {
		log.Fatal(err)
	}
	defer w.Close()

	// Create an archiver with 8 concurrent workers
	archiver, err := zip.NewArchiver(w, sourceDir, zip.WithArchiverConcurrency(8))
	if err != nil {
		log.Fatal(err)
	}
	defer archiver.Close()

	// Gather files to be archived
	files := make(map[string]os.FileInfo)
	filepath.Walk(sourceDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		// Skip the root directory itself
		if path != sourceDir {
			files[path] = info
		}
		return nil
	})

	// Archive all files concurrently
	if err := archiver.Archive(context.Background(), files); err != nil {
		log.Fatal(err)
	}

	log.Println("Archiving complete!")
}

3. In-Place Archive Updates

Modify an archive without rewriting it from scratch using the Updater.

f, err := os.OpenFile("archive.zip", os.O_RDWR, 0)
if err != nil {
	log.Fatal(err)
}
defer f.Close()

updater, err := zip.NewUpdater(f)
if err != nil {
	log.Fatal(err)
}

// Overwrite an existing file with new content
w, err := updater.Append("config.json", zip.APPEND_MODE_OVERWRITE)
if err != nil {
	log.Fatal(err)
}
w.Write([]byte(`{"updated": true}`))

if err := updater.Close(); err != nil {
	log.Fatal(err)
}

4. Create an AES-256 Encrypted Archive

Provide a password in the FileHeader to enable strong WinZip-compatible AES encryption.

w, _ := os.Create("secure.zip")
defer w.Close()

zw := zip.NewWriter(w)
defer zw.Close()

fh := &zip.FileHeader{
	Name:        "secret.txt",
	Method:      zip.Deflate,
	Password:    "super-secret-password",
	AESStrength: 3, // 1 for 128-bit, 2 for 192-bit, 3 for 256-bit
}

f, err := zw.CreateHeader(fh)
if err != nil {
	log.Fatal(err)
}
f.Write([]byte("this is top secret data"))

5. Create an "Invisible" Archive (Central Directory Encryption)

Encrypt the archive's file list itself, making it impossible to see the contents without a password.

w, _ := os.Create("stealth.zip")
defer w.Close()

zw := zip.NewWriter(w)
defer zw.Close()

// Encrypt the list of files (the central directory)
zw.SetEncryptCentralDirectory(true, "master-password")

// Note: Individual files can still have their own passwords or be unencrypted.
// Here, we encrypt the file with the same password for simplicity.
fh := &zip.FileHeader{
	Name:     "secret.txt",
	Password: "master-password",
}
f, err := zw.CreateHeader(fh)
if err != nil {
	log.Fatal(err)
}
f.Write([]byte("top secret data"))

6. Reading a Multi-Volume Archive

The library handles split archives automatically. Just open the final .zip file.

// This will transparently read from archive.z01, archive.z02, etc.
r, err := zip.OpenReader("archive.zip")
if err != nil {
	log.Fatal(err)
}
defer r.Close()

// You can now access all files as if it were a single archive
for _, f := range r.File {
	fmt.Println("Found file:", f.Name)
}

Format Extensions

This library extends the standard ZIP format by proposing f4 zip extensions. These extensions provide advanced metadata support while remaining fully standard-compliant (standard ZIP utilities will safely skip them).

See the technical specification in f4zip.md.

TorrentZip Specification

Our implementation is 100% bit-exact compatible with the official C-based trrntzip converter. We have documented the exact technical requirements of the format for future reference.

See the technical specification in torrentzip.md.

Why "f4"?

The name comes from the f4 file manager, a cross-platform asynchronous clone of Far Manager. This library was built to provide f4 with high-fidelity archive support, ensuring that system-specific metadata like ACLs and Xattrs are preserved when moving data between Linux, Windows, and macOS.

License

This project is released under the BSD-3-Clause License. See the LICENSE file for details.

Acknowledgements

This library is inspired by several other open-source zip implementations. Please see CREDITS.md for a detailed list of acknowledgements.