zip.go

// Package archiver makes it super easy to create and open .zip,
// .tar.gz, and .tar.bz2 files.
package archiver

import (
	"archive/zip"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path"
	"path/filepath"
	"strings"
)

// Zip is for Zip format
var Zip zipFormat

func init() {
	RegisterFormat("Zip", Zip)
}

type zipFormat struct{}

func (zipFormat) Match(filename string) bool {
	return strings.HasSuffix(strings.ToLower(filename), ".zip") || isZip(filename)
}

// isZip checks the file has the Zip format signature by reading its beginning
// bytes and matching it against "PK\x03\x04"
func isZip(zipPath string) bool {
	f, err := os.Open(zipPath)
	if err != nil {
		return false
	}
	defer f.Close()

	buf := make([]byte, 4)
	if n, err := f.Read(buf); err != nil || n < 4 {
		return false
	}

	return bytes.Equal(buf, []byte("PK\x03\x04"))
}

// Write outputs a .zip file to the given writer with
// the contents of files listed in filePaths. File paths
// can be those of regular files or directories. Regular
// files are stored at the 'root' of the archive, and
// directories are recursively added.
//
// Files with an extension for formats that are already
// compressed will be stored only, not compressed.
func (zipFormat) Write(output io.Writer, filePaths []string) error {
	w := zip.NewWriter(output)
	for _, fpath := range filePaths {
		if err := zipFile(w, fpath); err != nil {
			w.Close()
			return err
		}
	}

	return w.Close()
}

// Make creates a .zip file in the location zipPath containing
// the contents of files listed in filePaths. File paths
// can be those of regular files or directories. Regular
// files are stored at the 'root' of the archive, and
// directories are recursively added.
//
// Files with an extension for formats that are already
// compressed will be stored only, not compressed.
func (zipFormat) Make(zipPath string, filePaths []string) error {
	out, err := os.Create(zipPath)
	if err != nil {
		return fmt.Errorf("error creating %s: %v", zipPath, err)
	}
	defer out.Close()

	return Zip.Write(out, filePaths)
}

func zipFile(w *zip.Writer, source string) error {
	sourceInfo, err := os.Stat(source)
	if err != nil {
		return fmt.Errorf("%s: stat: %v", source, err)
	}

	var baseDir string
	if sourceInfo.IsDir() {
		baseDir = filepath.Base(source)
	}

	return filepath.Walk(source, func(fpath string, info os.FileInfo, err error) error {
		if err != nil {
			return fmt.Errorf("walking to %s: %v", fpath, err)
		}

		header, err := zip.FileInfoHeader(info)
		if err != nil {
			return fmt.Errorf("%s: getting header: %v", fpath, err)
		}

		if baseDir != "" {
			name, err := filepath.Rel(source, fpath)
			if err != nil {
				return err
			}
			header.Name = path.Join(baseDir, filepath.ToSlash(name))
		}

		if info.IsDir() {
			header.Name += "/"
			header.Method = zip.Store
		} else {
			ext := strings.ToLower(path.Ext(header.Name))
			if _, ok := compressedFormats[ext]; ok {
				header.Method = zip.Store
			} else {
				header.Method = zip.Deflate
			}
		}

		writer, err := w.CreateHeader(header)
		if err != nil {
			return fmt.Errorf("%s: making header: %v", fpath, err)
		}

		if info.IsDir() {
			return nil
		}

		if header.Mode().IsRegular() {
			file, err := os.Open(fpath)
			if err != nil {
				return fmt.Errorf("%s: opening: %v", fpath, err)
			}
			defer file.Close()

			_, err = io.CopyN(writer, file, info.Size())
			if err != nil && err != io.EOF {
				return fmt.Errorf("%s: copying contents: %v", fpath, err)
			}
		}

		return nil
	})
}

// Read unzips the .zip file read from the input Reader into destination.
func (zipFormat) Read(input io.Reader, destination string) error {
	buf, err := ioutil.ReadAll(input)
	if err != nil {
		return err
	}

	rdr := bytes.NewReader(buf)
	r, err := zip.NewReader(rdr, rdr.Size())
	if err != nil {
		return err
	}

	return unzipAll(r, destination)
}

// Open unzips the .zip file at source into destination.
func (zipFormat) Open(source, destination string) error {
	r, err := zip.OpenReader(source)
	if err != nil {
		return err
	}
	defer r.Close()

	return unzipAll(&r.Reader, destination)
}

func unzipAll(r *zip.Reader, destination string) error {
	for _, zf := range r.File {
		if err := unzipFile(zf, destination); err != nil {
			return err
		}
	}

	return nil
}

func unzipFile(zf *zip.File, destination string) error {
	if strings.HasSuffix(zf.Name, "/") {
		return mkdir(filepath.Join(destination, zf.Name))
	}

	rc, err := zf.Open()
	if err != nil {
		return fmt.Errorf("%s: open compressed file: %v", zf.Name, err)
	}
	defer rc.Close()

	return writeNewFile(filepath.Join(destination, zf.Name), rc, zf.FileInfo().Mode())
}

// compressedFormats is a (non-exhaustive) set of lowercased
// file extensions for formats that are typically already
// compressed. Compressing already-compressed files often
// results in a larger file, so when possible, we check this
// set to avoid that.
var compressedFormats = map[string]struct{}{
	".7z":   {},
	".avi":  {},
	".bz2":  {},
	".cab":  {},
	".gif":  {},
	".gz":   {},
	".jar":  {},
	".jpeg": {},
	".jpg":  {},
	".lz":   {},
	".lzma": {},
	".mov":  {},
	".mp3":  {},
	".mp4":  {},
	".mpeg": {},
	".mpg":  {},
	".png":  {},
	".rar":  {},
	".tbz2": {},
	".tgz":  {},
	".txz":  {},
	".xz":   {},
	".zip":  {},
	".zipx": {},
}