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tar.go
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tar.go
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package archiver
import (
"archive/tar"
"bytes"
"fmt"
"io"
"os"
"path/filepath"
"strconv"
"strings"
)
// Tar is for Tar format
var Tar tarFormat
func init() {
RegisterFormat("Tar", Tar)
}
type tarFormat struct{}
func (tarFormat) Match(filename string) bool {
return strings.HasSuffix(strings.ToLower(filename), ".tar") || isTar(filename)
}
const tarBlockSize int = 512
// isTar checks the file has the Tar format header by reading its beginning
// block.
func isTar(tarPath string) bool {
f, err := os.Open(tarPath)
if err != nil {
return false
}
defer f.Close()
buf := make([]byte, tarBlockSize)
if _, err = io.ReadFull(f, buf); err != nil {
return false
}
return hasTarHeader(buf)
}
// hasTarHeader checks passed bytes has a valid tar header or not. buf must
// contain at least 512 bytes and if not, it always returns false.
func hasTarHeader(buf []byte) bool {
if len(buf) < tarBlockSize {
return false
}
b := buf[148:156]
b = bytes.Trim(b, " \x00") // clean up all spaces and null bytes
if len(b) == 0 {
return false // unknown format
}
hdrSum, err := strconv.ParseUint(string(b), 8, 64)
if err != nil {
return false
}
// According to the go official archive/tar, Sun tar uses signed byte
// values so this calcs both signed and unsigned
var usum uint64
var sum int64
for i, c := range buf {
if 148 <= i && i < 156 {
c = ' ' // checksum field itself is counted as branks
}
usum += uint64(uint8(c))
sum += int64(int8(c))
}
if hdrSum != usum && int64(hdrSum) != sum {
return false // invalid checksum
}
return true
}
// Write outputs a .tar file to a Writer 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.
func (tarFormat) Write(output io.Writer, filePaths []string) error {
return writeTar(filePaths, output, "")
}
// Make creates a .tar file at tarPath 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.
func (tarFormat) Make(tarPath string, filePaths []string) error {
out, err := os.Create(tarPath)
if err != nil {
return fmt.Errorf("error creating %s: %v", tarPath, err)
}
defer out.Close()
return writeTar(filePaths, out, tarPath)
}
func writeTar(filePaths []string, output io.Writer, dest string) error {
tarWriter := tar.NewWriter(output)
defer tarWriter.Close()
return tarball(filePaths, tarWriter, dest)
}
// tarball writes all files listed in filePaths into tarWriter, which is
// writing into a file located at dest.
func tarball(filePaths []string, tarWriter *tar.Writer, dest string) error {
for _, fpath := range filePaths {
err := tarFile(tarWriter, fpath, dest)
if err != nil {
return err
}
}
return nil
}
// tarFile writes the file at source into tarWriter. It does so
// recursively for directories.
func tarFile(tarWriter *tar.Writer, source, dest 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(path string, info os.FileInfo, err error) error {
if err != nil {
return fmt.Errorf("error walking to %s: %v", path, err)
}
header, err := tar.FileInfoHeader(info, path)
if err != nil {
return fmt.Errorf("%s: making header: %v", path, err)
}
if baseDir != "" {
header.Name = filepath.Join(baseDir, strings.TrimPrefix(path, source))
}
if header.Name == dest {
// our new tar file is inside the directory being archived; skip it
return nil
}
if info.IsDir() {
header.Name += "/"
}
err = tarWriter.WriteHeader(header)
if err != nil {
return fmt.Errorf("%s: writing header: %v", path, err)
}
if info.IsDir() {
return nil
}
if header.Typeflag == tar.TypeReg {
file, err := os.Open(path)
if err != nil {
return fmt.Errorf("%s: open: %v", path, err)
}
defer file.Close()
_, err = io.CopyN(tarWriter, file, info.Size())
if err != nil && err != io.EOF {
return fmt.Errorf("%s: copying contents: %v", path, err)
}
}
return nil
})
}
// Read untars a .tar file read from a Reader and puts
// the contents into destination.
func (tarFormat) Read(input io.Reader, destination string) error {
return untar(tar.NewReader(input), destination)
}
// Open untars source and puts the contents into destination.
func (tarFormat) Open(source, destination string) error {
f, err := os.Open(source)
if err != nil {
return fmt.Errorf("%s: failed to open archive: %v", source, err)
}
defer f.Close()
return Tar.Read(f, destination)
}
// untar un-tarballs the contents of tr into destination.
func untar(tr *tar.Reader, destination string) error {
for {
header, err := tr.Next()
if err == io.EOF {
break
} else if err != nil {
return err
}
if err := untarFile(tr, header, destination); err != nil {
return err
}
}
return nil
}
// untarFile untars a single file from tr with header header into destination.
func untarFile(tr *tar.Reader, header *tar.Header, destination string) error {
switch header.Typeflag {
case tar.TypeDir:
return mkdir(filepath.Join(destination, header.Name))
case tar.TypeReg, tar.TypeRegA, tar.TypeChar, tar.TypeBlock, tar.TypeFifo:
return writeNewFile(filepath.Join(destination, header.Name), tr, header.FileInfo().Mode())
case tar.TypeSymlink:
return writeNewSymbolicLink(filepath.Join(destination, header.Name), header.Linkname)
case tar.TypeLink:
return writeNewHardLink(filepath.Join(destination, header.Name), filepath.Join(destination, header.Linkname))
default:
return fmt.Errorf("%s: unknown type flag: %c", header.Name, header.Typeflag)
}
}