gtar.go

package main

import (
	"archive/tar"
	"compress/gzip"
	"flag"
	"io"
	"path"
	"log"
	"os"
	"fmt"
)

const uploadbloks int64 = 100 * 1024 * 1024

func isEmptyBuffer(buf []byte) bool {
	for _, b := range buf {
		if b != '\x00' {
			return false
		}
	}
	return true
}

// shamelessly copied from io.copybuffer and adapted to skip zero writes
func copy(src io.Reader, dst *os.File) (written int64, err error) {
	buf := make([]byte, 1024*4)
	var seek int64

	for {
		nr, er := src.Read(buf)
		if nr > 0 {
			if isEmptyBuffer(buf[0:nr]) {
				seek += int64(nr)
				continue
			}
			if seek != 0 {
				_, err := dst.Seek(seek, 1)
				if err != nil {
					return 0, err
				}
				seek = 0
			}
			nw, ew := dst.Write(buf[0:nr])
			if nw > 0 {
				written += int64(nw)
			}
			if ew != nil {
				err = ew
				break
			}
			if nr != nw {
				err = io.ErrShortWrite
				break
			}
		}
		if er != nil {
			if er != io.EOF {
				err = er
			}
			break
		}
	}
	return
}

func writeFile(filepath string, size int64, reader *tar.Reader) error {
	file, err := os.OpenFile(filepath, os.O_RDWR | os.O_CREATE, 0666)
	if err != nil {
		return err
	}
	file.Truncate(size)
	defer file.Close()
	datawritten, err := copy(reader, file)
	if err != nil {
		return err
	}
	file.Sync()
	log.Printf("Written %d data", datawritten)
	return nil
}


func writeFiles(reader io.Reader) error {
	gzipreader, err := gzip.NewReader(reader)
	if err != nil {
		return err
	}
	tarreader := tar.NewReader(gzipreader)
	for {
		hdr, err := tarreader.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		log.Printf("Extracting %s", hdr.Name)
		err = writeFile(path.Base(hdr.Name), hdr.Size, tarreader)
		if err != nil {
			return err
		}
	}
	return nil
}

func main() {
	var file string
	flag.StringVar(&file, "file", "", "File to extract")
	flag.Parse()
	var reader io.ReadCloser
	if file == "-" {
		reader, _ = os.Open("/dev/stdin")
	} else {
		reader, _ = os.Open(file)
	}
	defer reader.Close()
	err := writeFiles(reader)
	if err != nil {
		fmt.Print(err)
	}
}