tarfile.go

package main

import (
	"archive/tar"
	"io"
	"log"
	"os"
	"path/filepath"
)

func untar(tarball, target string) error {
	hardLinks := make(map[string]string)
	reader, err := os.Open(tarball)
	if err != nil {
		return err
	}
	defer reader.Close()
	tarReader := tar.NewReader(reader)

	for {
		header, err := tarReader.Next()
		if err == io.EOF {
			break
		} else if err != nil {
			return err
		}

		path := filepath.Join(target, header.Name)
		info := header.FileInfo()

		switch header.Typeflag {
		case tar.TypeDir:
			if err = os.MkdirAll(path, info.Mode()); err != nil {
				return err
			}
			continue

		case tar.TypeLink:
			/* Store details of hard links, which we process finally */
			linkPath := filepath.Join(target, header.Linkname)
			linkPath2 := filepath.Join(target, header.Name)
			hardLinks[linkPath2] = linkPath
			continue

		case tar.TypeSymlink:
			linkPath := filepath.Join(target, header.Name)
			if err := os.Symlink(header.Linkname, linkPath); err != nil {
				if os.IsExist(err) {
					continue
				}
				return err
			}
			continue

		case tar.TypeReg:
			/* Ensure any missing directories are created */
			if _, err := os.Stat(filepath.Dir(path)); os.IsNotExist(err) {
				os.MkdirAll(filepath.Dir(path), 0755)
			}
			file, err := os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, info.Mode())
			if os.IsExist(err) {
				continue
			}
			if err != nil {
				return err
			}
			_, err = io.Copy(file, tarReader)
			file.Close()
			if err != nil {
				return err
			}

		default:
			log.Printf("Warning: File type %d unhandled by untar function!\n", header.Typeflag)
		}
	}

	/* To create hard links the targets must exist, so we do this finally */
	for k, v := range hardLinks {
		if err := os.Link(v, k); err != nil {
			return err
		}
	}
	return nil
}