package archive import ( "archive/tar" "bufio" "bytes" "compress/bzip2" "compress/gzip" "errors" "fmt" "io" "io/ioutil" "os" "os/exec" "path/filepath" "runtime" "strings" "syscall" "github.com/Sirupsen/logrus" "github.com/docker/docker/pkg/fileutils" "github.com/docker/docker/pkg/pools" "github.com/docker/docker/pkg/promise" "github.com/docker/docker/pkg/system" ) type ( // Archive is a type of io.ReadCloser which has two interfaces Read and Closer. Archive io.ReadCloser // Reader is a type of io.Reader. Reader io.Reader // Compression is the state represtents if compressed or not. Compression int // TarChownOptions wraps the chown options UID and GID. TarChownOptions struct { UID, GID int } // TarOptions wraps the tar options. TarOptions struct { IncludeFiles []string ExcludePatterns []string Compression Compression NoLchown bool ChownOpts *TarChownOptions IncludeSourceDir bool // When unpacking, specifies whether overwriting a directory with a // non-directory is allowed and vice versa. NoOverwriteDirNonDir bool // For each include when creating an archive, the included name will be // replaced with the matching name from this map. RebaseNames map[string]string } // Archiver allows the reuse of most utility functions of this package // with a pluggable Untar function. Archiver struct { Untar func(io.Reader, string, *TarOptions) error } // breakoutError is used to differentiate errors related to breaking out // When testing archive breakout in the unit tests, this error is expected // in order for the test to pass. breakoutError error ) var ( // ErrNotImplemented is the error message of function not implemented. ErrNotImplemented = errors.New("Function not implemented") defaultArchiver = &Archiver{Untar} ) const ( // Uncompressed represents the uncompressed. Uncompressed Compression = iota // Bzip2 is bzip2 compression algorithm. Bzip2 // Gzip is gzip compression algorithm. Gzip // Xz is xz compression algorithm. Xz ) // IsArchive checks if it is a archive by the header. func IsArchive(header []byte) bool { compression := DetectCompression(header) if compression != Uncompressed { return true } r := tar.NewReader(bytes.NewBuffer(header)) _, err := r.Next() return err == nil } // DetectCompression detects the compression algorithm of the source. func DetectCompression(source []byte) Compression { for compression, m := range map[Compression][]byte{ Bzip2: {0x42, 0x5A, 0x68}, Gzip: {0x1F, 0x8B, 0x08}, Xz: {0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00}, } { if len(source) < len(m) { logrus.Debugf("Len too short") continue } if bytes.Compare(m, source[:len(m)]) == 0 { return compression } } return Uncompressed } func xzDecompress(archive io.Reader) (io.ReadCloser, error) { args := []string{"xz", "-d", "-c", "-q"} return CmdStream(exec.Command(args[0], args[1:]...), archive) } // DecompressStream decompress the archive and returns a ReaderCloser with the decompressed archive. func DecompressStream(archive io.Reader) (io.ReadCloser, error) { p := pools.BufioReader32KPool buf := p.Get(archive) bs, err := buf.Peek(10) if err != nil { return nil, err } compression := DetectCompression(bs) switch compression { case Uncompressed: readBufWrapper := p.NewReadCloserWrapper(buf, buf) return readBufWrapper, nil case Gzip: gzReader, err := gzip.NewReader(buf) if err != nil { return nil, err } readBufWrapper := p.NewReadCloserWrapper(buf, gzReader) return readBufWrapper, nil case Bzip2: bz2Reader := bzip2.NewReader(buf) readBufWrapper := p.NewReadCloserWrapper(buf, bz2Reader) return readBufWrapper, nil case Xz: xzReader, err := xzDecompress(buf) if err != nil { return nil, err } readBufWrapper := p.NewReadCloserWrapper(buf, xzReader) return readBufWrapper, nil default: return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension()) } } // CompressStream compresses the dest with specified compression algorithm. func CompressStream(dest io.WriteCloser, compression Compression) (io.WriteCloser, error) { p := pools.BufioWriter32KPool buf := p.Get(dest) switch compression { case Uncompressed: writeBufWrapper := p.NewWriteCloserWrapper(buf, buf) return writeBufWrapper, nil case Gzip: gzWriter := gzip.NewWriter(dest) writeBufWrapper := p.NewWriteCloserWrapper(buf, gzWriter) return writeBufWrapper, nil case Bzip2, Xz: // archive/bzip2 does not support writing, and there is no xz support at all // However, this is not a problem as docker only currently generates gzipped tars return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension()) default: return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension()) } } // Extension returns the extension of a file that uses the specified compression algorithm. func (compression *Compression) Extension() string { switch *compression { case Uncompressed: return "tar" case Bzip2: return "tar.bz2" case Gzip: return "tar.gz" case Xz: return "tar.xz" } return "" } type tarAppender struct { TarWriter *tar.Writer Buffer *bufio.Writer // for hardlink mapping SeenFiles map[uint64]string } // canonicalTarName provides a platform-independent and consistent posix-style //path for files and directories to be archived regardless of the platform. func canonicalTarName(name string, isDir bool) (string, error) { name, err := CanonicalTarNameForPath(name) if err != nil { return "", err } // suffix with '/' for directories if isDir && !strings.HasSuffix(name, "/") { name += "/" } return name, nil } func (ta *tarAppender) addTarFile(path, name string) error { fi, err := os.Lstat(path) if err != nil { return err } link := "" if fi.Mode()&os.ModeSymlink != 0 { if link, err = os.Readlink(path); err != nil { return err } } hdr, err := tar.FileInfoHeader(fi, link) if err != nil { return err } hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode))) name, err = canonicalTarName(name, fi.IsDir()) if err != nil { return fmt.Errorf("tar: cannot canonicalize path: %v", err) } hdr.Name = name nlink, inode, err := setHeaderForSpecialDevice(hdr, ta, name, fi.Sys()) if err != nil { return err } // if it's a regular file and has more than 1 link, // it's hardlinked, so set the type flag accordingly if fi.Mode().IsRegular() && nlink > 1 { // a link should have a name that it links too // and that linked name should be first in the tar archive if oldpath, ok := ta.SeenFiles[inode]; ok { hdr.Typeflag = tar.TypeLink hdr.Linkname = oldpath hdr.Size = 0 // This Must be here for the writer math to add up! } else { ta.SeenFiles[inode] = name } } capability, _ := system.Lgetxattr(path, "security.capability") if capability != nil { hdr.Xattrs = make(map[string]string) hdr.Xattrs["security.capability"] = string(capability) } if err := ta.TarWriter.WriteHeader(hdr); err != nil { return err } if hdr.Typeflag == tar.TypeReg { file, err := os.Open(path) if err != nil { return err } ta.Buffer.Reset(ta.TarWriter) defer ta.Buffer.Reset(nil) _, err = io.Copy(ta.Buffer, file) file.Close() if err != nil { return err } err = ta.Buffer.Flush() if err != nil { return err } } return nil } func createTarFile(path, extractDir string, hdr *tar.Header, reader io.Reader, Lchown bool, chownOpts *TarChownOptions) error { // hdr.Mode is in linux format, which we can use for sycalls, // but for os.Foo() calls we need the mode converted to os.FileMode, // so use hdrInfo.Mode() (they differ for e.g. setuid bits) hdrInfo := hdr.FileInfo() switch hdr.Typeflag { case tar.TypeDir: // Create directory unless it exists as a directory already. // In that case we just want to merge the two if fi, err := os.Lstat(path); !(err == nil && fi.IsDir()) { if err := os.Mkdir(path, hdrInfo.Mode()); err != nil { return err } } case tar.TypeReg, tar.TypeRegA: // Source is regular file file, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, hdrInfo.Mode()) if err != nil { return err } if _, err := io.Copy(file, reader); err != nil { file.Close() return err } file.Close() case tar.TypeBlock, tar.TypeChar, tar.TypeFifo: // Handle this is an OS-specific way if err := handleTarTypeBlockCharFifo(hdr, path); err != nil { return err } case tar.TypeLink: targetPath := filepath.Join(extractDir, hdr.Linkname) // check for hardlink breakout if !strings.HasPrefix(targetPath, extractDir) { return breakoutError(fmt.Errorf("invalid hardlink %q -> %q", targetPath, hdr.Linkname)) } if err := os.Link(targetPath, path); err != nil { return err } case tar.TypeSymlink: // path -> hdr.Linkname = targetPath // e.g. /extractDir/path/to/symlink -> ../2/file = /extractDir/path/2/file targetPath := filepath.Join(filepath.Dir(path), hdr.Linkname) // the reason we don't need to check symlinks in the path (with FollowSymlinkInScope) is because // that symlink would first have to be created, which would be caught earlier, at this very check: if !strings.HasPrefix(targetPath, extractDir) { return breakoutError(fmt.Errorf("invalid symlink %q -> %q", path, hdr.Linkname)) } if err := os.Symlink(hdr.Linkname, path); err != nil { return err } case tar.TypeXGlobalHeader: logrus.Debugf("PAX Global Extended Headers found and ignored") return nil default: return fmt.Errorf("Unhandled tar header type %d\n", hdr.Typeflag) } // Lchown is not supported on Windows. if Lchown && runtime.GOOS != "windows" { if chownOpts == nil { chownOpts = &TarChownOptions{UID: hdr.Uid, GID: hdr.Gid} } if err := os.Lchown(path, chownOpts.UID, chownOpts.GID); err != nil { return err } } for key, value := range hdr.Xattrs { if err := system.Lsetxattr(path, key, []byte(value), 0); err != nil { return err } } // There is no LChmod, so ignore mode for symlink. Also, this // must happen after chown, as that can modify the file mode if err := handleLChmod(hdr, path, hdrInfo); err != nil { return err } ts := []syscall.Timespec{timeToTimespec(hdr.AccessTime), timeToTimespec(hdr.ModTime)} // syscall.UtimesNano doesn't support a NOFOLLOW flag atm if hdr.Typeflag == tar.TypeLink { if fi, err := os.Lstat(hdr.Linkname); err == nil && (fi.Mode()&os.ModeSymlink == 0) { if err := system.UtimesNano(path, ts); err != nil && err != system.ErrNotSupportedPlatform { return err } } } else if hdr.Typeflag != tar.TypeSymlink { if err := system.UtimesNano(path, ts); err != nil && err != system.ErrNotSupportedPlatform { return err } } else { if err := system.LUtimesNano(path, ts); err != nil && err != system.ErrNotSupportedPlatform { return err } } return nil } // Tar creates an archive from the directory at `path`, and returns it as a // stream of bytes. func Tar(path string, compression Compression) (io.ReadCloser, error) { return TarWithOptions(path, &TarOptions{Compression: compression}) } // TarWithOptions creates an archive from the directory at `path`, only including files whose relative // paths are included in `options.IncludeFiles` (if non-nil) or not in `options.ExcludePatterns`. func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error) { // Fix the source path to work with long path names. This is a no-op // on platforms other than Windows. srcPath = fixVolumePathPrefix(srcPath) patterns, patDirs, exceptions, err := fileutils.CleanPatterns(options.ExcludePatterns) if err != nil { return nil, err } pipeReader, pipeWriter := io.Pipe() compressWriter, err := CompressStream(pipeWriter, options.Compression) if err != nil { return nil, err } go func() { ta := &tarAppender{ TarWriter: tar.NewWriter(compressWriter), Buffer: pools.BufioWriter32KPool.Get(nil), SeenFiles: make(map[uint64]string), } defer func() { // Make sure to check the error on Close. if err := ta.TarWriter.Close(); err != nil { logrus.Debugf("Can't close tar writer: %s", err) } if err := compressWriter.Close(); err != nil { logrus.Debugf("Can't close compress writer: %s", err) } if err := pipeWriter.Close(); err != nil { logrus.Debugf("Can't close pipe writer: %s", err) } }() // this buffer is needed for the duration of this piped stream defer pools.BufioWriter32KPool.Put(ta.Buffer) // In general we log errors here but ignore them because // during e.g. a diff operation the container can continue // mutating the filesystem and we can see transient errors // from this stat, err := os.Lstat(srcPath) if err != nil { return } if !stat.IsDir() { // We can't later join a non-dir with any includes because the // 'walk' will error if "file/." is stat-ed and "file" is not a // directory. So, we must split the source path and use the // basename as the include. if len(options.IncludeFiles) > 0 { logrus.Warn("Tar: Can't archive a file with includes") } dir, base := SplitPathDirEntry(srcPath) srcPath = dir options.IncludeFiles = []string{base} } if len(options.IncludeFiles) == 0 { options.IncludeFiles = []string{"."} } seen := make(map[string]bool) for _, include := range options.IncludeFiles { rebaseName := options.RebaseNames[include] walkRoot := getWalkRoot(srcPath, include) filepath.Walk(walkRoot, func(filePath string, f os.FileInfo, err error) error { if err != nil { logrus.Debugf("Tar: Can't stat file %s to tar: %s", srcPath, err) return nil } relFilePath, err := filepath.Rel(srcPath, filePath) if err != nil || (!options.IncludeSourceDir && relFilePath == "." && f.IsDir()) { // Error getting relative path OR we are looking // at the source directory path. Skip in both situations. return nil } if options.IncludeSourceDir && include == "." && relFilePath != "." { relFilePath = strings.Join([]string{".", relFilePath}, string(filepath.Separator)) } skip := false // If "include" is an exact match for the current file // then even if there's an "excludePatterns" pattern that // matches it, don't skip it. IOW, assume an explicit 'include' // is asking for that file no matter what - which is true // for some files, like .dockerignore and Dockerfile (sometimes) if include != relFilePath { skip, err = fileutils.OptimizedMatches(relFilePath, patterns, patDirs) if err != nil { logrus.Debugf("Error matching %s: %v", relFilePath, err) return err } } if skip { if !exceptions && f.IsDir() { return filepath.SkipDir } return nil } if seen[relFilePath] { return nil } seen[relFilePath] = true // Rename the base resource. if rebaseName != "" { var replacement string if rebaseName != string(filepath.Separator) { // Special case the root directory to replace with an // empty string instead so that we don't end up with // double slashes in the paths. replacement = rebaseName } relFilePath = strings.Replace(relFilePath, include, replacement, 1) } if err := ta.addTarFile(filePath, relFilePath); err != nil { logrus.Debugf("Can't add file %s to tar: %s", filePath, err) } return nil }) } }() return pipeReader, nil } // Unpack unpacks the decompressedArchive to dest with options. func Unpack(decompressedArchive io.Reader, dest string, options *TarOptions) error { tr := tar.NewReader(decompressedArchive) trBuf := pools.BufioReader32KPool.Get(nil) defer pools.BufioReader32KPool.Put(trBuf) var dirs []*tar.Header // Iterate through the files in the archive. loop: for { hdr, err := tr.Next() if err == io.EOF { // end of tar archive break } if err != nil { return err } // Normalize name, for safety and for a simple is-root check // This keeps "../" as-is, but normalizes "/../" to "/". Or Windows: // This keeps "..\" as-is, but normalizes "\..\" to "\". hdr.Name = filepath.Clean(hdr.Name) for _, exclude := range options.ExcludePatterns { if strings.HasPrefix(hdr.Name, exclude) { continue loop } } // After calling filepath.Clean(hdr.Name) above, hdr.Name will now be in // the filepath format for the OS on which the daemon is running. Hence // the check for a slash-suffix MUST be done in an OS-agnostic way. if !strings.HasSuffix(hdr.Name, string(os.PathSeparator)) { // Not the root directory, ensure that the parent directory exists parent := filepath.Dir(hdr.Name) parentPath := filepath.Join(dest, parent) if _, err := os.Lstat(parentPath); err != nil && os.IsNotExist(err) { err = system.MkdirAll(parentPath, 0777) if err != nil { return err } } } path := filepath.Join(dest, hdr.Name) rel, err := filepath.Rel(dest, path) if err != nil { return err } if strings.HasPrefix(rel, ".."+string(os.PathSeparator)) { return breakoutError(fmt.Errorf("%q is outside of %q", hdr.Name, dest)) } // If path exits we almost always just want to remove and replace it // The only exception is when it is a directory *and* the file from // the layer is also a directory. Then we want to merge them (i.e. // just apply the metadata from the layer). if fi, err := os.Lstat(path); err == nil { if options.NoOverwriteDirNonDir && fi.IsDir() && hdr.Typeflag != tar.TypeDir { // If NoOverwriteDirNonDir is true then we cannot replace // an existing directory with a non-directory from the archive. return fmt.Errorf("cannot overwrite directory %q with non-directory %q", path, dest) } if options.NoOverwriteDirNonDir && !fi.IsDir() && hdr.Typeflag == tar.TypeDir { // If NoOverwriteDirNonDir is true then we cannot replace // an existing non-directory with a directory from the archive. return fmt.Errorf("cannot overwrite non-directory %q with directory %q", path, dest) } if fi.IsDir() && hdr.Name == "." { continue } if !(fi.IsDir() && hdr.Typeflag == tar.TypeDir) { if err := os.RemoveAll(path); err != nil { return err } } } trBuf.Reset(tr) if err := createTarFile(path, dest, hdr, trBuf, !options.NoLchown, options.ChownOpts); err != nil { return err } // Directory mtimes must be handled at the end to avoid further // file creation in them to modify the directory mtime if hdr.Typeflag == tar.TypeDir { dirs = append(dirs, hdr) } } for _, hdr := range dirs { path := filepath.Join(dest, hdr.Name) ts := []syscall.Timespec{timeToTimespec(hdr.AccessTime), timeToTimespec(hdr.ModTime)} if err := syscall.UtimesNano(path, ts); err != nil { return err } } return nil } // Untar reads a stream of bytes from `archive`, parses it as a tar archive, // and unpacks it into the directory at `dest`. // The archive may be compressed with one of the following algorithms: // identity (uncompressed), gzip, bzip2, xz. // FIXME: specify behavior when target path exists vs. doesn't exist. func Untar(tarArchive io.Reader, dest string, options *TarOptions) error { return untarHandler(tarArchive, dest, options, true) } // UntarUncompressed reads a stream of bytes from `archive`, parses it as a tar archive, // and unpacks it into the directory at `dest`. // The archive must be an uncompressed stream. func UntarUncompressed(tarArchive io.Reader, dest string, options *TarOptions) error { return untarHandler(tarArchive, dest, options, false) } // Handler for teasing out the automatic decompression func untarHandler(tarArchive io.Reader, dest string, options *TarOptions, decompress bool) error { if tarArchive == nil { return fmt.Errorf("Empty archive") } dest = filepath.Clean(dest) if options == nil { options = &TarOptions{} } if options.ExcludePatterns == nil { options.ExcludePatterns = []string{} } r := tarArchive if decompress { decompressedArchive, err := DecompressStream(tarArchive) if err != nil { return err } defer decompressedArchive.Close() r = decompressedArchive } return Unpack(r, dest, options) } // TarUntar is a convenience function which calls Tar and Untar, with the output of one piped into the other. // If either Tar or Untar fails, TarUntar aborts and returns the error. func (archiver *Archiver) TarUntar(src, dst string) error { logrus.Debugf("TarUntar(%s %s)", src, dst) archive, err := TarWithOptions(src, &TarOptions{Compression: Uncompressed}) if err != nil { return err } defer archive.Close() return archiver.Untar(archive, dst, nil) } // TarUntar is a convenience function which calls Tar and Untar, with the output of one piped into the other. // If either Tar or Untar fails, TarUntar aborts and returns the error. func TarUntar(src, dst string) error { return defaultArchiver.TarUntar(src, dst) } // UntarPath untar a file from path to a destination, src is the source tar file path. func (archiver *Archiver) UntarPath(src, dst string) error { archive, err := os.Open(src) if err != nil { return err } defer archive.Close() if err := archiver.Untar(archive, dst, nil); err != nil { return err } return nil } // UntarPath is a convenience function which looks for an archive // at filesystem path `src`, and unpacks it at `dst`. func UntarPath(src, dst string) error { return defaultArchiver.UntarPath(src, dst) } // CopyWithTar creates a tar archive of filesystem path `src`, and // unpacks it at filesystem path `dst`. // The archive is streamed directly with fixed buffering and no // intermediary disk IO. func (archiver *Archiver) CopyWithTar(src, dst string) error { srcSt, err := os.Stat(src) if err != nil { return err } if !srcSt.IsDir() { return archiver.CopyFileWithTar(src, dst) } // Create dst, copy src's content into it logrus.Debugf("Creating dest directory: %s", dst) if err := system.MkdirAll(dst, 0755); err != nil { return err } logrus.Debugf("Calling TarUntar(%s, %s)", src, dst) return archiver.TarUntar(src, dst) } // CopyWithTar creates a tar archive of filesystem path `src`, and // unpacks it at filesystem path `dst`. // The archive is streamed directly with fixed buffering and no // intermediary disk IO. func CopyWithTar(src, dst string) error { return defaultArchiver.CopyWithTar(src, dst) } // CopyFileWithTar emulates the behavior of the 'cp' command-line // for a single file. It copies a regular file from path `src` to // path `dst`, and preserves all its metadata. func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) { logrus.Debugf("CopyFileWithTar(%s, %s)", src, dst) srcSt, err := os.Stat(src) if err != nil { return err } if srcSt.IsDir() { return fmt.Errorf("Can't copy a directory") } // Clean up the trailing slash. This must be done in an operating // system specific manner. if dst[len(dst)-1] == os.PathSeparator { dst = filepath.Join(dst, filepath.Base(src)) } // Create the holding directory if necessary if err := system.MkdirAll(filepath.Dir(dst), 0700); err != nil { return err } r, w := io.Pipe() errC := promise.Go(func() error { defer w.Close() srcF, err := os.Open(src) if err != nil { return err } defer srcF.Close() hdr, err := tar.FileInfoHeader(srcSt, "") if err != nil { return err } hdr.Name = filepath.Base(dst) hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode))) tw := tar.NewWriter(w) defer tw.Close() if err := tw.WriteHeader(hdr); err != nil { return err } if _, err := io.Copy(tw, srcF); err != nil { return err } return nil }) defer func() { if er := <-errC; err != nil { err = er } }() return archiver.Untar(r, filepath.Dir(dst), nil) } // CopyFileWithTar emulates the behavior of the 'cp' command-line // for a single file. It copies a regular file from path `src` to // path `dst`, and preserves all its metadata. // // Destination handling is in an operating specific manner depending // where the daemon is running. If `dst` ends with a trailing slash // the final destination path will be `dst/base(src)` (Linux) or // `dst\base(src)` (Windows). func CopyFileWithTar(src, dst string) (err error) { return defaultArchiver.CopyFileWithTar(src, dst) } // CmdStream executes a command, and returns its stdout as a stream. // If the command fails to run or doesn't complete successfully, an error // will be returned, including anything written on stderr. func CmdStream(cmd *exec.Cmd, input io.Reader) (io.ReadCloser, error) { if input != nil { stdin, err := cmd.StdinPipe() if err != nil { return nil, err } // Write stdin if any go func() { io.Copy(stdin, input) stdin.Close() }() } stdout, err := cmd.StdoutPipe() if err != nil { return nil, err } stderr, err := cmd.StderrPipe() if err != nil { return nil, err } pipeR, pipeW := io.Pipe() errChan := make(chan []byte) // Collect stderr, we will use it in case of an error go func() { errText, e := ioutil.ReadAll(stderr) if e != nil { errText = []byte("(...couldn't fetch stderr: " + e.Error() + ")") } errChan <- errText }() // Copy stdout to the returned pipe go func() { _, err := io.Copy(pipeW, stdout) if err != nil { pipeW.CloseWithError(err) } errText := <-errChan if err := cmd.Wait(); err != nil { pipeW.CloseWithError(fmt.Errorf("%s: %s", err, errText)) } else { pipeW.Close() } }() // Run the command and return the pipe if err := cmd.Start(); err != nil { return nil, err } return pipeR, nil } // NewTempArchive reads the content of src into a temporary file, and returns the contents // of that file as an archive. The archive can only be read once - as soon as reading completes, // the file will be deleted. func NewTempArchive(src Archive, dir string) (*TempArchive, error) { f, err := ioutil.TempFile(dir, "") if err != nil { return nil, err } if _, err := io.Copy(f, src); err != nil { return nil, err } if _, err := f.Seek(0, 0); err != nil { return nil, err } st, err := f.Stat() if err != nil { return nil, err } size := st.Size() return &TempArchive{File: f, Size: size}, nil } // TempArchive is a temporary archive. The archive can only be read once - as soon as reading completes, // the file will be deleted. type TempArchive struct { *os.File Size int64 // Pre-computed from Stat().Size() as a convenience read int64 closed bool } // Close closes the underlying file if it's still open, or does a no-op // to allow callers to try to close the TempArchive multiple times safely. func (archive *TempArchive) Close() error { if archive.closed { return nil } archive.closed = true return archive.File.Close() } func (archive *TempArchive) Read(data []byte) (int, error) { n, err := archive.File.Read(data) archive.read += int64(n) if err != nil || archive.read == archive.Size { archive.Close() os.Remove(archive.File.Name()) } return n, err }