From a96a26c62f6333e61134759256db43a7f5946631 Mon Sep 17 00:00:00 2001
From: Alexander Larsson <alexl@redhat.com>
Date: Tue, 17 Dec 2013 14:19:48 +0100
Subject: [PATCH 1/2] Handle compressed tars in ApplyLayer

When pulling from a registry we get a compressed tar archive, so
we need to wrap the stream in the right kind of compress reader.

Unfortunately go doesn't have an Xz decompression method, but I
don't think any docker layers use that atm anyway.
---
 archive/archive.go | 31 +++++++++++++++++++++++++++++++
 archive/diff.go    |  5 +++++
 2 files changed, 36 insertions(+)

diff --git a/archive/archive.go b/archive/archive.go
index 838f8f6e7f..78d5aae18c 100644
--- a/archive/archive.go
+++ b/archive/archive.go
@@ -3,6 +3,8 @@ package archive
 import (
 	"archive/tar"
 	"bytes"
+	"compress/gzip"
+	"compress/bzip2"
 	"fmt"
 	"github.com/dotcloud/docker/utils"
 	"io"
@@ -59,6 +61,35 @@ func DetectCompression(source []byte) Compression {
 	return Uncompressed
 }
 
+func DecompressStream(archive io.Reader) (io.Reader, error) {
+	buf := make([]byte, 10)
+	totalN := 0
+	for totalN < 10 {
+		n, err := archive.Read(buf[totalN:])
+		if err != nil {
+			if err == io.EOF {
+				return nil, fmt.Errorf("Tarball too short")
+			}
+			return nil, err
+		}
+		totalN += n
+		utils.Debugf("[tar autodetect] n: %d", n)
+	}
+	compression := DetectCompression(buf)
+	wrap := io.MultiReader(bytes.NewReader(buf), archive)
+
+	switch compression {
+	case Uncompressed:
+		return wrap, nil
+	case Gzip:
+		return gzip.NewReader(wrap)
+	case Bzip2:
+		return bzip2.NewReader(wrap), nil
+	default:
+		return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension())
+	}
+}
+
 func (compression *Compression) Flag() string {
 	switch *compression {
 	case Bzip2:
diff --git a/archive/diff.go b/archive/diff.go
index 87457f38c1..72a53de02e 100644
--- a/archive/diff.go
+++ b/archive/diff.go
@@ -34,6 +34,11 @@ func ApplyLayer(dest string, layer Archive) error {
 	oldmask := syscall.Umask(0)
 	defer syscall.Umask(oldmask)
 
+	layer, err := DecompressStream(layer)
+	if err != nil {
+		return err
+	}
+
 	tr := tar.NewReader(layer)
 
 	var dirs []*tar.Header

From b8a4f570fb31091f43caeba5b824ae38a5bc69e8 Mon Sep 17 00:00:00 2001
From: Alexander Larsson <alexl@redhat.com>
Date: Wed, 18 Dec 2013 10:50:22 +0100
Subject: [PATCH 2/2] archive: Re-add XZ compression support

This shells out to the xz binary to support .tar.xz layers, as
there is no compression/xz support in go.
---
 archive/archive.go | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/archive/archive.go b/archive/archive.go
index 78d5aae18c..ae2c030cb7 100644
--- a/archive/archive.go
+++ b/archive/archive.go
@@ -61,6 +61,12 @@ func DetectCompression(source []byte) Compression {
 	return Uncompressed
 }
 
+func xzDecompress(archive io.Reader) (io.Reader, error) {
+	args := []string{"xz", "-d", "-c", "-q"}
+
+	return CmdStream(exec.Command(args[0], args[1:]...), archive, nil)
+}
+
 func DecompressStream(archive io.Reader) (io.Reader, error) {
 	buf := make([]byte, 10)
 	totalN := 0
@@ -85,6 +91,8 @@ func DecompressStream(archive io.Reader) (io.Reader, error) {
 		return gzip.NewReader(wrap)
 	case Bzip2:
 		return bzip2.NewReader(wrap), nil
+	case Xz:
+		return xzDecompress(wrap)
 	default:
 		return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension())
 	}
@@ -186,7 +194,7 @@ func TarFilter(path string, options *TarOptions) (io.Reader, error) {
 		}
 	}
 
-	return CmdStream(exec.Command(args[0], args[1:]...), &files, func() {
+	return CmdStream(exec.Command(args[0], args[1:]...), bytes.NewBufferString(files), func() {
 		if tmpDir != "" {
 			_ = os.RemoveAll(tmpDir)
 		}
@@ -332,7 +340,7 @@ func CopyFileWithTar(src, dst string) error {
 // 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 *string, atEnd func()) (io.Reader, error) {
+func CmdStream(cmd *exec.Cmd, input io.Reader, atEnd func()) (io.Reader, error) {
 	if input != nil {
 		stdin, err := cmd.StdinPipe()
 		if err != nil {
@@ -343,7 +351,7 @@ func CmdStream(cmd *exec.Cmd, input *string, atEnd func()) (io.Reader, error) {
 		}
 		// Write stdin if any
 		go func() {
-			_, _ = stdin.Write([]byte(*input))
+			io.Copy(stdin, input)
 			stdin.Close()
 		}()
 	}