Remove unused functions from archive.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

12 files changed, 104 insertions, 185 deletions

diff --git a/container/container_unix.go b/container/container_unix.go
index b46e100bb1..530343d5ca 100644
--- a/container/container_unix.go
+++ b/container/container_unix.go
@@ -425,7 +425,7 @@ func copyExistingContents(source, destination string) error {
 		}
 		if len(srcList) == 0 {
 			// If the source volume is empty, copies files from the root into the volume
-			if err := chrootarchive.CopyWithTar(source, destination); err != nil {
+			if err := chrootarchive.NewArchiver(nil).CopyWithTar(source, destination); err != nil {
 				return err
 			}
 		}
diff --git a/daemon/archive.go b/daemon/archive.go
index c41298df0e..79b2ae362f 100644
--- a/daemon/archive.go
+++ b/daemon/archive.go
@@ -413,12 +413,7 @@ func (daemon *Daemon) CopyOnBuild(cID, destPath, srcRoot, srcPath string, decomp
 		destExists = false
 	}
 
-	archiver := &archive.Archiver{
-		Untar:   chrootarchive.Untar,
-		UIDMaps: daemon.idMappings.UIDs(),
-		GIDMaps: daemon.idMappings.GIDs(),
-	}
-
+	archiver := chrootarchive.NewArchiver(daemon.idMappings)
 	src, err := os.Stat(fullSrcPath)
 	if err != nil {
 		return err
diff --git a/daemon/archive_tarcopyoptions_unix.go b/daemon/archive_tarcopyoptions_unix.go
index 7b68bc463d..e7f47058a4 100644
--- a/daemon/archive_tarcopyoptions_unix.go
+++ b/daemon/archive_tarcopyoptions_unix.go
@@ -20,9 +20,6 @@ func (daemon *Daemon) tarCopyOptions(container *container.Container, noOverwrite
 
 	return &archive.TarOptions{
 		NoOverwriteDirNonDir: noOverwriteDirNonDir,
-		ChownOpts: &archive.TarChownOptions{
-			UID: user.Uid,
-			GID: user.Gid,
-		},
+		ChownOpts:            idtools.IDPair{UID: user.Uid, GID: user.Gid},
 	}, nil
 }
diff --git a/daemon/graphdriver/vfs/driver.go b/daemon/graphdriver/vfs/driver.go
index 846215e810..26dc89c36d 100644
--- a/daemon/graphdriver/vfs/driver.go
+++ b/daemon/graphdriver/vfs/driver.go
@@ -15,7 +15,7 @@ import (
 
 var (
 	// CopyWithTar defines the copy method to use.
-	CopyWithTar = chrootarchive.CopyWithTar
+	CopyWithTar = chrootarchive.NewArchiver(nil).CopyWithTar
 )
 
 func init() {
diff --git a/distribution/registry_unit_test.go b/distribution/registry_unit_test.go
index ebe6ecad97..910061f45a 100644
--- a/distribution/registry_unit_test.go
+++ b/distribution/registry_unit_test.go
@@ -152,7 +152,7 @@ func testDirectory(templateDir string) (dir string, err error) {
 		return
 	}
 	if templateDir != "" {
-		if err = archive.CopyWithTar(templateDir, dir); err != nil {
+		if err = archive.NewDefaultArchiver().CopyWithTar(templateDir, dir); err != nil {
 			return
 		}
 	}
diff --git a/layer/layer_test.go b/layer/layer_test.go
index 5c4da4f9a9..56340d3012 100644
--- a/layer/layer_test.go
+++ b/layer/layer_test.go
@@ -20,7 +20,8 @@ import (
 
 func init() {
 	graphdriver.ApplyUncompressedLayer = archive.UnpackLayer
-	vfs.CopyWithTar = archive.CopyWithTar
+	defaultArchiver := archive.NewDefaultArchiver()
+	vfs.CopyWithTar = defaultArchiver.CopyWithTar
 }
 
 func newVFSGraphDriver(td string) (graphdriver.Driver, error) {
diff --git a/pkg/archive/archive.go b/pkg/archive/archive.go
index 30b3c5b36f..bf5ed85566 100644
--- a/pkg/archive/archive.go
+++ b/pkg/archive/archive.go
@@ -6,7 +6,6 @@ import (
 	"bytes"
 	"compress/bzip2"
 	"compress/gzip"
-	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -31,10 +30,6 @@ type (
 	Compression int
 	// WhiteoutFormat is the format of whiteouts unpacked
 	WhiteoutFormat int
-	// TarChownOptions wraps the chown options UID and GID.
-	TarChownOptions struct {
-		UID, GID int
-	}
 
 	// TarOptions wraps the tar options.
 	TarOptions struct {
@@ -44,7 +39,7 @@ type (
 		NoLchown         bool
 		UIDMaps          []idtools.IDMap
 		GIDMaps          []idtools.IDMap
-		ChownOpts        *TarChownOptions
+		ChownOpts        idtools.IDPair
 		IncludeSourceDir bool
 		// WhiteoutFormat is the expected on disk format for whiteout files.
 		// This format will be converted to the standard format on pack
@@ -58,33 +53,26 @@ type (
 		RebaseNames map[string]string
 		InUserNS    bool
 	}
-
-	// Archiver allows the reuse of most utility functions of this package
-	// with a pluggable Untar function. Also, to facilitate the passing of
-	// specific id mappings for untar, an archiver can be created with maps
-	// which will then be passed to Untar operations
-	Archiver struct {
-		Untar   func(io.Reader, string, *TarOptions) error
-		UIDMaps []idtools.IDMap
-		GIDMaps []idtools.IDMap
-	}
-
-	// 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: Untar, UIDMaps: nil, GIDMaps: nil}
-)
+// Archiver allows the reuse of most utility functions of this package
+// with a pluggable Untar function. Also, to facilitate the passing of
+// specific id mappings for untar, an archiver can be created with maps
+// which will then be passed to Untar operations
+type Archiver struct {
+	Untar      func(io.Reader, string, *TarOptions) error
+	IDMappings *idtools.IDMappings
+}
 
-const (
-	// HeaderSize is the size in bytes of a tar header
-	HeaderSize = 512
-)
+// NewDefaultArchiver returns a new Archiver without any IDMappings
+func NewDefaultArchiver() *Archiver {
+	return &Archiver{Untar: Untar, IDMappings: &idtools.IDMappings{}}
+}
+
+// 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.
+type breakoutError error
 
 const (
 	// Uncompressed represents the uncompressed.
@@ -105,18 +93,6 @@ const (
 	OverlayWhiteoutFormat
 )
 
-// IsArchive checks for the magic bytes of a tar or any supported compression
-// algorithm.
-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
-}
-
 // IsArchivePath checks if the (possibly compressed) file at the given path
 // starts with a tar file header.
 func IsArchivePath(path string) bool {
@@ -496,7 +472,7 @@ func (ta *tarAppender) addTarFile(path, name string) error {
 	return nil
 }
 
-func createTarFile(path, extractDir string, hdr *tar.Header, reader io.Reader, Lchown bool, chownOpts *TarChownOptions, inUserns bool) error {
+func createTarFile(path, extractDir string, hdr *tar.Header, reader io.Reader, Lchown bool, chownOpts *idtools.IDPair, inUserns bool) 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)
@@ -576,7 +552,7 @@ func createTarFile(path, extractDir string, hdr *tar.Header, reader io.Reader, L
 	// Lchown is not supported on Windows.
 	if Lchown && runtime.GOOS != "windows" {
 		if chownOpts == nil {
-			chownOpts = &TarChownOptions{UID: hdr.Uid, GID: hdr.Gid}
+			chownOpts = &idtools.IDPair{UID: hdr.Uid, GID: hdr.Gid}
 		}
 		if err := os.Lchown(path, chownOpts.UID, chownOpts.GID); err != nil {
 			return err
@@ -941,7 +917,7 @@ loop:
 			}
 		}
 
-		if err := createTarFile(path, dest, hdr, trBuf, !options.NoLchown, options.ChownOpts, options.InUserNS); err != nil {
+		if err := createTarFile(path, dest, hdr, trBuf, !options.NoLchown, &options.ChownOpts, options.InUserNS); err != nil {
 			return err
 		}
 
@@ -1013,23 +989,13 @@ func (archiver *Archiver) TarUntar(src, dst string) error {
 		return err
 	}
 	defer archive.Close()
-
-	var options *TarOptions
-	if archiver.UIDMaps != nil || archiver.GIDMaps != nil {
-		options = &TarOptions{
-			UIDMaps: archiver.UIDMaps,
-			GIDMaps: archiver.GIDMaps,
-		}
+	options := &TarOptions{
+		UIDMaps: archiver.IDMappings.UIDs(),
+		GIDMaps: archiver.IDMappings.GIDs(),
 	}
 	return archiver.Untar(archive, dst, 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 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)
@@ -1037,22 +1003,13 @@ func (archiver *Archiver) UntarPath(src, dst string) error {
 		return err
 	}
 	defer archive.Close()
-	var options *TarOptions
-	if archiver.UIDMaps != nil || archiver.GIDMaps != nil {
-		options = &TarOptions{
-			UIDMaps: archiver.UIDMaps,
-			GIDMaps: archiver.GIDMaps,
-		}
+	options := &TarOptions{
+		UIDMaps: archiver.IDMappings.UIDs(),
+		GIDMaps: archiver.IDMappings.GIDs(),
 	}
 	return archiver.Untar(archive, dst, options)
 }
 
-// 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
@@ -1069,27 +1026,19 @@ func (archiver *Archiver) CopyWithTar(src, dst string) error {
 	// if this archiver is set up with ID mapping we need to create
 	// the new destination directory with the remapped root UID/GID pair
 	// as owner
-	rootUID, rootGID, err := idtools.GetRootUIDGID(archiver.UIDMaps, archiver.GIDMaps)
+	rootIDs, err := archiver.IDMappings.RootPair()
 	if err != nil {
 		return err
 	}
 	// Create dst, copy src's content into it
 	logrus.Debugf("Creating dest directory: %s", dst)
-	if err := idtools.MkdirAllNewAs(dst, 0755, rootUID, rootGID); err != nil {
+	if err := idtools.MkdirAllAndChownNew(dst, 0755, rootIDs); 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.
@@ -1131,26 +1080,24 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
 		hdr.Name = filepath.Base(dst)
 		hdr.Mode = int64(chmodTarEntry(os.FileMode(hdr.Mode)))
 
-		remappedRootUID, remappedRootGID, err := idtools.GetRootUIDGID(archiver.UIDMaps, archiver.GIDMaps)
+		remappedRootIDs, err := archiver.IDMappings.RootPair()
 		if err != nil {
 			return err
 		}
 
 		// only perform mapping if the file being copied isn't already owned by the
 		// uid or gid of the remapped root in the container
-		if remappedRootUID != hdr.Uid {
-			xUID, err := idtools.ToHost(hdr.Uid, archiver.UIDMaps)
+		if remappedRootIDs.UID != hdr.Uid {
+			hdr.Uid, err = archiver.IDMappings.UIDToHost(hdr.Uid)
 			if err != nil {
 				return err
 			}
-			hdr.Uid = xUID
 		}
-		if remappedRootGID != hdr.Gid {
-			xGID, err := idtools.ToHost(hdr.Gid, archiver.GIDMaps)
+		if remappedRootIDs.GID != hdr.Gid {
+			hdr.Gid, err = archiver.IDMappings.GIDToHost(hdr.Gid)
 			if err != nil {
 				return err
 			}
-			hdr.Gid = xGID
 		}
 
 		tw := tar.NewWriter(w)
@@ -1176,18 +1123,6 @@ func (archiver *Archiver) CopyFileWithTar(src, dst string) (err error) {
 	return err
 }
 
-// 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.
diff --git a/pkg/archive/archive_test.go b/pkg/archive/archive_test.go
index e351a0455b..e85878fd0f 100644
--- a/pkg/archive/archive_test.go
+++ b/pkg/archive/archive_test.go
@@ -27,35 +27,22 @@ func init() {
 	}
 }
 
-func TestIsArchiveNilHeader(t *testing.T) {
-	out := IsArchive(nil)
-	if out {
-		t.Fatalf("isArchive should return false as nil is not a valid archive header")
-	}
+var defaultArchiver = NewDefaultArchiver()
+
+func defaultTarUntar(src, dst string) error {
+	return defaultArchiver.TarUntar(src, dst)
 }
 
-func TestIsArchiveInvalidHeader(t *testing.T) {
-	header := []byte{0x00, 0x01, 0x02}
-	out := IsArchive(header)
-	if out {
-		t.Fatalf("isArchive should return false as %s is not a valid archive header", header)
-	}
+func defaultUntarPath(src, dst string) error {
+	return defaultArchiver.UntarPath(src, dst)
 }
 
-func TestIsArchiveBzip2(t *testing.T) {
-	header := []byte{0x42, 0x5A, 0x68}
-	out := IsArchive(header)
-	if !out {
-		t.Fatalf("isArchive should return true as %s is a bz2 header", header)
-	}
+func defaultCopyFileWithTar(src, dst string) (err error) {
+	return defaultArchiver.CopyFileWithTar(src, dst)
 }
 
-func TestIsArchive7zip(t *testing.T) {
-	header := []byte{0x50, 0x4b, 0x03, 0x04}
-	out := IsArchive(header)
-	if out {
-		t.Fatalf("isArchive should return false as %s is a 7z header and it is not supported", header)
-	}
+func defaultCopyWithTar(src, dst string) error {
+	return defaultArchiver.CopyWithTar(src, dst)
 }
 
 func TestIsArchivePathDir(t *testing.T) {
@@ -301,7 +288,7 @@ func TestUntarPathWithInvalidDest(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = UntarPath(tarFile, invalidDestFolder)
+	err = defaultUntarPath(tarFile, invalidDestFolder)
 	if err == nil {
 		t.Fatalf("UntarPath with invalid destination path should throw an error.")
 	}
@@ -313,7 +300,7 @@ func TestUntarPathWithInvalidSrc(t *testing.T) {
 		t.Fatalf("Fail to create the destination file")
 	}
 	defer os.RemoveAll(dest)
-	err = UntarPath("/invalid/path", dest)
+	err = defaultUntarPath("/invalid/path", dest)
 	if err == nil {
 		t.Fatalf("UntarPath with invalid src path should throw an error.")
 	}
@@ -348,7 +335,7 @@ func TestUntarPath(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = UntarPath(tarFile, destFolder)
+	err = defaultUntarPath(tarFile, destFolder)
 	if err != nil {
 		t.Fatalf("UntarPath shouldn't throw an error, %s.", err)
 	}
@@ -387,7 +374,7 @@ func TestUntarPathWithDestinationFile(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Fail to create the destination file")
 	}
-	err = UntarPath(tarFile, destFile)
+	err = defaultUntarPath(tarFile, destFile)
 	if err == nil {
 		t.Fatalf("UntarPath should throw an error if the destination if a file")
 	}
@@ -430,7 +417,7 @@ func TestUntarPathWithDestinationSrcFileAsFolder(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = UntarPath(tarFile, destFolder)
+	err = defaultUntarPath(tarFile, destFolder)
 	if err != nil {
 		t.Fatalf("UntarPath should throw not throw an error if the extracted file already exists and is a folder")
 	}
@@ -447,7 +434,7 @@ func TestCopyWithTarInvalidSrc(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = CopyWithTar(invalidSrc, destFolder)
+	err = defaultCopyWithTar(invalidSrc, destFolder)
 	if err == nil {
 		t.Fatalf("archiver.CopyWithTar with invalid src path should throw an error.")
 	}
@@ -464,7 +451,7 @@ func TestCopyWithTarInexistentDestWillCreateIt(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = CopyWithTar(srcFolder, inexistentDestFolder)
+	err = defaultCopyWithTar(srcFolder, inexistentDestFolder)
 	if err != nil {
 		t.Fatalf("CopyWithTar with an inexistent folder shouldn't fail.")
 	}
@@ -493,7 +480,7 @@ func TestCopyWithTarSrcFile(t *testing.T) {
 		t.Fatal(err)
 	}
 	ioutil.WriteFile(src, []byte("content"), 0777)
-	err = CopyWithTar(src, dest)
+	err = defaultCopyWithTar(src, dest)
 	if err != nil {
 		t.Fatalf("archiver.CopyWithTar shouldn't throw an error, %s.", err)
 	}
@@ -522,7 +509,7 @@ func TestCopyWithTarSrcFolder(t *testing.T) {
 		t.Fatal(err)
 	}
 	ioutil.WriteFile(filepath.Join(src, "file"), []byte("content"), 0777)
-	err = CopyWithTar(src, dest)
+	err = defaultCopyWithTar(src, dest)
 	if err != nil {
 		t.Fatalf("archiver.CopyWithTar shouldn't throw an error, %s.", err)
 	}
@@ -545,7 +532,7 @@ func TestCopyFileWithTarInvalidSrc(t *testing.T) {
 		t.Fatal(err)
 	}
 	invalidFile := filepath.Join(tempFolder, "doesnotexists")
-	err = CopyFileWithTar(invalidFile, destFolder)
+	err = defaultCopyFileWithTar(invalidFile, destFolder)
 	if err == nil {
 		t.Fatalf("archiver.CopyWithTar with invalid src path should throw an error.")
 	}
@@ -563,7 +550,7 @@ func TestCopyFileWithTarInexistentDestWillCreateIt(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = CopyFileWithTar(srcFile, inexistentDestFolder)
+	err = defaultCopyFileWithTar(srcFile, inexistentDestFolder)
 	if err != nil {
 		t.Fatalf("CopyWithTar with an inexistent folder shouldn't fail.")
 	}
@@ -590,7 +577,7 @@ func TestCopyFileWithTarSrcFolder(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = CopyFileWithTar(src, dest)
+	err = defaultCopyFileWithTar(src, dest)
 	if err == nil {
 		t.Fatalf("CopyFileWithTar should throw an error with a folder.")
 	}
@@ -614,7 +601,7 @@ func TestCopyFileWithTarSrcFile(t *testing.T) {
 		t.Fatal(err)
 	}
 	ioutil.WriteFile(src, []byte("content"), 0777)
-	err = CopyWithTar(src, dest+"/")
+	err = defaultCopyWithTar(src, dest+"/")
 	if err != nil {
 		t.Fatalf("archiver.CopyFileWithTar shouldn't throw an error, %s.", err)
 	}
@@ -657,7 +644,7 @@ func checkNoChanges(fileNum int, hardlinks bool) error {
 		return err
 	}
 
-	err = TarUntar(srcDir, destDir)
+	err = defaultTarUntar(srcDir, destDir)
 	if err != nil {
 		return err
 	}
@@ -871,7 +858,7 @@ func BenchmarkTarUntar(b *testing.B) {
 	b.ResetTimer()
 	b.SetBytes(int64(n))
 	for n := 0; n < b.N; n++ {
-		err := TarUntar(origin, target)
+		err := defaultTarUntar(origin, target)
 		if err != nil {
 			b.Fatal(err)
 		}
@@ -899,7 +886,7 @@ func BenchmarkTarUntarWithLinks(b *testing.B) {
 	b.ResetTimer()
 	b.SetBytes(int64(n))
 	for n := 0; n < b.N; n++ {
-		err := TarUntar(origin, target)
+		err := defaultTarUntar(origin, target)
 		if err != nil {
 			b.Fatal(err)
 		}
diff --git a/pkg/archive/archive_windows_test.go b/pkg/archive/archive_windows_test.go
index 9dd937f296..685e114baf 100644
--- a/pkg/archive/archive_windows_test.go
+++ b/pkg/archive/archive_windows_test.go
@@ -27,7 +27,7 @@ func TestCopyFileWithInvalidDest(t *testing.T) {
 		t.Fatal(err)
 	}
 	ioutil.WriteFile(src, []byte("content"), 0777)
-	err = CopyWithTar(src, dest)
+	err = defaultCopyWithTar(src, dest)
 	if err == nil {
 		t.Fatalf("archiver.CopyWithTar should throw an error on invalid dest.")
 	}
diff --git a/pkg/chrootarchive/archive.go b/pkg/chrootarchive/archive.go
index a7814f5b90..d996ef774a 100644
--- a/pkg/chrootarchive/archive.go
+++ b/pkg/chrootarchive/archive.go
@@ -11,7 +11,13 @@ import (
 	"github.com/docker/docker/pkg/idtools"
 )
 
-var chrootArchiver = &archive.Archiver{Untar: Untar}
+// NewArchiver returns a new Archiver which uses chrootarchive.Untar
+func NewArchiver(idMappings *idtools.IDMappings) *archive.Archiver {
+	if idMappings == nil {
+		idMappings = &idtools.IDMappings{}
+	}
+	return &archive.Archiver{Untar: Untar, IDMappings: idMappings}
+}
 
 // Untar reads a stream of bytes from `archive`, parses it as a tar archive,
 // and unpacks it into the directory at `dest`.
@@ -30,7 +36,6 @@ func UntarUncompressed(tarArchive io.Reader, dest string, options *archive.TarOp
 
 // Handler for teasing out the automatic decompression
 func untarHandler(tarArchive io.Reader, dest string, options *archive.TarOptions, decompress bool) error {
-
 	if tarArchive == nil {
 		return fmt.Errorf("Empty archive")
 	}
@@ -65,33 +70,3 @@ func untarHandler(tarArchive io.Reader, dest string, options *archive.TarOptions
 
 	return invokeUnpack(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 TarUntar(src, dst string) error {
-	return chrootArchiver.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 chrootArchiver.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.
-//
-// If `dst` ends with a trailing slash '/' ('\' on Windows), the final
-// destination path will be `dst/base(src)` or `dst\base(src)`
-func CopyFileWithTar(src, dst string) (err error) {
-	return chrootArchiver.CopyFileWithTar(src, dst)
-}
-
-// 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 chrootArchiver.UntarPath(src, dst)
-}
diff --git a/pkg/chrootarchive/archive_test.go b/pkg/chrootarchive/archive_test.go
index 80e54a0edc..4780f3be08 100644
--- a/pkg/chrootarchive/archive_test.go
+++ b/pkg/chrootarchive/archive_test.go
@@ -22,6 +22,24 @@ func init() {
 	reexec.Init()
 }
 
+var chrootArchiver = NewArchiver(nil)
+
+func TarUntar(src, dst string) error {
+	return chrootArchiver.TarUntar(src, dst)
+}
+
+func CopyFileWithTar(src, dst string) (err error) {
+	return chrootArchiver.CopyFileWithTar(src, dst)
+}
+
+func UntarPath(src, dst string) error {
+	return chrootArchiver.UntarPath(src, dst)
+}
+
+func CopyWithTar(src, dst string) error {
+	return chrootArchiver.CopyWithTar(src, dst)
+}
+
 func TestChrootTarUntar(t *testing.T) {
 	tmpdir, err := ioutil.TempDir("", "docker-TestChrootTarUntar")
 	if err != nil {
diff --git a/pkg/idtools/idtools.go b/pkg/idtools/idtools.go
index d7a3a45387..39c9805df2 100644
--- a/pkg/idtools/idtools.go
+++ b/pkg/idtools/idtools.go
@@ -118,6 +118,7 @@ func ToContainer(hostID int, idMap []IDMap) (int, error) {
 // ToHost takes an id mapping and a remapped ID, and translates the
 // ID to the mapped host ID. If no map is provided, then the translation
 // assumes a 1-to-1 mapping and returns the passed in id #
+// Depercated: use IDMappings.UIDToHost and IDMappings.GIDToHost
 func ToHost(contID int, idMap []IDMap) (int, error) {
 	if idMap == nil {
 		return contID, nil
@@ -174,6 +175,16 @@ func (i *IDMappings) RootPair() (IDPair, error) {
 	return IDPair{UID: uid, GID: gid}, err
 }
 
+// UIDToHost returns the host UID for the container uid
+func (i *IDMappings) UIDToHost(uid int) (int, error) {
+	return ToHost(uid, i.uids)
+}
+
+// GIDToHost returns the host GID for the container gid
+func (i *IDMappings) GIDToHost(gid int) (int, error) {
+	return ToHost(gid, i.gids)
+}
+
 // UIDs return the UID mapping
 // TODO: remove this once everything has been refactored to use pairs
 func (i *IDMappings) UIDs() []IDMap {