copy: add --dest-compress-format and --dest-compress-level

add the possibility to specify the format and the level to use when
compressing blobs.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

cmd/skopeo/utils.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"strings"
 
+	"github.com/containers/image/pkg/compression"
 	"github.com/containers/image/transports/alltransports"
 	"github.com/containers/image/types"
 	"github.com/urfave/cli"
@@ -147,6 +148,7 @@ func (opts *imageOptions) newSystemContext() (*types.SystemContext, error) {
 	if opts.noCreds {
 		ctx.DockerAuthConfig = &types.DockerAuthConfig{}
 	}
+
 	return ctx, nil
 }
 
@@ -156,6 +158,8 @@ type imageDestOptions struct {
 	osTreeTmpDir                string      // A directory to use for OSTree temporary files
 	dirForceCompression         bool        // Compress layers when saving to the dir: transport
 	ociAcceptUncompressedLayers bool        // Whether to accept uncompressed layers in the oci: transport
+	compressionFormat           string      // Format to use for the compression
+	compressionLevel            optionalInt // Level to use for the compression
 }
 
 // imageDestFlags prepares a collection of CLI flags writing into imageDestOptions, and the managed imageDestOptions structure.
@@ -179,6 +183,16 @@ func imageDestFlags(global *globalOptions, shared *sharedImageOptions, flagPrefi
 			Usage:       "Allow uncompressed image layers when saving to an OCI image using the 'oci' transport. (default is to compress things that aren't compressed)",
 			Destination: &opts.ociAcceptUncompressedLayers,
 		},
+		cli.StringFlag{
+			Name:        flagPrefix + "compress-format",
+			Usage:       "`FORMAT` to use for the compression",
+			Destination: &opts.compressionFormat,
+		},
+		cli.GenericFlag{
+			Name:  flagPrefix + "compress-level",
+			Usage: "`LEVEL` to use for the compression",
+			Value: newOptionalIntValue(&opts.compressionLevel),
+		},
 	}...), &opts
 }
 
@@ -193,6 +207,16 @@ func (opts *imageDestOptions) newSystemContext() (*types.SystemContext, error) {
 	ctx.OSTreeTmpDirPath = opts.osTreeTmpDir
 	ctx.DirForceCompress = opts.dirForceCompression
 	ctx.OCIAcceptUncompressedLayers = opts.ociAcceptUncompressedLayers
+	if opts.compressionFormat != "" {
+		cf, err := compression.AlgorithmByName(opts.compressionFormat)
+		if err != nil {
+			return nil, err
+		}
+		ctx.CompressionFormat = &cf
+	}
+	if opts.compressionLevel.present {
+		ctx.CompressionLevel = &opts.compressionLevel.value
+	}
 	return ctx, err
 }
 

docs/skopeo-copy.1.md

@@ -58,6 +58,10 @@ If the authorization state is not found there, $HOME/.docker/config.json is chec
 
 Existing signatures, if any, are preserved as well.
 
+**--dest-compress-format** _format_ Specifies the compression format to use.  Supported values are: `gzip` and `zstd`.
+
+**--dest-compress-level** _format_ Specifies the compression level to use.  The value is specific to the compression algorithm used, e.g. for zstd the accepted values are in the range 1-20 (inclusive), while for gzip it is 1-9 (inclusive).
+
 ## EXAMPLES
 
 To copy the layers of the docker.io busybox image to a local directory:

go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/VividCortex/ewma v1.1.1 // indirect
 	github.com/containerd/continuity v0.0.0-20180216233310-d8fb8589b0e8 // indirect
 	github.com/containers/buildah v1.8.4
-	github.com/containers/image v3.0.1+incompatible
+	github.com/containers/image v1.5.2-0.20190821161828-0cc0e97405db
 	github.com/containers/storage v1.13.0
 	github.com/docker/distribution v0.0.0-20170817175659-5f6282db7d65 // indirect
 	github.com/docker/docker v0.0.0-20180522102801-da99009bbb11

go.sum

@@ -17,6 +17,10 @@ github.com/containers/image v1.5.2-0.20190717062552-2178abd5f9b1 h1:RGlzwWSoGBbc
 github.com/containers/image v1.5.2-0.20190717062552-2178abd5f9b1/go.mod h1:8Vtij257IWSanUQKe1tAeNOm2sRVkSqQTVQ1IlwI3+M=
 github.com/containers/image v1.5.2-0.20190725091050-48acc3dcbb76 h1:+9unAKrV92Jvifb06UK8H4xTKf7h7XQDOsn4EC9eqH4=
 github.com/containers/image v1.5.2-0.20190725091050-48acc3dcbb76/go.mod h1:8Vtij257IWSanUQKe1tAeNOm2sRVkSqQTVQ1IlwI3+M=
+github.com/containers/image v1.5.2-0.20190821113801-e003ccfc74de h1:6M4DvYlNvVUJppB9rWaYFw30fgzt09z2dCj4VlOl3e4=
+github.com/containers/image v1.5.2-0.20190821113801-e003ccfc74de/go.mod h1:8Vtij257IWSanUQKe1tAeNOm2sRVkSqQTVQ1IlwI3+M=
+github.com/containers/image v1.5.2-0.20190821161828-0cc0e97405db h1:ZtTWr+vb7qTLWjEW0CNP56ltYuj5t6y8AUkCxQAfH+Y=
+github.com/containers/image v1.5.2-0.20190821161828-0cc0e97405db/go.mod h1:8Vtij257IWSanUQKe1tAeNOm2sRVkSqQTVQ1IlwI3+M=
 github.com/containers/image v2.0.0+incompatible h1:FTr6Br7jlIKNCKMjSOMbAxKp2keQ0//jzJaYNTVhauk=
 github.com/containers/image v2.0.0+incompatible/go.mod h1:8Vtij257IWSanUQKe1tAeNOm2sRVkSqQTVQ1IlwI3+M=
 github.com/containers/image v3.0.0+incompatible h1:pdUHY//H+3jYNnoTt+rqY8NsStX4ZBLKzPTlMC+XvnU=
@@ -49,6 +53,12 @@ github.com/etcd-io/bbolt v1.3.2 h1:RLRQ0TKLX7DlBRXAJHvbmXL17Q3KNnTBtZ9B6Qo+/Y0=
 github.com/etcd-io/bbolt v1.3.2/go.mod h1:ZF2nL25h33cCyBtcyWeZ2/I3HQOfTP+0PIEvHjkjCrw=
 github.com/ghodss/yaml v0.0.0-20150909031657-73d445a93680 h1:ZktWZesgun21uEDrwW7iEV1zPCGQldM2atlJZ3TdvVM=
 github.com/ghodss/yaml v0.0.0-20150909031657-73d445a93680/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
+github.com/giuseppe/image v0.0.0-20190723195852-da7a70cbb5f1 h1:j+wcaSLeY2xPBzeSU37obWjSdWvYjf8soPscPvmOGpY=
+github.com/giuseppe/image v0.0.0-20190723195852-da7a70cbb5f1/go.mod h1:t1Xf5SPi6pYsMJfQTMHfTpWgaQkRuy+0HMhAOJOj01E=
+github.com/giuseppe/image v0.0.0-20190806095912-8e15c8a868fc h1:qvH3jFNG7pyTd58rs/gNmtfTv7E9q8Xo7/RKLZn+zag=
+github.com/giuseppe/image v0.0.0-20190806095912-8e15c8a868fc/go.mod h1:t1Xf5SPi6pYsMJfQTMHfTpWgaQkRuy+0HMhAOJOj01E=
+github.com/giuseppe/image v0.0.0-20190813140229-9b055a514f21 h1:nUR9MenOi9gs8LlU5BSQ4zCmdTLc1Js5gT7rdymI3ZE=
+github.com/giuseppe/image v0.0.0-20190813140229-9b055a514f21/go.mod h1:t1Xf5SPi6pYsMJfQTMHfTpWgaQkRuy+0HMhAOJOj01E=
 github.com/go-check/check v0.0.0-20180628173108-788fd7840127 h1:0gkP6mzaMqkmpcJYCFOLkIBwI7xFExG03bbkOkCvUPI=
 github.com/go-check/check v0.0.0-20180628173108-788fd7840127/go.mod h1:9ES+weclKsC9YodN5RgxqK/VD9HM9JsCSh7rNhMZE98=
 github.com/gogo/protobuf v0.0.0-20170815085658-fcdc5011193f h1:r/AdTzqktq9nQpFlFePWcp+scVi+oFRajfjRJ3UnETg=

systemtest/020-copy.bats

@@ -44,6 +44,21 @@ function setup() {
     diff -urN $dir1 $dir2
 }
 
+# Compression zstd
+@test "copy: oci, round trip" {
+    local remote_image=docker://busybox:latest
+
+    local dir=$TESTDIR/dir
+
+    run_skopeo copy --dest-compress --dest-compress-format=zstd $remote_image oci:$dir:latest
+
+    # zstd magic number
+    local magic=$(printf "\x28\xb5\x2f\xfd")
+
+    # Check there is at least one file that has the zstd magic number as the first 4 bytes
+    (for i in $dir/blobs/sha256/*; do test "$(head -c 4 $i)" = $magic && exit 0; done; exit 1)
+}
+
 # Same image, extracted once with :tag and once without
 @test "copy: oci w/ and w/o tags" {
     local remote_image=docker://busybox:latest

vendor/github.com/containers/image/copy/copy.go

@@ -21,7 +21,6 @@ import (
 	"github.com/containers/image/signature"
 	"github.com/containers/image/transports"
 	"github.com/containers/image/types"
-	"github.com/klauspost/pgzip"
 	digest "github.com/opencontainers/go-digest"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -43,6 +42,9 @@ type digestingReader struct {
 // downloads.  Let's follow Firefox by limiting it to 6.
 var maxParallelDownloads = 6
 
+// compressionBufferSize is the buffer size used to compress a blob
+var compressionBufferSize = 1048576
+
 // newDigestingReader returns an io.Reader implementation with contents of source, which will eventually return a non-EOF error
 // or set validationSucceeded/validationFailed to true if the source stream does/does not match expectedDigest.
 // (neither is set if EOF is never reached).
@@ -94,6 +96,8 @@ type copier struct {
 	progress          chan types.ProgressProperties
 	blobInfoCache     types.BlobInfoCache
 	copyInParallel    bool
+	compressionFormat compression.Algorithm
+	compressionLevel  *int
 }
 
 // imageCopier tracks state specific to a single image (possibly an item of a manifest list)
@@ -166,6 +170,7 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		progressOutput = ioutil.Discard
 	}
 	copyInParallel := dest.HasThreadSafePutBlob() && rawSource.HasThreadSafeGetBlob()
+
 	c := &copier{
 		dest:             dest,
 		rawSource:        rawSource,
@@ -178,6 +183,17 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		// For now, use DestinationCtx (because blob reuse changes the behavior of the destination side more); eventually
 		// we might want to add a separate CommonCtx — or would that be too confusing?
 		blobInfoCache:    blobinfocache.DefaultCache(options.DestinationCtx),
+		compressionLevel: options.DestinationCtx.CompressionLevel,
+	}
+	// Default to using gzip compression unless specified otherwise.
+	if options.DestinationCtx.CompressionFormat == nil {
+		algo, err := compression.AlgorithmByName("gzip")
+		if err != nil {
+			return nil, err
+		}
+		c.compressionFormat = algo
+	} else {
+		c.compressionFormat = *options.DestinationCtx.CompressionFormat
 	}
 
 	unparsedToplevel := image.UnparsedInstance(rawSource, nil)
@@ -805,7 +821,7 @@ func (c *copier) copyBlobFromStream(ctx context.Context, srcStream io.Reader, sr
 
 	// === Detect compression of the input stream.
 	// This requires us to “peek ahead” into the stream to read the initial part, which requires us to chain through another io.Reader returned by DetectCompression.
-	decompressor, destStream, err := compression.DetectCompression(destStream) // We could skip this in some cases, but let's keep the code path uniform
+	compressionFormat, decompressor, destStream, err := compression.DetectCompressionFormat(destStream) // We could skip this in some cases, but let's keep the code path uniform
 	if err != nil {
 		return types.BlobInfo{}, errors.Wrapf(err, "Error reading blob %s", srcInfo.Digest)
 	}
@@ -819,6 +835,8 @@ func (c *copier) copyBlobFromStream(ctx context.Context, srcStream io.Reader, sr
 		originalLayerReader = destStream
 	}
 
+	desiredCompressionFormat := c.compressionFormat
+
 	// === Deal with layer compression/decompression if necessary
 	var inputInfo types.BlobInfo
 	var compressionOperation types.LayerCompression
@@ -831,7 +849,27 @@ func (c *copier) copyBlobFromStream(ctx context.Context, srcStream io.Reader, sr
 		// If this fails while writing data, it will do pipeWriter.CloseWithError(); if it fails otherwise,
 		// e.g. because we have exited and due to pipeReader.Close() above further writing to the pipe has failed,
 		// we don’t care.
-		go compressGoroutine(pipeWriter, destStream) // Closes pipeWriter
+		go c.compressGoroutine(pipeWriter, destStream, desiredCompressionFormat) // Closes pipeWriter
+		destStream = pipeReader
+		inputInfo.Digest = ""
+		inputInfo.Size = -1
+	} else if canModifyBlob && c.dest.DesiredLayerCompression() == types.Compress && isCompressed && desiredCompressionFormat.Name() != compressionFormat.Name() {
+		// When the blob is compressed, but the desired format is different, it first needs to be decompressed and finally
+		// re-compressed using the desired format.
+		logrus.Debugf("Blob will be converted")
+
+		compressionOperation = types.PreserveOriginal
+		s, err := decompressor(destStream)
+		if err != nil {
+			return types.BlobInfo{}, err
+		}
+		defer s.Close()
+
+		pipeReader, pipeWriter := io.Pipe()
+		defer pipeReader.Close()
+
+		go c.compressGoroutine(pipeWriter, s, desiredCompressionFormat) // Closes pipeWriter
+
 		destStream = pipeReader
 		inputInfo.Digest = ""
 		inputInfo.Size = -1
@@ -847,6 +885,7 @@ func (c *copier) copyBlobFromStream(ctx context.Context, srcStream io.Reader, sr
 		inputInfo.Digest = ""
 		inputInfo.Size = -1
 	} else {
+		// PreserveOriginal might also need to recompress the original blob if the desired compression format is different.
 		logrus.Debugf("Using original blob without modification")
 		compressionOperation = types.PreserveOriginal
 		inputInfo = srcInfo
@@ -907,14 +946,19 @@ func (c *copier) copyBlobFromStream(ctx context.Context, srcStream io.Reader, sr
 }
 
 // compressGoroutine reads all input from src and writes its compressed equivalent to dest.
-func compressGoroutine(dest *io.PipeWriter, src io.Reader) {
+func (c *copier) compressGoroutine(dest *io.PipeWriter, src io.Reader, compressionFormat compression.Algorithm) {
 	err := errors.New("Internal error: unexpected panic in compressGoroutine")
 	defer func() { // Note that this is not the same as {defer dest.CloseWithError(err)}; we need err to be evaluated lazily.
 		dest.CloseWithError(err) // CloseWithError(nil) is equivalent to Close()
 	}()
 
-	zipper := pgzip.NewWriter(dest)
-	defer zipper.Close()
-
-	_, err = io.Copy(zipper, src) // Sets err to nil, i.e. causes dest.Close()
+	compressor, err := compression.CompressStream(dest, compressionFormat, c.compressionLevel)
+	if err != nil {
+		return
+	}
+	defer compressor.Close()
+
+	buf := make([]byte, compressionBufferSize)
+
+	_, err = io.CopyBuffer(compressor, src, buf) // Sets err to nil, i.e. causes dest.Close()
 }

vendor/github.com/containers/image/ostree/ostree_src.go

@@ -59,9 +59,15 @@ func (s *ostreeImageSource) Close() error {
 	return nil
 }
 
-func (s *ostreeImageSource) getLayerSize(blob string) (int64, error) {
+func (s *ostreeImageSource) getBlobUncompressedSize(blob string, isCompressed bool) (int64, error) {
+	var metadataKey string
+	if isCompressed {
+		metadataKey = "docker.uncompressed_size"
+	} else {
+		metadataKey = "docker.size"
+	}
 	b := fmt.Sprintf("ociimage/%s", blob)
-	found, data, err := readMetadata(s.repo, b, "docker.size")
+	found, data, err := readMetadata(s.repo, b, metadataKey)
 	if err != nil || !found {
 		return 0, err
 	}
@@ -275,8 +281,8 @@ func (s *ostreeImageSource) GetBlob(ctx context.Context, info types.BlobInfo, ca
 		}
 
 	}
-	compressedBlob, found := s.compressed[info.Digest]
-	if found {
+	compressedBlob, isCompressed := s.compressed[info.Digest]
+	if isCompressed {
 		blob = compressedBlob.Hex()
 	}
 	branch := fmt.Sprintf("ociimage/%s", blob)
@@ -289,7 +295,7 @@ func (s *ostreeImageSource) GetBlob(ctx context.Context, info types.BlobInfo, ca
 		s.repo = repo
 	}
 
-	layerSize, err := s.getLayerSize(blob)
+	layerSize, err := s.getBlobUncompressedSize(blob, isCompressed)
 	if err != nil {
 		return nil, 0, err
 	}

vendor/github.com/containers/image/pkg/compression/compression.go

@@ -3,6 +3,7 @@ package compression
 import (
 	"bytes"
 	"compress/bzip2"
+	"fmt"
 	"io"
 	"io/ioutil"
 
@@ -35,32 +36,82 @@ func XzDecompressor(r io.Reader) (io.ReadCloser, error) {
 	return ioutil.NopCloser(r), nil
 }
 
-// compressionAlgos is an internal implementation detail of DetectCompression
-var compressionAlgos = map[string]struct {
-	prefix       []byte
-	decompressor DecompressorFunc
-}{
-	"gzip":  {[]byte{0x1F, 0x8B, 0x08}, GzipDecompressor},                 // gzip (RFC 1952)
-	"bzip2": {[]byte{0x42, 0x5A, 0x68}, Bzip2Decompressor},                // bzip2 (decompress.c:BZ2_decompress)
-	"xz":    {[]byte{0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00}, XzDecompressor}, // xz (/usr/share/doc/xz/xz-file-format.txt)
+// compressorFunc writes the compressed stream to the given writer using the specified compression level.
+// The caller must call Close() on the stream (even if the input stream does not need closing!).
+type compressorFunc func(io.Writer, *int) (io.WriteCloser, error)
+
+// gzipCompressor is a CompressorFunc for the gzip compression algorithm.
+func gzipCompressor(r io.Writer, level *int) (io.WriteCloser, error) {
+	if level != nil {
+		return pgzip.NewWriterLevel(r, *level)
+	}
+	return pgzip.NewWriter(r), nil
 }
 
-// DetectCompression returns a DecompressorFunc if the input is recognized as a compressed format, nil otherwise.
+// bzip2Compressor is a CompressorFunc for the bzip2 compression algorithm.
+func bzip2Compressor(r io.Writer, level *int) (io.WriteCloser, error) {
+	return nil, fmt.Errorf("bzip2 compression not supported")
+}
+
+// xzCompressor is a CompressorFunc for the xz compression algorithm.
+func xzCompressor(r io.Writer, level *int) (io.WriteCloser, error) {
+	return xz.NewWriter(r)
+}
+
+// Algorithm is a compression algorithm that can be used for CompressStream.
+type Algorithm struct {
+	name         string
+	prefix       []byte
+	decompressor DecompressorFunc
+	compressor   compressorFunc
+}
+
+// Name returns the name for the compression algorithm.
+func (c Algorithm) Name() string {
+	return c.name
+}
+
+// compressionAlgos is an internal implementation detail of DetectCompression
+var compressionAlgos = []Algorithm{
+	{"gzip", []byte{0x1F, 0x8B, 0x08}, GzipDecompressor, gzipCompressor},             // gzip (RFC 1952)
+	{"bzip2", []byte{0x42, 0x5A, 0x68}, Bzip2Decompressor, bzip2Compressor},          // bzip2 (decompress.c:BZ2_decompress)
+	{"xz", []byte{0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00}, XzDecompressor, xzCompressor}, // xz (/usr/share/doc/xz/xz-file-format.txt)
+	{"zstd", []byte{0x28, 0xb5, 0x2f, 0xfd}, ZstdDecompressor, zstdCompressor},       // zstd (http://www.zstd.net)
+}
+
+// AlgorithmByName returns the compressor by its name
+func AlgorithmByName(name string) (Algorithm, error) {
+	for _, c := range compressionAlgos {
+		if c.name == name {
+			return c, nil
+		}
+	}
+	return Algorithm{}, fmt.Errorf("cannot find compressor for %q", name)
+}
+
+// CompressStream returns the compressor by its name
+func CompressStream(dest io.Writer, algo Algorithm, level *int) (io.WriteCloser, error) {
+	return algo.compressor(dest, level)
+}
+
+// DetectCompressionFormat returns a DecompressorFunc if the input is recognized as a compressed format, nil otherwise.
 // Because it consumes the start of input, other consumers must use the returned io.Reader instead to also read from the beginning.
-func DetectCompression(input io.Reader) (DecompressorFunc, io.Reader, error) {
+func DetectCompressionFormat(input io.Reader) (Algorithm, DecompressorFunc, io.Reader, error) {
 	buffer := [8]byte{}
 
 	n, err := io.ReadAtLeast(input, buffer[:], len(buffer))
 	if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
 		// This is a “real” error. We could just ignore it this time, process the data we have, and hope that the source will report the same error again.
 		// Instead, fail immediately with the original error cause instead of a possibly secondary/misleading error returned later.
-		return nil, nil, err
+		return Algorithm{}, nil, nil, err
 	}
 
+	var retAlgo Algorithm
 	var decompressor DecompressorFunc
-	for name, algo := range compressionAlgos {
+	for _, algo := range compressionAlgos {
 		if bytes.HasPrefix(buffer[:n], algo.prefix) {
-			logrus.Debugf("Detected compression format %s", name)
+			logrus.Debugf("Detected compression format %s", algo.name)
+			retAlgo = algo
 			decompressor = algo.decompressor
 			break
 		}
@@ -69,7 +120,14 @@ func DetectCompression(input io.Reader) (DecompressorFunc, io.Reader, error) {
 		logrus.Debugf("No compression detected")
 	}
 
-	return decompressor, io.MultiReader(bytes.NewReader(buffer[:n]), input), nil
+	return retAlgo, decompressor, io.MultiReader(bytes.NewReader(buffer[:n]), input), nil
+}
+
+// DetectCompression returns a DecompressorFunc if the input is recognized as a compressed format, nil otherwise.
+// Because it consumes the start of input, other consumers must use the returned io.Reader instead to also read from the beginning.
+func DetectCompression(input io.Reader) (DecompressorFunc, io.Reader, error) {
+	_, d, r, e := DetectCompressionFormat(input)
+	return d, r, e
 }
 
 // AutoDecompress takes a stream and returns an uncompressed version of the

vendor/github.com/containers/image/pkg/compression/zstd.go

@@ -0,0 +1,59 @@
+package compression
+
+import (
+	"io"
+
+	"github.com/klauspost/compress/zstd"
+)
+
+type wrapperZstdDecoder struct {
+	decoder *zstd.Decoder
+}
+
+func (w *wrapperZstdDecoder) Close() error {
+	w.decoder.Close()
+	return nil
+}
+
+func (w *wrapperZstdDecoder) DecodeAll(input, dst []byte) ([]byte, error) {
+	return w.decoder.DecodeAll(input, dst)
+}
+
+func (w *wrapperZstdDecoder) Read(p []byte) (int, error) {
+	return w.decoder.Read(p)
+}
+
+func (w *wrapperZstdDecoder) Reset(r io.Reader) error {
+	return w.decoder.Reset(r)
+}
+
+func (w *wrapperZstdDecoder) WriteTo(wr io.Writer) (int64, error) {
+	return w.decoder.WriteTo(wr)
+}
+
+func zstdReader(buf io.Reader) (io.ReadCloser, error) {
+	decoder, err := zstd.NewReader(buf)
+	return &wrapperZstdDecoder{decoder: decoder}, err
+}
+
+func zstdWriter(dest io.Writer) (io.WriteCloser, error) {
+	return zstd.NewWriter(dest)
+}
+
+func zstdWriterWithLevel(dest io.Writer, level int) (io.WriteCloser, error) {
+	el := zstd.EncoderLevelFromZstd(level)
+	return zstd.NewWriter(dest, zstd.WithEncoderLevel(el))
+}
+
+// zstdCompressor is a CompressorFunc for the zstd compression algorithm.
+func zstdCompressor(r io.Writer, level *int) (io.WriteCloser, error) {
+	if level == nil {
+		return zstdWriter(r)
+	}
+	return zstdWriterWithLevel(r, *level)
+}
+
+// ZstdDecompressor is a DecompressorFunc for the zstd compression algorithm.
+func ZstdDecompressor(r io.Reader) (io.ReadCloser, error) {
+	return zstdReader(r)
+}

vendor/github.com/containers/image/pkg/docker/config/config.go

@@ -32,6 +32,8 @@ var (
 	dockerHomePath          = filepath.FromSlash(".docker/config.json")
 	dockerLegacyHomePath    = ".dockercfg"
 
+	enableKeyring = false
+
 	// ErrNotLoggedIn is returned for users not logged into a registry
 	// that they are trying to logout of
 	ErrNotLoggedIn = errors.New("not logged in")
@@ -46,11 +48,11 @@ func SetAuthentication(sys *types.SystemContext, registry, username, password st
 			return false, setAuthToCredHelper(ch, registry, username, password)
 		}
 
-		// Set the credentials to kernel keyring if sys.AuthFile is not specified.
+		// Set the credentials to kernel keyring if enableKeyring is true.
 		// The keyring might not work in all environments (e.g., missing capability) and isn't supported on all platforms.
 		// Hence, we want to fall-back to using the authfile in case the keyring failed.
-		// However, if the sys.AuthFilePath is set, we want adhere to the user specification and not use the keyring.
-		if sys.AuthFilePath == "" {
+		// However, if the enableKeyring is false, we want adhere to the user specification and not use the keyring.
+		if enableKeyring {
 			err := setAuthToKernelKeyring(registry, username, password)
 			if err == nil {
 				logrus.Debugf("credentials for (%s, %s) were stored in the kernel keyring\n", registry, username)
@@ -74,11 +76,13 @@ func GetAuthentication(sys *types.SystemContext, registry string) (string, strin
 		return sys.DockerAuthConfig.Username, sys.DockerAuthConfig.Password, nil
 	}
 
+	if enableKeyring {
 		username, password, err := getAuthFromKernelKeyring(registry)
 		if err == nil {
 			logrus.Debug("returning credentials from kernel keyring")
 			return username, password, nil
 		}
+	}
 
 	dockerLegacyPath := filepath.Join(homedir.Get(), dockerLegacyHomePath)
 	var paths []string
@@ -117,13 +121,15 @@ func RemoveAuthentication(sys *types.SystemContext, registry string) error {
 			return false, deleteAuthFromCredHelper(ch, registry)
 		}
 
-		// Next try kernel keyring
+		// Next if keyring is enabled try kernel keyring
+		if enableKeyring {
 			err := deleteAuthFromKernelKeyring(registry)
 			if err == nil {
 				logrus.Debugf("credentials for %s were deleted from the kernel keyring", registry)
 				return false, nil
 			}
 			logrus.Debugf("failed to delete credentials from the kernel keyring, falling back to authfiles")
+		}
 
 		if _, ok := auths.AuthConfigs[registry]; ok {
 			delete(auths.AuthConfigs, registry)

vendor/github.com/containers/image/types/types.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/containers/image/docker/reference"
+	"github.com/containers/image/pkg/compression"
 	"github.com/opencontainers/go-digest"
 	"github.com/opencontainers/image-spec/specs-go/v1"
 )
@@ -511,6 +512,11 @@ type SystemContext struct {
 	// === dir.Transport overrides ===
 	// DirForceCompress compresses the image layers if set to true
 	DirForceCompress bool
+
+	// CompressionFormat is the format to use for the compression of the blobs
+	CompressionFormat *compression.Algorithm
+	// CompressionLevel specifies what compression level is used
+	CompressionLevel *int
 }
 
 // ProgressProperties is used to pass information from the copy code to a monitor which

vendor/github.com/containers/image/version/version.go

@@ -8,10 +8,10 @@ const (
 	// VersionMinor is for functionality in a backwards-compatible manner
 	VersionMinor = 0
 	// VersionPatch is for backwards-compatible bug fixes
-	VersionPatch = 1
+	VersionPatch = 3
 
 	// VersionDev indicates development branch. Releases will be empty string.
-	VersionDev = ""
+	VersionDev = "-dev"
 )
 
 // Version is the specification version that the package types support.

vendor/modules.txt

@@ -26,7 +26,7 @@ github.com/VividCortex/ewma
 github.com/containerd/continuity/pathdriver
 # github.com/containers/buildah v1.8.4
 github.com/containers/buildah/pkg/unshare
-# github.com/containers/image v3.0.1+incompatible
+# github.com/containers/image v1.5.2-0.20190821161828-0cc0e97405db
 github.com/containers/image/copy
 github.com/containers/image/directory
 github.com/containers/image/docker
@@ -34,12 +34,12 @@ github.com/containers/image/docker/reference
 github.com/containers/image/image
 github.com/containers/image/manifest
 github.com/containers/image/pkg/blobinfocache
+github.com/containers/image/pkg/compression
 github.com/containers/image/signature
 github.com/containers/image/storage
 github.com/containers/image/transports
 github.com/containers/image/transports/alltransports
 github.com/containers/image/types
-github.com/containers/image/pkg/compression
 github.com/containers/image/directory/explicitfilepath
 github.com/containers/image/docker/policyconfiguration
 github.com/containers/image/pkg/blobinfocache/none
@@ -164,11 +164,11 @@ github.com/gorilla/mux
 # github.com/imdario/mergo v0.0.0-20141206190957-6633656539c1
 github.com/imdario/mergo
 # github.com/klauspost/compress v1.7.2
-github.com/klauspost/compress/flate
 github.com/klauspost/compress/zstd
 github.com/klauspost/compress/huff0
 github.com/klauspost/compress/snappy
 github.com/klauspost/compress/zstd/internal/xxhash
+github.com/klauspost/compress/flate
 github.com/klauspost/compress/fse
 # github.com/klauspost/cpuid v1.2.1
 github.com/klauspost/cpuid