Added support for zstd compression

Using github.com/klauspost/compress go module has brought in a
list of other compression implementations. Therefore the vendor
folder has gotten larger. Some files were also modified due to
the bump up in compress's version.

Apart from these, this commit adds an implementation for zstd
compression and a corresponding test.

Fixes opencontainers#316

Signed-off-by: Nisha K <nishak@vmware.com>

go.mod

@@ -9,7 +9,7 @@ require (
  github.com/docker/go-units v0.4.0
  github.com/golang/protobuf v1.4.2
  github.com/google/go-cmp v0.5.0 // indirect
- github.com/klauspost/compress v1.10.9 // indirect
+ github.com/klauspost/compress v1.11.3
  github.com/klauspost/pgzip v1.2.4
  github.com/kr/text v0.2.0 // indirect
  github.com/mattn/go-colorable v0.1.6 // indirect

go.sum

@@ -56,6 +56,8 @@ github.com/jmespath/go-jmespath v0.0.0-20180206201540-c2b33e8439af/go.mod h1:Nht
 github.com/jpillora/backoff v0.0.0-20180909062703-3050d21c67d7/go.mod h1:2iMrUgbbvHEiQClaW2NsSzMyGHqN+rDFqY705q49KG0=
 github.com/klauspost/compress v1.10.9 h1:pPRt1Z78crspaHISkpSSHjDlx+Tt9suHe519dsI0vF4=
 github.com/klauspost/compress v1.10.9/go.mod h1:aoV0uJVorq1K+umq18yTdKaF57EivdYsUV+/s2qKfXs=
+github.com/klauspost/compress v1.11.3 h1:dB4Bn0tN3wdCzQxnS8r06kV74qN/TAfaIS0bVE8h3jc=
+github.com/klauspost/compress v1.11.3/go.mod h1:aoV0uJVorq1K+umq18yTdKaF57EivdYsUV+/s2qKfXs=
 github.com/klauspost/pgzip v1.2.4 h1:TQ7CNpYKovDOmqzRHKxJh0BeaBI7UdQZYc6p7pMQh1A=
 github.com/klauspost/pgzip v1.2.4/go.mod h1:Ch1tH69qFZu15pkjo5kYi6mth2Zzwzt50oCQKQE9RUs=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=

mutate/compress.go

@@ -5,6 +5,7 @@ import (
  "io/ioutil"
  "runtime"
 
+ zstd "github.com/klauspost/compress/zstd"
  gzip "github.com/klauspost/pgzip"
  "github.com/pkg/errors"
 )
@@ -67,3 +68,37 @@ func (gz gzipCompressor) Compress(reader io.Reader) (io.ReadCloser, error) {
 func (gz gzipCompressor) MediaTypeSuffix() string {
  return "gzip"
 }
+
+// ZstdCompressor provides zstd compression.
+var ZstdCompressor Compressor = zstdCompressor{}
+
+type zstdCompressor struct{}
+
+func (zs zstdCompressor) Compress(reader io.Reader) (io.ReadCloser, error) {
+
+ pipeReader, pipeWriter := io.Pipe()
+ zenc, err := zstd.NewWriter(pipeWriter)
+ if err != nil {
+ return nil, err
+ }
+ go func() {
+ if _, err := io.Copy(zenc, reader); err != nil {
+ // #nosec G104
+ _ = pipeWriter.CloseWithError(errors.Wrap(err, "compressing layer"))
+ }
+ if err := zenc.Close(); err != nil {
+ // #nosec G104
+ _ = pipeWriter.CloseWithError(errors.Wrap(err, "close gzip writer"))
+ }
+ if err := pipeWriter.Close(); err != nil {
+ // #nosec G104
+ _ = pipeWriter.CloseWithError(errors.Wrap(err, "close pipe writer"))
+ }
+ }()
+
+ return pipeReader, nil
+}
+
+func (zs zstdCompressor) MediaTypeSuffix() string {
+ return "zstd"
+}

mutate/compress_test.go

@@ -2,9 +2,11 @@ package mutate
 
 import (
  "bytes"
+ "io"
  "io/ioutil"
  "testing"
 
+ zstd "github.com/klauspost/compress/zstd"
  gzip "github.com/klauspost/pgzip"
  "github.com/stretchr/testify/assert"
 )
@@ -45,3 +47,22 @@ func TestGzipCompressor(t *testing.T) {
 
  assert.Equal(string(content), fact)
 }
+
+func TestZstdCompressor(t *testing.T) {
+ assert := assert.New(t)
+
+ buf := bytes.NewBufferString(fact)
+ c := ZstdCompressor
+
+ r, err := c.Compress(buf)
+ assert.NoError(err)
+ assert.Equal(c.MediaTypeSuffix(), "zstd")
+
+ dec, err := zstd.NewReader(r)
+ assert.NoError(err)
+
+ var content bytes.Buffer
+ _, err = io.Copy(&content, dec)
+ assert.NoError(err)
+ assert.Equal(content.String(), fact)
+}