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compression: add support for the zstd algorithm
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zstd is a compression algorithm that has a very fast decoder, while
providing also good compression ratios.  The fast decoder makes it
suitable for container images, as decompressing the tarballs is a very
expensive operation.

opencontainers/image-spec#788 added support
for zstd to the OCI image specs.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
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giuseppe committed Sep 16, 2021
1 parent 5176095 commit 993d8cc
Showing 1 changed file with 11 additions and 0 deletions.
11 changes: 11 additions & 0 deletions pkg/archive/archive.go
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ import (
"github.com/docker/docker/pkg/ioutils"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/system"
"github.com/klauspost/compress/zstd"
"github.com/sirupsen/logrus"
exec "golang.org/x/sys/execabs"
)
Expand Down Expand Up @@ -83,6 +84,8 @@ const (
Gzip
// Xz is xz compression algorithm.
Xz
// Zstd is zstd compression algorithm.
Zstd
)

const (
Expand Down Expand Up @@ -127,6 +130,7 @@ func DetectCompression(source []byte) Compression {
Bzip2: {0x42, 0x5A, 0x68},
Gzip: {0x1F, 0x8B, 0x08},
Xz: {0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00},
Zstd: {0x28, 0xb5, 0x2f, 0xfd},
} {
if bytes.HasPrefix(source, m) {
return compression
Expand Down Expand Up @@ -215,6 +219,13 @@ func DecompressStream(archive io.Reader) (io.ReadCloser, error) {
}
readBufWrapper := p.NewReadCloserWrapper(buf, xzReader)
return wrapReadCloser(readBufWrapper, cancel), nil
case Zstd:
zstdReader, err := zstd.NewReader(buf)
if err != nil {
return nil, err
}
readBufWrapper := p.NewReadCloserWrapper(buf, zstdReader)
return readBufWrapper, nil
default:
return nil, fmt.Errorf("Unsupported compression format %s", (&compression).Extension())
}
Expand Down

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