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61 lines
1.4 KiB
Go
61 lines
1.4 KiB
Go
package layer // import "github.com/docker/docker/layer"
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import (
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"archive/tar"
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"bytes"
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"fmt"
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"io"
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"io/ioutil"
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)
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// DigestSHA256EmptyTar is the canonical sha256 digest of empty tar file -
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// (1024 NULL bytes)
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const DigestSHA256EmptyTar = DiffID("sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef")
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type emptyLayer struct{}
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// EmptyLayer is a layer that corresponds to empty tar.
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var EmptyLayer = &emptyLayer{}
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func (el *emptyLayer) TarStream() (io.ReadCloser, error) {
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buf := new(bytes.Buffer)
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tarWriter := tar.NewWriter(buf)
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tarWriter.Close()
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return ioutil.NopCloser(buf), nil
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}
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func (el *emptyLayer) TarStreamFrom(p ChainID) (io.ReadCloser, error) {
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if p == "" {
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return el.TarStream()
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}
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return nil, fmt.Errorf("can't get parent tar stream of an empty layer")
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}
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func (el *emptyLayer) ChainID() ChainID {
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return ChainID(DigestSHA256EmptyTar)
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}
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func (el *emptyLayer) DiffID() DiffID {
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return DigestSHA256EmptyTar
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}
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func (el *emptyLayer) Parent() Layer {
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return nil
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}
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func (el *emptyLayer) Size() (size int64, err error) {
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return 0, nil
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}
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func (el *emptyLayer) DiffSize() (size int64, err error) {
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return 0, nil
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}
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func (el *emptyLayer) Metadata() (map[string]string, error) {
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return make(map[string]string), nil
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}
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// IsEmpty returns true if the layer is an EmptyLayer
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func IsEmpty(diffID DiffID) bool {
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return diffID == DigestSHA256EmptyTar
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}
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