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moby--moby/layer/empty.go
Aaron Lehmann 21278efaee Make TarStream return an io.ReadCloser
Currently, the resources associated with the io.Reader returned by
TarStream are only freed when it is read until EOF. This means that
partial uploads or exports (for example, in the case of a full disk or
severed connection) can leak a goroutine and open file. This commit
changes TarStream to return an io.ReadCloser. Resources are freed when
Close is called.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
2015-11-25 16:39:54 -08:00

48 lines
1 KiB
Go

package layer
import (
"archive/tar"
"bytes"
"io"
"io/ioutil"
)
// DigestSHA256EmptyTar is the canonical sha256 digest of empty tar file -
// (1024 NULL bytes)
const DigestSHA256EmptyTar = DiffID("sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef")
type emptyLayer struct{}
// EmptyLayer is a layer that corresponds to empty tar.
var EmptyLayer = &emptyLayer{}
func (el *emptyLayer) TarStream() (io.ReadCloser, error) {
buf := new(bytes.Buffer)
tarWriter := tar.NewWriter(buf)
tarWriter.Close()
return ioutil.NopCloser(buf), nil
}
func (el *emptyLayer) ChainID() ChainID {
return ChainID(DigestSHA256EmptyTar)
}
func (el *emptyLayer) DiffID() DiffID {
return DigestSHA256EmptyTar
}
func (el *emptyLayer) Parent() Layer {
return nil
}
func (el *emptyLayer) Size() (size int64, err error) {
return 0, nil
}
func (el *emptyLayer) DiffSize() (size int64, err error) {
return 0, nil
}
func (el *emptyLayer) Metadata() (map[string]string, error) {
return make(map[string]string), nil
}