Initial commit

vendor/github.com/hyperhq/hypercli/layer/empty.go

@@ -0,0 +1,48 @@
+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
+}