1 files changed, 54 insertions, 0 deletions
diff --git a/internal/estargz/estargz.go b/internal/estargz/estargz.go
new file mode 100644
index 0000000..69021bc
--- /dev/null
+++ b/internal/estargz/estargz.go
@@ -0,0 +1,54 @@
+// Copyright 2020 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package estargz adapts the containerd estargz package to our abstractions.
+package estargz
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/containerd/stargz-snapshotter/estargz"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+)
+
+// Assert that what we're returning is an io.ReadCloser
+var _ io.ReadCloser = (*estargz.Blob)(nil)
+
+// ReadCloser reads uncompressed tarball input from the io.ReadCloser and
+// returns:
+//   - An io.ReadCloser from which compressed data may be read, and
+//   - A v1.Hash with the hash of the estargz table of contents, or
+//   - An error if the estargz processing encountered a problem.
+//
+// Refer to estargz for the options:
+// https://pkg.go.dev/github.com/containerd/stargz-snapshotter/estargz@v0.4.1#Option
+func ReadCloser(r io.ReadCloser, opts ...estargz.Option) (*estargz.Blob, v1.Hash, error) {
+	defer r.Close()
+
+	// TODO(#876): Avoid buffering into memory.
+	bs, err := io.ReadAll(r)
+	if err != nil {
+		return nil, v1.Hash{}, err
+	}
+	br := bytes.NewReader(bs)
+
+	rc, err := estargz.Build(io.NewSectionReader(br, 0, int64(len(bs))), opts...)
+	if err != nil {
+		return nil, v1.Hash{}, err
+	}
+
+	h, err := v1.NewHash(rc.TOCDigest().String())
+	return rc, h, err
+}