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// Copyright 2018 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 crane
import (
"io"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/mutate"
)
// Export writes the filesystem contents (as a tarball) of img to w.
// If img has a single layer, just write the (uncompressed) contents to w so
// that this "just works" for images that just wrap a single blob.
func Export(img v1.Image, w io.Writer) error {
layers, err := img.Layers()
if err != nil {
return err
}
if len(layers) == 1 {
// If it's a single layer...
l := layers[0]
mt, err := l.MediaType()
if err != nil {
return err
}
if !mt.IsLayer() {
// ...and isn't an OCI mediaType, we don't have to flatten it.
// This lets export work for single layer, non-tarball images.
rc, err := l.Uncompressed()
if err != nil {
return err
}
_, err = io.Copy(w, rc)
return err
}
}
fs := mutate.Extract(img)
_, err = io.Copy(w, fs)
return err
}
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