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// Copyright 2023 Sylabs Inc. All rights reserved.
//
// SPDX-License-Identifier: Apache-2.0
package sif
import (
"bytes"
"errors"
"io"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/types"
"github.com/sylabs/sif/v2/pkg/sif"
)
// writeBlobToFileImage writes a blob to f.
func (f *fileImage) writeBlobToFileImage(r io.Reader, rootIndex bool) error {
t := sif.DataOCIBlob
if rootIndex {
t = sif.DataOCIRootIndex
}
di, err := sif.NewDescriptorInput(t, r)
if err != nil {
return err
}
return f.AddObject(di)
}
// writeIndexToSIF writes an image and all of its manifests and blobs to f.
func (f *fileImage) writeImageToFileImage(img v1.Image) error {
ls, err := img.Layers()
if err != nil {
return err
}
for _, l := range ls {
rc, err := l.Compressed()
if err != nil {
return err
}
if err := f.writeBlobToFileImage(rc, false); err != nil {
return err
}
}
cfg, err := img.RawConfigFile()
if err != nil {
return err
}
if err := f.writeBlobToFileImage(bytes.NewReader(cfg), false); err != nil {
return err
}
rm, err := img.RawManifest()
if err != nil {
return err
}
return f.writeBlobToFileImage(bytes.NewReader(rm), false)
}
type withBlob interface {
Blob(v1.Hash) (io.ReadCloser, error)
}
type withLayer interface {
Layer(v1.Hash) (v1.Layer, error)
}
var errUnableToReadBlob = errors.New("unable to read blob from index")
// blobFromIndex returns a ReadCloser corresponding to the digest. Unfortunately, the v1.ImageIndex
// does not expose arbitrary blobs (https://github.com/google/go-containerregistry/issues/819) so
// attempt to work around that.
func blobFromIndex(ii v1.ImageIndex, digest v1.Hash) (io.ReadCloser, error) {
if wb, ok := ii.(withBlob); ok {
return wb.Blob(digest)
}
if wl, ok := ii.(withLayer); ok {
l, err := wl.Layer(digest)
if err != nil {
return nil, err
}
return l.Compressed()
}
return nil, errUnableToReadBlob
}
// writeIndexToFileImage writes an index and all of its child indexes, manifests and blobs to f.
func (f *fileImage) writeIndexToFileImage(ii v1.ImageIndex, rootIndex bool) error {
index, err := ii.IndexManifest()
if err != nil {
return err
}
for _, desc := range index.Manifests {
//nolint:exhaustive // Exhaustive cases not appropriate.
switch desc.MediaType {
case types.DockerManifestList, types.OCIImageIndex:
ii, err := ii.ImageIndex(desc.Digest)
if err != nil {
return err
}
if err := f.writeIndexToFileImage(ii, false); err != nil {
return err
}
case types.DockerManifestSchema2, types.OCIManifestSchema1:
img, err := ii.Image(desc.Digest)
if err != nil {
return err
}
if err := f.writeImageToFileImage(img); err != nil {
return err
}
default:
rc, err := blobFromIndex(ii, desc.Digest)
if err != nil {
return err
}
defer rc.Close()
if err := f.writeBlobToFileImage(rc, false); err != nil {
return err
}
}
}
m, err := ii.RawManifest()
if err != nil {
return err
}
return f.writeBlobToFileImage(bytes.NewReader(m), rootIndex)
}
// Write constructs a SIF at path from an ImageIndex.
func Write(path string, ii v1.ImageIndex) error {
fi, err := sif.CreateContainerAtPath(path, sif.OptCreateDeterministic())
if err != nil {
return err
}
defer func() { _ = fi.UnloadContainer() }()
f := fileImage{fi}
return f.writeIndexToFileImage(ii, true)
}
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