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tar_reader.go
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tar_reader.go
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// Copyright 2020 VMware, Inc.
// SPDX-License-Identifier: Apache-2.0
package imagetar
import (
"fmt"
"io"
"github.com/google/go-containerregistry/pkg/name"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/vmware-tanzu/carvel-imgpkg/pkg/imgpkg/imagedesc"
"github.com/vmware-tanzu/carvel-imgpkg/pkg/imgpkg/imageutils/verify"
)
type TarReader struct {
path string
}
func NewTarReader(path string) TarReader {
return TarReader{path}
}
func (r TarReader) Read() ([]imagedesc.ImageOrIndex, error) {
file := tarFile{r.path}
ids, err := r.getIdsFromManifest(file)
if err != nil {
return nil, err
}
return imagedesc.NewDescribedReader(ids, file).Read(), nil
}
// PresentLayers retrieves all the layers that are present in a tar file
func (r TarReader) PresentLayers() ([]v1.Layer, error) {
var result []v1.Layer
allImages, err := r.Read()
if err != nil {
return nil, err
}
for _, image := range allImages {
if image.Image != nil {
img := *image.Image
layers, err := r.presentLayersForImage(img)
if err != nil {
return nil, fmt.Errorf("Processing Image %s: %s", image.OrigRef, err)
}
result = append(result, layers...)
} else if image.Index != nil {
idx := *image.Index
layers, err := r.presentLayersForIndex(image.Ref(), idx)
if err != nil {
return nil, fmt.Errorf("Processing Index %s: %s", image.OrigRef, err)
}
result = append(result, layers...)
}
}
return result, nil
}
func (r TarReader) presentLayersForImage(img v1.Image) ([]v1.Layer, error) {
var result []v1.Layer
layers, err := img.Layers()
if err != nil {
return nil, fmt.Errorf("Unable to retrieve layers: %s", err)
}
for _, layer := range layers {
h, err := layer.Digest()
if err != nil {
return nil, fmt.Errorf("Unable to get digest from layer: %s", err)
}
r, err := layer.Compressed()
if err != nil {
continue
}
size, err := layer.Size()
if err != nil {
return nil, err
}
closer, err := verify.ReadCloser(r, size, h)
if err != nil {
return nil, err
}
_, err = io.Copy(io.Discard, closer)
if err != nil {
continue
}
result = append(result, layer)
}
return result, nil
}
func (r TarReader) presentLayersForIndex(indexRef string, idx v1.ImageIndex) ([]v1.Layer, error) {
var result []v1.Layer
dIdx, correct := idx.(imagedesc.DescribedImageIndex)
if !correct {
panic(fmt.Sprintf("Internal inconsistency: unexpected index type with ref: %s", indexRef))
}
for _, image := range dIdx.Images() {
layersPresent, err := r.presentLayersForImage(image)
if err != nil {
return nil, err
}
result = append(result, layersPresent...)
}
idxRef, err := name.ParseReference(indexRef)
if err != nil {
return nil, err
}
for _, idx := range dIdx.Indexes() {
digest, err := idx.Digest()
if err != nil {
return nil, err
}
idxDigest := idxRef.Context().Digest(digest.String())
layersPresent, err := r.presentLayersForIndex(idxDigest.String(), idx)
if err != nil {
return nil, err
}
result = append(result, layersPresent...)
}
return result, nil
}
func (r TarReader) getIdsFromManifest(file tarFile) (*imagedesc.ImageRefDescriptors, error) {
manifestFile, err := file.Chunk("manifest.json").Open()
if err != nil {
return nil, err
}
defer manifestFile.Close()
manifestBytes, err := io.ReadAll(manifestFile)
if err != nil {
return nil, err
}
ids, err := imagedesc.NewImageRefDescriptorsFromBytes(manifestBytes)
if err != nil {
return nil, err
}
return ids, nil
}