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// Copyright 2023 Sylabs Inc. All rights reserved.
//
// SPDX-License-Identifier: Apache-2.0
package mutate
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"sync"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/partial"
"github.com/google/go-containerregistry/pkg/v1/types"
)
type image struct {
base v1.Image
overrides []v1.Layer
history *v1.History
configFileOverride any
configTypeOverride types.MediaType
computed bool
diffIDs []v1.Hash
byDiffID map[v1.Hash]v1.Layer
byDigest map[v1.Hash]v1.Layer
manifest *v1.Manifest
configFile any
rawConfigFile []byte
sync.Mutex
}
var errUnexpectedConfigFileType = errors.New("unexpected config file type")
// populate populates various fields in img.
func (img *image) populate() error {
img.Lock()
defer img.Unlock()
if img.computed {
return nil
}
manifest, err := img.base.Manifest()
if err != nil {
return err
}
manifest = manifest.DeepCopy()
ls, err := img.base.Layers()
if err != nil {
return err
}
layers := make([]v1.Descriptor, 0, len(img.overrides))
diffIDs := make([]v1.Hash, 0, len(img.overrides))
byDiffID := make(map[v1.Hash]v1.Layer, len(img.overrides))
byDigest := make(map[v1.Hash]v1.Layer, len(img.overrides))
for i, l := range img.overrides {
if l == nil {
l = ls[i]
}
d, err := partial.Descriptor(l)
if err != nil {
return err
}
diffID, err := l.DiffID()
if err != nil {
return err
}
layers = append(layers, *d)
diffIDs = append(diffIDs, diffID)
byDiffID[diffID] = l
byDigest[d.Digest] = l
}
manifest.Layers = layers
configFile := img.configFileOverride
configType := img.configTypeOverride
// If configFile is not overridden, populate from the base image.
if configFile == nil {
configType = manifest.Config.MediaType
if configType.IsConfig() {
cf, err := img.base.ConfigFile()
if err != nil {
return err
}
configFile = cf
}
}
// If configType is one of the standard formats, mutate it if requested.
if configType.IsConfig() {
cf, ok := configFile.(*v1.ConfigFile)
if !ok {
return fmt.Errorf("%w: %T", errUnexpectedConfigFileType, configFile)
}
cf = cf.DeepCopy()
cf.RootFS.DiffIDs = diffIDs
// Replace history, if applicable.
if img.history != nil {
cf.History = []v1.History{*img.history}
}
configFile = cf
}
// Populate raw config.
var config []byte
if configFile != nil {
b, err := json.Marshal(configFile)
if err != nil {
return err
}
config = b
} else {
b, err := img.base.RawConfigFile()
if err != nil {
return err
}
config = b
}
digest, size, err := v1.SHA256(bytes.NewBuffer(config))
if err != nil {
return err
}
manifest.Config.MediaType = configType
manifest.Config.Digest = digest
manifest.Config.Size = size
if manifest.Config.Data != nil {
manifest.Config.Data = config
}
img.computed = true
img.diffIDs = diffIDs
img.byDiffID = byDiffID
img.byDigest = byDigest
img.manifest = manifest
img.configFile = configFile
img.rawConfigFile = config
return nil
}
// MediaType of this image's manifest.
func (img *image) MediaType() (types.MediaType, error) {
return img.base.MediaType()
}
// Size returns the size of the manifest.
func (img *image) Size() (int64, error) {
return partial.Size(img)
}
// Digest returns the sha256 of this image's manifest.
func (img *image) Digest() (v1.Hash, error) {
return partial.Digest(img)
}
// Manifest returns this image's Manifest object.
func (img *image) Manifest() (*v1.Manifest, error) {
if err := img.populate(); err != nil {
return nil, err
}
return img.manifest, nil
}
// RawManifest returns the serialized bytes of Manifest().
func (img *image) RawManifest() ([]byte, error) {
if err := img.populate(); err != nil {
return nil, err
}
return json.Marshal(img.manifest)
}
// ConfigName returns the hash of the image's config file, also known as
// the Image ID.
func (img *image) ConfigName() (v1.Hash, error) {
return partial.ConfigName(img)
}
// ConfigFile returns this image's config file.
func (img *image) ConfigFile() (*v1.ConfigFile, error) {
if err := img.populate(); err != nil {
return nil, err
}
cf, ok := img.configFile.(*v1.ConfigFile)
if !ok {
return nil, fmt.Errorf("%w: %T", errUnexpectedConfigFileType, img.configFile)
}
return cf, nil
}
// RawConfigFile returns the serialized bytes of ConfigFile().
func (img *image) RawConfigFile() ([]byte, error) {
if err := img.populate(); err != nil {
return nil, err
}
return img.rawConfigFile, nil
}
// Layers returns the ordered collection of filesystem layers that comprise this image.
func (img *image) Layers() ([]v1.Layer, error) {
if err := img.populate(); err != nil {
return nil, err
}
ls := make([]v1.Layer, 0, len(img.diffIDs))
for _, h := range img.diffIDs {
l, err := img.LayerByDiffID(h)
if err != nil {
return nil, err
}
ls = append(ls, l)
}
return ls, nil
}
var errLayerNotFound = errors.New("layer not found")
// LayerByDigest returns a Layer for interacting with a particular layer of the image, looking it
// up by "digest" (the compressed hash).
func (img *image) LayerByDigest(h v1.Hash) (v1.Layer, error) {
if err := img.populate(); err != nil {
return nil, err
}
if l, ok := img.byDigest[h]; ok {
return l, nil
}
return nil, errLayerNotFound
}
// LayerByDiffID is an analog to LayerByDigest, looking up by "diff id" (the uncompressed hash).
func (img *image) LayerByDiffID(h v1.Hash) (v1.Layer, error) {
if err := img.populate(); err != nil {
return nil, err
}
if l, ok := img.byDiffID[h]; ok {
return l, nil
}
return nil, errLayerNotFound
}
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