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ociindex.go
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ociindex.go
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package ociindex
import (
"encoding/json"
"io"
"os"
"path"
"github.com/gofrs/flock"
ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
)
const (
// lockFileSuffix is the suffix of the lock file
lockFileSuffix = ".lock"
)
type StoreIndex struct {
indexPath string
lockPath string
layoutPath string
}
func NewStoreIndex(storePath string) StoreIndex {
indexPath := path.Join(storePath, ocispecs.ImageIndexFile)
layoutPath := path.Join(storePath, ocispecs.ImageLayoutFile)
return StoreIndex{
indexPath: indexPath,
lockPath: indexPath + lockFileSuffix,
layoutPath: layoutPath,
}
}
func (s StoreIndex) Read() (*ocispecs.Index, error) {
lock := flock.New(s.lockPath)
locked, err := lock.TryRLock()
if err != nil {
return nil, errors.Wrapf(err, "could not lock %s", s.lockPath)
}
if !locked {
return nil, errors.Errorf("could not lock %s", s.lockPath)
}
defer func() {
lock.Unlock()
os.RemoveAll(s.lockPath)
}()
b, err := os.ReadFile(s.indexPath)
if err != nil {
return nil, errors.Wrapf(err, "could not read %s", s.indexPath)
}
var idx ocispecs.Index
if err := json.Unmarshal(b, &idx); err != nil {
return nil, errors.Wrapf(err, "could not unmarshal %s (%q)", s.indexPath, string(b))
}
return &idx, nil
}
func (s StoreIndex) Put(tag string, desc ocispecs.Descriptor) error {
// lock the store to prevent concurrent access
lock := flock.New(s.lockPath)
locked, err := lock.TryLock()
if err != nil {
return errors.Wrapf(err, "could not lock %s", s.lockPath)
}
if !locked {
return errors.Errorf("could not lock %s", s.lockPath)
}
defer func() {
lock.Unlock()
os.RemoveAll(s.lockPath)
}()
// create the oci-layout file
layout := ocispecs.ImageLayout{
Version: ocispecs.ImageLayoutVersion,
}
layoutData, err := json.Marshal(layout)
if err != nil {
return err
}
if err := os.WriteFile(s.layoutPath, layoutData, 0644); err != nil {
return err
}
// modify the index file
idxFile, err := os.OpenFile(s.indexPath, os.O_RDWR|os.O_CREATE, 0644)
if err != nil {
return errors.Wrapf(err, "could not open %s", s.indexPath)
}
defer idxFile.Close()
var idx ocispecs.Index
idxData, err := io.ReadAll(idxFile)
if err != nil {
return errors.Wrapf(err, "could not read %s", s.indexPath)
}
if len(idxData) > 0 {
if err := json.Unmarshal(idxData, &idx); err != nil {
return errors.Wrapf(err, "could not unmarshal %s (%q)", s.indexPath, string(idxData))
}
}
if err = insertDesc(&idx, desc, tag); err != nil {
return err
}
idxData, err = json.Marshal(idx)
if err != nil {
return err
}
if _, err = idxFile.WriteAt(idxData, 0); err != nil {
return errors.Wrapf(err, "could not write %s", s.indexPath)
}
if err = idxFile.Truncate(int64(len(idxData))); err != nil {
return errors.Wrapf(err, "could not truncate %s", s.indexPath)
}
return nil
}
func (s StoreIndex) Get(tag string) (*ocispecs.Descriptor, error) {
idx, err := s.Read()
if err != nil {
return nil, err
}
for _, m := range idx.Manifests {
if t, ok := m.Annotations[ocispecs.AnnotationRefName]; ok && t == tag {
return &m, nil
}
}
return nil, nil
}
func (s StoreIndex) GetSingle() (*ocispecs.Descriptor, error) {
idx, err := s.Read()
if err != nil {
return nil, err
}
if len(idx.Manifests) == 1 {
return &idx.Manifests[0], nil
}
return nil, nil
}
// insertDesc puts desc to index with tag.
// Existing manifests with the same tag will be removed from the index.
func insertDesc(index *ocispecs.Index, desc ocispecs.Descriptor, tag string) error {
if index == nil {
return nil
}
if index.SchemaVersion == 0 {
index.SchemaVersion = 2
}
if tag != "" {
if desc.Annotations == nil {
desc.Annotations = make(map[string]string)
}
desc.Annotations[ocispecs.AnnotationRefName] = tag
// remove existing manifests with the same tag
var manifests []ocispecs.Descriptor
for _, m := range index.Manifests {
if m.Annotations[ocispecs.AnnotationRefName] != tag {
manifests = append(manifests, m)
}
}
index.Manifests = manifests
}
index.Manifests = append(index.Manifests, desc)
return nil
}