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cache_linux.go
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cache_linux.go
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package chunked
import (
"bytes"
"encoding/binary"
"encoding/hex"
"errors"
"fmt"
"io"
"os"
"runtime"
"sort"
"strings"
"sync"
"time"
storage "github.com/containers/storage"
graphdriver "github.com/containers/storage/drivers"
"github.com/containers/storage/pkg/chunked/internal"
"github.com/containers/storage/pkg/ioutils"
jsoniter "github.com/json-iterator/go"
digest "github.com/opencontainers/go-digest"
"github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
)
const (
cacheKey = "chunked-manifest-cache"
cacheVersion = 3
digestSha256Empty = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
// Using 3 hashes functions and n/m = 10 gives a false positive rate of ~1.7%:
// https://pages.cs.wisc.edu/~cao/papers/summary-cache/node8.html
bloomFilterScale = 10 // how much bigger is the bloom filter than the number of entries
bloomFilterHashes = 3 // number of hash functions for the bloom filter
)
type cacheFile struct {
tagLen int
digestLen int
fnamesLen int
tags []byte
vdata []byte
fnames []byte
bloomFilter *bloomFilter
}
type layer struct {
id string
cacheFile *cacheFile
target string
// mmapBuffer is nil when the cache file is fully loaded in memory.
// Otherwise it points to a mmap'ed buffer that is referenced by cacheFile.vdata.
mmapBuffer []byte
// reloadWithMmap is set when the current process generates the cache file,
// and cacheFile reuses the memory buffer used by the generation function.
// Next time the layer cache is used, attempt to reload the file using
// mmap.
reloadWithMmap bool
}
type layersCache struct {
layers []*layer
refs int
store storage.Store
mutex sync.RWMutex
created time.Time
}
var (
cacheMutex sync.Mutex
cache *layersCache
)
func (c *layer) release() {
runtime.SetFinalizer(c, nil)
if c.mmapBuffer != nil {
unix.Munmap(c.mmapBuffer)
}
}
func layerFinalizer(c *layer) {
c.release()
}
func (c *layersCache) release() {
cacheMutex.Lock()
defer cacheMutex.Unlock()
c.refs--
if c.refs != 0 {
return
}
for _, l := range c.layers {
l.release()
}
cache = nil
}
func getLayersCacheRef(store storage.Store) *layersCache {
cacheMutex.Lock()
defer cacheMutex.Unlock()
if cache != nil && cache.store == store && time.Since(cache.created).Minutes() < 10 {
cache.refs++
return cache
}
cache := &layersCache{
store: store,
refs: 1,
created: time.Now(),
}
return cache
}
func getLayersCache(store storage.Store) (*layersCache, error) {
c := getLayersCacheRef(store)
if err := c.load(); err != nil {
c.release()
return nil, err
}
return c, nil
}
// loadLayerBigData attempts to load the specified cacheKey from a file and mmap its content.
// If the cache is not backed by a file, then it loads the entire content in memory.
// Returns the cache content, and if mmap'ed, the mmap buffer to Munmap.
func (c *layersCache) loadLayerBigData(layerID, bigDataKey string) ([]byte, []byte, error) {
inputFile, err := c.store.LayerBigData(layerID, bigDataKey)
if err != nil {
return nil, nil, err
}
defer inputFile.Close()
// if the cache is backed by a file, attempt to mmap it.
if osFile, ok := inputFile.(*os.File); ok {
st, err := osFile.Stat()
if err != nil {
logrus.Warningf("Error stat'ing cache file for layer %q: %v", layerID, err)
goto fallback
}
size := st.Size()
if size == 0 {
logrus.Warningf("Cache file size is zero for layer %q: %v", layerID, err)
goto fallback
}
buf, err := unix.Mmap(int(osFile.Fd()), 0, int(size), unix.PROT_READ, unix.MAP_SHARED)
if err != nil {
logrus.Warningf("Error mmap'ing cache file for layer %q: %v", layerID, err)
goto fallback
}
// best effort advise to the kernel.
_ = unix.Madvise(buf, unix.MADV_RANDOM)
return buf, buf, nil
}
fallback:
buf, err := io.ReadAll(inputFile)
return buf, nil, err
}
func makeBinaryDigest(stringDigest string) ([]byte, error) {
d, err := digest.Parse(stringDigest)
if err != nil {
return nil, err
}
digestBytes, err := hex.DecodeString(d.Encoded())
if err != nil {
return nil, err
}
algo := []byte(d.Algorithm())
buf := make([]byte, 0, len(algo)+1+len(digestBytes))
buf = append(buf, algo...)
buf = append(buf, ':')
buf = append(buf, digestBytes...)
return buf, nil
}
func (c *layersCache) loadLayerCache(layerID string) (_ *layer, errRet error) {
buffer, mmapBuffer, err := c.loadLayerBigData(layerID, cacheKey)
if err != nil && !errors.Is(err, os.ErrNotExist) {
return nil, err
}
// there is no existing cache to load
if err != nil || buffer == nil {
return nil, nil
}
defer func() {
if errRet != nil && mmapBuffer != nil {
unix.Munmap(mmapBuffer)
}
}()
cacheFile, err := readCacheFileFromMemory(buffer)
if err != nil {
return nil, err
}
return c.createLayer(layerID, cacheFile, mmapBuffer)
}
// createCacheFileFromTOC attempts to create a cache file for the specified layer.
// If a TOC is not available, the cache won't be created and nil is returned.
func (c *layersCache) createCacheFileFromTOC(layerID string) (*layer, error) {
clFile, err := c.store.LayerBigData(layerID, chunkedLayerDataKey)
if err != nil && !errors.Is(err, os.ErrNotExist) {
return nil, err
}
var lcd chunkedLayerData
if err == nil && clFile != nil {
defer clFile.Close()
cl, err := io.ReadAll(clFile)
if err != nil {
return nil, fmt.Errorf("open manifest file: %w", err)
}
json := jsoniter.ConfigCompatibleWithStandardLibrary
if err := json.Unmarshal(cl, &lcd); err != nil {
return nil, err
}
}
manifestReader, err := c.store.LayerBigData(layerID, bigDataKey)
if err != nil {
// the cache file is not needed since there is no manifest file.
if errors.Is(err, os.ErrNotExist) {
return nil, nil
}
return nil, err
}
defer manifestReader.Close()
manifest, err := io.ReadAll(manifestReader)
if err != nil {
return nil, fmt.Errorf("read manifest file: %w", err)
}
cacheFile, err := writeCache(manifest, lcd.Format, layerID, c.store)
if err != nil {
return nil, err
}
l, err := c.createLayer(layerID, cacheFile, nil)
if err != nil {
return nil, err
}
l.reloadWithMmap = true
return l, nil
}
func (c *layersCache) load() error {
c.mutex.Lock()
defer c.mutex.Unlock()
loadedLayers := make(map[string]*layer)
for _, r := range c.layers {
loadedLayers[r.id] = r
}
allLayers, err := c.store.Layers()
if err != nil {
return err
}
var newLayers []*layer
for _, r := range allLayers {
// The layer is present in the store and it is already loaded. Attempt to
// re-use it if mmap'ed.
if l, found := loadedLayers[r.ID]; found {
// If the layer is not marked for re-load, move it to newLayers.
if !l.reloadWithMmap {
delete(loadedLayers, r.ID)
newLayers = append(newLayers, l)
continue
}
}
// try to read the existing cache file.
l, err := c.loadLayerCache(r.ID)
if err != nil {
logrus.Infof("Error loading cache file for layer %q: %v", r.ID, err)
}
if l != nil {
newLayers = append(newLayers, l)
continue
}
// the cache file is either not present or broken. Try to generate it from the TOC.
l, err = c.createCacheFileFromTOC(r.ID)
if err != nil {
logrus.Warningf("Error creating cache file for layer %q: %v", r.ID, err)
}
if l != nil {
newLayers = append(newLayers, l)
}
}
// The layers that are still in loadedLayers are either stale or fully loaded in memory. Clean them up.
for _, l := range loadedLayers {
l.release()
}
c.layers = newLayers
return nil
}
// calculateHardLinkFingerprint calculates a hash that can be used to verify if a file
// is usable for deduplication with hardlinks.
// To calculate the digest, it uses the file payload digest, UID, GID, mode and xattrs.
func calculateHardLinkFingerprint(f *fileMetadata) (string, error) {
digester := digest.Canonical.Digester()
modeString := fmt.Sprintf("%d:%d:%o", f.UID, f.GID, f.Mode)
hash := digester.Hash()
if _, err := hash.Write([]byte(f.Digest)); err != nil {
return "", err
}
if _, err := hash.Write([]byte(modeString)); err != nil {
return "", err
}
if len(f.Xattrs) > 0 {
keys := make([]string, 0, len(f.Xattrs))
for k := range f.Xattrs {
keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
if _, err := hash.Write([]byte(k)); err != nil {
return "", err
}
if _, err := hash.Write([]byte(f.Xattrs[k])); err != nil {
return "", err
}
}
}
return string(digester.Digest()), nil
}
// generateFileLocation generates a file location in the form $OFFSET$LEN$PATH_POS
func generateFileLocation(pathPos int, offset, len uint64) []byte {
var buf []byte
buf = binary.AppendUvarint(buf, uint64(pathPos))
buf = binary.AppendUvarint(buf, offset)
buf = binary.AppendUvarint(buf, len)
return buf
}
// parseFileLocation reads what was written by generateFileLocation.
func parseFileLocation(locationData []byte) (int, uint64, uint64, error) {
reader := bytes.NewReader(locationData)
pathPos, err := binary.ReadUvarint(reader)
if err != nil {
return 0, 0, 0, err
}
offset, err := binary.ReadUvarint(reader)
if err != nil {
return 0, 0, 0, err
}
len, err := binary.ReadUvarint(reader)
if err != nil {
return 0, 0, 0, err
}
return int(pathPos), offset, len, nil
}
// appendTag appends the $OFFSET$LEN information to the provided $DIGEST.
// The [OFFSET; LEN] points to the variable length data where the file locations
// are stored. $DIGEST has length digestLen stored in the cache file file header.
func appendTag(digest []byte, offset, len uint64) ([]byte, error) {
digest = binary.LittleEndian.AppendUint64(digest, offset)
digest = binary.LittleEndian.AppendUint64(digest, len)
return digest, nil
}
type setBigData interface {
// SetLayerBigData stores a (possibly large) chunk of named data
SetLayerBigData(id, key string, data io.Reader) error
}
func bloomFilterFromTags(tags [][]byte, digestLen int) *bloomFilter {
bloomFilter := newBloomFilter(len(tags)*bloomFilterScale, bloomFilterHashes)
for _, t := range tags {
bloomFilter.add(t[:digestLen])
}
return bloomFilter
}
func writeCacheFileToWriter(writer io.Writer, bloomFilter *bloomFilter, tags [][]byte, tagLen, digestLen int, vdata, fnames bytes.Buffer, tagsBuffer *bytes.Buffer) error {
sort.Slice(tags, func(i, j int) bool {
return bytes.Compare(tags[i], tags[j]) == -1
})
for _, t := range tags {
if _, err := tagsBuffer.Write(t); err != nil {
return err
}
}
// version
if err := binary.Write(writer, binary.LittleEndian, uint64(cacheVersion)); err != nil {
return err
}
// len of a tag
if err := binary.Write(writer, binary.LittleEndian, uint64(tagLen)); err != nil {
return err
}
// len of a digest
if err := binary.Write(writer, binary.LittleEndian, uint64(digestLen)); err != nil {
return err
}
// bloom filter
if err := bloomFilter.writeTo(writer); err != nil {
return err
}
// tags length
if err := binary.Write(writer, binary.LittleEndian, uint64(tagsBuffer.Len())); err != nil {
return err
}
// vdata length
if err := binary.Write(writer, binary.LittleEndian, uint64(vdata.Len())); err != nil {
return err
}
// fnames length
if err := binary.Write(writer, binary.LittleEndian, uint64(fnames.Len())); err != nil {
return err
}
// tags
if _, err := writer.Write(tagsBuffer.Bytes()); err != nil {
return err
}
// variable length data
if _, err := writer.Write(vdata.Bytes()); err != nil {
return err
}
// file names
if _, err := writer.Write(fnames.Bytes()); err != nil {
return err
}
return nil
}
// writeCache write a cache for the layer ID.
// It generates a sorted list of digests with their offset to the path location and offset.
// The same cache is used to lookup files, chunks and candidates for deduplication with hard links.
// There are 3 kind of digests stored:
// - digest(file.payload))
// - digest(digest(file.payload) + file.UID + file.GID + file.mode + file.xattrs)
// - digest(i) for each i in chunks(file payload)
func writeCache(manifest []byte, format graphdriver.DifferOutputFormat, id string, dest setBigData) (*cacheFile, error) {
var vdata, tagsBuffer, fnames bytes.Buffer
tagLen := 0
digestLen := 0
toc, err := prepareCacheFile(manifest, format)
if err != nil {
return nil, err
}
fnamesMap := make(map[string]int)
getFileNamePosition := func(name string) (int, error) {
if pos, found := fnamesMap[name]; found {
return pos, nil
}
pos := fnames.Len()
fnamesMap[name] = pos
if err := binary.Write(&fnames, binary.LittleEndian, uint32(len(name))); err != nil {
return 0, err
}
if _, err := fnames.WriteString(name); err != nil {
return 0, err
}
return pos, nil
}
var tags [][]byte
for _, k := range toc {
if k.Digest != "" {
digest, err := makeBinaryDigest(k.Digest)
if err != nil {
return nil, err
}
fileNamePos, err := getFileNamePosition(k.Name)
if err != nil {
return nil, err
}
location := generateFileLocation(fileNamePos, 0, uint64(k.Size))
off := uint64(vdata.Len())
l := uint64(len(location))
tag, err := appendTag(digest, off, l)
if err != nil {
return nil, err
}
if tagLen == 0 {
tagLen = len(tag)
}
if tagLen != len(tag) {
return nil, errors.New("digest with different length found")
}
tags = append(tags, tag)
fp, err := calculateHardLinkFingerprint(k)
if err != nil {
return nil, err
}
digestHardLink, err := makeBinaryDigest(fp)
if err != nil {
return nil, err
}
tag, err = appendTag(digestHardLink, off, l)
if err != nil {
return nil, err
}
if tagLen != len(tag) {
return nil, errors.New("digest with different length found")
}
tags = append(tags, tag)
if _, err := vdata.Write(location); err != nil {
return nil, err
}
digestLen = len(digestHardLink)
}
if k.ChunkDigest != "" {
fileNamePos, err := getFileNamePosition(k.Name)
if err != nil {
return nil, err
}
location := generateFileLocation(fileNamePos, uint64(k.ChunkOffset), uint64(k.ChunkSize))
off := uint64(vdata.Len())
l := uint64(len(location))
digest, err := makeBinaryDigest(k.ChunkDigest)
if err != nil {
return nil, err
}
d, err := appendTag(digest, off, l)
if err != nil {
return nil, err
}
if tagLen == 0 {
tagLen = len(d)
}
if tagLen != len(d) {
return nil, errors.New("digest with different length found")
}
tags = append(tags, d)
if _, err := vdata.Write(location); err != nil {
return nil, err
}
digestLen = len(digest)
}
}
bloomFilter := bloomFilterFromTags(tags, digestLen)
pipeReader, pipeWriter := io.Pipe()
errChan := make(chan error, 1)
go func() {
defer pipeWriter.Close()
defer close(errChan)
errChan <- writeCacheFileToWriter(pipeWriter, bloomFilter, tags, tagLen, digestLen, vdata, fnames, &tagsBuffer)
}()
defer pipeReader.Close()
counter := ioutils.NewWriteCounter(io.Discard)
r := io.TeeReader(pipeReader, counter)
if err := dest.SetLayerBigData(id, cacheKey, r); err != nil {
return nil, err
}
if err := <-errChan; err != nil {
return nil, err
}
logrus.Debugf("Written lookaside cache for layer %q with length %v", id, counter.Count)
return &cacheFile{
digestLen: digestLen,
tagLen: tagLen,
tags: tagsBuffer.Bytes(),
vdata: vdata.Bytes(),
fnames: fnames.Bytes(),
fnamesLen: len(fnames.Bytes()),
bloomFilter: bloomFilter,
}, nil
}
func readCacheFileFromMemory(bigDataBuffer []byte) (*cacheFile, error) {
bigData := bytes.NewReader(bigDataBuffer)
var version, tagLen, digestLen, tagsLen, fnamesLen, vdataLen uint64
if err := binary.Read(bigData, binary.LittleEndian, &version); err != nil {
return nil, err
}
if version != cacheVersion {
return nil, nil //nolint: nilnil
}
if err := binary.Read(bigData, binary.LittleEndian, &tagLen); err != nil {
return nil, err
}
if err := binary.Read(bigData, binary.LittleEndian, &digestLen); err != nil {
return nil, err
}
bloomFilter, err := readBloomFilter(bigData)
if err != nil {
return nil, err
}
if err := binary.Read(bigData, binary.LittleEndian, &tagsLen); err != nil {
return nil, err
}
if err := binary.Read(bigData, binary.LittleEndian, &vdataLen); err != nil {
return nil, err
}
if err := binary.Read(bigData, binary.LittleEndian, &fnamesLen); err != nil {
return nil, err
}
tags := make([]byte, tagsLen)
if _, err := bigData.Read(tags); err != nil {
return nil, err
}
// retrieve the unread part of the buffer.
remaining := bigDataBuffer[len(bigDataBuffer)-bigData.Len():]
vdata := remaining[:vdataLen]
fnames := remaining[vdataLen:]
return &cacheFile{
bloomFilter: bloomFilter,
digestLen: int(digestLen),
fnames: fnames,
fnamesLen: int(fnamesLen),
tagLen: int(tagLen),
tags: tags,
vdata: vdata,
}, nil
}
func prepareCacheFile(manifest []byte, format graphdriver.DifferOutputFormat) ([]*fileMetadata, error) {
toc, err := unmarshalToc(manifest)
if err != nil {
// ignore errors here. They might be caused by a different manifest format.
logrus.Debugf("could not unmarshal manifest: %v", err)
return nil, nil //nolint: nilnil
}
var entries []fileMetadata
for i := range toc.Entries {
entries = append(entries, fileMetadata{
FileMetadata: toc.Entries[i],
})
}
switch format {
case graphdriver.DifferOutputFormatDir:
case graphdriver.DifferOutputFormatFlat:
entries, err = makeEntriesFlat(entries)
if err != nil {
return nil, err
}
default:
return nil, fmt.Errorf("unknown format %q", format)
}
var r []*fileMetadata
chunkSeen := make(map[string]bool)
for i := range entries {
d := entries[i].Digest
if d != "" {
r = append(r, &entries[i])
continue
}
// chunks do not use hard link dedup so keeping just one candidate is enough
cd := toc.Entries[i].ChunkDigest
if cd != "" && !chunkSeen[cd] {
r = append(r, &entries[i])
chunkSeen[cd] = true
}
}
return r, nil
}
func (c *layersCache) createLayer(id string, cacheFile *cacheFile, mmapBuffer []byte) (*layer, error) {
target, err := c.store.DifferTarget(id)
if err != nil {
return nil, fmt.Errorf("get checkout directory layer %q: %w", id, err)
}
l := &layer{
id: id,
cacheFile: cacheFile,
target: target,
mmapBuffer: mmapBuffer,
}
if mmapBuffer != nil {
runtime.SetFinalizer(l, layerFinalizer)
}
return l, nil
}
func findBinaryTag(binaryDigest []byte, cacheFile *cacheFile) (bool, uint64, uint64) {
nElements := len(cacheFile.tags) / cacheFile.tagLen
i := sort.Search(nElements, func(i int) bool {
d := cacheFile.tags[i*cacheFile.tagLen : i*cacheFile.tagLen+cacheFile.digestLen]
return bytes.Compare(d, binaryDigest) >= 0
})
if i < nElements {
d := cacheFile.tags[i*cacheFile.tagLen : i*cacheFile.tagLen+cacheFile.digestLen]
if bytes.Equal(binaryDigest, d) {
startOff := i*cacheFile.tagLen + cacheFile.digestLen
// check for corrupted data, there must be 2 u64 (off and len) after the digest.
if cacheFile.tagLen < cacheFile.digestLen+16 {
return false, 0, 0
}
offsetAndLen := cacheFile.tags[startOff : (i+1)*cacheFile.tagLen]
off := binary.LittleEndian.Uint64(offsetAndLen[:8])
len := binary.LittleEndian.Uint64(offsetAndLen[8:16])
return true, off, len
}
}
return false, 0, 0
}
func (c *layersCache) findDigestInternal(digest string) (string, string, int64, error) {
if digest == "" {
return "", "", -1, nil
}
binaryDigest, err := makeBinaryDigest(digest)
if err != nil {
return "", "", 0, err
}
c.mutex.RLock()
defer c.mutex.RUnlock()
for _, layer := range c.layers {
if !layer.cacheFile.bloomFilter.maybeContains(binaryDigest) {
continue
}
found, off, tagLen := findBinaryTag(binaryDigest, layer.cacheFile)
if found {
if uint64(len(layer.cacheFile.vdata)) < off+tagLen {
return "", "", 0, fmt.Errorf("corrupted cache file for layer %q", layer.id)
}
fileLocationData := layer.cacheFile.vdata[off : off+tagLen]
fnamePosition, offFile, _, err := parseFileLocation(fileLocationData)
if err != nil {
return "", "", 0, fmt.Errorf("corrupted cache file for layer %q", layer.id)
}
if len(layer.cacheFile.fnames) < fnamePosition+4 {
return "", "", 0, fmt.Errorf("corrupted cache file for layer %q", layer.id)
}
lenPath := int(binary.LittleEndian.Uint32(layer.cacheFile.fnames[fnamePosition : fnamePosition+4]))
if len(layer.cacheFile.fnames) < fnamePosition+lenPath+4 {
return "", "", 0, fmt.Errorf("corrupted cache file for layer %q", layer.id)
}
path := string(layer.cacheFile.fnames[fnamePosition+4 : fnamePosition+lenPath+4])
// parts[1] is the chunk length, currently unused.
return layer.target, path, int64(offFile), nil
}
}
return "", "", -1, nil
}
// findFileInOtherLayers finds the specified file in other layers.
// file is the file to look for.
func (c *layersCache) findFileInOtherLayers(file *fileMetadata, useHardLinks bool) (string, string, error) {
digest := file.Digest
if useHardLinks {
var err error
digest, err = calculateHardLinkFingerprint(file)
if err != nil {
return "", "", err
}
}
target, name, off, err := c.findDigestInternal(digest)
if off == 0 {
return target, name, err
}
return "", "", nil
}
func (c *layersCache) findChunkInOtherLayers(chunk *internal.FileMetadata) (string, string, int64, error) {
return c.findDigestInternal(chunk.ChunkDigest)
}
func unmarshalToc(manifest []byte) (*internal.TOC, error) {
var toc internal.TOC
iter := jsoniter.ParseBytes(jsoniter.ConfigFastest, manifest)
for field := iter.ReadObject(); field != ""; field = iter.ReadObject() {
switch strings.ToLower(field) {
case "version":
toc.Version = iter.ReadInt()
case "entries":
for iter.ReadArray() {
var m internal.FileMetadata
for field := iter.ReadObject(); field != ""; field = iter.ReadObject() {
switch strings.ToLower(field) {
case "type":
m.Type = iter.ReadString()
case "name":
m.Name = iter.ReadString()
case "linkname":
m.Linkname = iter.ReadString()
case "mode":
m.Mode = iter.ReadInt64()
case "size":
m.Size = iter.ReadInt64()
case "uid":
m.UID = iter.ReadInt()
case "gid":
m.GID = iter.ReadInt()
case "modtime":
time, err := time.Parse(time.RFC3339, iter.ReadString())
if err != nil {
return nil, err
}
m.ModTime = &time
case "accesstime":
time, err := time.Parse(time.RFC3339, iter.ReadString())
if err != nil {
return nil, err
}
m.AccessTime = &time
case "changetime":
time, err := time.Parse(time.RFC3339, iter.ReadString())
if err != nil {
return nil, err
}
m.ChangeTime = &time
case "devmajor":
m.Devmajor = iter.ReadInt64()
case "devminor":
m.Devminor = iter.ReadInt64()
case "digest":
m.Digest = iter.ReadString()
case "offset":
m.Offset = iter.ReadInt64()
case "endoffset":
m.EndOffset = iter.ReadInt64()
case "chunksize":
m.ChunkSize = iter.ReadInt64()
case "chunkoffset":
m.ChunkOffset = iter.ReadInt64()
case "chunkdigest":
m.ChunkDigest = iter.ReadString()
case "chunktype":
m.ChunkType = iter.ReadString()
case "xattrs":
m.Xattrs = make(map[string]string)
for key := iter.ReadObject(); key != ""; key = iter.ReadObject() {
m.Xattrs[key] = iter.ReadString()
}
default:
iter.Skip()
}
}
if m.Type == TypeReg && m.Size == 0 && m.Digest == "" {
m.Digest = digestSha256Empty
}
toc.Entries = append(toc.Entries, m)
}
case "tarsplitdigest": // strings.ToLower("tarSplitDigest")
s := iter.ReadString()
d, err := digest.Parse(s)
if err != nil {
return nil, fmt.Errorf("Invalid tarSplitDigest %q: %w", s, err)
}
toc.TarSplitDigest = d
default:
iter.Skip()
}
}
// validate there is no extra data in the provided input. This is a security measure to avoid
// that the digest we calculate for the TOC refers to the entire document.
if iter.Error != nil && iter.Error != io.EOF {
return nil, iter.Error
}
if iter.WhatIsNext() != jsoniter.InvalidValue || !errors.Is(iter.Error, io.EOF) {
return nil, fmt.Errorf("unexpected data after manifest")
}
return &toc, nil
}