repository: implement pack compression

This commit is contained in:
Michael Eischer 2022-02-13 17:24:09 +01:00
parent 362ab06023
commit 6fb408d90e
10 changed files with 184 additions and 84 deletions

View file

@ -32,7 +32,7 @@ func NewPacker(k *crypto.Key, wr io.Writer) *Packer {
// Add saves the data read from rd as a new blob to the packer. Returned is the
// number of bytes written to the pack.
func (p *Packer) Add(t restic.BlobType, id restic.ID, data []byte) (int, error) {
func (p *Packer) Add(t restic.BlobType, id restic.ID, data []byte, uncompressedLength int) (int, error) {
p.m.Lock()
defer p.m.Unlock()
@ -41,20 +41,23 @@ func (p *Packer) Add(t restic.BlobType, id restic.ID, data []byte) (int, error)
n, err := p.wr.Write(data)
c.Length = uint(n)
c.Offset = p.bytes
c.UncompressedLength = uint(uncompressedLength)
p.bytes += uint(n)
p.blobs = append(p.blobs, c)
return n, errors.Wrap(err, "Write")
}
var entrySize = uint(binary.Size(restic.BlobType(0)) + headerLengthSize + len(restic.ID{}))
var entrySize = uint(binary.Size(restic.BlobType(0)) + 2*headerLengthSize + len(restic.ID{}))
var plainEntrySize = uint(binary.Size(restic.BlobType(0)) + headerLengthSize + len(restic.ID{}))
// headerEntry describes the format of header entries. It serves only as
// documentation.
type headerEntry struct {
Type uint8
Length uint32
ID restic.ID
Type uint8
Length uint32
ID restic.ID
CompressedLength uint32
}
// Finalize writes the header for all added blobs and finalizes the pack.
@ -70,7 +73,7 @@ func (p *Packer) Finalize() (uint, error) {
return 0, err
}
encryptedHeader := make([]byte, 0, len(header)+p.k.Overhead()+p.k.NonceSize())
encryptedHeader := make([]byte, 0, restic.CiphertextLength(len(header)))
nonce := crypto.NewRandomNonce()
encryptedHeader = append(encryptedHeader, nonce...)
encryptedHeader = p.k.Seal(encryptedHeader, nonce, header, nil)
@ -81,7 +84,7 @@ func (p *Packer) Finalize() (uint, error) {
return 0, errors.Wrap(err, "Write")
}
hdrBytes := restic.CiphertextLength(len(header))
hdrBytes := len(encryptedHeader)
if n != hdrBytes {
return 0, errors.New("wrong number of bytes written")
}
@ -104,11 +107,15 @@ func (p *Packer) makeHeader() ([]byte, error) {
buf := make([]byte, 0, len(p.blobs)*int(entrySize))
for _, b := range p.blobs {
switch b.Type {
case restic.DataBlob:
switch {
case b.Type == restic.DataBlob && b.UncompressedLength == 0:
buf = append(buf, 0)
case restic.TreeBlob:
case b.Type == restic.TreeBlob && b.UncompressedLength == 0:
buf = append(buf, 1)
case b.Type == restic.DataBlob && b.UncompressedLength != 0:
buf = append(buf, 2)
case b.Type == restic.TreeBlob && b.UncompressedLength != 0:
buf = append(buf, 3)
default:
return nil, errors.Errorf("invalid blob type %v", b.Type)
}
@ -116,6 +123,10 @@ func (p *Packer) makeHeader() ([]byte, error) {
var lenLE [4]byte
binary.LittleEndian.PutUint32(lenLE[:], uint32(b.Length))
buf = append(buf, lenLE[:]...)
if b.UncompressedLength != 0 {
binary.LittleEndian.PutUint32(lenLE[:], uint32(b.UncompressedLength))
buf = append(buf, lenLE[:]...)
}
buf = append(buf, b.ID[:]...)
}
@ -152,7 +163,7 @@ func (p *Packer) String() string {
var (
// we require at least one entry in the header, and one blob for a pack file
minFileSize = entrySize + crypto.Extension + uint(headerLengthSize)
minFileSize = plainEntrySize + crypto.Extension + uint(headerLengthSize)
)
const (
@ -167,16 +178,11 @@ const (
eagerEntries = 15
)
// readRecords reads up to max records from the underlying ReaderAt, returning
// the raw header, the total number of records in the header, and any error.
// If the header contains fewer than max entries, the header is truncated to
// readRecords reads up to bufsize bytes from the underlying ReaderAt, returning
// the raw header, the total number of bytes in the header, and any error.
// If the header contains fewer than bufsize bytes, the header is truncated to
// the appropriate size.
func readRecords(rd io.ReaderAt, size int64, max int) ([]byte, int, error) {
var bufsize int
bufsize += max * int(entrySize)
bufsize += crypto.Extension
bufsize += headerLengthSize
func readRecords(rd io.ReaderAt, size int64, bufsize int) ([]byte, int, error) {
if bufsize > int(size) {
bufsize = int(size)
}
@ -197,8 +203,6 @@ func readRecords(rd io.ReaderAt, size int64, max int) ([]byte, int, error) {
err = InvalidFileError{Message: "header length is zero"}
case hlen < crypto.Extension:
err = InvalidFileError{Message: "header length is too small"}
case (hlen-crypto.Extension)%uint32(entrySize) != 0:
err = InvalidFileError{Message: "header length is invalid"}
case int64(hlen) > size-int64(headerLengthSize):
err = InvalidFileError{Message: "header is larger than file"}
case int64(hlen) > MaxHeaderSize-int64(headerLengthSize):
@ -208,8 +212,8 @@ func readRecords(rd io.ReaderAt, size int64, max int) ([]byte, int, error) {
return nil, 0, errors.Wrap(err, "readHeader")
}
total := (int(hlen) - crypto.Extension) / int(entrySize)
if total < max {
total := int(hlen + headerLengthSize)
if total < bufsize {
// truncate to the beginning of the pack header
b = b[len(b)-int(hlen):]
}
@ -230,11 +234,12 @@ func readHeader(rd io.ReaderAt, size int64) ([]byte, error) {
// eagerly download eagerEntries header entries as part of header-length request.
// only make second request if actual number of entries is greater than eagerEntries
b, c, err := readRecords(rd, size, eagerEntries)
eagerSize := eagerEntries*int(entrySize) + headerSize
b, c, err := readRecords(rd, size, eagerSize)
if err != nil {
return nil, err
}
if c <= eagerEntries {
if c <= eagerSize {
// eager read sufficed, return what we got
return b, nil
}
@ -262,7 +267,7 @@ func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, hdr
return nil, 0, err
}
if len(buf) < k.NonceSize()+k.Overhead() {
if len(buf) < restic.CiphertextLength(0) {
return nil, 0, errors.New("invalid header, too small")
}
@ -274,11 +279,12 @@ func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, hdr
return nil, 0, err
}
entries = make([]restic.Blob, 0, uint(len(buf))/entrySize)
// might over allocate a bit if all blobs have EntrySize but only by a few percent
entries = make([]restic.Blob, 0, uint(len(buf))/plainEntrySize)
pos := uint(0)
for len(buf) > 0 {
entry, err := parseHeaderEntry(buf)
entry, headerSize, err := parseHeaderEntry(buf)
if err != nil {
return nil, 0, err
}
@ -286,36 +292,60 @@ func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, hdr
entries = append(entries, entry)
pos += entry.Length
buf = buf[entrySize:]
buf = buf[headerSize:]
}
return entries, hdrSize, nil
}
func parseHeaderEntry(p []byte) (b restic.Blob, err error) {
if uint(len(p)) < entrySize {
func parseHeaderEntry(p []byte) (b restic.Blob, size uint, err error) {
l := uint(len(p))
size = plainEntrySize
if l < plainEntrySize {
err = errors.Errorf("parseHeaderEntry: buffer of size %d too short", len(p))
return b, err
return b, size, err
}
p = p[:entrySize]
tpe := p[0]
switch p[0] {
case 0:
switch tpe {
case 0, 2:
b.Type = restic.DataBlob
case 1:
case 1, 3:
b.Type = restic.TreeBlob
default:
return b, errors.Errorf("invalid type %d", p[0])
return b, size, errors.Errorf("invalid type %d", tpe)
}
b.Length = uint(binary.LittleEndian.Uint32(p[1:5]))
copy(b.ID[:], p[5:])
p = p[5:]
if tpe == 2 || tpe == 3 {
size = entrySize
if l < entrySize {
err = errors.Errorf("parseHeaderEntry: buffer of size %d too short", len(p))
return b, size, err
}
b.UncompressedLength = uint(binary.LittleEndian.Uint32(p[0:4]))
p = p[4:]
}
return b, nil
copy(b.ID[:], p[:])
return b, size, nil
}
func CalculateEntrySize(blob restic.Blob) int {
if blob.UncompressedLength != 0 {
return int(entrySize)
}
return int(plainEntrySize)
}
func CalculateHeaderSize(blobs []restic.Blob) int {
return headerSize + len(blobs)*int(entrySize)
size := headerSize
for _, blob := range blobs {
size += CalculateEntrySize(blob)
}
return size
}
// Size returns the size of all packs computed by index information.
@ -333,7 +363,7 @@ func Size(ctx context.Context, mi restic.MasterIndex, onlyHdr bool) map[restic.I
if !onlyHdr {
size += int64(blob.Length)
}
packSize[blob.PackID] = size + int64(entrySize)
packSize[blob.PackID] = size + int64(CalculateEntrySize(blob.Blob))
}
return packSize

View file

@ -23,9 +23,10 @@ func TestParseHeaderEntry(t *testing.T) {
buf := new(bytes.Buffer)
_ = binary.Write(buf, binary.LittleEndian, &h)
b, err := parseHeaderEntry(buf.Bytes())
b, size, err := parseHeaderEntry(buf.Bytes())
rtest.OK(t, err)
rtest.Equals(t, restic.DataBlob, b.Type)
rtest.Equals(t, plainEntrySize, size)
t.Logf("%v %v", h.ID, b.ID)
rtest.Assert(t, bytes.Equal(h.ID[:], b.ID[:]), "id mismatch")
rtest.Equals(t, uint(h.Length), b.Length)
@ -34,14 +35,14 @@ func TestParseHeaderEntry(t *testing.T) {
buf.Reset()
_ = binary.Write(buf, binary.LittleEndian, &h)
b, err = parseHeaderEntry(buf.Bytes())
b, _, err = parseHeaderEntry(buf.Bytes())
rtest.Assert(t, err != nil, "no error for invalid type")
h.Type = 0
buf.Reset()
_ = binary.Write(buf, binary.LittleEndian, &h)
b, err = parseHeaderEntry(buf.Bytes()[:entrySize-1])
b, _, err = parseHeaderEntry(buf.Bytes()[:plainEntrySize-1])
rtest.Assert(t, err != nil, "no error for short input")
}
@ -97,7 +98,8 @@ func TestReadHeaderEagerLoad(t *testing.T) {
func TestReadRecords(t *testing.T) {
testReadRecords := func(dataSize, entryCount, totalRecords int) {
totalHeader := rtest.Random(0, totalRecords*int(entrySize)+crypto.Extension)
off := len(totalHeader) - (entryCount*int(entrySize) + crypto.Extension)
bufSize := entryCount*int(entrySize) + crypto.Extension
off := len(totalHeader) - bufSize
if off < 0 {
off = 0
}
@ -110,10 +112,10 @@ func TestReadRecords(t *testing.T) {
rd := bytes.NewReader(buf.Bytes())
header, count, err := readRecords(rd, int64(rd.Len()), entryCount)
header, count, err := readRecords(rd, int64(rd.Len()), bufSize+4)
rtest.OK(t, err)
rtest.Equals(t, len(totalHeader)+4, count)
rtest.Equals(t, expectedHeader, header)
rtest.Equals(t, totalRecords, count)
}
// basic

View file

@ -38,7 +38,7 @@ func newPack(t testing.TB, k *crypto.Key, lengths []int) ([]Buf, []byte, uint) {
var buf bytes.Buffer
p := pack.NewPacker(k, &buf)
for _, b := range bufs {
_, err := p.Add(restic.TreeBlob, b.id, b.data)
_, err := p.Add(restic.TreeBlob, b.id, b.data, 2*len(b.data))
rtest.OK(t, err)
}

View file

@ -75,12 +75,12 @@ const maxuint32 = 1<<32 - 1
func (idx *Index) store(packIndex int, blob restic.Blob) {
// assert that offset and length fit into uint32!
if blob.Offset > maxuint32 || blob.Length > maxuint32 {
if blob.Offset > maxuint32 || blob.Length > maxuint32 || blob.UncompressedLength > maxuint32 {
panic("offset or length does not fit in uint32. You have packs > 4GB!")
}
m := &idx.byType[blob.Type]
m.add(blob.ID, packIndex, uint32(blob.Offset), uint32(blob.Length))
m.add(blob.ID, packIndex, uint32(blob.Offset), uint32(blob.Length), uint32(blob.UncompressedLength))
}
// Final returns true iff the index is already written to the repository, it is
@ -169,8 +169,9 @@ func (idx *Index) toPackedBlob(e *indexEntry, t restic.BlobType) restic.PackedBl
BlobHandle: restic.BlobHandle{
ID: e.id,
Type: t},
Length: uint(e.length),
Offset: uint(e.offset),
Length: uint(e.length),
Offset: uint(e.offset),
UncompressedLength: uint(e.uncompressedLength),
},
PackID: idx.packs[e.packIndex],
}
@ -225,6 +226,9 @@ func (idx *Index) LookupSize(bh restic.BlobHandle) (plaintextLength uint, found
if e == nil {
return 0, false
}
if e.uncompressedLength != 0 {
return uint(e.uncompressedLength), true
}
return uint(restic.PlaintextLength(int(e.length))), true
}
@ -357,10 +361,11 @@ type packJSON struct {
}
type blobJSON struct {
ID restic.ID `json:"id"`
Type restic.BlobType `json:"type"`
Offset uint `json:"offset"`
Length uint `json:"length"`
ID restic.ID `json:"id"`
Type restic.BlobType `json:"type"`
Offset uint `json:"offset"`
Length uint `json:"length"`
UncompressedLength uint `json:"uncompressed_length,omitempty"`
}
// generatePackList returns a list of packs.
@ -391,10 +396,11 @@ func (idx *Index) generatePackList() ([]*packJSON, error) {
// add blob
p.Blobs = append(p.Blobs, blobJSON{
ID: e.id,
Type: restic.BlobType(typ),
Offset: uint(e.offset),
Length: uint(e.length),
ID: e.id,
Type: restic.BlobType(typ),
Offset: uint(e.offset),
Length: uint(e.length),
UncompressedLength: uint(e.uncompressedLength),
})
return true
@ -553,7 +559,7 @@ func (idx *Index) merge(idx2 *Index) error {
m2.foreach(func(e2 *indexEntry) bool {
if !hasIdenticalEntry(e2) {
// packIndex needs to be changed as idx2.pack was appended to idx.pack, see above
m.add(e2.id, e2.packIndex+packlen, e2.offset, e2.length)
m.add(e2.id, e2.packIndex+packlen, e2.offset, e2.length, e2.uncompressedLength)
}
return true
})
@ -601,8 +607,9 @@ func DecodeIndex(buf []byte, id restic.ID) (idx *Index, oldFormat bool, err erro
BlobHandle: restic.BlobHandle{
Type: blob.Type,
ID: blob.ID},
Offset: blob.Offset,
Length: blob.Length,
Offset: blob.Offset,
Length: blob.Length,
UncompressedLength: blob.UncompressedLength,
})
switch blob.Type {
@ -648,6 +655,7 @@ func decodeOldIndex(buf []byte) (idx *Index, err error) {
ID: blob.ID},
Offset: blob.Offset,
Length: blob.Length,
// no compressed length in the old index format
})
switch blob.Type {

View file

@ -32,7 +32,7 @@ const (
// add inserts an indexEntry for the given arguments into the map,
// using id as the key.
func (m *indexMap) add(id restic.ID, packIdx int, offset, length uint32) {
func (m *indexMap) add(id restic.ID, packIdx int, offset, length uint32, uncompressedLength uint32) {
switch {
case m.numentries == 0: // Lazy initialization.
m.init()
@ -47,6 +47,7 @@ func (m *indexMap) add(id restic.ID, packIdx int, offset, length uint32) {
e.packIndex = packIdx
e.offset = offset
e.length = length
e.uncompressedLength = uncompressedLength
m.buckets[h] = e
m.numentries++
@ -152,9 +153,10 @@ func (m *indexMap) newEntry() *indexEntry {
}
type indexEntry struct {
id restic.ID
next *indexEntry
packIndex int // Position in containing Index's packs field.
offset uint32
length uint32
id restic.ID
next *indexEntry
packIndex int // Position in containing Index's packs field.
offset uint32
length uint32
uncompressedLength uint32
}

View file

@ -22,7 +22,7 @@ func TestIndexMapBasic(t *testing.T) {
r.Read(id[:])
rtest.Assert(t, m.get(id) == nil, "%v retrieved but not added", id)
m.add(id, 0, 0, 0)
m.add(id, 0, 0, 0, 0)
rtest.Assert(t, m.get(id) != nil, "%v added but not retrieved", id)
rtest.Equals(t, uint(i), m.len())
}
@ -41,7 +41,7 @@ func TestIndexMapForeach(t *testing.T) {
for i := 0; i < N; i++ {
var id restic.ID
id[0] = byte(i)
m.add(id, i, uint32(i), uint32(i))
m.add(id, i, uint32(i), uint32(i), uint32(i/2))
}
seen := make(map[int]struct{})
@ -51,6 +51,7 @@ func TestIndexMapForeach(t *testing.T) {
rtest.Equals(t, i, e.packIndex)
rtest.Equals(t, i, int(e.length))
rtest.Equals(t, i, int(e.offset))
rtest.Equals(t, i/2, int(e.uncompressedLength))
seen[i] = struct{}{}
return true
@ -85,13 +86,13 @@ func TestIndexMapForeachWithID(t *testing.T) {
// Test insertion and retrieval of duplicates.
for i := 0; i < ndups; i++ {
m.add(id, i, 0, 0)
m.add(id, i, 0, 0, 0)
}
for i := 0; i < 100; i++ {
var otherid restic.ID
r.Read(otherid[:])
m.add(otherid, -1, 0, 0)
m.add(otherid, -1, 0, 0, 0)
}
n = 0
@ -109,7 +110,7 @@ func TestIndexMapForeachWithID(t *testing.T) {
func BenchmarkIndexMapHash(b *testing.B) {
var m indexMap
m.add(restic.ID{}, 0, 0, 0) // Trigger lazy initialization.
m.add(restic.ID{}, 0, 0, 0, 0) // Trigger lazy initialization.
ids := make([]restic.ID, 128) // 4 KiB.
r := rand.New(rand.NewSource(time.Now().UnixNano()))

View file

@ -70,7 +70,7 @@ func fillPacks(t testing.TB, rnd *rand.Rand, be Saver, pm *packerManager, buf []
// Only change a few bytes so we know we're not benchmarking the RNG.
rnd.Read(buf[:min(l, 4)])
n, err := packer.Add(restic.DataBlob, id, buf)
n, err := packer.Add(restic.DataBlob, id, buf, 0)
if err != nil {
t.Fatal(err)
}

View file

@ -235,12 +235,23 @@ func (r *Repository) LoadBlob(ctx context.Context, t restic.BlobType, id restic.
continue
}
if blob.IsCompressed() {
plaintext, err = r.dec.DecodeAll(plaintext, make([]byte, 0, blob.DataLength()))
if err != nil {
lastError = errors.Errorf("decompressing blob %v failed: %v", id, err)
continue
}
}
// check hash
if !restic.Hash(plaintext).Equal(id) {
lastError = errors.Errorf("blob %v returned invalid hash", id)
continue
}
if len(plaintext) > cap(buf) {
return plaintext, nil
}
// move decrypted data to the start of the buffer
copy(buf, plaintext)
return buf[:len(plaintext)], nil
@ -275,6 +286,12 @@ func (r *Repository) LookupBlobSize(id restic.ID, tpe restic.BlobType) (uint, bo
func (r *Repository) saveAndEncrypt(ctx context.Context, t restic.BlobType, data []byte, id restic.ID) error {
debug.Log("save id %v (%v, %d bytes)", id, t, len(data))
uncompressedLength := 0
if r.cfg.Version > 1 {
uncompressedLength = len(data)
data = r.enc.EncodeAll(data, nil)
}
nonce := crypto.NewRandomNonce()
ciphertext := make([]byte, 0, restic.CiphertextLength(len(data)))
@ -301,7 +318,7 @@ func (r *Repository) saveAndEncrypt(ctx context.Context, t restic.BlobType, data
}
// save ciphertext
_, err = packer.Add(t, id, ciphertext)
_, err = packer.Add(t, id, ciphertext, uncompressedLength)
if err != nil {
return err
}
@ -536,6 +553,17 @@ func (r *Repository) LoadIndex(ctx context.Context) error {
return err
}
if r.cfg.Version < 2 {
// sanity check
ctx, cancel := context.WithCancel(ctx)
defer cancel()
for blob := range r.idx.Each(ctx) {
if blob.IsCompressed() {
return errors.Fatal("index uses feature not supported by repository version 1")
}
}
}
// remove index files from the cache which have been removed in the repo
return r.PrepareCache(validIndex)
}
@ -834,9 +862,15 @@ func StreamPack(ctx context.Context, beLoad BackendLoadFn, key *crypto.Key, pack
debug.Log("streaming pack %v (%d to %d bytes), blobs: %v", packID, dataStart, dataEnd, len(blobs))
dec, err := zstd.NewReader(nil)
if err != nil {
panic(dec)
}
defer dec.Close()
ctx, cancel := context.WithCancel(ctx)
// stream blobs in pack
err := beLoad(ctx, h, int(dataEnd-dataStart), int64(dataStart), func(rd io.Reader) error {
err = beLoad(ctx, h, int(dataEnd-dataStart), int64(dataStart), func(rd io.Reader) error {
// prevent callbacks after cancelation
if ctx.Err() != nil {
return ctx.Err()
@ -849,6 +883,7 @@ func StreamPack(ctx context.Context, beLoad BackendLoadFn, key *crypto.Key, pack
bufRd := bufio.NewReaderSize(rd, bufferSize)
currentBlobEnd := dataStart
var buf []byte
var decode []byte
for _, entry := range blobs {
skipBytes := int(entry.Offset - currentBlobEnd)
if skipBytes < 0 {
@ -888,6 +923,16 @@ func StreamPack(ctx context.Context, beLoad BackendLoadFn, key *crypto.Key, pack
// decryption errors are likely permanent, give the caller a chance to skip them
nonce, ciphertext := buf[:key.NonceSize()], buf[key.NonceSize():]
plaintext, err := key.Open(ciphertext[:0], nonce, ciphertext, nil)
if err == nil && entry.IsCompressed() {
if cap(decode) < int(entry.DataLength()) {
decode = make([]byte, 0, entry.DataLength())
}
decode, err = dec.DecodeAll(plaintext, decode[:0])
plaintext = decode
if err != nil {
err = errors.Errorf("decompressing blob %v failed: %v", h, err)
}
}
if err == nil {
id := restic.Hash(plaintext)
if !id.Equal(entry.ID) {

View file

@ -9,13 +9,25 @@ import (
// Blob is one part of a file or a tree.
type Blob struct {
BlobHandle
Length uint
Offset uint
Length uint
Offset uint
UncompressedLength uint
}
func (b Blob) String() string {
return fmt.Sprintf("<Blob (%v) %v, offset %v, length %v>",
b.Type, b.ID.Str(), b.Offset, b.Length)
return fmt.Sprintf("<Blob (%v) %v, offset %v, length %v, uncompressed length %v>",
b.Type, b.ID.Str(), b.Offset, b.Length, b.UncompressedLength)
}
func (b Blob) DataLength() uint {
if b.UncompressedLength != 0 {
return b.UncompressedLength
}
return uint(PlaintextLength(int(b.Length)))
}
func (b Blob) IsCompressed() bool {
return b.UncompressedLength != 0
}
// PackedBlob is a blob stored within a file.

View file

@ -117,7 +117,7 @@ func (r *fileRestorer) restoreFiles(ctx context.Context) error {
err := r.forEachBlob(fileBlobs, func(packID restic.ID, blob restic.Blob) {
if largeFile {
packsMap[packID] = append(packsMap[packID], fileBlobInfo{id: blob.ID, offset: fileOffset})
fileOffset += int64(restic.PlaintextLength(int(blob.Length)))
fileOffset += int64(blob.DataLength())
}
pack, ok := packs[packID]
if !ok {
@ -195,7 +195,7 @@ func (r *fileRestorer) downloadPack(ctx context.Context, pack *packInfo) error {
if packID.Equal(pack.id) {
addBlob(blob, fileOffset)
}
fileOffset += int64(restic.PlaintextLength(int(blob.Length)))
fileOffset += int64(blob.DataLength())
})
if err != nil {
// restoreFiles should have caught this error before