repository: implement pack compression

internal/pack/pack.go

@@ -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

internal/pack/pack_internal_test.go

@@ -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

internal/pack/pack_test.go

@@ -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)
 	}