Add lib/litonlylzma.FileFormatXz
diff --git a/lib/litonlylzma/example_test.go b/lib/litonlylzma/example_test.go
index d2a3b59..1825030 100644
--- a/lib/litonlylzma/example_test.go
+++ b/lib/litonlylzma/example_test.go
@@ -21,7 +21,7 @@
"github.com/google/wuffs/lib/litonlylzma"
)
-func ExampleRoundTrip() {
+func ExampleRoundTripLZMA() {
original := []byte("Hello world.\n")
compressed, err := litonlylzma.FileFormatLZMA.Encode(nil, original)
if err != nil {
@@ -31,15 +31,51 @@
if err != nil {
log.Fatalf("Decode: %v", err)
}
+
for i, c := range compressed {
- if i > 0 {
+ if (i & 15) > 0 {
fmt.Printf(" ")
}
fmt.Printf("%02X", c)
+ if ((i & 15) == 15) || ((i + 1) == len(compressed)) {
+ fmt.Println()
+ }
}
- fmt.Printf("\n%s\n", recovered)
+ fmt.Printf("%s", recovered)
// Output:
- // 5D 00 10 00 00 0D 00 00 00 00 00 00 00 00 24 19 49 86 E7 D5 E5 E2 56 ED 6A E6 0E 81 FE B8 00 00
+ // 5D 00 10 00 00 0D 00 00 00 00 00 00 00 00 24 19
+ // 49 86 E7 D5 E5 E2 56 ED 6A E6 0E 81 FE B8 00 00
+ // Hello world.
+}
+
+func ExampleRoundTripXz() {
+ original := []byte("Hello world.\n")
+ compressed, err := litonlylzma.FileFormatXz.Encode(nil, original)
+ if err != nil {
+ log.Fatalf("Encode: %v", err)
+ }
+ recovered, _, err := litonlylzma.FileFormatXz.Decode(nil, compressed)
+ if err != nil {
+ log.Fatalf("Decode: %v", err)
+ }
+
+ for i, c := range compressed {
+ if (i & 15) > 0 {
+ fmt.Printf(" ")
+ }
+ fmt.Printf("%02X", c)
+ if ((i & 15) == 15) || ((i + 1) == len(compressed)) {
+ fmt.Println()
+ }
+ }
+ fmt.Printf("%s", recovered)
+
+ // Output:
+ // FD 37 7A 58 5A 00 00 01 69 22 DE 36 02 00 21 01
+ // 00 00 00 00 37 27 97 D6 01 00 0C 48 65 6C 6C 6F
+ // 20 77 6F 72 6C 64 2E 0A 00 00 00 00 8E F8 31 35
+ // 00 01 21 0D 75 DC A8 D2 90 42 99 0D 01 00 00 00
+ // 00 01 59 5A
// Hello world.
}
diff --git a/lib/litonlylzma/litonlylzma.go b/lib/litonlylzma/litonlylzma.go
index 53ce400..70286a2 100644
--- a/lib/litonlylzma/litonlylzma.go
+++ b/lib/litonlylzma/litonlylzma.go
@@ -14,23 +14,28 @@
// ----------------
-// Package litonlylzma provides a decoder and encoder for Literal Only LZMA, a
-// subset of the LZMA compressed file format.
+// Package litonlylzma provides a decoder and encoder for Literal Only LZMA (or
+// Literal Only Xz), a subset of the LZMA (or Xz) compressed file formats.
//
-// Subset means that the Encode method's output is a valid LZMA file and can be
-// decompressed by the tools available at https://www.7-zip.org/sdk.html (and
-// available as /usr/bin/lzma on a Debian system).
+// Subset means that:
+// - the Encode methods' output is a valid LZMA/Xz file and can be
+// decompressed by the tools available at https://www.7-zip.org/sdk.html or
+// https://tukaani.org/xz/ (and available as /usr/bin/lzma or /usr/bin/xz
+// on a Debian system).
+// - the Decode methods supports the Encode methods' output but they do not
+// support the full set of valid LZMA/Xz files.
+// - this codec's compression ratios are not as good as full LZMA/Xz
+// (although compression times are much faster). Moderate compression is
+// still achieved, through range coding, but there are no Lempel Ziv
+// back-references.
//
-// Subset also means that this codec's compression ratios are not as good as
-// full-LZMA (although compression times are much faster). Moderate compression
-// is still achieved, through range coding, but there are no Lempel Ziv
-// back-references. The main benefit, compared to full-LZMA, is that this
-// implementation is much simpler and hence easier to study. It is only a few
-// hundred lines of code.
+// The main benefit, compared to full LZMA/Xz, is that this implementation is
+// much simpler and hence easier to study. It is around 800 lines of code.
//
// Example compression numbers on a small English text file (at
// https://github.com/google/wuffs/blob/main/test/data/romeo.txt):
// - romeo.txt is 942 bytes (100%).
+// - romeo.txt.litonlyxz is 708 bytes (75%).
// - romeo.txt.litonlylzma is 659 bytes (70%).
// - romeo.txt.xz is 644 bytes (68%).
// - romeo.txt.lzma is 598 bytes (63%).
@@ -41,6 +46,7 @@
// Example compression numbers on a large archive of source code (at
// https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.0.1.tar.xz):
// - linux-5.0.1.tar is 863313920 bytes (100%).
+// - linux-5.0.1.tar.litonlyxz is 454480932 bytes (53%).
// - linux-5.0.1.tar.litonlylzma is 449726070 bytes (52%).
// - linux-5.0.1.tar.gz is 164575959 bytes (19%).
// - linux-5.0.1.tar.zst is 156959897 bytes (18%).
@@ -55,13 +61,16 @@
import (
"errors"
+ "hash/crc32"
)
var (
- // ErrUnsupportedLZMAData is potentially returned by Decode.
+ // ErrUnsupportedXxxData is potentially returned by Decode.
ErrUnsupportedLZMAData = errors.New("litonlylzma: unsupported LZMA data")
+ ErrUnsupportedXzData = errors.New("litonlylzma: unsupported Xz data")
errInvalidLZMAData = errors.New("litonlylzma: invalid LZMA data")
+ errInvalidXzData = errors.New("litonlylzma: invalid Xz data")
errUnexpectedEOF = errors.New("litonlylzma: unexpected EOF")
errUnsupportedFileFormat = errors.New("litonlylzma: unsupported FileFormat")
)
@@ -79,13 +88,30 @@
pbMask = (1 << pb) - 1
)
-// lzmaHeader5 is the first 5 bytes of the LZMA header using the hard-coded
-// configuration for the subset-of-LZMA that this package supports. 0x5D
-// encodes the (lc, lp, pb) triple and the next four bytes hold the u32le
-// dictionary size. 0x1000 is LZMA's minimum dictionary size, although our
+// lzmaHeader5 is the first 5 bytes of an LZMA file using the hard-coded
+// configuration for the subset-of-LZMA that this package supports.
+//
+// 0x5D encodes the (lc, lp, pb) triple and the next four bytes hold the u32le
+// dictionary size. 0x00001000 is LZMA's minimum dictionary size, although our
// subset-of-LZMA does not use a dictionary (also called a "sliding window").
const lzmaHeader5 = "\x5D\x00\x10\x00\x00"
+// xzHeader24 is the first 24 bytes of an Xz file using the hard-coded
+// configuration for the subset-of-Xz that this package supports.
+const xzHeader24 = "" +
+ "\xFD\x37\x7A\x58\x5A\x00" + // Stream Header Magic Bytes.
+ // ----
+ "\x00\x01" + // Stream Flags (0x01 means CRC-32).
+ "\x69\x22\xDE\x36" + // CRC-32 of the previous 2 bytes.
+ // ----
+ "\x02" + // Block Header Size (0x02 * 4 = 8 bytes).
+ "\x00" + // Block Flags.
+ "\x21" + // Filter ID (0x21 means LZMA2).
+ "\x01" + // Size of Filter Properties (size of the next line).
+ "\x00" + // Filter Properties (0x00 means an 0x1000 dictionary size).
+ "\x00\x00\x00" + // Padding to 4-byte alignment.
+ "\x37\x27\x97\xD6" // CRC-32 of the previous 8 bytes.
+
// rangeDecoder and rangeEncoder hold the state for range coding (also known as
// arithmetic coding, roughly speaking). "range" is a keyword in Go, so in this
// implementation, what's traditionally called the "range" fields are called
@@ -120,13 +146,13 @@
// digit is stashed as the pendingHead field. low is set to 8872, width is set
// to (46055 - 38872) = 7183 and we progress until the width drops below 1000,
// causing a 'zoom in' event. There are three cases:
-// - if low is less than 9000 (but starts with an '8'), we can emit the '3'
-// with confidence (and then stash '8' in the pendingHead field).
-// - if low overflows 9999, we can emit the '4' with confidence (and then stash
-// low's 'thousands digit' in the pendingHead field).
-// - if low is in 9000 ..= 9999 then we could still be unsure. Keep the '3'
-// pending but extend it so that there are two pending digits: '39'. If this
-// occurs again: '399', and so on.
+// - if low is less than 9000 (but starts with an '8'), we can emit the '3'
+// with confidence (and then stash '8' in the pendingHead field).
+// - if low overflows 9999, we can emit the '4' with confidence (and then
+// stash low's 'thousands digit' in the pendingHead field).
+// - if low is in 9000 ..= 9999 then we could still be unsure. Keep the '3'
+// pending but extend it so that there are two pending digits: '39'. If
+// this occurs again: '399', and so on.
//
// In all three cases, 'zooming in' causes us to shift out the most significant
// digit of the low field. This method is therefore named shiftLow here, the
@@ -320,7 +346,7 @@
}
// FileFormat is a compressed file format, either the original LZMA format
-// itself or something that builds on or varies that.
+// itself or something like Xz that builds on or varies that.
//
// Each valid FileFormatXxx value does not distinguish between the full file
// format (as spoken by numerous Xxx software tools) and the subset-of-Xxx
@@ -328,26 +354,27 @@
// produce compressed data that is valid full-LZMA (and is also valid
// subset-of-LZMA). FileFormatLZMA.Decode can decode subset-of-LZMA (but not
// full-LZMA).
-//
-// This package currently defines only one valid FileFormatXxx value:
-// FileFormatLZMA. Future versions of this package could define e.g.
-// FileFormatLZMA2 or FileFormatXz such that FileFormatXz.Encode would produce
-// valid full-XZ data: a valid XZ file (that could be decoded by official XZ
-// tools) that used the LZMA compression filter, but elected not to use the
-// full capabilities of that filter (using LZ literals only, not matches).
type FileFormat uint32
const (
FileFormatInvalid = FileFormat(0)
FileFormatLZMA = FileFormat(1)
+ FileFormatXz = FileFormat(2)
)
-// Decode converts src from the Literal Only LZMA compressed file format,
+func (f FileFormat) String() string {
+ switch f {
+ case FileFormatLZMA:
+ return "FileFormatLZMA"
+ case FileFormatXz:
+ return "FileFormatXz"
+ }
+ return "FileFormatInvalid"
+}
+
+// Decode converts src from the Literal Only LZMA/Xz compressed file format,
// appending the decoding to dst.
//
-// f should be FileFormatLZMA but future versions of this package may support
-// other file formats.
-//
// It is valid to pass a nil dst, like the way it's valid to pass nil to the
// built-in append function.
//
@@ -356,14 +383,19 @@
// It can also return partial results. The appendedDst and remainingSrc return
// values may be non-zero even if retErr is non-zero.
//
-// It returns ErrUnsupportedLZMAData if the source bytes look like LZMA
-// formatted data that is outside the subset-of-LZMA that this package
-// implements.
+// It returns ErrUnsupportedXxxData if the source bytes look like Xxx formatted
+// data that is outside the subset-of-Xxx that this package implements.
func (f FileFormat) Decode(dst []byte, src []byte) (appendedDst []byte, remainingSrc []byte, retErr error) {
- if f != FileFormatLZMA {
- return dst, nil, errUnsupportedFileFormat
+ switch f {
+ case FileFormatLZMA:
+ return decodeLZMA(dst, src)
+ case FileFormatXz:
+ return decodeXz(dst, src)
}
+ return nil, nil, errUnsupportedFileFormat
+}
+func decodeLZMA(dst []byte, src []byte) (appendedDst []byte, remainingSrc []byte, retErr error) {
// LZMA consists of a 13 byte header and then at least a 5 byte payload
// (range coded data). The 13 byte header is:
// - 1 byte for the (lc, lp, pb) triple with max values (8, 4, 4),
@@ -371,12 +403,7 @@
// - 8 bytes i64le uncompressed size.
if (len(src) < 18) || (src[0] >= (9 * 5 * 5)) {
return dst, nil, errInvalidLZMAData
- } else if (src[0] != lzmaHeader5[0]) ||
- (src[1] != lzmaHeader5[1]) ||
- (src[2] != lzmaHeader5[2]) ||
- (src[3] != lzmaHeader5[3]) ||
- (src[4] != lzmaHeader5[4]) ||
- (src[13] != 0x00) {
+ } else if string(src[:5]) != lzmaHeader5 {
return dst, nil, ErrUnsupportedLZMAData
}
@@ -390,12 +417,151 @@
return dst, nil, ErrUnsupportedLZMAData
}
+ return decodeRaw(dst, src[13:], size, ErrUnsupportedLZMAData)
+}
+
+func decodeXz(dst []byte, src []byte) (appendedDst []byte, remainingSrc []byte, retErr error) {
+ originalDstLen := len(dst)
+ originalSrcLen := len(src)
+
+ // Decode the headers.
+ if (len(src) < 24) || (string(src[:6]) != xzHeader24[:6]) {
+ return dst, src, errInvalidXzData
+ } else if string(src[6:24]) != xzHeader24[6:24] {
+ return dst, src, ErrUnsupportedXzData
+ }
+ src = src[24:]
+
+ // Decode the payload as multiple chunks.
+ for {
+ if len(src) == 0 {
+ return dst, src, errInvalidXzData
+
+ } else if src[0] == 0x00 { // No more chunks.
+ src = src[1:]
+ break
+
+ } else if src[0] == 0x01 { // Independent uncompressed chunk.
+ if len(src) < 3 {
+ return dst, src, errInvalidXzData
+ }
+ uncompressedSize := (uint32(src[1]) << 8) + (uint32(src[2]) << 0) + 1
+ src = src[3:]
+ if uint64(uncompressedSize) > uint64(len(src)) {
+ return dst, src, errInvalidXzData
+ }
+ dst = append(dst, src[:uncompressedSize]...)
+ src = src[uncompressedSize:]
+
+ } else if src[0] == 0xE0 { // Independent LZMA chunk.
+ if len(src) < 6 {
+ return dst, src, errInvalidXzData
+ } else if src[5] != 0x5D { // Like lzmaHeader5[0], this encodes lc=3, lp=0, pb=2.
+ return dst, src, ErrUnsupportedXzData
+ }
+ uncompressedSize := (uint32(src[1]) << 8) + (uint32(src[2]) << 0) + 1
+ compressedSize := (uint32(src[3]) << 8) + (uint32(src[4]) << 0) + 1
+ src = src[6:]
+ if uint64(compressedSize) > uint64(len(src)) {
+ return dst, src, errInvalidXzData
+ }
+ lenSrc := len(src)
+ dst, src, retErr = decodeRaw(dst, src, uint64(uncompressedSize), ErrUnsupportedXzData)
+ if retErr != nil {
+ return dst, src, retErr
+ } else if lenSrc != (len(src) + int(compressedSize)) {
+ return dst, src, errInvalidXzData
+ }
+
+ } else {
+ return dst, src, ErrUnsupportedXzData
+ }
+ }
+ unpaddedSizeWant := uint64((originalSrcLen - 12) - len(src) + 4)
+ for i := unpaddedSizeWant & 3; (i & 3) != 0; i++ {
+ if (len(src) == 0) || (src[0] != 0x00) {
+ return dst, src, errInvalidXzData
+ }
+ src = src[1:]
+ }
+ if len(src) < 4 {
+ return dst, src, errInvalidXzData
+ }
+ checksum := crc32.ChecksumIEEE(dst[originalDstLen:])
+ if (src[0] != uint8(checksum>>0)) ||
+ (src[1] != uint8(checksum>>8)) ||
+ (src[2] != uint8(checksum>>16)) ||
+ (src[3] != uint8(checksum>>24)) {
+ return dst, src, errInvalidXzData
+ }
+ src = src[4:]
+
+ // Decode the index.
+ srcCheckpoint1 := src
+ if (len(src) < 2) || (src[0] != 0x00) || (src[1] != 0x01) {
+ return dst, src, errInvalidXzData
+ }
+ src = src[2:]
+ src, unpaddedSizeHave, ok := decodeUvarint(src)
+ if !ok || (unpaddedSizeHave != unpaddedSizeWant) {
+ return dst, src, errInvalidXzData
+ }
+ src, uncompressedSize, ok := decodeUvarint(src)
+ if !ok || (uncompressedSize != uint64(len(dst)-originalDstLen)) {
+ return dst, src, errInvalidXzData
+ }
+ for i := (len(srcCheckpoint1) - len(src)) & 3; (i & 3) != 0; i++ {
+ if (len(src) == 0) || (src[0] != 0x00) {
+ return dst, src, errInvalidXzData
+ }
+ src = src[1:]
+ }
+ backwardSize := (len(srcCheckpoint1) - len(src)) >> 2
+ if len(src) < 4 {
+ return dst, src, errInvalidXzData
+ }
+ checksum = crc32.ChecksumIEEE(srcCheckpoint1[:len(srcCheckpoint1)-len(src)])
+ if (src[0] != uint8(checksum>>0)) ||
+ (src[1] != uint8(checksum>>8)) ||
+ (src[2] != uint8(checksum>>16)) ||
+ (src[3] != uint8(checksum>>24)) {
+ return dst, src, errInvalidXzData
+ }
+ src = src[4:]
+
+ // Decode the footer.
+ if len(src) < 12 {
+ return dst, src, errInvalidXzData
+ }
+ checksum = crc32.ChecksumIEEE(src[4:10])
+ if (src[0] != uint8(checksum>>0)) || // Checksum.
+ (src[1] != uint8(checksum>>8)) ||
+ (src[2] != uint8(checksum>>16)) ||
+ (src[3] != uint8(checksum>>24)) ||
+ (src[4] != uint8(backwardSize>>0)) || // Backward Size.
+ (src[5] != uint8(backwardSize>>8)) ||
+ (src[6] != uint8(backwardSize>>16)) ||
+ (src[7] != uint8(backwardSize>>24)) ||
+ (src[8] != xzHeader24[6]) || // Stream Flags again.
+ (src[9] != xzHeader24[7]) ||
+ (src[10] != 0x59) || // Stream Footer Magic Bytes.
+ (src[11] != 0x5A) {
+ return dst, src, errInvalidXzData
+ }
+ return dst, src[12:], nil
+}
+
+func decodeRaw(dst []byte, src []byte, size uint64, errUnsupported error) (appendedDst []byte, remainingSrc []byte, retErr error) {
+ if (len(src) < 5) || (src[0] != 0x00) {
+ return dst, src, errUnsupported
+ }
+
rDec := rangeDecoder{
- src: src[18:],
- bits: (uint32(src[14]) << 24) |
- (uint32(src[15]) << 16) |
- (uint32(src[16]) << 8) |
- (uint32(src[17]) << 0),
+ src: src[5:],
+ bits: (uint32(src[1]) << 24) |
+ (uint32(src[2]) << 16) |
+ (uint32(src[3]) << 8) |
+ (uint32(src[4]) << 0),
width: 0xFFFF_FFFF,
}
@@ -412,12 +578,12 @@
curr := byte(0)
for ; size > 0; size-- {
if bitValue, err := posProbs[pos&pbMask].decodeBit(&rDec); err != nil {
- return dst, nil, err
+ return dst, rDec.src, err
} else if bitValue != 0 {
// A full-LZMA decoder would implement Lempel Ziv matches (or the
// End of Stream marker) here. Our simpler subset-of-LZMA decoder
// only uses literals.
- return dst, rDec.src, ErrUnsupportedLZMAData
+ return dst, rDec.src, errUnsupported
}
i := (pos & lpMask) << lc
@@ -433,26 +599,141 @@
return dst, rDec.src, nil
}
+func decodeUvarint(src []byte) (remainingSrc []byte, x uint64, ok bool) {
+ for i := uint32(0); (i < 63) && (len(src) > 0); i += 7 {
+ s := src[0]
+ src = src[1:]
+ x |= uint64(s&0x7F) << i
+ if (s & 0x80) == 0 {
+ return src, x, true
+ }
+ }
+ return src, 0, false
+}
+
// Encode converts src to the Literal Only LZMA compressed file format,
// appending the encoding to dst.
//
-// f should be FileFormatLZMA but future versions of this package may support
-// other file formats.
-//
// It is valid to pass a nil dst, like the way it's valid to pass nil to the
// built-in append function.
func (f FileFormat) Encode(dst []byte, src []byte) (appendedDst []byte, retErr error) {
- if f != FileFormatLZMA {
- return nil, errUnsupportedFileFormat
+ switch f {
+ case FileFormatLZMA:
+ return encodeLZMA(dst, src)
+ case FileFormatXz:
+ return encodeXz(dst, src)
}
+ return nil, errUnsupportedFileFormat
+}
+func encodeLZMA(dst []byte, src []byte) (appendedDst []byte, retErr error) {
dst = append(dst, lzmaHeader5...)
size := len(src)
for i := 0; i < 8; i++ {
dst = append(dst, byte(size))
size >>= 8
}
+ return encodeRaw(dst, src), nil
+}
+func encodeXz(dst []byte, src []byte) (appendedDst []byte, retErr error) {
+ // Encode the headers (12 byte stream header then 12 byte block header).
+ // The block's unpaddedSize calculation ignores the stream header.
+ dstLen0 := len(dst) + 12
+ dst = append(dst, xzHeader24...)
+
+ // Encode the payload as multiple chunks.
+ //
+ // Later XZ chunks can depend on earlier ones (and doing so can help
+ // compression ratios) but for simplicity, this encoder emits independent
+ // chunks. Each chunk's maximum compressed and uncompressed size are both
+ // equal to 0x10000 = 65536 bytes, roughly speaking. The encoder partitions
+ // the src into 65536 byte sub-slices. If a sub-slice's LZMA-compressed
+ // form would be longer, the encoder emits an uncompressed chunk instead.
+ rawLZMA := []byte(nil)
+ for remaining := src; len(remaining) > 0; {
+ srcChunk := []byte(nil)
+ if len(remaining) > 0x10000 {
+ srcChunk, remaining = remaining[:0x10000], remaining[0x10000:]
+ } else {
+ srcChunk, remaining = remaining, nil
+ }
+
+ rawLZMA = encodeRaw(rawLZMA[:0], srcChunk)
+ if (len(srcChunk) + 3) <= (len(rawLZMA) + 6) {
+ dst = append(dst,
+ 0x01, // Independent uncompressed chunk.
+ uint8((len(srcChunk)-1)>>8),
+ uint8((len(srcChunk)-1)>>0),
+ )
+ dst = append(dst, srcChunk...)
+ } else {
+ dst = append(dst,
+ 0xE0, // Independent LZMA chunk.
+ uint8((len(srcChunk)-1)>>8),
+ uint8((len(srcChunk)-1)>>0),
+ uint8((len(rawLZMA)-1)>>8),
+ uint8((len(rawLZMA)-1)>>0),
+ 0x5D, // Like lzmaHeader5[0], this encodes lc=3, lp=0, pb=2.
+ )
+ dst = append(dst, rawLZMA...)
+ }
+ }
+ dst = append(dst, 0x00) // No more chunks.
+ unpaddedSize := uint64(len(dst)-dstLen0) + 4 // +4 for the upcoming checksum.
+ for 0 != 3&(len(dst)-dstLen0) {
+ dst = append(dst, 0x00) // Padding
+ }
+ checksum := crc32.ChecksumIEEE(src)
+ dst = append(dst,
+ uint8(checksum>>0),
+ uint8(checksum>>8),
+ uint8(checksum>>16),
+ uint8(checksum>>24),
+ )
+
+ // Encode the index.
+ dstLen1 := len(dst)
+ dst = append(dst,
+ 0x00, // Index Indicator.
+ 0x01, // Number of Records.
+ )
+ dst = encodeUvarint(dst, unpaddedSize)
+ dst = encodeUvarint(dst, uint64(len(src)))
+ for 0 != 3&(len(dst)-dstLen1) {
+ dst = append(dst, 0x00) // Padding
+ }
+ backwardSize := (len(dst) - dstLen1) >> 2
+ checksum = crc32.ChecksumIEEE(dst[dstLen1:])
+ dst = append(dst,
+ uint8(checksum>>0),
+ uint8(checksum>>8),
+ uint8(checksum>>16),
+ uint8(checksum>>24),
+ )
+
+ // Encode the footer.
+ dstLen2 := len(dst)
+ dst = append(dst,
+ 0, 0, 0, 0, // Space for the checksum.
+ uint8(backwardSize>>0), // Backward Size.
+ uint8(backwardSize>>8),
+ uint8(backwardSize>>16),
+ uint8(backwardSize>>24),
+ xzHeader24[6], // Stream Flags again.
+ xzHeader24[7],
+ 0x59, // Stream Footer Magic Bytes.
+ 0x5A,
+ )
+ checksum = crc32.ChecksumIEEE(dst[dstLen2+4 : dstLen2+10])
+ dst[dstLen2+0] = uint8(checksum >> 0)
+ dst[dstLen2+1] = uint8(checksum >> 8)
+ dst[dstLen2+2] = uint8(checksum >> 16)
+ dst[dstLen2+3] = uint8(checksum >> 24)
+ return dst, nil
+}
+
+func encodeRaw(dst []byte, src []byte) (appendedDst []byte) {
rEnc := rangeEncoder{
dst: dst,
width: 0xFFFF_FFFF,
@@ -487,5 +768,12 @@
rEnc.shiftLow()
}
- return rEnc.dst, nil
+ return rEnc.dst
+}
+
+func encodeUvarint(dst []byte, x uint64) []byte {
+ for ; x >= 0x80; x >>= 7 {
+ dst = append(dst, byte(x)|0x80)
+ }
+ return append(dst, byte(x))
}
diff --git a/lib/litonlylzma/litonlylzma_test.go b/lib/litonlylzma/litonlylzma_test.go
index 3c68191..2935a6c 100644
--- a/lib/litonlylzma/litonlylzma_test.go
+++ b/lib/litonlylzma/litonlylzma_test.go
@@ -43,16 +43,23 @@
original = o
}
- compressed, err := FileFormatLZMA.Encode(nil, original)
- if err != nil {
- tt.Fatalf("Encode: %v", err)
+ fileFormats := [...]FileFormat{
+ FileFormatLZMA,
+ FileFormatXz,
}
- recovered, _, err := FileFormatLZMA.Decode(nil, compressed)
- if err != nil {
- tt.Fatalf("Decode: %v", err)
- }
- if !bytes.Equal(original, recovered) {
- tt.Fatalf("round trip produced different bytes")
+
+ for _, f := range fileFormats {
+ compressed, err := f.Encode(nil, original)
+ if err != nil {
+ tt.Fatalf("%v.Encode: %v", f, err)
+ }
+ recovered, _, err := f.Decode(nil, compressed)
+ if err != nil {
+ tt.Fatalf("%v.Decode: %v", f, err)
+ }
+ if !bytes.Equal(original, recovered) {
+ tt.Fatalf("%v: round trip produced different bytes", f)
+ }
}
}
