1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434
|
// Copyright 2019+ Klaus Post. All rights reserved.
// License information can be found in the LICENSE file.
// Based on work by Yann Collet, released under BSD License.
package zstd
import (
"encoding/binary"
"errors"
"hash/crc32"
"io"
"github.com/klauspost/compress/huff0"
snappy "github.com/klauspost/compress/internal/snapref"
)
const (
snappyTagLiteral = 0x00
snappyTagCopy1 = 0x01
snappyTagCopy2 = 0x02
snappyTagCopy4 = 0x03
)
const (
snappyChecksumSize = 4
snappyMagicBody = "sNaPpY"
// snappyMaxBlockSize is the maximum size of the input to encodeBlock. It is not
// part of the wire format per se, but some parts of the encoder assume
// that an offset fits into a uint16.
//
// Also, for the framing format (Writer type instead of Encode function),
// https://github.com/google/snappy/blob/master/framing_format.txt says
// that "the uncompressed data in a chunk must be no longer than 65536
// bytes".
snappyMaxBlockSize = 65536
// snappyMaxEncodedLenOfMaxBlockSize equals MaxEncodedLen(snappyMaxBlockSize), but is
// hard coded to be a const instead of a variable, so that obufLen can also
// be a const. Their equivalence is confirmed by
// TestMaxEncodedLenOfMaxBlockSize.
snappyMaxEncodedLenOfMaxBlockSize = 76490
)
const (
chunkTypeCompressedData = 0x00
chunkTypeUncompressedData = 0x01
chunkTypePadding = 0xfe
chunkTypeStreamIdentifier = 0xff
)
var (
// ErrSnappyCorrupt reports that the input is invalid.
ErrSnappyCorrupt = errors.New("snappy: corrupt input")
// ErrSnappyTooLarge reports that the uncompressed length is too large.
ErrSnappyTooLarge = errors.New("snappy: decoded block is too large")
// ErrSnappyUnsupported reports that the input isn't supported.
ErrSnappyUnsupported = errors.New("snappy: unsupported input")
errUnsupportedLiteralLength = errors.New("snappy: unsupported literal length")
)
// SnappyConverter can read SnappyConverter-compressed streams and convert them to zstd.
// Conversion is done by converting the stream directly from Snappy without intermediate
// full decoding.
// Therefore the compression ratio is much less than what can be done by a full decompression
// and compression, and a faulty Snappy stream may lead to a faulty Zstandard stream without
// any errors being generated.
// No CRC value is being generated and not all CRC values of the Snappy stream are checked.
// However, it provides really fast recompression of Snappy streams.
// The converter can be reused to avoid allocations, even after errors.
type SnappyConverter struct {
r io.Reader
err error
buf []byte
block *blockEnc
}
// Convert the Snappy stream supplied in 'in' and write the zStandard stream to 'w'.
// If any error is detected on the Snappy stream it is returned.
// The number of bytes written is returned.
func (r *SnappyConverter) Convert(in io.Reader, w io.Writer) (int64, error) {
initPredefined()
r.err = nil
r.r = in
if r.block == nil {
r.block = &blockEnc{}
r.block.init()
}
r.block.initNewEncode()
if len(r.buf) != snappyMaxEncodedLenOfMaxBlockSize+snappyChecksumSize {
r.buf = make([]byte, snappyMaxEncodedLenOfMaxBlockSize+snappyChecksumSize)
}
r.block.litEnc.Reuse = huff0.ReusePolicyNone
var written int64
var readHeader bool
{
header := frameHeader{WindowSize: snappyMaxBlockSize}.appendTo(r.buf[:0])
var n int
n, r.err = w.Write(header)
if r.err != nil {
return written, r.err
}
written += int64(n)
}
for {
if !r.readFull(r.buf[:4], true) {
// Add empty last block
r.block.reset(nil)
r.block.last = true
err := r.block.encodeLits(r.block.literals, false)
if err != nil {
return written, err
}
n, err := w.Write(r.block.output)
if err != nil {
return written, err
}
written += int64(n)
return written, r.err
}
chunkType := r.buf[0]
if !readHeader {
if chunkType != chunkTypeStreamIdentifier {
println("chunkType != chunkTypeStreamIdentifier", chunkType)
r.err = ErrSnappyCorrupt
return written, r.err
}
readHeader = true
}
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
if chunkLen > len(r.buf) {
println("chunkLen > len(r.buf)", chunkType)
r.err = ErrSnappyUnsupported
return written, r.err
}
// The chunk types are specified at
// https://github.com/google/snappy/blob/master/framing_format.txt
switch chunkType {
case chunkTypeCompressedData:
// Section 4.2. Compressed data (chunk type 0x00).
if chunkLen < snappyChecksumSize {
println("chunkLen < snappyChecksumSize", chunkLen, snappyChecksumSize)
r.err = ErrSnappyCorrupt
return written, r.err
}
buf := r.buf[:chunkLen]
if !r.readFull(buf, false) {
return written, r.err
}
//checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
buf = buf[snappyChecksumSize:]
n, hdr, err := snappyDecodedLen(buf)
if err != nil {
r.err = err
return written, r.err
}
buf = buf[hdr:]
if n > snappyMaxBlockSize {
println("n > snappyMaxBlockSize", n, snappyMaxBlockSize)
r.err = ErrSnappyCorrupt
return written, r.err
}
r.block.reset(nil)
r.block.pushOffsets()
if err := decodeSnappy(r.block, buf); err != nil {
r.err = err
return written, r.err
}
if r.block.size+r.block.extraLits != n {
printf("invalid size, want %d, got %d\n", n, r.block.size+r.block.extraLits)
r.err = ErrSnappyCorrupt
return written, r.err
}
err = r.block.encode(nil, false, false)
switch err {
case errIncompressible:
r.block.popOffsets()
r.block.reset(nil)
r.block.literals, err = snappy.Decode(r.block.literals[:n], r.buf[snappyChecksumSize:chunkLen])
if err != nil {
return written, err
}
err = r.block.encodeLits(r.block.literals, false)
if err != nil {
return written, err
}
case nil:
default:
return written, err
}
n, r.err = w.Write(r.block.output)
if r.err != nil {
return written, err
}
written += int64(n)
continue
case chunkTypeUncompressedData:
if debugEncoder {
println("Uncompressed, chunklen", chunkLen)
}
// Section 4.3. Uncompressed data (chunk type 0x01).
if chunkLen < snappyChecksumSize {
println("chunkLen < snappyChecksumSize", chunkLen, snappyChecksumSize)
r.err = ErrSnappyCorrupt
return written, r.err
}
r.block.reset(nil)
buf := r.buf[:snappyChecksumSize]
if !r.readFull(buf, false) {
return written, r.err
}
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
// Read directly into r.decoded instead of via r.buf.
n := chunkLen - snappyChecksumSize
if n > snappyMaxBlockSize {
println("n > snappyMaxBlockSize", n, snappyMaxBlockSize)
r.err = ErrSnappyCorrupt
return written, r.err
}
r.block.literals = r.block.literals[:n]
if !r.readFull(r.block.literals, false) {
return written, r.err
}
if snappyCRC(r.block.literals) != checksum {
println("literals crc mismatch")
r.err = ErrSnappyCorrupt
return written, r.err
}
err := r.block.encodeLits(r.block.literals, false)
if err != nil {
return written, err
}
n, r.err = w.Write(r.block.output)
if r.err != nil {
return written, err
}
written += int64(n)
continue
case chunkTypeStreamIdentifier:
if debugEncoder {
println("stream id", chunkLen, len(snappyMagicBody))
}
// Section 4.1. Stream identifier (chunk type 0xff).
if chunkLen != len(snappyMagicBody) {
println("chunkLen != len(snappyMagicBody)", chunkLen, len(snappyMagicBody))
r.err = ErrSnappyCorrupt
return written, r.err
}
if !r.readFull(r.buf[:len(snappyMagicBody)], false) {
return written, r.err
}
for i := 0; i < len(snappyMagicBody); i++ {
if r.buf[i] != snappyMagicBody[i] {
println("r.buf[i] != snappyMagicBody[i]", r.buf[i], snappyMagicBody[i], i)
r.err = ErrSnappyCorrupt
return written, r.err
}
}
continue
}
if chunkType <= 0x7f {
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
println("chunkType <= 0x7f")
r.err = ErrSnappyUnsupported
return written, r.err
}
// Section 4.4 Padding (chunk type 0xfe).
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
if !r.readFull(r.buf[:chunkLen], false) {
return written, r.err
}
}
}
// decodeSnappy writes the decoding of src to dst. It assumes that the varint-encoded
// length of the decompressed bytes has already been read.
func decodeSnappy(blk *blockEnc, src []byte) error {
//decodeRef(make([]byte, snappyMaxBlockSize), src)
var s, length int
lits := blk.extraLits
var offset uint32
for s < len(src) {
switch src[s] & 0x03 {
case snappyTagLiteral:
x := uint32(src[s] >> 2)
switch {
case x < 60:
s++
case x == 60:
s += 2
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, src)
return ErrSnappyCorrupt
}
x = uint32(src[s-1])
case x == 61:
s += 3
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, src)
return ErrSnappyCorrupt
}
x = uint32(src[s-2]) | uint32(src[s-1])<<8
case x == 62:
s += 4
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, src)
return ErrSnappyCorrupt
}
x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
case x == 63:
s += 5
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, src)
return ErrSnappyCorrupt
}
x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
}
if x > snappyMaxBlockSize {
println("x > snappyMaxBlockSize", x, snappyMaxBlockSize)
return ErrSnappyCorrupt
}
length = int(x) + 1
if length <= 0 {
println("length <= 0 ", length)
return errUnsupportedLiteralLength
}
//if length > snappyMaxBlockSize-d || uint32(length) > len(src)-s {
// return ErrSnappyCorrupt
//}
blk.literals = append(blk.literals, src[s:s+length]...)
//println(length, "litLen")
lits += length
s += length
continue
case snappyTagCopy1:
s += 2
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, len(src))
return ErrSnappyCorrupt
}
length = 4 + int(src[s-2])>>2&0x7
offset = uint32(src[s-2])&0xe0<<3 | uint32(src[s-1])
case snappyTagCopy2:
s += 3
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, len(src))
return ErrSnappyCorrupt
}
length = 1 + int(src[s-3])>>2
offset = uint32(src[s-2]) | uint32(src[s-1])<<8
case snappyTagCopy4:
s += 5
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
println("uint(s) > uint(len(src)", s, len(src))
return ErrSnappyCorrupt
}
length = 1 + int(src[s-5])>>2
offset = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
}
if offset <= 0 || blk.size+lits < int(offset) /*|| length > len(blk)-d */ {
println("offset <= 0 || blk.size+lits < int(offset)", offset, blk.size+lits, int(offset), blk.size, lits)
return ErrSnappyCorrupt
}
// Check if offset is one of the recent offsets.
// Adjusts the output offset accordingly.
// Gives a tiny bit of compression, typically around 1%.
if false {
offset = blk.matchOffset(offset, uint32(lits))
} else {
offset += 3
}
blk.sequences = append(blk.sequences, seq{
litLen: uint32(lits),
offset: offset,
matchLen: uint32(length) - zstdMinMatch,
})
blk.size += length + lits
lits = 0
}
blk.extraLits = lits
return nil
}
func (r *SnappyConverter) readFull(p []byte, allowEOF bool) (ok bool) {
if _, r.err = io.ReadFull(r.r, p); r.err != nil {
if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
r.err = ErrSnappyCorrupt
}
return false
}
return true
}
var crcTable = crc32.MakeTable(crc32.Castagnoli)
// crc implements the checksum specified in section 3 of
// https://github.com/google/snappy/blob/master/framing_format.txt
func snappyCRC(b []byte) uint32 {
c := crc32.Update(0, crcTable, b)
return c>>15 | c<<17 + 0xa282ead8
}
// snappyDecodedLen returns the length of the decoded block and the number of bytes
// that the length header occupied.
func snappyDecodedLen(src []byte) (blockLen, headerLen int, err error) {
v, n := binary.Uvarint(src)
if n <= 0 || v > 0xffffffff {
return 0, 0, ErrSnappyCorrupt
}
const wordSize = 32 << (^uint(0) >> 32 & 1)
if wordSize == 32 && v > 0x7fffffff {
return 0, 0, ErrSnappyTooLarge
}
return int(v), n, nil
}
|