khenaidoo | 106c61a | 2021-08-11 18:05:46 -0400 | [diff] [blame^] | 1 | // Copyright 2019+ Klaus Post. All rights reserved. |
| 2 | // License information can be found in the LICENSE file. |
| 3 | // Based on work by Yann Collet, released under BSD License. |
| 4 | |
| 5 | package zstd |
| 6 | |
| 7 | import ( |
| 8 | "encoding/binary" |
| 9 | "errors" |
| 10 | "hash/crc32" |
| 11 | "io" |
| 12 | |
| 13 | "github.com/golang/snappy" |
| 14 | "github.com/klauspost/compress/huff0" |
| 15 | ) |
| 16 | |
| 17 | const ( |
| 18 | snappyTagLiteral = 0x00 |
| 19 | snappyTagCopy1 = 0x01 |
| 20 | snappyTagCopy2 = 0x02 |
| 21 | snappyTagCopy4 = 0x03 |
| 22 | ) |
| 23 | |
| 24 | const ( |
| 25 | snappyChecksumSize = 4 |
| 26 | snappyMagicBody = "sNaPpY" |
| 27 | |
| 28 | // snappyMaxBlockSize is the maximum size of the input to encodeBlock. It is not |
| 29 | // part of the wire format per se, but some parts of the encoder assume |
| 30 | // that an offset fits into a uint16. |
| 31 | // |
| 32 | // Also, for the framing format (Writer type instead of Encode function), |
| 33 | // https://github.com/google/snappy/blob/master/framing_format.txt says |
| 34 | // that "the uncompressed data in a chunk must be no longer than 65536 |
| 35 | // bytes". |
| 36 | snappyMaxBlockSize = 65536 |
| 37 | |
| 38 | // snappyMaxEncodedLenOfMaxBlockSize equals MaxEncodedLen(snappyMaxBlockSize), but is |
| 39 | // hard coded to be a const instead of a variable, so that obufLen can also |
| 40 | // be a const. Their equivalence is confirmed by |
| 41 | // TestMaxEncodedLenOfMaxBlockSize. |
| 42 | snappyMaxEncodedLenOfMaxBlockSize = 76490 |
| 43 | ) |
| 44 | |
| 45 | const ( |
| 46 | chunkTypeCompressedData = 0x00 |
| 47 | chunkTypeUncompressedData = 0x01 |
| 48 | chunkTypePadding = 0xfe |
| 49 | chunkTypeStreamIdentifier = 0xff |
| 50 | ) |
| 51 | |
| 52 | var ( |
| 53 | // ErrSnappyCorrupt reports that the input is invalid. |
| 54 | ErrSnappyCorrupt = errors.New("snappy: corrupt input") |
| 55 | // ErrSnappyTooLarge reports that the uncompressed length is too large. |
| 56 | ErrSnappyTooLarge = errors.New("snappy: decoded block is too large") |
| 57 | // ErrSnappyUnsupported reports that the input isn't supported. |
| 58 | ErrSnappyUnsupported = errors.New("snappy: unsupported input") |
| 59 | |
| 60 | errUnsupportedLiteralLength = errors.New("snappy: unsupported literal length") |
| 61 | ) |
| 62 | |
| 63 | // SnappyConverter can read SnappyConverter-compressed streams and convert them to zstd. |
| 64 | // Conversion is done by converting the stream directly from Snappy without intermediate |
| 65 | // full decoding. |
| 66 | // Therefore the compression ratio is much less than what can be done by a full decompression |
| 67 | // and compression, and a faulty Snappy stream may lead to a faulty Zstandard stream without |
| 68 | // any errors being generated. |
| 69 | // No CRC value is being generated and not all CRC values of the Snappy stream are checked. |
| 70 | // However, it provides really fast recompression of Snappy streams. |
| 71 | // The converter can be reused to avoid allocations, even after errors. |
| 72 | type SnappyConverter struct { |
| 73 | r io.Reader |
| 74 | err error |
| 75 | buf []byte |
| 76 | block *blockEnc |
| 77 | } |
| 78 | |
| 79 | // Convert the Snappy stream supplied in 'in' and write the zStandard stream to 'w'. |
| 80 | // If any error is detected on the Snappy stream it is returned. |
| 81 | // The number of bytes written is returned. |
| 82 | func (r *SnappyConverter) Convert(in io.Reader, w io.Writer) (int64, error) { |
| 83 | initPredefined() |
| 84 | r.err = nil |
| 85 | r.r = in |
| 86 | if r.block == nil { |
| 87 | r.block = &blockEnc{} |
| 88 | r.block.init() |
| 89 | } |
| 90 | r.block.initNewEncode() |
| 91 | if len(r.buf) != snappyMaxEncodedLenOfMaxBlockSize+snappyChecksumSize { |
| 92 | r.buf = make([]byte, snappyMaxEncodedLenOfMaxBlockSize+snappyChecksumSize) |
| 93 | } |
| 94 | r.block.litEnc.Reuse = huff0.ReusePolicyNone |
| 95 | var written int64 |
| 96 | var readHeader bool |
| 97 | { |
| 98 | var header []byte |
| 99 | var n int |
| 100 | header, r.err = frameHeader{WindowSize: snappyMaxBlockSize}.appendTo(r.buf[:0]) |
| 101 | |
| 102 | n, r.err = w.Write(header) |
| 103 | if r.err != nil { |
| 104 | return written, r.err |
| 105 | } |
| 106 | written += int64(n) |
| 107 | } |
| 108 | |
| 109 | for { |
| 110 | if !r.readFull(r.buf[:4], true) { |
| 111 | // Add empty last block |
| 112 | r.block.reset(nil) |
| 113 | r.block.last = true |
| 114 | err := r.block.encodeLits(r.block.literals, false) |
| 115 | if err != nil { |
| 116 | return written, err |
| 117 | } |
| 118 | n, err := w.Write(r.block.output) |
| 119 | if err != nil { |
| 120 | return written, err |
| 121 | } |
| 122 | written += int64(n) |
| 123 | |
| 124 | return written, r.err |
| 125 | } |
| 126 | chunkType := r.buf[0] |
| 127 | if !readHeader { |
| 128 | if chunkType != chunkTypeStreamIdentifier { |
| 129 | println("chunkType != chunkTypeStreamIdentifier", chunkType) |
| 130 | r.err = ErrSnappyCorrupt |
| 131 | return written, r.err |
| 132 | } |
| 133 | readHeader = true |
| 134 | } |
| 135 | chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16 |
| 136 | if chunkLen > len(r.buf) { |
| 137 | println("chunkLen > len(r.buf)", chunkType) |
| 138 | r.err = ErrSnappyUnsupported |
| 139 | return written, r.err |
| 140 | } |
| 141 | |
| 142 | // The chunk types are specified at |
| 143 | // https://github.com/google/snappy/blob/master/framing_format.txt |
| 144 | switch chunkType { |
| 145 | case chunkTypeCompressedData: |
| 146 | // Section 4.2. Compressed data (chunk type 0x00). |
| 147 | if chunkLen < snappyChecksumSize { |
| 148 | println("chunkLen < snappyChecksumSize", chunkLen, snappyChecksumSize) |
| 149 | r.err = ErrSnappyCorrupt |
| 150 | return written, r.err |
| 151 | } |
| 152 | buf := r.buf[:chunkLen] |
| 153 | if !r.readFull(buf, false) { |
| 154 | return written, r.err |
| 155 | } |
| 156 | //checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24 |
| 157 | buf = buf[snappyChecksumSize:] |
| 158 | |
| 159 | n, hdr, err := snappyDecodedLen(buf) |
| 160 | if err != nil { |
| 161 | r.err = err |
| 162 | return written, r.err |
| 163 | } |
| 164 | buf = buf[hdr:] |
| 165 | if n > snappyMaxBlockSize { |
| 166 | println("n > snappyMaxBlockSize", n, snappyMaxBlockSize) |
| 167 | r.err = ErrSnappyCorrupt |
| 168 | return written, r.err |
| 169 | } |
| 170 | r.block.reset(nil) |
| 171 | r.block.pushOffsets() |
| 172 | if err := decodeSnappy(r.block, buf); err != nil { |
| 173 | r.err = err |
| 174 | return written, r.err |
| 175 | } |
| 176 | if r.block.size+r.block.extraLits != n { |
| 177 | printf("invalid size, want %d, got %d\n", n, r.block.size+r.block.extraLits) |
| 178 | r.err = ErrSnappyCorrupt |
| 179 | return written, r.err |
| 180 | } |
| 181 | err = r.block.encode(nil, false, false) |
| 182 | switch err { |
| 183 | case errIncompressible: |
| 184 | r.block.popOffsets() |
| 185 | r.block.reset(nil) |
| 186 | r.block.literals, err = snappy.Decode(r.block.literals[:n], r.buf[snappyChecksumSize:chunkLen]) |
| 187 | if err != nil { |
| 188 | return written, err |
| 189 | } |
| 190 | err = r.block.encodeLits(r.block.literals, false) |
| 191 | if err != nil { |
| 192 | return written, err |
| 193 | } |
| 194 | case nil: |
| 195 | default: |
| 196 | return written, err |
| 197 | } |
| 198 | |
| 199 | n, r.err = w.Write(r.block.output) |
| 200 | if r.err != nil { |
| 201 | return written, err |
| 202 | } |
| 203 | written += int64(n) |
| 204 | continue |
| 205 | case chunkTypeUncompressedData: |
| 206 | if debug { |
| 207 | println("Uncompressed, chunklen", chunkLen) |
| 208 | } |
| 209 | // Section 4.3. Uncompressed data (chunk type 0x01). |
| 210 | if chunkLen < snappyChecksumSize { |
| 211 | println("chunkLen < snappyChecksumSize", chunkLen, snappyChecksumSize) |
| 212 | r.err = ErrSnappyCorrupt |
| 213 | return written, r.err |
| 214 | } |
| 215 | r.block.reset(nil) |
| 216 | buf := r.buf[:snappyChecksumSize] |
| 217 | if !r.readFull(buf, false) { |
| 218 | return written, r.err |
| 219 | } |
| 220 | checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24 |
| 221 | // Read directly into r.decoded instead of via r.buf. |
| 222 | n := chunkLen - snappyChecksumSize |
| 223 | if n > snappyMaxBlockSize { |
| 224 | println("n > snappyMaxBlockSize", n, snappyMaxBlockSize) |
| 225 | r.err = ErrSnappyCorrupt |
| 226 | return written, r.err |
| 227 | } |
| 228 | r.block.literals = r.block.literals[:n] |
| 229 | if !r.readFull(r.block.literals, false) { |
| 230 | return written, r.err |
| 231 | } |
| 232 | if snappyCRC(r.block.literals) != checksum { |
| 233 | println("literals crc mismatch") |
| 234 | r.err = ErrSnappyCorrupt |
| 235 | return written, r.err |
| 236 | } |
| 237 | err := r.block.encodeLits(r.block.literals, false) |
| 238 | if err != nil { |
| 239 | return written, err |
| 240 | } |
| 241 | n, r.err = w.Write(r.block.output) |
| 242 | if r.err != nil { |
| 243 | return written, err |
| 244 | } |
| 245 | written += int64(n) |
| 246 | continue |
| 247 | |
| 248 | case chunkTypeStreamIdentifier: |
| 249 | if debug { |
| 250 | println("stream id", chunkLen, len(snappyMagicBody)) |
| 251 | } |
| 252 | // Section 4.1. Stream identifier (chunk type 0xff). |
| 253 | if chunkLen != len(snappyMagicBody) { |
| 254 | println("chunkLen != len(snappyMagicBody)", chunkLen, len(snappyMagicBody)) |
| 255 | r.err = ErrSnappyCorrupt |
| 256 | return written, r.err |
| 257 | } |
| 258 | if !r.readFull(r.buf[:len(snappyMagicBody)], false) { |
| 259 | return written, r.err |
| 260 | } |
| 261 | for i := 0; i < len(snappyMagicBody); i++ { |
| 262 | if r.buf[i] != snappyMagicBody[i] { |
| 263 | println("r.buf[i] != snappyMagicBody[i]", r.buf[i], snappyMagicBody[i], i) |
| 264 | r.err = ErrSnappyCorrupt |
| 265 | return written, r.err |
| 266 | } |
| 267 | } |
| 268 | continue |
| 269 | } |
| 270 | |
| 271 | if chunkType <= 0x7f { |
| 272 | // Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f). |
| 273 | println("chunkType <= 0x7f") |
| 274 | r.err = ErrSnappyUnsupported |
| 275 | return written, r.err |
| 276 | } |
| 277 | // Section 4.4 Padding (chunk type 0xfe). |
| 278 | // Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd). |
| 279 | if !r.readFull(r.buf[:chunkLen], false) { |
| 280 | return written, r.err |
| 281 | } |
| 282 | } |
| 283 | } |
| 284 | |
| 285 | // decodeSnappy writes the decoding of src to dst. It assumes that the varint-encoded |
| 286 | // length of the decompressed bytes has already been read. |
| 287 | func decodeSnappy(blk *blockEnc, src []byte) error { |
| 288 | //decodeRef(make([]byte, snappyMaxBlockSize), src) |
| 289 | var s, length int |
| 290 | lits := blk.extraLits |
| 291 | var offset uint32 |
| 292 | for s < len(src) { |
| 293 | switch src[s] & 0x03 { |
| 294 | case snappyTagLiteral: |
| 295 | x := uint32(src[s] >> 2) |
| 296 | switch { |
| 297 | case x < 60: |
| 298 | s++ |
| 299 | case x == 60: |
| 300 | s += 2 |
| 301 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 302 | println("uint(s) > uint(len(src)", s, src) |
| 303 | return ErrSnappyCorrupt |
| 304 | } |
| 305 | x = uint32(src[s-1]) |
| 306 | case x == 61: |
| 307 | s += 3 |
| 308 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 309 | println("uint(s) > uint(len(src)", s, src) |
| 310 | return ErrSnappyCorrupt |
| 311 | } |
| 312 | x = uint32(src[s-2]) | uint32(src[s-1])<<8 |
| 313 | case x == 62: |
| 314 | s += 4 |
| 315 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 316 | println("uint(s) > uint(len(src)", s, src) |
| 317 | return ErrSnappyCorrupt |
| 318 | } |
| 319 | x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16 |
| 320 | case x == 63: |
| 321 | s += 5 |
| 322 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 323 | println("uint(s) > uint(len(src)", s, src) |
| 324 | return ErrSnappyCorrupt |
| 325 | } |
| 326 | x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24 |
| 327 | } |
| 328 | if x > snappyMaxBlockSize { |
| 329 | println("x > snappyMaxBlockSize", x, snappyMaxBlockSize) |
| 330 | return ErrSnappyCorrupt |
| 331 | } |
| 332 | length = int(x) + 1 |
| 333 | if length <= 0 { |
| 334 | println("length <= 0 ", length) |
| 335 | |
| 336 | return errUnsupportedLiteralLength |
| 337 | } |
| 338 | //if length > snappyMaxBlockSize-d || uint32(length) > len(src)-s { |
| 339 | // return ErrSnappyCorrupt |
| 340 | //} |
| 341 | |
| 342 | blk.literals = append(blk.literals, src[s:s+length]...) |
| 343 | //println(length, "litLen") |
| 344 | lits += length |
| 345 | s += length |
| 346 | continue |
| 347 | |
| 348 | case snappyTagCopy1: |
| 349 | s += 2 |
| 350 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 351 | println("uint(s) > uint(len(src)", s, len(src)) |
| 352 | return ErrSnappyCorrupt |
| 353 | } |
| 354 | length = 4 + int(src[s-2])>>2&0x7 |
| 355 | offset = uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]) |
| 356 | |
| 357 | case snappyTagCopy2: |
| 358 | s += 3 |
| 359 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 360 | println("uint(s) > uint(len(src)", s, len(src)) |
| 361 | return ErrSnappyCorrupt |
| 362 | } |
| 363 | length = 1 + int(src[s-3])>>2 |
| 364 | offset = uint32(src[s-2]) | uint32(src[s-1])<<8 |
| 365 | |
| 366 | case snappyTagCopy4: |
| 367 | s += 5 |
| 368 | if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line. |
| 369 | println("uint(s) > uint(len(src)", s, len(src)) |
| 370 | return ErrSnappyCorrupt |
| 371 | } |
| 372 | length = 1 + int(src[s-5])>>2 |
| 373 | offset = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24 |
| 374 | } |
| 375 | |
| 376 | if offset <= 0 || blk.size+lits < int(offset) /*|| length > len(blk)-d */ { |
| 377 | println("offset <= 0 || blk.size+lits < int(offset)", offset, blk.size+lits, int(offset), blk.size, lits) |
| 378 | |
| 379 | return ErrSnappyCorrupt |
| 380 | } |
| 381 | |
| 382 | // Check if offset is one of the recent offsets. |
| 383 | // Adjusts the output offset accordingly. |
| 384 | // Gives a tiny bit of compression, typically around 1%. |
| 385 | if false { |
| 386 | offset = blk.matchOffset(offset, uint32(lits)) |
| 387 | } else { |
| 388 | offset += 3 |
| 389 | } |
| 390 | |
| 391 | blk.sequences = append(blk.sequences, seq{ |
| 392 | litLen: uint32(lits), |
| 393 | offset: offset, |
| 394 | matchLen: uint32(length) - zstdMinMatch, |
| 395 | }) |
| 396 | blk.size += length + lits |
| 397 | lits = 0 |
| 398 | } |
| 399 | blk.extraLits = lits |
| 400 | return nil |
| 401 | } |
| 402 | |
| 403 | func (r *SnappyConverter) readFull(p []byte, allowEOF bool) (ok bool) { |
| 404 | if _, r.err = io.ReadFull(r.r, p); r.err != nil { |
| 405 | if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) { |
| 406 | r.err = ErrSnappyCorrupt |
| 407 | } |
| 408 | return false |
| 409 | } |
| 410 | return true |
| 411 | } |
| 412 | |
| 413 | var crcTable = crc32.MakeTable(crc32.Castagnoli) |
| 414 | |
| 415 | // crc implements the checksum specified in section 3 of |
| 416 | // https://github.com/google/snappy/blob/master/framing_format.txt |
| 417 | func snappyCRC(b []byte) uint32 { |
| 418 | c := crc32.Update(0, crcTable, b) |
| 419 | return c>>15 | c<<17 + 0xa282ead8 |
| 420 | } |
| 421 | |
| 422 | // snappyDecodedLen returns the length of the decoded block and the number of bytes |
| 423 | // that the length header occupied. |
| 424 | func snappyDecodedLen(src []byte) (blockLen, headerLen int, err error) { |
| 425 | v, n := binary.Uvarint(src) |
| 426 | if n <= 0 || v > 0xffffffff { |
| 427 | return 0, 0, ErrSnappyCorrupt |
| 428 | } |
| 429 | |
| 430 | const wordSize = 32 << (^uint(0) >> 32 & 1) |
| 431 | if wordSize == 32 && v > 0x7fffffff { |
| 432 | return 0, 0, ErrSnappyTooLarge |
| 433 | } |
| 434 | return int(v), n, nil |
| 435 | } |