diff options
Diffstat (limited to 'vendor/github.com/xi2/xz/dec_stream.go')
| -rw-r--r-- | vendor/github.com/xi2/xz/dec_stream.go | 932 |
1 files changed, 932 insertions, 0 deletions
diff --git a/vendor/github.com/xi2/xz/dec_stream.go b/vendor/github.com/xi2/xz/dec_stream.go new file mode 100644 index 0000000..9381a3c --- /dev/null +++ b/vendor/github.com/xi2/xz/dec_stream.go @@ -0,0 +1,932 @@ +/* + * .xz Stream decoder + * + * Author: Lasse Collin <lasse.collin@tukaani.org> + * + * Translation to Go: Michael Cross <https://github.com/xi2> + * + * This file has been put into the public domain. + * You can do whatever you want with this file. + */ + +package xz + +import ( + "bytes" + "crypto/sha256" + "hash" + "hash/crc32" + "hash/crc64" +) + +/* from linux/lib/xz/xz_stream.h **************************************/ + +/* + * See the .xz file format specification at + * http://tukaani.org/xz/xz-file-format.txt + * to understand the container format. + */ +const ( + streamHeaderSize = 12 + headerMagic = "\xfd7zXZ\x00" + footerMagic = "YZ" +) + +/* + * Variable-length integer can hold a 63-bit unsigned integer or a special + * value indicating that the value is unknown. + */ +type vliType uint64 + +const ( + vliUnknown vliType = ^vliType(0) + /* Maximum encoded size of a VLI */ + vliBytesMax = 8 * 8 / 7 // (Sizeof(vliType) * 8 / 7) +) + +/* from linux/lib/xz/xz_dec_stream.c **********************************/ + +/* Hash used to validate the Index field */ +type xzDecHash struct { + unpadded vliType + uncompressed vliType + sha256 hash.Hash +} + +// type of xzDec.sequence +type xzDecSeq int + +const ( + seqStreamHeader xzDecSeq = iota + seqBlockStart + seqBlockHeader + seqBlockUncompress + seqBlockPadding + seqBlockCheck + seqIndex + seqIndexPadding + seqIndexCRC32 + seqStreamFooter +) + +// type of xzDec.index.sequence +type xzDecIndexSeq int + +const ( + seqIndexCount xzDecIndexSeq = iota + seqIndexUnpadded + seqIndexUncompressed +) + +/** + * xzDec - Opaque type to hold the XZ decoder state + */ +type xzDec struct { + /* Position in decMain */ + sequence xzDecSeq + /* Position in variable-length integers and Check fields */ + pos int + /* Variable-length integer decoded by decVLI */ + vli vliType + /* Saved inPos and outPos */ + inStart int + outStart int + /* CRC32 checksum hash used in Index */ + crc32 hash.Hash + /* Hashes used in Blocks */ + checkCRC32 hash.Hash + checkCRC64 hash.Hash + checkSHA256 hash.Hash + /* for checkTypes CRC32/CRC64/SHA256, check is one of the above 3 hashes */ + check hash.Hash + /* Embedded stream header struct containing CheckType */ + *Header + /* + * True if the next call to xzDecRun is allowed to return + * xzBufError. + */ + allowBufError bool + /* Information stored in Block Header */ + blockHeader struct { + /* + * Value stored in the Compressed Size field, or + * vliUnknown if Compressed Size is not present. + */ + compressed vliType + /* + * Value stored in the Uncompressed Size field, or + * vliUnknown if Uncompressed Size is not present. + */ + uncompressed vliType + /* Size of the Block Header field */ + size int + } + /* Information collected when decoding Blocks */ + block struct { + /* Observed compressed size of the current Block */ + compressed vliType + /* Observed uncompressed size of the current Block */ + uncompressed vliType + /* Number of Blocks decoded so far */ + count vliType + /* + * Hash calculated from the Block sizes. This is used to + * validate the Index field. + */ + hash xzDecHash + } + /* Variables needed when verifying the Index field */ + index struct { + /* Position in decIndex */ + sequence xzDecIndexSeq + /* Size of the Index in bytes */ + size vliType + /* Number of Records (matches block.count in valid files) */ + count vliType + /* + * Hash calculated from the Records (matches block.hash in + * valid files). + */ + hash xzDecHash + } + /* + * Temporary buffer needed to hold Stream Header, Block Header, + * and Stream Footer. The Block Header is the biggest (1 KiB) + * so we reserve space according to that. bufArray has to be aligned + * to a multiple of four bytes; the variables before it + * should guarantee this. + */ + temp struct { + pos int + buf []byte // slice buf will be backed by bufArray + bufArray [1024]byte + } + // chain is the function (or to be more precise, closure) which + // does the decompression and will call into the lzma2 and other + // filter code as needed. It is constructed by decBlockHeader + chain func(b *xzBuf) xzRet + // lzma2 holds the state of the last filter (which must be LZMA2) + lzma2 *xzDecLZMA2 + // pointers to allocated BCJ/Delta filters + bcjs []*xzDecBCJ + deltas []*xzDecDelta + // number of currently in use BCJ/Delta filters from the above + bcjsUsed int + deltasUsed int +} + +/* Sizes of the Check field with different Check IDs */ +var checkSizes = [...]byte{ + 0, + 4, 4, 4, + 8, 8, 8, + 16, 16, 16, + 32, 32, 32, + 64, 64, 64, +} + +/* + * Fill s.temp by copying data starting from b.in[b.inPos]. Caller + * must have set s.temp.pos to indicate how much data we are supposed + * to copy into s.temp.buf. Return true once s.temp.pos has reached + * len(s.temp.buf). + */ +func fillTemp(s *xzDec, b *xzBuf) bool { + copySize := len(b.in) - b.inPos + tempRemaining := len(s.temp.buf) - s.temp.pos + if copySize > tempRemaining { + copySize = tempRemaining + } + copy(s.temp.buf[s.temp.pos:], b.in[b.inPos:]) + b.inPos += copySize + s.temp.pos += copySize + if s.temp.pos == len(s.temp.buf) { + s.temp.pos = 0 + return true + } + return false +} + +/* Decode a variable-length integer (little-endian base-128 encoding) */ +func decVLI(s *xzDec, in []byte, inPos *int) xzRet { + var byte byte + if s.pos == 0 { + s.vli = 0 + } + for *inPos < len(in) { + byte = in[*inPos] + *inPos++ + s.vli |= vliType(byte&0x7f) << uint(s.pos) + if byte&0x80 == 0 { + /* Don't allow non-minimal encodings. */ + if byte == 0 && s.pos != 0 { + return xzDataError + } + s.pos = 0 + return xzStreamEnd + } + s.pos += 7 + if s.pos == 7*vliBytesMax { + return xzDataError + } + } + return xzOK +} + +/* + * Decode the Compressed Data field from a Block. Update and validate + * the observed compressed and uncompressed sizes of the Block so that + * they don't exceed the values possibly stored in the Block Header + * (validation assumes that no integer overflow occurs, since vliType + * is uint64). Update s.check if presence of the CRC32/CRC64/SHA256 + * field was indicated in Stream Header. + * + * Once the decoding is finished, validate that the observed sizes match + * the sizes possibly stored in the Block Header. Update the hash and + * Block count, which are later used to validate the Index field. + */ +func decBlock(s *xzDec, b *xzBuf) xzRet { + var ret xzRet + s.inStart = b.inPos + s.outStart = b.outPos + ret = s.chain(b) + s.block.compressed += vliType(b.inPos - s.inStart) + s.block.uncompressed += vliType(b.outPos - s.outStart) + /* + * There is no need to separately check for vliUnknown since + * the observed sizes are always smaller than vliUnknown. + */ + if s.block.compressed > s.blockHeader.compressed || + s.block.uncompressed > s.blockHeader.uncompressed { + return xzDataError + } + switch s.CheckType { + case CheckCRC32, CheckCRC64, CheckSHA256: + _, _ = s.check.Write(b.out[s.outStart:b.outPos]) + } + if ret == xzStreamEnd { + if s.blockHeader.compressed != vliUnknown && + s.blockHeader.compressed != s.block.compressed { + return xzDataError + } + if s.blockHeader.uncompressed != vliUnknown && + s.blockHeader.uncompressed != s.block.uncompressed { + return xzDataError + } + s.block.hash.unpadded += + vliType(s.blockHeader.size) + s.block.compressed + s.block.hash.unpadded += vliType(checkSizes[s.CheckType]) + s.block.hash.uncompressed += s.block.uncompressed + var buf [2 * 8]byte // 2*Sizeof(vliType) + putLE64(uint64(s.block.hash.unpadded), buf[:]) + putLE64(uint64(s.block.hash.uncompressed), buf[8:]) + _, _ = s.block.hash.sha256.Write(buf[:]) + s.block.count++ + } + return ret +} + +/* Update the Index size and the CRC32 hash. */ +func indexUpdate(s *xzDec, b *xzBuf) { + inUsed := b.inPos - s.inStart + s.index.size += vliType(inUsed) + _, _ = s.crc32.Write(b.in[s.inStart : s.inStart+inUsed]) +} + +/* + * Decode the Number of Records, Unpadded Size, and Uncompressed Size + * fields from the Index field. That is, Index Padding and CRC32 are not + * decoded by this function. + * + * This can return xzOK (more input needed), xzStreamEnd (everything + * successfully decoded), or xzDataError (input is corrupt). + */ +func decIndex(s *xzDec, b *xzBuf) xzRet { + var ret xzRet + for { + ret = decVLI(s, b.in, &b.inPos) + if ret != xzStreamEnd { + indexUpdate(s, b) + return ret + } + switch s.index.sequence { + case seqIndexCount: + s.index.count = s.vli + /* + * Validate that the Number of Records field + * indicates the same number of Records as + * there were Blocks in the Stream. + */ + if s.index.count != s.block.count { + return xzDataError + } + s.index.sequence = seqIndexUnpadded + case seqIndexUnpadded: + s.index.hash.unpadded += s.vli + s.index.sequence = seqIndexUncompressed + case seqIndexUncompressed: + s.index.hash.uncompressed += s.vli + var buf [2 * 8]byte // 2*Sizeof(vliType) + putLE64(uint64(s.index.hash.unpadded), buf[:]) + putLE64(uint64(s.index.hash.uncompressed), buf[8:]) + _, _ = s.index.hash.sha256.Write(buf[:]) + s.index.count-- + s.index.sequence = seqIndexUnpadded + } + if !(s.index.count > 0) { + break + } + } + return xzStreamEnd +} + +/* + * Validate that the next 4 bytes match s.crc32.Sum(nil). s.pos must + * be zero when starting to validate the first byte. + */ +func crcValidate(s *xzDec, b *xzBuf) xzRet { + sum := s.crc32.Sum(nil) + // CRC32 - reverse slice + sum[0], sum[1], sum[2], sum[3] = sum[3], sum[2], sum[1], sum[0] + for { + if b.inPos == len(b.in) { + return xzOK + } + if sum[s.pos] != b.in[b.inPos] { + return xzDataError + } + b.inPos++ + s.pos++ + if !(s.pos < 4) { + break + } + } + s.crc32.Reset() + s.pos = 0 + return xzStreamEnd +} + +/* + * Validate that the next 4/8/32 bytes match s.check.Sum(nil). s.pos + * must be zero when starting to validate the first byte. + */ +func checkValidate(s *xzDec, b *xzBuf) xzRet { + sum := s.check.Sum(nil) + if s.CheckType == CheckCRC32 || s.CheckType == CheckCRC64 { + // CRC32/64 - reverse slice + for i, j := 0, len(sum)-1; i < j; i, j = i+1, j-1 { + sum[i], sum[j] = sum[j], sum[i] + } + } + for { + if b.inPos == len(b.in) { + return xzOK + } + if sum[s.pos] != b.in[b.inPos] { + return xzDataError + } + b.inPos++ + s.pos++ + if !(s.pos < len(sum)) { + break + } + } + s.check.Reset() + s.pos = 0 + return xzStreamEnd +} + +/* + * Skip over the Check field when the Check ID is not supported. + * Returns true once the whole Check field has been skipped over. + */ +func checkSkip(s *xzDec, b *xzBuf) bool { + for s.pos < int(checkSizes[s.CheckType]) { + if b.inPos == len(b.in) { + return false + } + b.inPos++ + s.pos++ + } + s.pos = 0 + return true +} + +/* polynomial table used in decStreamHeader below */ +var xzCRC64Table = crc64.MakeTable(crc64.ECMA) + +/* Decode the Stream Header field (the first 12 bytes of the .xz Stream). */ +func decStreamHeader(s *xzDec) xzRet { + if string(s.temp.buf[:len(headerMagic)]) != headerMagic { + return xzFormatError + } + if crc32.ChecksumIEEE(s.temp.buf[len(headerMagic):len(headerMagic)+2]) != + getLE32(s.temp.buf[len(headerMagic)+2:]) { + return xzDataError + } + if s.temp.buf[len(headerMagic)] != 0 { + return xzOptionsError + } + /* + * Of integrity checks, we support none (Check ID = 0), + * CRC32 (Check ID = 1), CRC64 (Check ID = 4) and SHA256 (Check ID = 10) + * However, we will accept other check types too, but then the check + * won't be verified and a warning (xzUnsupportedCheck) will be given. + */ + s.CheckType = CheckID(s.temp.buf[len(headerMagic)+1]) + if s.CheckType > checkMax { + return xzOptionsError + } + switch s.CheckType { + case CheckNone: + // CheckNone: no action needed + case CheckCRC32: + if s.checkCRC32 == nil { + s.checkCRC32 = crc32.NewIEEE() + } else { + s.checkCRC32.Reset() + } + s.check = s.checkCRC32 + case CheckCRC64: + if s.checkCRC64 == nil { + s.checkCRC64 = crc64.New(xzCRC64Table) + } else { + s.checkCRC64.Reset() + } + s.check = s.checkCRC64 + case CheckSHA256: + if s.checkSHA256 == nil { + s.checkSHA256 = sha256.New() + } else { + s.checkSHA256.Reset() + } + s.check = s.checkSHA256 + default: + return xzUnsupportedCheck + } + return xzOK +} + +/* Decode the Stream Footer field (the last 12 bytes of the .xz Stream) */ +func decStreamFooter(s *xzDec) xzRet { + if string(s.temp.buf[10:10+len(footerMagic)]) != footerMagic { + return xzDataError + } + if crc32.ChecksumIEEE(s.temp.buf[4:10]) != getLE32(s.temp.buf) { + return xzDataError + } + /* + * Validate Backward Size. Note that we never added the size of the + * Index CRC32 field to s->index.size, thus we use s->index.size / 4 + * instead of s->index.size / 4 - 1. + */ + if s.index.size>>2 != vliType(getLE32(s.temp.buf[4:])) { + return xzDataError + } + if s.temp.buf[8] != 0 || CheckID(s.temp.buf[9]) != s.CheckType { + return xzDataError + } + /* + * Use xzStreamEnd instead of xzOK to be more convenient + * for the caller. + */ + return xzStreamEnd +} + +/* Decode the Block Header and initialize the filter chain. */ +func decBlockHeader(s *xzDec) xzRet { + var ret xzRet + /* + * Validate the CRC32. We know that the temp buffer is at least + * eight bytes so this is safe. + */ + crc := getLE32(s.temp.buf[len(s.temp.buf)-4:]) + s.temp.buf = s.temp.buf[:len(s.temp.buf)-4] + if crc32.ChecksumIEEE(s.temp.buf) != crc { + return xzDataError + } + s.temp.pos = 2 + /* + * Catch unsupported Block Flags. + */ + if s.temp.buf[1]&0x3C != 0 { + return xzOptionsError + } + /* Compressed Size */ + if s.temp.buf[1]&0x40 != 0 { + if decVLI(s, s.temp.buf, &s.temp.pos) != xzStreamEnd { + return xzDataError + } + if s.vli >= 1<<63-8 { + // the whole block must stay smaller than 2^63 bytes + // the block header cannot be smaller than 8 bytes + return xzDataError + } + if s.vli == 0 { + // compressed size must be non-zero + return xzDataError + } + s.blockHeader.compressed = s.vli + } else { + s.blockHeader.compressed = vliUnknown + } + /* Uncompressed Size */ + if s.temp.buf[1]&0x80 != 0 { + if decVLI(s, s.temp.buf, &s.temp.pos) != xzStreamEnd { + return xzDataError + } + s.blockHeader.uncompressed = s.vli + } else { + s.blockHeader.uncompressed = vliUnknown + } + // get total number of filters (1-4) + filterTotal := int(s.temp.buf[1]&0x03) + 1 + // slice to hold decoded filters + filterList := make([]struct { + id xzFilterID + props uint32 + }, filterTotal) + // decode the non-last filters which cannot be LZMA2 + for i := 0; i < filterTotal-1; i++ { + /* Valid Filter Flags always take at least two bytes. */ + if len(s.temp.buf)-s.temp.pos < 2 { + return xzDataError + } + s.temp.pos += 2 + switch id := xzFilterID(s.temp.buf[s.temp.pos-2]); id { + case idDelta: + // delta filter + if s.temp.buf[s.temp.pos-1] != 0x01 { + return xzOptionsError + } + /* Filter Properties contains distance - 1 */ + if len(s.temp.buf)-s.temp.pos < 1 { + return xzDataError + } + props := uint32(s.temp.buf[s.temp.pos]) + s.temp.pos++ + filterList[i] = struct { + id xzFilterID + props uint32 + }{id: id, props: props} + case idBCJX86, idBCJPowerPC, idBCJIA64, + idBCJARM, idBCJARMThumb, idBCJSPARC: + // bcj filter + var props uint32 + switch s.temp.buf[s.temp.pos-1] { + case 0x00: + props = 0 + case 0x04: + if len(s.temp.buf)-s.temp.pos < 4 { + return xzDataError + } + props = getLE32(s.temp.buf[s.temp.pos:]) + s.temp.pos += 4 + default: + return xzOptionsError + } + filterList[i] = struct { + id xzFilterID + props uint32 + }{id: id, props: props} + default: + return xzOptionsError + } + } + /* + * decode the last filter which must be LZMA2 + */ + if len(s.temp.buf)-s.temp.pos < 2 { + return xzDataError + } + /* Filter ID = LZMA2 */ + if xzFilterID(s.temp.buf[s.temp.pos]) != idLZMA2 { + return xzOptionsError + } + s.temp.pos++ + /* Size of Properties = 1-byte Filter Properties */ + if s.temp.buf[s.temp.pos] != 0x01 { + return xzOptionsError + } + s.temp.pos++ + /* Filter Properties contains LZMA2 dictionary size. */ + if len(s.temp.buf)-s.temp.pos < 1 { + return xzDataError + } + props := uint32(s.temp.buf[s.temp.pos]) + s.temp.pos++ + filterList[filterTotal-1] = struct { + id xzFilterID + props uint32 + }{id: idLZMA2, props: props} + /* + * Process the filter list and create s.chain, going from last + * filter (LZMA2) to first filter + * + * First, LZMA2. + */ + ret = xzDecLZMA2Reset(s.lzma2, byte(filterList[filterTotal-1].props)) + if ret != xzOK { + return ret + } + s.chain = func(b *xzBuf) xzRet { + return xzDecLZMA2Run(s.lzma2, b) + } + /* + * Now the non-last filters + */ + for i := filterTotal - 2; i >= 0; i-- { + switch id := filterList[i].id; id { + case idDelta: + // delta filter + var delta *xzDecDelta + if s.deltasUsed < len(s.deltas) { + delta = s.deltas[s.deltasUsed] + } else { + delta = xzDecDeltaCreate() + s.deltas = append(s.deltas, delta) + } + s.deltasUsed++ + ret = xzDecDeltaReset(delta, int(filterList[i].props)+1) + if ret != xzOK { + return ret + } + chain := s.chain + s.chain = func(b *xzBuf) xzRet { + return xzDecDeltaRun(delta, b, chain) + } + case idBCJX86, idBCJPowerPC, idBCJIA64, + idBCJARM, idBCJARMThumb, idBCJSPARC: + // bcj filter + var bcj *xzDecBCJ + if s.bcjsUsed < len(s.bcjs) { + bcj = s.bcjs[s.bcjsUsed] + } else { + bcj = xzDecBCJCreate() + s.bcjs = append(s.bcjs, bcj) + } + s.bcjsUsed++ + ret = xzDecBCJReset(bcj, id, int(filterList[i].props)) + if ret != xzOK { + return ret + } + chain := s.chain + s.chain = func(b *xzBuf) xzRet { + return xzDecBCJRun(bcj, b, chain) + } + } + } + /* The rest must be Header Padding. */ + for s.temp.pos < len(s.temp.buf) { + if s.temp.buf[s.temp.pos] != 0x00 { + return xzOptionsError + } + s.temp.pos++ + } + s.temp.pos = 0 + s.block.compressed = 0 + s.block.uncompressed = 0 + return xzOK +} + +func decMain(s *xzDec, b *xzBuf) xzRet { + var ret xzRet + /* + * Store the start position for the case when we are in the middle + * of the Index field. + */ + s.inStart = b.inPos + for { + switch s.sequence { + case seqStreamHeader: + /* + * Stream Header is copied to s.temp, and then + * decoded from there. This way if the caller + * gives us only little input at a time, we can + * still keep the Stream Header decoding code + * simple. Similar approach is used in many places + * in this file. + */ + if !fillTemp(s, b) { + return xzOK + } + /* + * If decStreamHeader returns + * xzUnsupportedCheck, it is still possible + * to continue decoding. Thus, update s.sequence + * before calling decStreamHeader. + */ + s.sequence = seqBlockStart + ret = decStreamHeader(s) + if ret != xzOK { + return ret + } + fallthrough + case seqBlockStart: + /* We need one byte of input to continue. */ + if b.inPos == len(b.in) { + return xzOK + } + /* See if this is the beginning of the Index field. */ + if b.in[b.inPos] == 0 { + s.inStart = b.inPos + b.inPos++ + s.sequence = seqIndex + break + } + /* + * Calculate the size of the Block Header and + * prepare to decode it. + */ + s.blockHeader.size = (int(b.in[b.inPos]) + 1) * 4 + s.temp.buf = s.temp.bufArray[:s.blockHeader.size] + s.temp.pos = 0 + s.sequence = seqBlockHeader + fallthrough + case seqBlockHeader: + if !fillTemp(s, b) { + return xzOK + } + ret = decBlockHeader(s) + if ret != xzOK { + return ret + } + s.sequence = seqBlockUncompress + fallthrough + case seqBlockUncompress: + ret = decBlock(s, b) + if ret != xzStreamEnd { + return ret + } + s.sequence = seqBlockPadding + fallthrough + case seqBlockPadding: + /* + * Size of Compressed Data + Block Padding + * must be a multiple of four. We don't need + * s->block.compressed for anything else + * anymore, so we use it here to test the size + * of the Block Padding field. + */ + for s.block.compressed&3 != 0 { + if b.inPos == len(b.in) { + return xzOK + } + if b.in[b.inPos] != 0 { + return xzDataError + } + b.inPos++ + s.block.compressed++ + } + s.sequence = seqBlockCheck + fallthrough + case seqBlockCheck: + switch s.CheckType { + case CheckCRC32, CheckCRC64, CheckSHA256: + ret = checkValidate(s, b) + if ret != xzStreamEnd { + return ret + } + default: + if !checkSkip(s, b) { + return xzOK + } + } + s.sequence = seqBlockStart + case seqIndex: + ret = decIndex(s, b) + if ret != xzStreamEnd { + return ret + } + s.sequence = seqIndexPadding + fallthrough + case seqIndexPadding: + for (s.index.size+vliType(b.inPos-s.inStart))&3 != 0 { + if b.inPos == len(b.in) { + indexUpdate(s, b) + return xzOK + } + if b.in[b.inPos] != 0 { + return xzDataError + } + b.inPos++ + } + /* Finish the CRC32 value and Index size. */ + indexUpdate(s, b) + /* Compare the hashes to validate the Index field. */ + if !bytes.Equal( + s.block.hash.sha256.Sum(nil), s.index.hash.sha256.Sum(nil)) { + return xzDataError + } + s.sequence = seqIndexCRC32 + fallthrough + case seqIndexCRC32: + ret = crcValidate(s, b) + if ret != xzStreamEnd { + return ret + } + s.temp.buf = s.temp.bufArray[:streamHeaderSize] + s.sequence = seqStreamFooter + fallthrough + case seqStreamFooter: + if !fillTemp(s, b) { + return xzOK + } + return decStreamFooter(s) + } + } + /* Never reached */ +} + +/** + * xzDecRun - Run the XZ decoder + * @s: Decoder state allocated using xzDecInit + * @b: Input and output buffers + * + * See xzRet for details of return values. + * + * xzDecRun is a wrapper for decMain to handle some special cases. + * + * We must return xzBufError when it seems clear that we are not + * going to make any progress anymore. This is to prevent the caller + * from calling us infinitely when the input file is truncated or + * otherwise corrupt. Since zlib-style API allows that the caller + * fills the input buffer only when the decoder doesn't produce any + * new output, we have to be careful to avoid returning xzBufError + * too easily: xzBufError is returned only after the second + * consecutive call to xzDecRun that makes no progress. + */ +func xzDecRun(s *xzDec, b *xzBuf) xzRet { + inStart := b.inPos + outStart := b.outPos + ret := decMain(s, b) + if ret == xzOK && inStart == b.inPos && outStart == b.outPos { + if s.allowBufError { + ret = xzBufError + } + s.allowBufError = true + } else { + s.allowBufError = false + } + return ret +} + +/** + * xzDecInit - Allocate and initialize a XZ decoder state + * @dictMax: Maximum size of the LZMA2 dictionary (history buffer) for + * decoding. LZMA2 dictionary is always 2^n bytes + * or 2^n + 2^(n-1) bytes (the latter sizes are less common + * in practice), so other values for dictMax don't make sense. + * + * dictMax specifies the maximum allowed dictionary size that xzDecRun + * may allocate once it has parsed the dictionary size from the stream + * headers. This way excessive allocations can be avoided while still + * limiting the maximum memory usage to a sane value to prevent running the + * system out of memory when decompressing streams from untrusted sources. + * + * xzDecInit returns a pointer to an xzDec, which is ready to be used with + * xzDecRun. + */ +func xzDecInit(dictMax uint32, header *Header) *xzDec { + s := new(xzDec) + s.crc32 = crc32.NewIEEE() + s.Header = header + s.block.hash.sha256 = sha256.New() + s.index.hash.sha256 = sha256.New() + s.lzma2 = xzDecLZMA2Create(dictMax) + xzDecReset(s) + return s +} + +/** + * xzDecReset - Reset an already allocated decoder state + * @s: Decoder state allocated using xzDecInit + * + * This function can be used to reset the decoder state without + * reallocating memory with xzDecInit. + */ +func xzDecReset(s *xzDec) { + s.sequence = seqStreamHeader + s.allowBufError = false + s.pos = 0 + s.crc32.Reset() + s.check = nil + s.CheckType = checkUnset + s.block.compressed = 0 + s.block.uncompressed = 0 + s.block.count = 0 + s.block.hash.unpadded = 0 + s.block.hash.uncompressed = 0 + s.block.hash.sha256.Reset() + s.index.sequence = seqIndexCount + s.index.size = 0 + s.index.count = 0 + s.index.hash.unpadded = 0 + s.index.hash.uncompressed = 0 + s.index.hash.sha256.Reset() + s.temp.pos = 0 + s.temp.buf = s.temp.bufArray[:streamHeaderSize] + s.chain = nil + s.bcjsUsed = 0 + s.deltasUsed = 0 +} |