package huff0 import ( "errors" "fmt" "io" "github.com/klauspost/compress/fse" ) type dTable struct { single []dEntrySingle double []dEntryDouble } // single-symbols decoding type dEntrySingle struct { byte uint8 nBits uint8 } // double-symbols decoding type dEntryDouble struct { seq uint16 nBits uint8 len uint8 } // ReadTable will read a table from the input. // The size of the input may be larger than the table definition. // Any content remaining after the table definition will be returned. // If no Scratch is provided a new one is allocated. // The returned Scratch can be used for decoding input using this table. func ReadTable(in []byte, s *Scratch) (s2 *Scratch, remain []byte, err error) { s, err = s.prepare(in) if err != nil { return s, nil, err } if len(in) <= 1 { return s, nil, errors.New("input too small for table") } iSize := in[0] in = in[1:] if iSize >= 128 { // Uncompressed oSize := iSize - 127 iSize = (oSize + 1) / 2 if int(iSize) > len(in) { return s, nil, errors.New("input too small for table") } for n := uint8(0); n < oSize; n += 2 { v := in[n/2] s.huffWeight[n] = v >> 4 s.huffWeight[n+1] = v & 15 } s.symbolLen = uint16(oSize) in = in[iSize:] } else { if len(in) <= int(iSize) { return s, nil, errors.New("input too small for table") } // FSE compressed weights s.fse.DecompressLimit = 255 hw := s.huffWeight[:] s.fse.Out = hw b, err := fse.Decompress(in[:iSize], s.fse) s.fse.Out = nil if err != nil { return s, nil, err } if len(b) > 255 { return s, nil, errors.New("corrupt input: output table too large") } s.symbolLen = uint16(len(b)) in = in[iSize:] } // collect weight stats var rankStats [tableLogMax + 1]uint32 weightTotal := uint32(0) for _, v := range s.huffWeight[:s.symbolLen] { if v > tableLogMax { return s, nil, errors.New("corrupt input: weight too large") } rankStats[v]++ weightTotal += (1 << (v & 15)) >> 1 } if weightTotal == 0 { return s, nil, errors.New("corrupt input: weights zero") } // get last non-null symbol weight (implied, total must be 2^n) { tableLog := highBit32(weightTotal) + 1 if tableLog > tableLogMax { return s, nil, errors.New("corrupt input: tableLog too big") } s.actualTableLog = uint8(tableLog) // determine last weight { total := uint32(1) << tableLog rest := total - weightTotal verif := uint32(1) << highBit32(rest) lastWeight := highBit32(rest) + 1 if verif != rest { // last value must be a clean power of 2 return s, nil, errors.New("corrupt input: last value not power of two") } s.huffWeight[s.symbolLen] = uint8(lastWeight) s.symbolLen++ rankStats[lastWeight]++ } } if (rankStats[1] < 2) || (rankStats[1]&1 != 0) { // by construction : at least 2 elts of rank 1, must be even return s, nil, errors.New("corrupt input: min elt size, even check failed ") } // TODO: Choose between single/double symbol decoding // Calculate starting value for each rank { var nextRankStart uint32 for n := uint8(1); n < s.actualTableLog+1; n++ { current := nextRankStart nextRankStart += rankStats[n] << (n - 1) rankStats[n] = current } } // fill DTable (always full size) tSize := 1 << tableLogMax if len(s.dt.single) != tSize { s.dt.single = make([]dEntrySingle, tSize) } for n, w := range s.huffWeight[:s.symbolLen] { length := (uint32(1) << w) >> 1 d := dEntrySingle{ byte: uint8(n), nBits: s.actualTableLog + 1 - w, } for u := rankStats[w]; u < rankStats[w]+length; u++ { s.dt.single[u] = d } rankStats[w] += length } return s, in, nil } // Decompress1X will decompress a 1X encoded stream. // The length of the supplied input must match the end of a block exactly. // Before this is called, the table must be initialized with ReadTable unless // the encoder re-used the table. func (s *Scratch) Decompress1X(in []byte) (out []byte, err error) { if len(s.dt.single) == 0 { return nil, errors.New("no table loaded") } var br bitReader err = br.init(in) if err != nil { return nil, err } s.Out = s.Out[:0] decode := func() byte { val := br.peekBitsFast(s.actualTableLog) /* note : actualTableLog >= 1 */ v := s.dt.single[val] br.bitsRead += v.nBits return v.byte } hasDec := func(v dEntrySingle) byte { br.bitsRead += v.nBits return v.byte } // Avoid bounds check by always having full sized table. const tlSize = 1 << tableLogMax const tlMask = tlSize - 1 dt := s.dt.single[:tlSize] // Use temp table to avoid bound checks/append penalty. var tmp = s.huffWeight[:256] var off uint8 for br.off >= 8 { br.fillFast() tmp[off+0] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask]) tmp[off+1] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask]) br.fillFast() tmp[off+2] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask]) tmp[off+3] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask]) off += 4 if off == 0 { s.Out = append(s.Out, tmp...) } } s.Out = append(s.Out, tmp[:off]...) for !br.finished() { br.fill() s.Out = append(s.Out, decode()) } return s.Out, br.close() } // Decompress4X will decompress a 4X encoded stream. // Before this is called, the table must be initialized with ReadTable unless // the encoder re-used the table. // The length of the supplied input must match the end of a block exactly. // The destination size of the uncompressed data must be known and provided. func (s *Scratch) Decompress4X(in []byte, dstSize int) (out []byte, err error) { if len(s.dt.single) == 0 { return nil, errors.New("no table loaded") } if len(in) < 6+(4*1) { return nil, errors.New("input too small") } // TODO: We do not detect when we overrun a buffer, except if the last one does. var br [4]bitReader start := 6 for i := 0; i < 3; i++ { length := int(in[i*2]) | (int(in[i*2+1]) << 8) if start+length >= len(in) { return nil, errors.New("truncated input (or invalid offset)") } err = br[i].init(in[start : start+length]) if err != nil { return nil, err } start += length } err = br[3].init(in[start:]) if err != nil { return nil, err } // Prepare output if cap(s.Out) < dstSize { s.Out = make([]byte, 0, dstSize) } s.Out = s.Out[:dstSize] // destination, offset to match first output dstOut := s.Out dstEvery := (dstSize + 3) / 4 decode := func(br *bitReader) byte { val := br.peekBitsFast(s.actualTableLog) /* note : actualTableLog >= 1 */ v := s.dt.single[val] br.bitsRead += v.nBits return v.byte } // Use temp table to avoid bound checks/append penalty. var tmp = s.huffWeight[:256] var off uint8 // Decode 2 values from each decoder/loop. const bufoff = 256 / 4 bigloop: for { for i := range br { if br[i].off < 4 { break bigloop } br[i].fillFast() } tmp[off] = decode(&br[0]) tmp[off+bufoff] = decode(&br[1]) tmp[off+bufoff*2] = decode(&br[2]) tmp[off+bufoff*3] = decode(&br[3]) tmp[off+1] = decode(&br[0]) tmp[off+1+bufoff] = decode(&br[1]) tmp[off+1+bufoff*2] = decode(&br[2]) tmp[off+1+bufoff*3] = decode(&br[3]) off += 2 if off == bufoff { if bufoff > dstEvery { return nil, errors.New("corruption detected: stream overrun") } copy(dstOut, tmp[:bufoff]) copy(dstOut[dstEvery:], tmp[bufoff:bufoff*2]) copy(dstOut[dstEvery*2:], tmp[bufoff*2:bufoff*3]) copy(dstOut[dstEvery*3:], tmp[bufoff*3:bufoff*4]) off = 0 dstOut = dstOut[bufoff:] // There must at least be 3 buffers left. if len(dstOut) < dstEvery*3+3 { return nil, errors.New("corruption detected: stream overrun") } } } if off > 0 { ioff := int(off) if len(dstOut) < dstEvery*3+ioff { return nil, errors.New("corruption detected: stream overrun") } copy(dstOut, tmp[:off]) copy(dstOut[dstEvery:dstEvery+ioff], tmp[bufoff:bufoff*2]) copy(dstOut[dstEvery*2:dstEvery*2+ioff], tmp[bufoff*2:bufoff*3]) copy(dstOut[dstEvery*3:dstEvery*3+ioff], tmp[bufoff*3:bufoff*4]) dstOut = dstOut[off:] } for i := range br { offset := dstEvery * i br := &br[i] for !br.finished() { br.fill() if offset >= len(dstOut) { return nil, errors.New("corruption detected: stream overrun") } dstOut[offset] = decode(br) offset++ } err = br.close() if err != nil { return nil, err } } return s.Out, nil } // matches will compare a decoding table to a coding table. // Errors are written to the writer. // Nothing will be written if table is ok. func (s *Scratch) matches(ct cTable, w io.Writer) { if s == nil || len(s.dt.single) == 0 { return } dt := s.dt.single[:1< 0 { fmt.Fprintf(w, "%d errros in base, stopping\n", errs) continue } // Ensure that all combinations are covered. for i := uint16(0); i < (1 << ub); i++ { vval := top | i dec := dt[vval] if dec.nBits != enc.nBits { fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", vval, enc.nBits, dec.nBits) errs++ } if dec.byte != uint8(sym) { fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", vval, sym, dec.byte) errs++ } if errs > 20 { fmt.Fprintf(w, "%d errros, stopping\n", errs) break } } if errs == 0 { ok++ broken-- } } if broken > 0 { fmt.Fprintf(w, "%d broken, %d ok\n", broken, ok) } }