forked from gitea/gitea
473 lines
12 KiB
Go
473 lines
12 KiB
Go
package huff0
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import (
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"errors"
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"fmt"
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"io"
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"github.com/klauspost/compress/fse"
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)
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type dTable struct {
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single []dEntrySingle
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double []dEntryDouble
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}
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// single-symbols decoding
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type dEntrySingle struct {
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entry uint16
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}
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// double-symbols decoding
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type dEntryDouble struct {
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seq uint16
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nBits uint8
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len uint8
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}
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// ReadTable will read a table from the input.
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// The size of the input may be larger than the table definition.
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// Any content remaining after the table definition will be returned.
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// If no Scratch is provided a new one is allocated.
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// The returned Scratch can be used for decoding input using this table.
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func ReadTable(in []byte, s *Scratch) (s2 *Scratch, remain []byte, err error) {
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s, err = s.prepare(in)
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if err != nil {
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return s, nil, err
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}
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if len(in) <= 1 {
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return s, nil, errors.New("input too small for table")
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}
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iSize := in[0]
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in = in[1:]
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if iSize >= 128 {
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// Uncompressed
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oSize := iSize - 127
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iSize = (oSize + 1) / 2
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if int(iSize) > len(in) {
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return s, nil, errors.New("input too small for table")
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}
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for n := uint8(0); n < oSize; n += 2 {
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v := in[n/2]
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s.huffWeight[n] = v >> 4
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s.huffWeight[n+1] = v & 15
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}
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s.symbolLen = uint16(oSize)
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in = in[iSize:]
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} else {
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if len(in) <= int(iSize) {
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return s, nil, errors.New("input too small for table")
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}
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// FSE compressed weights
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s.fse.DecompressLimit = 255
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hw := s.huffWeight[:]
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s.fse.Out = hw
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b, err := fse.Decompress(in[:iSize], s.fse)
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s.fse.Out = nil
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if err != nil {
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return s, nil, err
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}
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if len(b) > 255 {
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return s, nil, errors.New("corrupt input: output table too large")
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}
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s.symbolLen = uint16(len(b))
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in = in[iSize:]
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}
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// collect weight stats
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var rankStats [16]uint32
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weightTotal := uint32(0)
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for _, v := range s.huffWeight[:s.symbolLen] {
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if v > tableLogMax {
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return s, nil, errors.New("corrupt input: weight too large")
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}
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v2 := v & 15
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rankStats[v2]++
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weightTotal += (1 << v2) >> 1
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}
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if weightTotal == 0 {
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return s, nil, errors.New("corrupt input: weights zero")
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}
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// get last non-null symbol weight (implied, total must be 2^n)
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{
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tableLog := highBit32(weightTotal) + 1
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if tableLog > tableLogMax {
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return s, nil, errors.New("corrupt input: tableLog too big")
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}
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s.actualTableLog = uint8(tableLog)
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// determine last weight
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{
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total := uint32(1) << tableLog
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rest := total - weightTotal
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verif := uint32(1) << highBit32(rest)
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lastWeight := highBit32(rest) + 1
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if verif != rest {
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// last value must be a clean power of 2
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return s, nil, errors.New("corrupt input: last value not power of two")
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}
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s.huffWeight[s.symbolLen] = uint8(lastWeight)
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s.symbolLen++
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rankStats[lastWeight]++
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}
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}
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if (rankStats[1] < 2) || (rankStats[1]&1 != 0) {
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// by construction : at least 2 elts of rank 1, must be even
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return s, nil, errors.New("corrupt input: min elt size, even check failed ")
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}
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// TODO: Choose between single/double symbol decoding
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// Calculate starting value for each rank
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{
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var nextRankStart uint32
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for n := uint8(1); n < s.actualTableLog+1; n++ {
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current := nextRankStart
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nextRankStart += rankStats[n] << (n - 1)
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rankStats[n] = current
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}
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}
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// fill DTable (always full size)
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tSize := 1 << tableLogMax
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if len(s.dt.single) != tSize {
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s.dt.single = make([]dEntrySingle, tSize)
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}
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for n, w := range s.huffWeight[:s.symbolLen] {
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if w == 0 {
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continue
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}
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length := (uint32(1) << w) >> 1
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d := dEntrySingle{
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entry: uint16(s.actualTableLog+1-w) | (uint16(n) << 8),
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}
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single := s.dt.single[rankStats[w] : rankStats[w]+length]
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for i := range single {
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single[i] = d
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}
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rankStats[w] += length
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}
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return s, in, nil
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}
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// Decompress1X will decompress a 1X encoded stream.
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// The length of the supplied input must match the end of a block exactly.
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// Before this is called, the table must be initialized with ReadTable unless
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// the encoder re-used the table.
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func (s *Scratch) Decompress1X(in []byte) (out []byte, err error) {
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if len(s.dt.single) == 0 {
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return nil, errors.New("no table loaded")
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}
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var br bitReader
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err = br.init(in)
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if err != nil {
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return nil, err
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}
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s.Out = s.Out[:0]
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decode := func() byte {
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val := br.peekBitsFast(s.actualTableLog) /* note : actualTableLog >= 1 */
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v := s.dt.single[val]
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br.bitsRead += uint8(v.entry)
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return uint8(v.entry >> 8)
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}
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hasDec := func(v dEntrySingle) byte {
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br.bitsRead += uint8(v.entry)
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return uint8(v.entry >> 8)
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}
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// Avoid bounds check by always having full sized table.
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const tlSize = 1 << tableLogMax
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const tlMask = tlSize - 1
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dt := s.dt.single[:tlSize]
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// Use temp table to avoid bound checks/append penalty.
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var tmp = s.huffWeight[:256]
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var off uint8
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for br.off >= 8 {
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br.fillFast()
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tmp[off+0] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
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tmp[off+1] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
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br.fillFast()
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tmp[off+2] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
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tmp[off+3] = hasDec(dt[br.peekBitsFast(s.actualTableLog)&tlMask])
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off += 4
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if off == 0 {
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if len(s.Out)+256 > s.MaxDecodedSize {
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br.close()
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return nil, ErrMaxDecodedSizeExceeded
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}
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s.Out = append(s.Out, tmp...)
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}
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}
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if len(s.Out)+int(off) > s.MaxDecodedSize {
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br.close()
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return nil, ErrMaxDecodedSizeExceeded
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}
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s.Out = append(s.Out, tmp[:off]...)
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for !br.finished() {
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br.fill()
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if len(s.Out) >= s.MaxDecodedSize {
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br.close()
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return nil, ErrMaxDecodedSizeExceeded
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}
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s.Out = append(s.Out, decode())
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}
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return s.Out, br.close()
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}
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// Decompress4X will decompress a 4X encoded stream.
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// Before this is called, the table must be initialized with ReadTable unless
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// the encoder re-used the table.
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// The length of the supplied input must match the end of a block exactly.
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// The destination size of the uncompressed data must be known and provided.
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func (s *Scratch) Decompress4X(in []byte, dstSize int) (out []byte, err error) {
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if len(s.dt.single) == 0 {
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return nil, errors.New("no table loaded")
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}
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if len(in) < 6+(4*1) {
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return nil, errors.New("input too small")
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}
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if dstSize > s.MaxDecodedSize {
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return nil, ErrMaxDecodedSizeExceeded
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}
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// TODO: We do not detect when we overrun a buffer, except if the last one does.
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var br [4]bitReader
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start := 6
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for i := 0; i < 3; i++ {
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length := int(in[i*2]) | (int(in[i*2+1]) << 8)
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if start+length >= len(in) {
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return nil, errors.New("truncated input (or invalid offset)")
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}
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err = br[i].init(in[start : start+length])
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if err != nil {
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return nil, err
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}
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start += length
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}
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err = br[3].init(in[start:])
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if err != nil {
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return nil, err
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}
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// Prepare output
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if cap(s.Out) < dstSize {
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s.Out = make([]byte, 0, dstSize)
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}
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s.Out = s.Out[:dstSize]
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// destination, offset to match first output
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dstOut := s.Out
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dstEvery := (dstSize + 3) / 4
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const tlSize = 1 << tableLogMax
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const tlMask = tlSize - 1
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single := s.dt.single[:tlSize]
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decode := func(br *bitReader) byte {
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val := br.peekBitsFast(s.actualTableLog) /* note : actualTableLog >= 1 */
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v := single[val&tlMask]
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br.bitsRead += uint8(v.entry)
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return uint8(v.entry >> 8)
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}
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// Use temp table to avoid bound checks/append penalty.
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var tmp = s.huffWeight[:256]
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var off uint8
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var decoded int
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// Decode 2 values from each decoder/loop.
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const bufoff = 256 / 4
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bigloop:
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for {
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for i := range br {
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br := &br[i]
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if br.off < 4 {
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break bigloop
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}
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br.fillFast()
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}
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{
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const stream = 0
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val := br[stream].peekBitsFast(s.actualTableLog)
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v := single[val&tlMask]
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br[stream].bitsRead += uint8(v.entry)
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val2 := br[stream].peekBitsFast(s.actualTableLog)
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v2 := single[val2&tlMask]
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tmp[off+bufoff*stream+1] = uint8(v2.entry >> 8)
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tmp[off+bufoff*stream] = uint8(v.entry >> 8)
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br[stream].bitsRead += uint8(v2.entry)
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}
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{
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const stream = 1
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val := br[stream].peekBitsFast(s.actualTableLog)
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v := single[val&tlMask]
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br[stream].bitsRead += uint8(v.entry)
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val2 := br[stream].peekBitsFast(s.actualTableLog)
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v2 := single[val2&tlMask]
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tmp[off+bufoff*stream+1] = uint8(v2.entry >> 8)
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tmp[off+bufoff*stream] = uint8(v.entry >> 8)
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br[stream].bitsRead += uint8(v2.entry)
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}
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{
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const stream = 2
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val := br[stream].peekBitsFast(s.actualTableLog)
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v := single[val&tlMask]
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br[stream].bitsRead += uint8(v.entry)
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val2 := br[stream].peekBitsFast(s.actualTableLog)
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v2 := single[val2&tlMask]
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tmp[off+bufoff*stream+1] = uint8(v2.entry >> 8)
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tmp[off+bufoff*stream] = uint8(v.entry >> 8)
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br[stream].bitsRead += uint8(v2.entry)
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}
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{
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const stream = 3
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val := br[stream].peekBitsFast(s.actualTableLog)
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v := single[val&tlMask]
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br[stream].bitsRead += uint8(v.entry)
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val2 := br[stream].peekBitsFast(s.actualTableLog)
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v2 := single[val2&tlMask]
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tmp[off+bufoff*stream+1] = uint8(v2.entry >> 8)
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tmp[off+bufoff*stream] = uint8(v.entry >> 8)
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br[stream].bitsRead += uint8(v2.entry)
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}
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off += 2
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if off == bufoff {
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if bufoff > dstEvery {
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return nil, errors.New("corruption detected: stream overrun 1")
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}
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copy(dstOut, tmp[:bufoff])
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copy(dstOut[dstEvery:], tmp[bufoff:bufoff*2])
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copy(dstOut[dstEvery*2:], tmp[bufoff*2:bufoff*3])
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copy(dstOut[dstEvery*3:], tmp[bufoff*3:bufoff*4])
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off = 0
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dstOut = dstOut[bufoff:]
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decoded += 256
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// There must at least be 3 buffers left.
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if len(dstOut) < dstEvery*3 {
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return nil, errors.New("corruption detected: stream overrun 2")
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}
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}
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}
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if off > 0 {
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ioff := int(off)
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if len(dstOut) < dstEvery*3+ioff {
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return nil, errors.New("corruption detected: stream overrun 3")
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}
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copy(dstOut, tmp[:off])
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copy(dstOut[dstEvery:dstEvery+ioff], tmp[bufoff:bufoff*2])
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copy(dstOut[dstEvery*2:dstEvery*2+ioff], tmp[bufoff*2:bufoff*3])
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copy(dstOut[dstEvery*3:dstEvery*3+ioff], tmp[bufoff*3:bufoff*4])
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decoded += int(off) * 4
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dstOut = dstOut[off:]
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}
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// Decode remaining.
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for i := range br {
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offset := dstEvery * i
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br := &br[i]
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for !br.finished() {
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br.fill()
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if offset >= len(dstOut) {
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return nil, errors.New("corruption detected: stream overrun 4")
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}
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dstOut[offset] = decode(br)
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offset++
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}
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decoded += offset - dstEvery*i
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err = br.close()
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if err != nil {
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return nil, err
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}
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}
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if dstSize != decoded {
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return nil, errors.New("corruption detected: short output block")
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}
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return s.Out, nil
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}
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// matches will compare a decoding table to a coding table.
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// Errors are written to the writer.
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// Nothing will be written if table is ok.
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func (s *Scratch) matches(ct cTable, w io.Writer) {
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if s == nil || len(s.dt.single) == 0 {
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return
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}
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dt := s.dt.single[:1<<s.actualTableLog]
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tablelog := s.actualTableLog
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ok := 0
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broken := 0
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for sym, enc := range ct {
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errs := 0
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broken++
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if enc.nBits == 0 {
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for _, dec := range dt {
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if uint8(dec.entry>>8) == byte(sym) {
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fmt.Fprintf(w, "symbol %x has decoder, but no encoder\n", sym)
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errs++
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break
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}
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}
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if errs == 0 {
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broken--
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}
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continue
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}
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// Unused bits in input
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ub := tablelog - enc.nBits
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top := enc.val << ub
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// decoder looks at top bits.
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dec := dt[top]
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if uint8(dec.entry) != enc.nBits {
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fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", sym, enc.nBits, uint8(dec.entry))
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errs++
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}
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if uint8(dec.entry>>8) != uint8(sym) {
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fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", sym, sym, uint8(dec.entry>>8))
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errs++
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}
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if errs > 0 {
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fmt.Fprintf(w, "%d errros in base, stopping\n", errs)
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continue
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}
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// Ensure that all combinations are covered.
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for i := uint16(0); i < (1 << ub); i++ {
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vval := top | i
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dec := dt[vval]
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if uint8(dec.entry) != enc.nBits {
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fmt.Fprintf(w, "symbol 0x%x bit size mismatch (enc: %d, dec:%d).\n", vval, enc.nBits, uint8(dec.entry))
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errs++
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}
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if uint8(dec.entry>>8) != uint8(sym) {
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fmt.Fprintf(w, "symbol 0x%x decoder output mismatch (enc: %d, dec:%d).\n", vval, sym, uint8(dec.entry>>8))
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errs++
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}
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if errs > 20 {
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fmt.Fprintf(w, "%d errros, stopping\n", errs)
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break
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}
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}
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if errs == 0 {
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ok++
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broken--
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}
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}
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if broken > 0 {
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fmt.Fprintf(w, "%d broken, %d ok\n", broken, ok)
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}
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}
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