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300 lines
7.5 KiB
300 lines
7.5 KiB
//go:build !amd64 || appengine || !gc || noasm
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// +build !amd64 appengine !gc noasm
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// This file contains a generic implementation of Decoder.Decompress4X.
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package huff0
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import (
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"errors"
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"fmt"
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)
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// Decompress4X will decompress a 4X encoded stream.
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// The length of the supplied input must match the end of a block exactly.
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// The *capacity* of the dst slice must match the destination size of
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// the uncompressed data exactly.
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func (d *Decoder) Decompress4X(dst, src []byte) ([]byte, error) {
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if len(d.dt.single) == 0 {
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return nil, errors.New("no table loaded")
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}
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if len(src) < 6+(4*1) {
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return nil, errors.New("input too small")
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}
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if use8BitTables && d.actualTableLog <= 8 {
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return d.decompress4X8bit(dst, src)
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}
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var br [4]bitReaderShifted
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// Decode "jump table"
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start := 6
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for i := 0; i < 3; i++ {
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length := int(src[i*2]) | (int(src[i*2+1]) << 8)
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if start+length >= len(src) {
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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(src[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(src[start:])
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if err != nil {
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return nil, err
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}
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// destination, offset to match first output
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dstSize := cap(dst)
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dst = dst[:dstSize]
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out := dst
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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 := d.dt.single[:tlSize]
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// Use temp table to avoid bound checks/append penalty.
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buf := d.buffer()
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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
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for {
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if br[0].off < 4 || br[1].off < 4 || br[2].off < 4 || br[3].off < 4 {
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break
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}
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{
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const stream = 0
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const stream2 = 1
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br[stream].fillFast()
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br[stream2].fillFast()
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val := br[stream].peekBitsFast(d.actualTableLog)
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val2 := br[stream2].peekBitsFast(d.actualTableLog)
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v := single[val&tlMask]
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v2 := single[val2&tlMask]
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br[stream].advance(uint8(v.entry))
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br[stream2].advance(uint8(v2.entry))
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buf[stream][off] = uint8(v.entry >> 8)
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buf[stream2][off] = uint8(v2.entry >> 8)
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val = br[stream].peekBitsFast(d.actualTableLog)
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val2 = br[stream2].peekBitsFast(d.actualTableLog)
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v = single[val&tlMask]
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v2 = single[val2&tlMask]
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br[stream].advance(uint8(v.entry))
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br[stream2].advance(uint8(v2.entry))
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buf[stream][off+1] = uint8(v.entry >> 8)
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buf[stream2][off+1] = uint8(v2.entry >> 8)
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}
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{
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const stream = 2
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const stream2 = 3
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br[stream].fillFast()
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br[stream2].fillFast()
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val := br[stream].peekBitsFast(d.actualTableLog)
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val2 := br[stream2].peekBitsFast(d.actualTableLog)
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v := single[val&tlMask]
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v2 := single[val2&tlMask]
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br[stream].advance(uint8(v.entry))
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br[stream2].advance(uint8(v2.entry))
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buf[stream][off] = uint8(v.entry >> 8)
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buf[stream2][off] = uint8(v2.entry >> 8)
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val = br[stream].peekBitsFast(d.actualTableLog)
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val2 = br[stream2].peekBitsFast(d.actualTableLog)
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v = single[val&tlMask]
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v2 = single[val2&tlMask]
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br[stream].advance(uint8(v.entry))
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br[stream2].advance(uint8(v2.entry))
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buf[stream][off+1] = uint8(v.entry >> 8)
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buf[stream2][off+1] = uint8(v2.entry >> 8)
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}
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off += 2
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if off == 0 {
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if bufoff > dstEvery {
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d.bufs.Put(buf)
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return nil, errors.New("corruption detected: stream overrun 1")
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}
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// There must at least be 3 buffers left.
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if len(out)-bufoff < dstEvery*3 {
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d.bufs.Put(buf)
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return nil, errors.New("corruption detected: stream overrun 2")
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}
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//copy(out, buf[0][:])
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//copy(out[dstEvery:], buf[1][:])
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//copy(out[dstEvery*2:], buf[2][:])
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//copy(out[dstEvery*3:], buf[3][:])
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*(*[bufoff]byte)(out) = buf[0]
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*(*[bufoff]byte)(out[dstEvery:]) = buf[1]
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*(*[bufoff]byte)(out[dstEvery*2:]) = buf[2]
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*(*[bufoff]byte)(out[dstEvery*3:]) = buf[3]
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out = out[bufoff:]
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decoded += bufoff * 4
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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(out) < dstEvery*3+ioff {
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d.bufs.Put(buf)
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return nil, errors.New("corruption detected: stream overrun 3")
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}
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copy(out, buf[0][:off])
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copy(out[dstEvery:], buf[1][:off])
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copy(out[dstEvery*2:], buf[2][:off])
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copy(out[dstEvery*3:], buf[3][:off])
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decoded += int(off) * 4
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out = out[off:]
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}
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// Decode remaining.
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remainBytes := dstEvery - (decoded / 4)
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for i := range br {
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offset := dstEvery * i
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endsAt := offset + remainBytes
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if endsAt > len(out) {
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endsAt = len(out)
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}
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br := &br[i]
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bitsLeft := br.remaining()
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for bitsLeft > 0 {
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br.fill()
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if offset >= endsAt {
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d.bufs.Put(buf)
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return nil, errors.New("corruption detected: stream overrun 4")
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}
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// Read value and increment offset.
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val := br.peekBitsFast(d.actualTableLog)
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v := single[val&tlMask].entry
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nBits := uint8(v)
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br.advance(nBits)
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bitsLeft -= uint(nBits)
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out[offset] = uint8(v >> 8)
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offset++
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}
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if offset != endsAt {
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d.bufs.Put(buf)
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return nil, fmt.Errorf("corruption detected: short output block %d, end %d != %d", i, offset, endsAt)
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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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d.bufs.Put(buf)
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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 dst, nil
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}
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// Decompress1X will decompress a 1X encoded stream.
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// The cap of the output buffer will be the maximum decompressed size.
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// The length of the supplied input must match the end of a block exactly.
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func (d *Decoder) Decompress1X(dst, src []byte) ([]byte, error) {
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if len(d.dt.single) == 0 {
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return nil, errors.New("no table loaded")
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}
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if use8BitTables && d.actualTableLog <= 8 {
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return d.decompress1X8Bit(dst, src)
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}
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var br bitReaderShifted
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err := br.init(src)
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if err != nil {
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return dst, err
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}
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maxDecodedSize := cap(dst)
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dst = dst[:0]
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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 := d.dt.single[:tlSize]
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// Use temp table to avoid bound checks/append penalty.
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bufs := d.buffer()
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buf := &bufs[0]
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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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v := dt[br.peekBitsFast(d.actualTableLog)&tlMask]
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br.advance(uint8(v.entry))
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buf[off+0] = uint8(v.entry >> 8)
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v = dt[br.peekBitsFast(d.actualTableLog)&tlMask]
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br.advance(uint8(v.entry))
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buf[off+1] = uint8(v.entry >> 8)
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// Refill
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br.fillFast()
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v = dt[br.peekBitsFast(d.actualTableLog)&tlMask]
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br.advance(uint8(v.entry))
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buf[off+2] = uint8(v.entry >> 8)
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v = dt[br.peekBitsFast(d.actualTableLog)&tlMask]
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br.advance(uint8(v.entry))
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buf[off+3] = uint8(v.entry >> 8)
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off += 4
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if off == 0 {
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if len(dst)+256 > maxDecodedSize {
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br.close()
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d.bufs.Put(bufs)
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return nil, ErrMaxDecodedSizeExceeded
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}
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dst = append(dst, buf[:]...)
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}
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}
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if len(dst)+int(off) > maxDecodedSize {
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d.bufs.Put(bufs)
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br.close()
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return nil, ErrMaxDecodedSizeExceeded
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}
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dst = append(dst, buf[:off]...)
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// br < 8, so uint8 is fine
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bitsLeft := uint8(br.off)*8 + 64 - br.bitsRead
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for bitsLeft > 0 {
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br.fill()
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if false && br.bitsRead >= 32 {
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if br.off >= 4 {
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v := br.in[br.off-4:]
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v = v[:4]
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low := (uint32(v[0])) | (uint32(v[1]) << 8) | (uint32(v[2]) << 16) | (uint32(v[3]) << 24)
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br.value = (br.value << 32) | uint64(low)
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br.bitsRead -= 32
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br.off -= 4
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} else {
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for br.off > 0 {
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br.value = (br.value << 8) | uint64(br.in[br.off-1])
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br.bitsRead -= 8
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br.off--
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}
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}
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}
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if len(dst) >= maxDecodedSize {
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d.bufs.Put(bufs)
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br.close()
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return nil, ErrMaxDecodedSizeExceeded
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}
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v := d.dt.single[br.peekBitsFast(d.actualTableLog)&tlMask]
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nBits := uint8(v.entry)
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br.advance(nBits)
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bitsLeft -= nBits
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dst = append(dst, uint8(v.entry>>8))
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}
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d.bufs.Put(bufs)
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return dst, br.close()
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}
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