diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/huff0/decompress_amd64.go')
-rw-r--r-- | vendor/github.com/klauspost/compress/huff0/decompress_amd64.go | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/vendor/github.com/klauspost/compress/huff0/decompress_amd64.go b/vendor/github.com/klauspost/compress/huff0/decompress_amd64.go new file mode 100644 index 000000000..d47f6644f --- /dev/null +++ b/vendor/github.com/klauspost/compress/huff0/decompress_amd64.go @@ -0,0 +1,181 @@ +//go:build amd64 && !appengine && !noasm && gc +// +build amd64,!appengine,!noasm,gc + +// This file contains the specialisation of Decoder.Decompress4X +// that uses an asm implementation of its main loop. +package huff0 + +import ( + "errors" + "fmt" +) + +// decompress4x_main_loop_x86 is an x86 assembler implementation +// of Decompress4X when tablelog > 8. +// go:noescape +func decompress4x_main_loop_x86(pbr0, pbr1, pbr2, pbr3 *bitReaderShifted, + peekBits uint8, buf *byte, tbl *dEntrySingle) uint8 + +// decompress4x_8b_loop_x86 is an x86 assembler implementation +// of Decompress4X when tablelog <= 8 which decodes 4 entries +// per loop. +// go:noescape +func decompress4x_8b_loop_x86(pbr0, pbr1, pbr2, pbr3 *bitReaderShifted, + peekBits uint8, buf *byte, tbl *dEntrySingle) uint8 + +// fallback8BitSize is the size where using Go version is faster. +const fallback8BitSize = 800 + +// Decompress4X will decompress a 4X encoded stream. +// The length of the supplied input must match the end of a block exactly. +// The *capacity* of the dst slice must match the destination size of +// the uncompressed data exactly. +func (d *Decoder) Decompress4X(dst, src []byte) ([]byte, error) { + if len(d.dt.single) == 0 { + return nil, errors.New("no table loaded") + } + if len(src) < 6+(4*1) { + return nil, errors.New("input too small") + } + + use8BitTables := d.actualTableLog <= 8 + if cap(dst) < fallback8BitSize && use8BitTables { + return d.decompress4X8bit(dst, src) + } + var br [4]bitReaderShifted + // Decode "jump table" + start := 6 + for i := 0; i < 3; i++ { + length := int(src[i*2]) | (int(src[i*2+1]) << 8) + if start+length >= len(src) { + return nil, errors.New("truncated input (or invalid offset)") + } + err := br[i].init(src[start : start+length]) + if err != nil { + return nil, err + } + start += length + } + err := br[3].init(src[start:]) + if err != nil { + return nil, err + } + + // destination, offset to match first output + dstSize := cap(dst) + dst = dst[:dstSize] + out := dst + dstEvery := (dstSize + 3) / 4 + + const tlSize = 1 << tableLogMax + const tlMask = tlSize - 1 + single := d.dt.single[:tlSize] + + // Use temp table to avoid bound checks/append penalty. + buf := d.buffer() + var off uint8 + var decoded int + + const debug = false + + // see: bitReaderShifted.peekBitsFast() + peekBits := uint8((64 - d.actualTableLog) & 63) + + // Decode 2 values from each decoder/loop. + const bufoff = 256 + for { + if br[0].off < 4 || br[1].off < 4 || br[2].off < 4 || br[3].off < 4 { + break + } + + if use8BitTables { + off = decompress4x_8b_loop_x86(&br[0], &br[1], &br[2], &br[3], peekBits, &buf[0][0], &single[0]) + } else { + off = decompress4x_main_loop_x86(&br[0], &br[1], &br[2], &br[3], peekBits, &buf[0][0], &single[0]) + } + if debug { + fmt.Print("DEBUG: ") + fmt.Printf("off=%d,", off) + for i := 0; i < 4; i++ { + fmt.Printf(" br[%d]={bitsRead=%d, value=%x, off=%d}", + i, br[i].bitsRead, br[i].value, br[i].off) + } + fmt.Println("") + } + + if off != 0 { + break + } + + if bufoff > dstEvery { + d.bufs.Put(buf) + return nil, errors.New("corruption detected: stream overrun 1") + } + copy(out, buf[0][:]) + copy(out[dstEvery:], buf[1][:]) + copy(out[dstEvery*2:], buf[2][:]) + copy(out[dstEvery*3:], buf[3][:]) + out = out[bufoff:] + decoded += bufoff * 4 + // There must at least be 3 buffers left. + if len(out) < dstEvery*3 { + d.bufs.Put(buf) + return nil, errors.New("corruption detected: stream overrun 2") + } + } + if off > 0 { + ioff := int(off) + if len(out) < dstEvery*3+ioff { + d.bufs.Put(buf) + return nil, errors.New("corruption detected: stream overrun 3") + } + copy(out, buf[0][:off]) + copy(out[dstEvery:], buf[1][:off]) + copy(out[dstEvery*2:], buf[2][:off]) + copy(out[dstEvery*3:], buf[3][:off]) + decoded += int(off) * 4 + out = out[off:] + } + + // Decode remaining. + remainBytes := dstEvery - (decoded / 4) + for i := range br { + offset := dstEvery * i + endsAt := offset + remainBytes + if endsAt > len(out) { + endsAt = len(out) + } + br := &br[i] + bitsLeft := br.remaining() + for bitsLeft > 0 { + br.fill() + if offset >= endsAt { + d.bufs.Put(buf) + return nil, errors.New("corruption detected: stream overrun 4") + } + + // Read value and increment offset. + val := br.peekBitsFast(d.actualTableLog) + v := single[val&tlMask].entry + nBits := uint8(v) + br.advance(nBits) + bitsLeft -= uint(nBits) + out[offset] = uint8(v >> 8) + offset++ + } + if offset != endsAt { + d.bufs.Put(buf) + return nil, fmt.Errorf("corruption detected: short output block %d, end %d != %d", i, offset, endsAt) + } + decoded += offset - dstEvery*i + err = br.close() + if err != nil { + return nil, err + } + } + d.bufs.Put(buf) + if dstSize != decoded { + return nil, errors.New("corruption detected: short output block") + } + return dst, nil +} |