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Use arrays for constant size copies (#659)
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* Use arrays for constant size copies

Requires Go 1.17
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@klauspost
klauspost committed Sep 9, 2022
1 parent 49d8cf2 commit 5d754d7
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Showing 7 changed files with 51 additions and 30 deletions.
3 changes: 2 additions & 1 deletion flate/deflate.go
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Expand Up @@ -131,7 +131,8 @@ func (d *compressor) fillDeflate(b []byte) int {
s := d.state
if s.index >= 2*windowSize-(minMatchLength+maxMatchLength) {
// shift the window by windowSize
copy(d.window[:], d.window[windowSize:2*windowSize])
//copy(d.window[:], d.window[windowSize:2*windowSize])
*(*[windowSize]byte)(d.window) = *(*[windowSize]byte)(d.window[windowSize:])
s.index -= windowSize
d.windowEnd -= windowSize
if d.blockStart >= windowSize {
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3 changes: 2 additions & 1 deletion flate/fast_encoder.go
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Expand Up @@ -104,7 +104,8 @@ func (e *fastGen) addBlock(src []byte) int32 {
}
// Move down
offset := int32(len(e.hist)) - maxMatchOffset
copy(e.hist[0:maxMatchOffset], e.hist[offset:])
// copy(e.hist[0:maxMatchOffset], e.hist[offset:])
*(*[maxMatchOffset]byte)(e.hist) = *(*[maxMatchOffset]byte)(e.hist[offset:])
e.cur += offset
e.hist = e.hist[:maxMatchOffset]
}
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8 changes: 5 additions & 3 deletions flate/huffman_bit_writer.go
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Expand Up @@ -790,9 +790,11 @@ func (w *huffmanBitWriter) fillTokens() {
// and offsetEncoding.
// The number of literal and offset tokens is returned.
func (w *huffmanBitWriter) indexTokens(t *tokens, filled bool) (numLiterals, numOffsets int) {
copy(w.literalFreq[:], t.litHist[:])
copy(w.literalFreq[256:], t.extraHist[:])
copy(w.offsetFreq[:], t.offHist[:offsetCodeCount])
//copy(w.literalFreq[:], t.litHist[:])
*(*[256]uint16)(w.literalFreq[:]) = t.litHist
//copy(w.literalFreq[256:], t.extraHist[:])
*(*[32]uint16)(w.literalFreq[256:]) = t.extraHist
w.offsetFreq = t.offHist

if t.n == 0 {
return
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36 changes: 22 additions & 14 deletions huff0/decompress.go
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Expand Up @@ -763,17 +763,20 @@ func (d *Decoder) decompress4X8bit(dst, src []byte) ([]byte, error) {
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 {
if len(out)-bufoff < dstEvery*3 {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 2")
}
//copy(out, buf[0][:])
//copy(out[dstEvery:], buf[1][:])
//copy(out[dstEvery*2:], buf[2][:])
*(*[bufoff]byte)(out) = buf[0]
*(*[bufoff]byte)(out[dstEvery:]) = buf[1]
*(*[bufoff]byte)(out[dstEvery*2:]) = buf[2]
*(*[bufoff]byte)(out[dstEvery*3:]) = buf[3]
out = out[bufoff:]
decoded += bufoff * 4
}
}
if off > 0 {
Expand Down Expand Up @@ -997,17 +1000,22 @@ func (d *Decoder) decompress4X8bitExactly(dst, src []byte) ([]byte, error) {
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 {
if len(out)-bufoff < dstEvery*3 {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 2")
}

//copy(out, buf[0][:])
//copy(out[dstEvery:], buf[1][:])
//copy(out[dstEvery*2:], buf[2][:])
// copy(out[dstEvery*3:], buf[3][:])
*(*[bufoff]byte)(out) = buf[0]
*(*[bufoff]byte)(out[dstEvery:]) = buf[1]
*(*[bufoff]byte)(out[dstEvery*2:]) = buf[2]
*(*[bufoff]byte)(out[dstEvery*3:]) = buf[3]
out = out[bufoff:]
decoded += bufoff * 4
}
}
if off > 0 {
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18 changes: 11 additions & 7 deletions huff0/decompress_generic.go
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Expand Up @@ -122,17 +122,21 @@ func (d *Decoder) Decompress4X(dst, src []byte) ([]byte, error) {
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 {
if len(out)-bufoff < dstEvery*3 {
d.bufs.Put(buf)
return nil, errors.New("corruption detected: stream overrun 2")
}
//copy(out, buf[0][:])
//copy(out[dstEvery:], buf[1][:])
//copy(out[dstEvery*2:], buf[2][:])
//copy(out[dstEvery*3:], buf[3][:])
*(*[bufoff]byte)(out) = buf[0]
*(*[bufoff]byte)(out[dstEvery:]) = buf[1]
*(*[bufoff]byte)(out[dstEvery*2:]) = buf[2]
*(*[bufoff]byte)(out[dstEvery*3:]) = buf[3]
out = out[bufoff:]
decoded += bufoff * 4
}
}
if off > 0 {
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7 changes: 5 additions & 2 deletions zstd/enc_dfast.go
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Expand Up @@ -1103,7 +1103,8 @@ func (e *doubleFastEncoderDict) Reset(d *dict, singleBlock bool) {
}

if allDirty || dirtyShardCnt > dLongTableShardCnt/2 {
copy(e.longTable[:], e.dictLongTable)
//copy(e.longTable[:], e.dictLongTable)
e.longTable = *(*[dFastLongTableSize]tableEntry)(e.dictLongTable)
for i := range e.longTableShardDirty {
e.longTableShardDirty[i] = false
}
Expand All @@ -1114,7 +1115,9 @@ func (e *doubleFastEncoderDict) Reset(d *dict, singleBlock bool) {
continue
}

copy(e.longTable[i*dLongTableShardSize:(i+1)*dLongTableShardSize], e.dictLongTable[i*dLongTableShardSize:(i+1)*dLongTableShardSize])
// copy(e.longTable[i*dLongTableShardSize:(i+1)*dLongTableShardSize], e.dictLongTable[i*dLongTableShardSize:(i+1)*dLongTableShardSize])
*(*[dLongTableShardSize]tableEntry)(e.longTable[i*dLongTableShardSize:]) = *(*[dLongTableShardSize]tableEntry)(e.dictLongTable[i*dLongTableShardSize:])

e.longTableShardDirty[i] = false
}
}
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6 changes: 4 additions & 2 deletions zstd/enc_fast.go
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Expand Up @@ -871,7 +871,8 @@ func (e *fastEncoderDict) Reset(d *dict, singleBlock bool) {
const shardCnt = tableShardCnt
const shardSize = tableShardSize
if e.allDirty || dirtyShardCnt > shardCnt*4/6 {
copy(e.table[:], e.dictTable)
//copy(e.table[:], e.dictTable)
e.table = *(*[tableSize]tableEntry)(e.dictTable)
for i := range e.tableShardDirty {
e.tableShardDirty[i] = false
}
Expand All @@ -883,7 +884,8 @@ func (e *fastEncoderDict) Reset(d *dict, singleBlock bool) {
continue
}

copy(e.table[i*shardSize:(i+1)*shardSize], e.dictTable[i*shardSize:(i+1)*shardSize])
//copy(e.table[i*shardSize:(i+1)*shardSize], e.dictTable[i*shardSize:(i+1)*shardSize])
*(*[shardSize]tableEntry)(e.table[i*shardSize:]) = *(*[shardSize]tableEntry)(e.dictTable[i*shardSize:])
e.tableShardDirty[i] = false
}
e.allDirty = false
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