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Small performance optimization in lz4 compressor implementation #1910

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Small performance optimization in lz4 compressor implementation #1910

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28 changes: 21 additions & 7 deletions lz4/lz4.go
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Original file line number Diff line number Diff line change
Expand Up @@ -53,16 +53,17 @@ func (s LZ4Compressor) AppendCompressedWithLength(dst, src []byte) ([]byte, erro
maxLength := lz4.CompressBlockBound(len(src))
oldDstLen := len(dst)
dst = grow(dst, maxLength+dataLengthSize)
slicedDst := sliceDest(dst, oldDstLen)

var compressor lz4.Compressor
n, err := compressor.CompressBlock(src, dst[oldDstLen+dataLengthSize:])
n, err := compressor.CompressBlock(src, slicedDst[dataLengthSize:])
// According to lz4.CompressBlock doc, it doesn't fail as long as the dst
// buffer length is at least lz4.CompressBlockBound(len(data))) bytes, but
// we check for error anyway just to be thorough.
if err != nil {
return nil, err
}
binary.BigEndian.PutUint32(dst[oldDstLen:oldDstLen+dataLengthSize], uint32(len(src)))
binary.BigEndian.PutUint32(slicedDst[:dataLengthSize], uint32(len(src)))
return dst[:oldDstLen+n+dataLengthSize], nil
}

Expand All @@ -76,7 +77,8 @@ func (s LZ4Compressor) AppendDecompressedWithLength(dst, src []byte) ([]byte, er
}
oldDstLen := len(dst)
dst = grow(dst, int(uncompressedLength))
n, err := lz4.UncompressBlock(src[dataLengthSize:], dst[oldDstLen:])
slicedDst := sliceDest(dst, oldDstLen)
n, err := lz4.UncompressBlock(src[dataLengthSize:], slicedDst)
return dst[:oldDstLen+n], err

}
Expand All @@ -85,9 +87,10 @@ func (s LZ4Compressor) AppendCompressed(dst, src []byte) ([]byte, error) {
maxLength := lz4.CompressBlockBound(len(src))
oldDstLen := len(dst)
dst = grow(dst, maxLength)
slicedDst := sliceDest(dst, oldDstLen)

var compressor lz4.Compressor
n, err := compressor.CompressBlock(src, dst[oldDstLen:])
n, err := compressor.CompressBlock(src, slicedDst)
if err != nil {
return nil, err
}
Expand All @@ -101,7 +104,8 @@ func (s LZ4Compressor) AppendDecompressed(dst, src []byte, uncompressedLength ui
}
oldDstLen := len(dst)
dst = grow(dst, int(uncompressedLength))
n, err := lz4.UncompressBlock(src, dst[oldDstLen:])
slicedDst := sliceDest(dst, oldDstLen)
n, err := lz4.UncompressBlock(src, slicedDst)
return dst[:oldDstLen+n], err
}

Expand All @@ -110,8 +114,18 @@ func grow(b []byte, n int) []byte {
oldLen := len(b)
if cap(b)-oldLen < n {
newBuf := make([]byte, oldLen+n)
copy(newBuf, b)
b = newBuf
if oldLen > 0 {
copy(newBuf, b)
}
return newBuf
}
return b[:oldLen+n]
}

func sliceDest(dst []byte, oldDstLen int) []byte {
if oldDstLen > 0 {
return dst[oldDstLen:]
} else {
return dst
}
}