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package compress
import (
"encoding/binary"
"github.com/go-faster/city"
"github.com/go-faster/errors"
"github.com/klauspost/compress/zstd"
"github.com/pierrec/lz4/v4"
)
// Writer encodes compressed blocks.
type Writer struct {
Data []byte
lz4 *lz4.Compressor
zstd *zstd.Encoder
}
// Compress buf into Data.
func (w *Writer) Compress(m Method, buf []byte) error {
maxSize := lz4.CompressBlockBound(len(buf))
w.Data = append(w.Data[:0], make([]byte, maxSize+headerSize)...)
_ = w.Data[:headerSize]
w.Data[hMethod] = byte(m)
var n int
switch m {
case LZ4:
compressedSize, err := w.lz4.CompressBlock(buf, w.Data[headerSize:])
if err != nil {
return errors.Wrap(err, "block")
}
n = compressedSize
case ZSTD:
w.Data = w.zstd.EncodeAll(buf, w.Data[:headerSize])
n = len(w.Data) - headerSize
case None:
n = copy(w.Data[headerSize:], buf)
}
w.Data = w.Data[:n+headerSize]
binary.LittleEndian.PutUint32(w.Data[hRawSize:], uint32(n+compressHeaderSize))
binary.LittleEndian.PutUint32(w.Data[hDataSize:], uint32(len(buf)))
h := city.CH128(w.Data[hMethod:])
binary.LittleEndian.PutUint64(w.Data[0:8], h.Low)
binary.LittleEndian.PutUint64(w.Data[8:16], h.High)
return nil
}
func NewWriter() *Writer {
w, err := zstd.NewWriter(nil,
zstd.WithEncoderLevel(zstd.SpeedDefault),
zstd.WithEncoderConcurrency(1),
zstd.WithLowerEncoderMem(true),
)
if err != nil {
panic(err)
}
return &Writer{
lz4: &lz4.Compressor{},
zstd: w,
}
}
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