コード例 #1
0
ファイル: writer.go プロジェクト: huangjiehua/tendermint
func (w *Writer) writeBlock(buf *util.Buffer, compression opt.Compression) (bh blockHandle, err error) {
	// Compress the buffer if necessary.
	var b []byte
	if compression == opt.SnappyCompression {
		// Allocate scratch enough for compression and block trailer.
		if n := snappy.MaxEncodedLen(buf.Len()) + blockTrailerLen; len(w.compressionScratch) < n {
			w.compressionScratch = make([]byte, n)
		}
		var compressed []byte
		compressed, err = snappy.Encode(w.compressionScratch, buf.Bytes())
		if err != nil {
			return
		}
		n := len(compressed)
		b = compressed[:n+blockTrailerLen]
		b[n] = blockTypeSnappyCompression
	} else {
		tmp := buf.Alloc(blockTrailerLen)
		tmp[0] = blockTypeNoCompression
		b = buf.Bytes()
	}

	// Calculate the checksum.
	n := len(b) - 4
	checksum := util.NewCRC(b[:n]).Value()
	binary.LittleEndian.PutUint32(b[n:], checksum)

	// Write the buffer to the file.
	_, err = w.writer.Write(b)
	if err != nil {
		return
	}
	bh = blockHandle{w.offset, uint64(len(b) - blockTrailerLen)}
	w.offset += uint64(len(b))
	return
}