Method writePackets

compress.go:152–193

writePackets sends one or some packets with compression. Use this instead of mc.netConn.Write() when mc.compress is true.

(packets []byte)

// writePackets sends one or some packets with compression.
// Use this instead of mc.netConn.Write() when mc.compress is true.
func (c *compIO) writePackets(packets []byte) (int, error) {
	totalBytes := len(packets)
	blankHeader := make([]byte, 7)
	buf := &c.buff

	for len(packets) > 0 {
		payloadLen := min(maxPayloadLen, len(packets))
		payload := packets[:payloadLen]
		uncompressedLen := payloadLen

		buf.Reset()
		buf.Write(blankHeader) // Buffer.Write() never returns error

		// If payload is less than minCompressLength, don't compress.
		if uncompressedLen < minCompressLength {
			buf.Write(payload)
			uncompressedLen = 0
		} else {
			err := zCompress(payload, buf)
			if debug && err != nil {
				fmt.Printf("zCompress error: %v", err)
			}
			// do not compress if compressed data is larger than uncompressed data
			// I intentionally miss 7 byte header in the buf; zCompress must compress more than 7 bytes.
			if err != nil || buf.Len() >= uncompressedLen {
				buf.Reset()
				buf.Write(blankHeader)
				buf.Write(payload)
				uncompressedLen = 0
			}
		}

		if n, err := c.writeCompressedPacket(buf.Bytes(), uncompressedLen); err != nil {
			// To allow returning ErrBadConn when sending really 0 bytes, we sum
			// up compressed bytes that is returned by underlying Write().
			return totalBytes - len(packets) + n, err
		}
		packets = packets[payloadLen:]
	}

	return totalBytes, nil
}

// writeCompressedPacket writes a compressed packet with header.
// data should start with 7 size space for header followed by payload.