Golang Decoder.Decode方法代碼示例

// readUserMsg is used to decode a userMsg from a TCP stream
func (m *Memberlist) readUserMsg(bufConn io.Reader, dec *codec.Decoder) error {
	// Read the user message header
	var header userMsgHeader
	if err := dec.Decode(&header); err != nil {
		return err
	}

	// Read the user message into a buffer
	var userBuf []byte
	if header.UserMsgLen > 0 {
		userBuf = make([]byte, header.UserMsgLen)
		bytes, err := io.ReadAtLeast(bufConn, userBuf, header.UserMsgLen)
		if err == nil && bytes != header.UserMsgLen {
			err = fmt.Errorf(
				"Failed to read full user message (%d / %d)",
				bytes, header.UserMsgLen)
		}
		if err != nil {
			return err
		}

		d := m.config.Delegate
		if d != nil {
			d.NotifyMsg(userBuf)
		}
	}

	return nil
}

// Deserialize is used to deserialize the time table
// and restore the state
func (t *TimeTable) Deserialize(dec *codec.Decoder) error {
	// Decode the table
	var table []TimeTableEntry
	if err := dec.Decode(&table); err != nil {
		return err
	}

	// Witness from oldest to newest
	n := len(table)
	for i := n - 1; i >= 0; i-- {
		t.Witness(table[i].Index, table[i].Time)
	}
	return nil
}

// readRemoteState is used to read the remote state from a connection
func (m *Memberlist) readRemoteState(bufConn io.Reader, dec *codec.Decoder) (bool, []pushNodeState, []byte, error) {
	// Read the push/pull header
	var header pushPullHeader
	if err := dec.Decode(&header); err != nil {
		return false, nil, nil, err
	}

	// Allocate space for the transfer
	remoteNodes := make([]pushNodeState, header.Nodes)

	// Try to decode all the states
	for i := 0; i < header.Nodes; i++ {
		if err := dec.Decode(&remoteNodes[i]); err != nil {
			return false, nil, nil, err
		}
	}

	// Read the remote user state into a buffer
	var userBuf []byte
	if header.UserStateLen > 0 {
		userBuf = make([]byte, header.UserStateLen)
		bytes, err := io.ReadAtLeast(bufConn, userBuf, header.UserStateLen)
		if err == nil && bytes != header.UserStateLen {
			err = fmt.Errorf(
				"Failed to read full user state (%d / %d)",
				bytes, header.UserStateLen)
		}
		if err != nil {
			return false, nil, nil, err
		}
	}

	// For proto versions < 2, there is no port provided. Mask old
	// behavior by using the configured port
	for idx := range remoteNodes {
		if m.ProtocolVersion() < 2 || remoteNodes[idx].Port == 0 {
			remoteNodes[idx].Port = uint16(m.config.BindPort)
		}
	}

	return header.Join, remoteNodes, userBuf, nil
}

// handleCommand is used to decode and dispatch a single command.
func (n *NetworkTransport) handleCommand(r *bufio.Reader, dec *codec.Decoder, enc *codec.Encoder) error {
	// Get the rpc type
	rpcType, err := r.ReadByte()
	if err != nil {
		return err
	}

	// Create the RPC object
	respCh := make(chan RPCResponse, 1)
	rpc := RPC{
		RespChan: respCh,
	}

	// Decode the command
	isHeartbeat := false
	switch rpcType {
	case rpcAppendEntries:
		var req AppendEntriesRequest
		if err := dec.Decode(&req); err != nil {
			return err
		}
		rpc.Command = &req

		// Check if this is a heartbeat
		if req.Term != 0 && req.Leader != nil &&
			req.PrevLogEntry == 0 && req.PrevLogTerm == 0 &&
			len(req.Entries) == 0 && req.LeaderCommitIndex == 0 {
			isHeartbeat = true
		}

	case rpcRequestVote:
		var req RequestVoteRequest
		if err := dec.Decode(&req); err != nil {
			return err
		}
		rpc.Command = &req

	case rpcInstallSnapshot:
		var req InstallSnapshotRequest
		if err := dec.Decode(&req); err != nil {
			return err
		}
		rpc.Command = &req
		rpc.Reader = io.LimitReader(r, req.Size)

	default:
		return fmt.Errorf("unknown rpc type %d", rpcType)
	}

	// Check for heartbeat fast-path
	if isHeartbeat {
		n.heartbeatFnLock.Lock()
		fn := n.heartbeatFn
		n.heartbeatFnLock.Unlock()
		if fn != nil {
			fn(rpc)
			goto RESP
		}
	}

	// Dispatch the RPC
	select {
	case n.consumeCh <- rpc:
	case <-n.shutdownCh:
		return ErrTransportShutdown
	}

	// Wait for response
RESP:
	select {
	case resp := <-respCh:
		// Send the error first
		respErr := ""
		if resp.Error != nil {
			respErr = resp.Error.Error()
		}
		if err := enc.Encode(respErr); err != nil {
			return err
		}

		// Send the response
		if err := enc.Encode(resp.Response); err != nil {
			return err
		}
	case <-n.shutdownCh:
		return ErrTransportShutdown
	}
	return nil
}