decode() — netty Function Reference

Architecture documentation for the decode() function in MqttDecoder.java from the netty codebase.

Function java Buffer Allocators

Entity Profile

Buffer→ Allocators→ decode() — netty Function Reference

Dependency Diagram

graph TD
  a35298c8_9a5c_3e14_ccb3_e2c50cd85c73["decode()"]
  c4faa729_e212_a3dd_9d90_3e8fd908d755["MqttDecoder"]
  a35298c8_9a5c_3e14_ccb3_e2c50cd85c73 -->|defined in| c4faa729_e212_a3dd_9d90_3e8fd908d755
  style a35298c8_9a5c_3e14_ccb3_e2c50cd85c73 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

codec-mqtt/src/main/java/io/netty/handler/codec/mqtt/MqttDecoder.java lines 111–168

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf buffer, List<Object> out) throws Exception {
        switch (state()) {
            case READ_FIXED_HEADER: try {
                mqttFixedHeader = decodeFixedHeader(ctx, buffer);
                bytesRemainingInVariablePart = mqttFixedHeader.remainingLength();
                checkpoint(DecoderState.READ_VARIABLE_HEADER);
                // fall through
            } catch (Exception cause) {
                out.add(invalidMessage(cause));
                return;
            }

            case READ_VARIABLE_HEADER:  try {
                int bytesRemainingBeforeVariableHeader = bytesRemainingInVariablePart;
                variableHeader = decodeVariableHeader(ctx, buffer, mqttFixedHeader);
                if (bytesRemainingBeforeVariableHeader > maxBytesInMessage) {
                    buffer.skipBytes(actualReadableBytes());
                    throw new TooLongFrameException("message length exceeds " + maxBytesInMessage + ": "
                            + bytesRemainingBeforeVariableHeader);
                }
                checkpoint(DecoderState.READ_PAYLOAD);
                // fall through
            } catch (Exception cause) {
                out.add(invalidMessage(cause));
                return;
            }

            case READ_PAYLOAD: try {
                final Object decodedPayload =
                        decodePayload(
                                ctx,
                                buffer,
                                mqttFixedHeader.messageType(),
                                maxClientIdLength,
                                variableHeader);
                checkpoint(DecoderState.READ_FIXED_HEADER);
                MqttMessage message = MqttMessageFactory.newMessage(
                        mqttFixedHeader, variableHeader, decodedPayload);
                mqttFixedHeader = null;
                variableHeader = null;
                out.add(message);
                break;
            } catch (Exception cause) {
                out.add(invalidMessage(cause));
                return;
            }

            case BAD_MESSAGE:
                // Keep discarding until disconnection.
                buffer.skipBytes(actualReadableBytes());
                break;

            default:
                // Shouldn't reach here.
                throw new Error("Unexpected mqtt decoder state: " + state());
        }
    }