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/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package net.dreamlu.iot.mqtt.codec;
import net.dreamlu.iot.mqtt.codec.properties.*;
import org.tio.core.ChannelContext;
import org.tio.core.exception.TioDecodeException;
import org.tio.core.intf.Packet;
import org.tio.utils.buffer.ByteBufferUtil;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import static net.dreamlu.iot.mqtt.codec.MqttConstant.*;
/**
* Decodes Mqtt messages from bytes, following
* the MQTT protocol specification
* v3.1
* or
* v5.0, depending on the
* version specified in the CONNECT message that first goes through the channel.
*
* @author netty
* @author L.cm
*/
public final class MqttDecoder {
private static final String MQTT_FIXED_HEADER_KEY = "MQTT_F_H_K";
private final int maxBytesInMessage;
private final int maxClientIdLength;
public MqttDecoder() {
this(DEFAULT_MAX_BYTES_IN_MESSAGE);
}
public MqttDecoder(int maxBytesInMessage) {
this(maxBytesInMessage, DEFAULT_MAX_CLIENT_ID_LENGTH);
}
public MqttDecoder(int maxBytesInMessage, int maxClientIdLength) {
this.maxBytesInMessage = maxBytesInMessage;
this.maxClientIdLength = maxClientIdLength;
}
public Packet doDecode(ChannelContext ctx, ByteBuffer buffer, int readableLength) throws TioDecodeException {
// 1. 解析消息头
MqttFixedHeader mqttFixedHeader = getOrDecodeMqttFixedHeader(ctx, buffer, readableLength);
if (mqttFixedHeader == null) {
return null;
}
// 2. 判断消息长度
int messageLength = mqttFixedHeader.getMessageLength();
if (readableLength < messageLength) {
return null;
}
// 清除缓存
ctx.remove(MQTT_FIXED_HEADER_KEY);
// 3. 判断是否 ping 消息，ping 只有消息类型
MqttMessageType messageType = mqttFixedHeader.messageType();
if (MqttMessageType.PINGREQ == messageType){
return MqttMessage.PINGREQ;
} else if (MqttMessageType.PINGRESP == messageType) {
return MqttMessage.PINGRESP;
}
MqttMessage message = decodeMqttMessage(ctx, buffer, messageType, mqttFixedHeader);
// 4. 解码异常
DecoderResult decoderResult = message.decoderResult();
if (decoderResult.isFailure()) {
throw new TioDecodeException(decoderResult.getCause());
}
return message;
}
private MqttFixedHeader getOrDecodeMqttFixedHeader(ChannelContext ctx, ByteBuffer buffer, int readableLength) throws TioDecodeException {
// 1. 缓存避免重复解析
MqttFixedHeader mqttFixedHeader = ctx.get(MQTT_FIXED_HEADER_KEY);
if (mqttFixedHeader != null) {
ByteBufferUtil.skipBytes(buffer, mqttFixedHeader.headLength());
return mqttFixedHeader;
}
// 2. 判断缓存中协议头是否读完（MQTT协议头为2字节）
if (readableLength < MQTT_PROTOCOL_LENGTH) {
return null;
}
// 3. 解析 FixedHeader 2~5 个字节
mqttFixedHeader = decodeFixedHeader(ctx, buffer);
// 不够读
if (mqttFixedHeader == null) {
return null;
}
int messageLength = mqttFixedHeader.getMessageLength();
// 超过最大包
if (messageLength > maxBytesInMessage) {
throw new TioDecodeException("too large message: " + messageLength + " bytes but maxBytesInMessage is " + maxBytesInMessage);
}
// 存储固定头，避免重复解析
ctx.set(MQTT_FIXED_HEADER_KEY, mqttFixedHeader);
// 3. 长度不够，直接返回 null
if (readableLength < messageLength) {
ctx.setPacketNeededLength(messageLength);
return null;
}
return mqttFixedHeader;
}
private MqttMessage decodeMqttMessage(ChannelContext ctx, ByteBuffer buffer, MqttMessageType messageType,
MqttFixedHeader mqttFixedHeader) {
// 1. 消息体长度
int bytesRemainingInVariablePart = mqttFixedHeader.remainingLength();
// 2. 解析头信息
Object variableHeader;
try {
Result decodedVariableHeader = decodeVariableHeader(ctx, buffer, messageType, mqttFixedHeader, bytesRemainingInVariablePart);
variableHeader = decodedVariableHeader.value;
bytesRemainingInVariablePart -= decodedVariableHeader.numberOfBytesConsumed;
} catch (Exception cause) {
return MqttMessageFactory.newInvalidMessage(mqttFixedHeader, null, cause);
}
// 3. 解析消息体
final Result decodedPayload;
try {
decodedPayload = decodePayload(buffer, maxClientIdLength, messageType, bytesRemainingInVariablePart, variableHeader);
bytesRemainingInVariablePart -= decodedPayload.numberOfBytesConsumed;
if (bytesRemainingInVariablePart != 0) {
throw new DecoderException("non-zero remaining payload bytes: " +
bytesRemainingInVariablePart + " (" + mqttFixedHeader.messageType() + ')');
}
return MqttMessageFactory.newMessage(mqttFixedHeader, variableHeader, decodedPayload.value);
} catch (Throwable cause) {
return MqttMessageFactory.newInvalidMessage(mqttFixedHeader, variableHeader, cause);
}
}
/**
* Decodes the fixed header. It's one byte for the flags and then variable bytes for the remaining length.
*
* @param buffer the buffer to decode from
* @return the fixed header
*/
private static MqttFixedHeader decodeFixedHeader(ChannelContext ctx, ByteBuffer buffer) throws TioDecodeException {
short b1 = ByteBufferUtil.readUnsignedByte(buffer);
MqttMessageType messageType = MqttMessageType.valueOf(b1 >> 4);
boolean dupFlag = (b1 & 0x08) == 0x08;
int qosLevel = (b1 & 0x06) >> 1;
boolean retain = (b1 & 0x01) != 0;
int remainingLength = 0;
int multiplier = 1;
short digit;
int loops = 0;
do {
if (!buffer.hasRemaining()) {
return null;
}
digit = ByteBufferUtil.readUnsignedByte(buffer);
remainingLength += (digit & 127) * multiplier;
multiplier *= 128;
loops++;
} while ((digit & 128) != 0 && loops < 4);
// MQTT protocol limits Remaining Length to 4 bytes
if (loops == 4 && (digit & 128) != 0) {
throw new TioDecodeException("remaining length exceeds 4 digits (" + messageType + ')');
}
int headLength = 1 + loops;
MqttFixedHeader decodedFixedHeader = new MqttFixedHeader(messageType, dupFlag, MqttQoS.valueOf(qosLevel), retain, headLength, remainingLength);
return MqttCodecUtil.validateFixedHeader(ctx, MqttCodecUtil.resetUnusedFields(decodedFixedHeader));
}
/**
* Decodes the variable header (if any)
*
* @param buffer the buffer to decode from
* @param mqttFixedHeader MqttFixedHeader of the same message
* @return the variable header
*/
private Result decodeVariableHeader(ChannelContext ctx, ByteBuffer buffer,
MqttMessageType messageType,
MqttFixedHeader mqttFixedHeader,
int bytesRemainingInVariablePart) {
switch (messageType) {
case CONNECT:
return decodeConnectionVariableHeader(ctx, buffer);
case CONNACK:
return decodeConnAckVariableHeader(ctx, buffer);
case UNSUBSCRIBE:
case SUBSCRIBE:
case SUBACK:
case UNSUBACK:
return decodeMessageIdAndPropertiesVariableHeader(ctx, buffer, mqttFixedHeader);
case PUBACK:
case PUBREC:
case PUBCOMP:
case PUBREL:
return decodePubReplyMessage(buffer, mqttFixedHeader, bytesRemainingInVariablePart);
case PUBLISH:
return decodePublishVariableHeader(ctx, buffer, mqttFixedHeader);
case DISCONNECT:
case AUTH:
return decodeReasonCodeAndPropertiesVariableHeader(buffer, bytesRemainingInVariablePart);
default:
//shouldn't reach here
throw new DecoderException("Unknown message type: " + messageType);
}
}
private static Result decodeConnectionVariableHeader(
ChannelContext ctx, ByteBuffer buffer) {
final Result protoString = decodeString(buffer);
int numberOfBytesConsumed = protoString.numberOfBytesConsumed;
final byte protocolLevel = buffer.get();
numberOfBytesConsumed += 1;
MqttVersion version = MqttVersion.fromProtocolNameAndLevel(protoString.value, protocolLevel);
MqttCodecUtil.setMqttVersion(ctx, version);
final int b1 = ByteBufferUtil.readUnsignedByte(buffer);
numberOfBytesConsumed += 1;
final int keepAlive = decodeMsbLsb(buffer);
numberOfBytesConsumed += 2;
final boolean hasUserName = (b1 & 0x80) == 0x80;
final boolean hasPassword = (b1 & 0x40) == 0x40;
final boolean willRetain = (b1 & 0x20) == 0x20;
final int willQos = (b1 & 0x18) >> 3;
final boolean willFlag = (b1 & 0x04) == 0x04;
final boolean cleanSession = (b1 & 0x02) == 0x02;
if (version == MqttVersion.MQTT_3_1_1 || version == MqttVersion.MQTT_5) {
final boolean zeroReservedFlag = (b1 & 0x01) == 0x0;
if (!zeroReservedFlag) {
// MQTT v3.1.1: The Server MUST validate that the reserved flag in the CONNECT Control Packet is
// set to zero and disconnect the Client if it is not zero.
// See https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc385349230
throw new DecoderException("non-zero reserved flag");
}
}
final MqttProperties properties;
if (version == MqttVersion.MQTT_5) {
final Result propertiesResult = decodeProperties(buffer);
properties = propertiesResult.value;
numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
} else {
properties = MqttProperties.NO_PROPERTIES;
}
final MqttConnectVariableHeader mqttConnectVariableHeader = new MqttConnectVariableHeader(
version.protocolName(),
version.protocolLevel(),
hasUserName,
hasPassword,
willRetain,
willQos,
willFlag,
cleanSession,
keepAlive,
properties);
return new Result<>(mqttConnectVariableHeader, numberOfBytesConsumed);
}
private static Result decodeConnAckVariableHeader(
ChannelContext ctx, ByteBuffer buffer) {
final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
final boolean sessionPresent = (ByteBufferUtil.readUnsignedByte(buffer) & 0x01) == 0x01;
byte returnCode = buffer.get();
int numberOfBytesConsumed = 2;
final MqttProperties properties;
if (mqttVersion == MqttVersion.MQTT_5) {
final Result propertiesResult = decodeProperties(buffer);
properties = propertiesResult.value;
numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
} else {
properties = MqttProperties.NO_PROPERTIES;
}
final MqttConnAckVariableHeader mqttConnAckVariableHeader =
new MqttConnAckVariableHeader(MqttConnectReasonCode.valueOf(returnCode), sessionPresent, properties);
return new Result<>(mqttConnAckVariableHeader, numberOfBytesConsumed);
}
private static Result decodeMessageIdAndPropertiesVariableHeader(
ChannelContext ctx, ByteBuffer buffer, MqttFixedHeader mqttFixedHeader) {
final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
final int packetId = decodeMessageId(buffer, mqttFixedHeader);
final MqttMessageIdAndPropertiesVariableHeader mqttVariableHeader;
final int mqtt5Consumed;
if (mqttVersion == MqttVersion.MQTT_5) {
final Result properties = decodeProperties(buffer);
mqttVariableHeader = new MqttMessageIdAndPropertiesVariableHeader(packetId, properties.value);
mqtt5Consumed = properties.numberOfBytesConsumed;
} else {
mqttVariableHeader = new MqttMessageIdAndPropertiesVariableHeader(packetId, MqttProperties.NO_PROPERTIES);
mqtt5Consumed = 0;
}
return new Result<>(mqttVariableHeader, 2 + mqtt5Consumed);
}
private Result decodePubReplyMessage(
ByteBuffer buffer, MqttFixedHeader mqttFixedHeader, int bytesRemainingInVariablePart) {
final int packetId = decodeMessageId(buffer, mqttFixedHeader);
final MqttPubReplyMessageVariableHeader mqttPubAckVariableHeader;
final int consumed;
final int packetIdNumberOfBytesConsumed = 2;
if (bytesRemainingInVariablePart > 3) {
final byte reasonCode = buffer.get();
final Result properties = decodeProperties(buffer);
mqttPubAckVariableHeader = new MqttPubReplyMessageVariableHeader(packetId,
reasonCode,
properties.value);
consumed = packetIdNumberOfBytesConsumed + 1 + properties.numberOfBytesConsumed;
} else if (bytesRemainingInVariablePart > 2) {
final byte reasonCode = buffer.get();
mqttPubAckVariableHeader = new MqttPubReplyMessageVariableHeader(packetId,
reasonCode,
MqttProperties.NO_PROPERTIES);
consumed = packetIdNumberOfBytesConsumed + 1;
} else {
mqttPubAckVariableHeader = new MqttPubReplyMessageVariableHeader(packetId,
(byte) 0,
MqttProperties.NO_PROPERTIES);
consumed = packetIdNumberOfBytesConsumed;
}
return new Result<>(mqttPubAckVariableHeader, consumed);
}
private Result decodeReasonCodeAndPropertiesVariableHeader(
ByteBuffer buffer, int bytesRemainingInVariablePart) {
final byte reasonCode;
final MqttProperties properties;
final int consumed;
if (bytesRemainingInVariablePart > 1) {
reasonCode = buffer.get();
final Result propertiesResult = decodeProperties(buffer);
properties = propertiesResult.value;
consumed = 1 + propertiesResult.numberOfBytesConsumed;
} else if (bytesRemainingInVariablePart > 0) {
reasonCode = buffer.get();
properties = MqttProperties.NO_PROPERTIES;
consumed = 1;
} else {
reasonCode = 0;
properties = MqttProperties.NO_PROPERTIES;
consumed = 0;
}
final MqttReasonCodeAndPropertiesVariableHeader mqttReasonAndPropsVariableHeader =
new MqttReasonCodeAndPropertiesVariableHeader(reasonCode, properties);
return new Result<>(mqttReasonAndPropsVariableHeader, consumed);
}
private Result decodePublishVariableHeader(
ChannelContext ctx, ByteBuffer buffer,
MqttFixedHeader mqttFixedHeader) {
final MqttVersion mqttVersion = MqttCodecUtil.getMqttVersion(ctx);
final Result decodedTopic = decodeString(buffer);
if (!MqttCodecUtil.isValidPublishTopicName(decodedTopic.value)) {
throw new DecoderException("invalid publish topic name: " + decodedTopic.value + " (contains wildcards)");
}
int numberOfBytesConsumed = decodedTopic.numberOfBytesConsumed;
int messageId = -1;
if (mqttFixedHeader.qosLevel().value() > 0) {
messageId = decodeMessageId(buffer, mqttFixedHeader);
numberOfBytesConsumed += 2;
}
final MqttProperties properties;
if (mqttVersion == MqttVersion.MQTT_5) {
final Result propertiesResult = decodeProperties(buffer);
properties = propertiesResult.value;
numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
} else {
properties = MqttProperties.NO_PROPERTIES;
}
final MqttPublishVariableHeader mqttPublishVariableHeader =
new MqttPublishVariableHeader(decodedTopic.value, messageId, properties);
return new Result<>(mqttPublishVariableHeader, numberOfBytesConsumed);
}
/**
* decodeMessageId
*
* @param buffer ByteBuffer
* @param mqttFixedHeader MqttFixedHeader
* @return messageId with numberOfBytesConsumed is 2
*/
private static int decodeMessageId(ByteBuffer buffer, MqttFixedHeader mqttFixedHeader) {
final int messageId = decodeMsbLsb(buffer);
// 注意：此处做 qos 降级处理，mqtt 规定 qos > 0，messageId 必须大于 0，固做降级处理
if (messageId == 0) {
mqttFixedHeader.downgradeQos();
}
return messageId;
}
/**
* Decodes the payload.
*
* @param buffer the buffer to decode from
* @param messageType type of the message being decoded
* @param bytesRemainingInVariablePart bytes remaining
* @param variableHeader variable header of the same message
* @return the payload
*/
private static Result decodePayload(ByteBuffer buffer, int maxClientIdLength,
MqttMessageType messageType, int bytesRemainingInVariablePart,
Object variableHeader) {
switch (messageType) {
case CONNECT:
return decodeConnectionPayload(buffer, maxClientIdLength, (MqttConnectVariableHeader) variableHeader);
case SUBSCRIBE:
return decodeSubscribePayload(buffer, bytesRemainingInVariablePart);
case SUBACK:
return decodeSubAckPayload(buffer, bytesRemainingInVariablePart);
case UNSUBSCRIBE:
return decodeUnsubscribePayload(buffer, bytesRemainingInVariablePart);
case UNSUBACK:
return decodeUnsubAckPayload(buffer, bytesRemainingInVariablePart);
case PUBLISH:
return decodePublishPayload(buffer, bytesRemainingInVariablePart);
default:
// unknown payload , no byte consumed
return new Result<>(null, 0);
}
}
private static Result decodeConnectionPayload(ByteBuffer buffer, int maxClientIdLength,
MqttConnectVariableHeader mqttConnectVariableHeader) {
final Result decodedClientId = decodeString(buffer);
final String decodedClientIdValue = decodedClientId.value;
final MqttVersion mqttVersion = MqttVersion.fromProtocolNameAndLevel(mqttConnectVariableHeader.name(),
(byte) mqttConnectVariableHeader.version());
if (!MqttCodecUtil.isValidClientId(mqttVersion, maxClientIdLength, decodedClientIdValue)) {
throw new MqttIdentifierRejectedException("invalid clientIdentifier: " + decodedClientIdValue);
}
int numberOfBytesConsumed = decodedClientId.numberOfBytesConsumed;
Result decodedWillTopic = null;
byte[] decodedWillMessage = null;
final MqttProperties willProperties;
if (mqttConnectVariableHeader.isWillFlag()) {
if (mqttVersion == MqttVersion.MQTT_5) {
final Result propertiesResult = decodeProperties(buffer);
willProperties = propertiesResult.value;
numberOfBytesConsumed += propertiesResult.numberOfBytesConsumed;
} else {
willProperties = MqttProperties.NO_PROPERTIES;
}
decodedWillTopic = decodeString(buffer, 0, 32767);
numberOfBytesConsumed += decodedWillTopic.numberOfBytesConsumed;
decodedWillMessage = decodeByteArray(buffer);
numberOfBytesConsumed += decodedWillMessage.length + 2;
} else {
willProperties = MqttProperties.NO_PROPERTIES;
}
Result decodedUserName = null;
byte[] decodedPassword = null;
if (mqttConnectVariableHeader.hasUserName()) {
decodedUserName = decodeString(buffer);
numberOfBytesConsumed += decodedUserName.numberOfBytesConsumed;
}
if (mqttConnectVariableHeader.hasPassword()) {
decodedPassword = decodeByteArray(buffer);
numberOfBytesConsumed += decodedPassword.length + 2;
}
final MqttConnectPayload mqttConnectPayload =
new MqttConnectPayload(
decodedClientId.value,
willProperties,
decodedWillTopic != null ? decodedWillTopic.value : null,
decodedWillMessage,
decodedUserName != null ? decodedUserName.value : null,
decodedPassword);
return new Result<>(mqttConnectPayload, numberOfBytesConsumed);
}
private static Result decodeSubscribePayload(ByteBuffer buffer, int bytesRemainingInVariablePart) {
final List subscribeTopics = new ArrayList<>();
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
final Result decodedTopicName = decodeString(buffer);
numberOfBytesConsumed += decodedTopicName.numberOfBytesConsumed;
//See 3.8.3.1 Subscription Options of MQTT 5.0 specification for optionByte details
final short optionByte = ByteBufferUtil.readUnsignedByte(buffer);
MqttQoS qos = MqttQoS.valueOf(optionByte & 0x03);
boolean noLocal = ((optionByte & 0x04) >> 2) == 1;
boolean retainAsPublished = ((optionByte & 0x08) >> 3) == 1;
MqttSubscriptionOption.RetainedHandlingPolicy retainHandling =
MqttSubscriptionOption.RetainedHandlingPolicy.valueOf((optionByte & 0x30) >> 4);
final MqttSubscriptionOption subscriptionOption = new MqttSubscriptionOption(qos,
noLocal, retainAsPublished, retainHandling);
numberOfBytesConsumed++;
subscribeTopics.add(new MqttTopicSubscription(decodedTopicName.value, subscriptionOption));
}
return new Result<>(new MqttSubscribePayload(subscribeTopics), numberOfBytesConsumed);
}
private static Result decodeSubAckPayload(ByteBuffer buffer, int bytesRemainingInVariablePart) {
final short[] grantedQos = new short[bytesRemainingInVariablePart];
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
short reasonCode = ByteBufferUtil.readUnsignedByte(buffer);
grantedQos[numberOfBytesConsumed] = reasonCode;
numberOfBytesConsumed++;
}
return new Result<>(new MqttSubAckPayload(grantedQos), numberOfBytesConsumed);
}
private static Result decodeUnsubAckPayload(ByteBuffer buffer, int bytesRemainingInVariablePart) {
final short[] reasonCodes = new short[bytesRemainingInVariablePart];
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
short reasonCode = ByteBufferUtil.readUnsignedByte(buffer);
reasonCodes[numberOfBytesConsumed] = reasonCode;
numberOfBytesConsumed++;
}
return new Result<>(new MqttUnsubAckPayload(reasonCodes), numberOfBytesConsumed);
}
private static Result decodeUnsubscribePayload(ByteBuffer buffer, int bytesRemainingInVariablePart) {
final List unsubscribeTopics = new ArrayList<>();
int numberOfBytesConsumed = 0;
while (numberOfBytesConsumed < bytesRemainingInVariablePart) {
final Result decodedTopicName = decodeString(buffer);
numberOfBytesConsumed += decodedTopicName.numberOfBytesConsumed;
unsubscribeTopics.add(decodedTopicName.value);
}
return new Result<>(new MqttUnsubscribePayload(unsubscribeTopics), numberOfBytesConsumed);
}
private static Result decodePublishPayload(ByteBuffer buffer, int bytesRemainingInVariablePart) {
byte[] payload = new byte[bytesRemainingInVariablePart];
buffer.get(payload, 0, bytesRemainingInVariablePart);
return new Result<>(payload, bytesRemainingInVariablePart);
}
private static Result decodeString(ByteBuffer buffer) {
return decodeString(buffer, 0, Integer.MAX_VALUE);
}
private static Result decodeString(ByteBuffer buffer, int minBytes, int maxBytes) {
int size = decodeMsbLsb(buffer);
int numberOfBytesConsumed = 2;
if (size < minBytes || size > maxBytes) {
ByteBufferUtil.skipBytes(buffer, size);
numberOfBytesConsumed += size;
return new Result<>(null, numberOfBytesConsumed);
}
String s = new String(buffer.array(), buffer.position(), size, StandardCharsets.UTF_8);
ByteBufferUtil.skipBytes(buffer, size);
numberOfBytesConsumed += size;
return new Result<>(s, numberOfBytesConsumed);
}
/**
* @return the decoded byte[], numberOfBytesConsumed = byte[].length + 2
*/
private static byte[] decodeByteArray(ByteBuffer buffer) {
int size = decodeMsbLsb(buffer);
byte[] bytes = new byte[size];
buffer.get(bytes);
return bytes;
}
// packing utils to reduce the amount of garbage while decoding ints
private static long packInts(int a, int b) {
return (((long) a) << 32) | (b & 0xFFFFFFFFL);
}
private static int unpackA(long ints) {
return (int) (ints >> 32);
}
private static int unpackB(long ints) {
return (int) ints;
}
/**
* numberOfBytesConsumed = 2. return decoded result.
*/
private static int decodeMsbLsb(ByteBuffer buffer) {
int min = 0;
int max = 65535;
short msbSize = ByteBufferUtil.readUnsignedByte(buffer);
short lsbSize = ByteBufferUtil.readUnsignedByte(buffer);
int result = msbSize << 8 | lsbSize;
if (result < min || result > max) {
result = -1;
}
return result;
}
/**
* See 1.5.5 Variable Byte Integer section of MQTT 5.0 specification for encoding/decoding rules
*
* @param buffer the buffer to decode from
* @return result pack with a = decoded integer, b = numberOfBytesConsumed. Need to unpack to read them.
* @throws DecoderException if bad MQTT protocol limits Remaining Length
*/
private static long decodeVariableByteInteger(ByteBuffer buffer) {
int remainingLength = 0;
int multiplier = 1;
short digit;
int loops = 0;
do {
digit = ByteBufferUtil.readUnsignedByte(buffer);
remainingLength += (digit & 127) * multiplier;
multiplier *= 128;
loops++;
} while ((digit & 128) != 0 && loops < 4);
if (loops == 4 && (digit & 128) != 0) {
throw new DecoderException("MQTT protocol limits Remaining Length to 4 bytes");
}
return packInts(remainingLength, loops);
}
private static final class Result {
private final T value;
private final int numberOfBytesConsumed;
Result(T value, int numberOfBytesConsumed) {
this.value = value;
this.numberOfBytesConsumed = numberOfBytesConsumed;
}
}
private static Result decodeProperties(ByteBuffer buffer) {
final long propertiesLength = decodeVariableByteInteger(buffer);
int totalPropertiesLength = unpackA(propertiesLength);
int numberOfBytesConsumed = unpackB(propertiesLength);
MqttProperties decodedProperties = new MqttProperties();
while (numberOfBytesConsumed < totalPropertiesLength) {
long propertyId = decodeVariableByteInteger(buffer);
final int propertyIdValue = unpackA(propertyId);
numberOfBytesConsumed += unpackB(propertyId);
MqttPropertyType propertyType = MqttPropertyType.valueOf(propertyIdValue);
switch (propertyType) {
case PAYLOAD_FORMAT_INDICATOR:
case REQUEST_PROBLEM_INFORMATION:
case REQUEST_RESPONSE_INFORMATION:
case MAXIMUM_QOS:
case RETAIN_AVAILABLE:
case WILDCARD_SUBSCRIPTION_AVAILABLE:
case SUBSCRIPTION_IDENTIFIER_AVAILABLE:
case SHARED_SUBSCRIPTION_AVAILABLE:
final int b1 = ByteBufferUtil.readUnsignedByte(buffer);
numberOfBytesConsumed++;
decodedProperties.add(new IntegerProperty(propertyIdValue, b1));
break;
case SERVER_KEEP_ALIVE:
case RECEIVE_MAXIMUM:
case TOPIC_ALIAS_MAXIMUM:
case TOPIC_ALIAS:
final int int2BytesResult = decodeMsbLsb(buffer);
numberOfBytesConsumed += 2;
decodedProperties.add(new IntegerProperty(propertyIdValue, int2BytesResult));
break;
case PUBLICATION_EXPIRY_INTERVAL:
case SESSION_EXPIRY_INTERVAL:
case WILL_DELAY_INTERVAL:
case MAXIMUM_PACKET_SIZE:
final int maxPacketSize = buffer.getInt();
numberOfBytesConsumed += 4;
decodedProperties.add(new IntegerProperty(propertyIdValue, maxPacketSize));
break;
case SUBSCRIPTION_IDENTIFIER:
long vbIntegerResult = decodeVariableByteInteger(buffer);
numberOfBytesConsumed += unpackB(vbIntegerResult);
decodedProperties.add(new IntegerProperty(propertyIdValue, unpackA(vbIntegerResult)));
break;
case CONTENT_TYPE:
case RESPONSE_TOPIC:
case ASSIGNED_CLIENT_IDENTIFIER:
case AUTHENTICATION_METHOD:
case RESPONSE_INFORMATION:
case SERVER_REFERENCE:
case REASON_STRING:
final Result stringResult = decodeString(buffer);
numberOfBytesConsumed += stringResult.numberOfBytesConsumed;
decodedProperties.add(new StringProperty(propertyIdValue, stringResult.value));
break;
case USER_PROPERTY:
final Result keyResult = decodeString(buffer);
final Result valueResult = decodeString(buffer);
numberOfBytesConsumed += keyResult.numberOfBytesConsumed;
numberOfBytesConsumed += valueResult.numberOfBytesConsumed;
decodedProperties.add(new UserProperty(keyResult.value, valueResult.value));
break;
case CORRELATION_DATA:
case AUTHENTICATION_DATA:
final byte[] binaryDataResult = decodeByteArray(buffer);
numberOfBytesConsumed += binaryDataResult.length + 2;
decodedProperties.add(new BinaryProperty(propertyIdValue, binaryDataResult));
break;
default:
//shouldn't reach here
throw new DecoderException("Unknown property type: " + propertyType);
}
}
return new Result<>(decodedProperties, numberOfBytesConsumed);
}
}
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