public static AddMsgLocation decode(final ByteBuffer buf) {
if (!buf.hasRemaining()) {
return null;
}
final long offset = buf.getLong();
final int length = buf.getInt();
final int checksum = buf.getInt();
final int descLen = buf.getInt();
final byte[] descBytes = new byte[descLen];
buf.get(descBytes);
final String desc = ByteUtils.getString(descBytes);
return new AddMsgLocation(offset, length, checksum, desc);
}
/**
* 消息位置序列化为:
*
* <ul>
* <li>8个字节的offset
* <li>4个字节的长度
* <li>4个字节checksum:这是指整个消息存储数据的checksum，跟message的checksum不同
* <li>4个字节长度，存储的分区名的长度
* <li>存储的分区名
* </ul>
*
* @return
*/
public ByteBuffer encode() {
if (this.buf == null) {
final byte[] storeDescBytes = ByteUtils.getBytes(this.storeDesc);
final ByteBuffer buf = ByteBuffer.allocate(4 + 4 + 8 + 4 + this.storeDesc.length());
buf.putLong(this.getOffset());
buf.putInt(this.getLength());
buf.putInt(this.checksum);
buf.putInt(storeDescBytes.length);
buf.put(storeDescBytes);
buf.flip();
this.buf = buf;
}
return this.buf;
}
/**
* 将消息属性和消息payload打包，结构如下：</br></br> 0或者1个定长attribute + payload
*
* @param message
* @return
*/
public static final byte[] encodePayload(final Message message) {
final byte[] payload = message.getData();
final String attribute = message.getAttribute();
byte[] attrData = null;
if (attribute != null) {
attrData = ByteUtils.getBytes(attribute);
} else {
return payload;
}
final int attrLen = attrData == null ? 0 : attrData.length;
final ByteBuffer buffer = ByteBuffer.allocate(4 + attrLen + payload.length);
if (attribute != null) {
buffer.putInt(attrLen);
if (attrData != null) {
buffer.put(attrData);
}
}
buffer.put(payload);
return buffer.array();
}
/**
* 从binary数据中解出消息
*
* @param topic
* @param data
* @param offset
* @return
* @throws InvalidMessageException
*/
public static final DecodedMessage decodeMessage(
final String topic, final byte[] data, final int offset) throws InvalidMessageException {
final ByteBuffer buf = ByteBuffer.wrap(data, offset, HEADER_LEN);
final int msgLen = buf.getInt();
final int checksum = buf.getInt();
vailidateMessage(offset + HEADER_LEN, msgLen, checksum, data);
final long id = buf.getLong();
// 取flag
final int flag = buf.getInt();
String attribute = null;
int payLoadOffset = offset + HEADER_LEN;
int payLoadLen = msgLen;
if (payLoadLen > MAX_READ_BUFFER_SIZE) {
throw new InvalidMessageException("Too much long payload length:" + payLoadLen);
}
// 如果有属性，需要解析属性
if (MessageFlagUtils.hasAttribute(flag)) {
// 取4个字节的属性长度
final int attrLen = getInt(offset + HEADER_LEN, data);
// 取消息属性
final byte[] attrData = new byte[attrLen];
System.arraycopy(data, offset + HEADER_LEN + 4, attrData, 0, attrLen);
attribute = ByteUtils.getString(attrData);
// 递增payloadOffset，加上4个字节的消息长度和消息长度本身
payLoadOffset = offset + HEADER_LEN + 4 + attrLen;
// payload长度递减，减去4个字节的消息长度和消息长度本身
payLoadLen = msgLen - 4 - attrLen;
}
// 获取payload
final byte[] payload = new byte[payLoadLen];
System.arraycopy(data, payLoadOffset, payload, 0, payLoadLen);
final Message msg = new Message(topic, payload);
MessageAccessor.setFlag(msg, flag);
msg.setAttribute(attribute);
MessageAccessor.setId(msg, id);
return new DecodedMessage(
payLoadOffset + payLoadLen,
msg,
ByteBuffer.wrap(data, offset, payLoadOffset + payLoadLen - offset));
}