receiverbase.java

来自「Logica lastest SMPP API」· Java 代码 · 共 408 行 · 第 1/2 页

	 * PDU from them and buffering data in case the PDU
	 * isn't still complete. It has timeout checking for incomplete
	 * messages: if the message isn't received completly for certain time
	 * and no new data are received for this time, then exception is thrown
	 * as this could indicate communication problem.
	 *
	 * @param connection the connection to receive the data from
	 * @return either PDU, if complete received or null
	 *
	 * @exception IOException exception during communication
	 * @exception PDUException incorrect format of PDU
	 * @throws TimeoutException rest of data not received for too long time
	 * @throws UnknownCommandIdException PDU with unknown id was received
	 * @see Connection
	 * @see Unprocessed
	 */
	final protected PDU receivePDUFromConnection(Connection connection,
												 Unprocessed unprocessed)
	throws UnknownCommandIdException,
		   TimeoutException,
		   PDUException,
		   IOException
	{
		debug.write(DRXTXD2,"ReceiverBase.receivePDUFromConnection start");
		PDU pdu = null;
		ByteBuffer buffer;
		ByteBuffer unprocBuffer;

		try {
			// first check if there is something left from the last time
			if (unprocessed.getHasUnprocessed()) {
				unprocBuffer = unprocessed.getUnprocessed();
				debug.write(DRXTX,"have unprocessed "+unprocBuffer.length()+" bytes from previous try");
				pdu = tryGetUnprocessedPDU(unprocessed);
			}
			if (pdu == null) { // only if we didn't manage to get pdu from unproc
				buffer = connection.receive();
				unprocBuffer = unprocessed.getUnprocessed();
				// if received something now or have something from the last receive
				if (buffer.length() != 0) {
					unprocBuffer.appendBuffer(buffer);
					unprocessed.setLastTimeReceived();
					pdu = tryGetUnprocessedPDU(unprocessed);
				} else {
					debug.write(DRXTXD2,"no data received this time.");
					// check if it's not too long since we received any data
					long timeout = getReceiveTimeout();
					if ((unprocBuffer.length() > 0) &&
						((unprocessed.getLastTimeReceived() + timeout) <
						 Data.getCurrentTime())) {
						debug.write(DRXTX,"and it's been very long time.");
						unprocessed.reset();
						throw new TimeoutException(timeout,
												   unprocessed.getExpected(),
												   unprocBuffer.length());
					}
				}
			}
		}
		catch (UnknownCommandIdException e) {
			// [e-mail]: if we got an UnknownCommandIdException here, the
			// chances are excellent that
			// some trailing garbage is hanging arounf in the unprocessed buffer.
			// given that it's unlikely that it contained a valid PDU, we don't
			// rethrow the error - nothing to respond to with a gnack.
			// Was originally just checking this if the unprocessed buffer had
			// content, but that's not enough.

			debug.write(DRXTX,"There is _probably_ garbage in the unprocessed buffer - flushing unprocessed buffer now.");
			event.write(e,"There is _probably_ garbage in the unprocessed buffer - flushing unprocessed buffer now.");
			unprocessed.reset();
		}

		debug.write(DRXTXD2,"ReceiverBase.receivePDUFromConnection finished");
		return pdu;
	}

	/**
	 * Tries to create a PDU from the buffer provided.
	 * Returns the PDU if successfull or null if not or an exception
	 * if the PDU is incorrect.
	 */
	private final PDU tryGetUnprocessedPDU(Unprocessed unprocessed)
	throws UnknownCommandIdException,
		   PDUException
	{
		debug.write(DRXTX,"trying to create pdu from unprocessed buffer");
		PDU pdu = null;
		ByteBuffer unprocBuffer = unprocessed.getUnprocessed();
		try {
			pdu = PDU.createPDU(unprocBuffer);
			//System.out.println("SEQ No In Receiver base: "+pdu.getSequenceNumber());
			unprocessed.check();
		} catch (HeaderIncompleteException e) {
			// the header wasn't received completly, we will try to
			// receive the rest next time
			debug.write(DRXTXD,"incomplete message header, will wait for the rest.");
			unprocessed.setHasUnprocessed(false); // as it's incomplete - wait for new data
			unprocessed.setExpected(Data.PDU_HEADER_SIZE);
		} catch (MessageIncompleteException e) {
			if (messageIncompleteRetryCount > 1) { // [e-mail]
				messageIncompleteRetryCount = 0;
				debug.write(DRXTXD,"Giving up on incomplete messages - probably garbage in unprocessed buffer. Flushing unprocessed buffer.");
				event.write("Giving up on incomplete messages - probably garbage in unprocessed buffer. Flushing unprocessed buffer.");
				unprocessed.reset();
			}

			// the message wasn't received completly, less bytes than command
			// length has been received, will try to receive the rest next time
			debug.write(DRXTXD,"incomplete message, will wait for the rest.");
			unprocessed.setHasUnprocessed(false); // as it's incomplete - wait for new data
			unprocessed.setExpected(Data.PDU_HEADER_SIZE);
			messageIncompleteRetryCount++;
		} catch (UnknownCommandIdException e) {
			// message with invalid id was received, should send generic_nack
			debug.write(DRXTX,"unknown pdu, might remove from unprocessed buffer. CommandId=" + e.getCommandId());
			if (e.getCommandLength() <= unprocBuffer.length()) {
				// have already enough to remove
				try {
					unprocBuffer.removeBytes(e.getCommandLength());
				} catch (NotEnoughDataInByteBufferException e1) {
					// can't happen, we've checked it above
					throw new Error("Not enough data in buffer even if previously checked that there was enough.");
				}
				unprocessed.check();
				throw e; // caller will decide what to do
			}
			// [e-mail]: added this: see why in caller. Advantage: lets
			// us trap garbage PDUs that break things by being trapped in the
			// unprocessed buffer eternally. Disadvantage: if this was a valid
			// (well-formed) PDU with an unknown command id AND it was not fully
			// read into the buffer in one go, then:
			// 1) we will respond to the part _was_ already read (which we know
			// contains at least a header - see code in PDU) with an error, which
			// is fine.
			// 2) when we receive the second part of the incomplete PDU, it will
			// effectively seem to us to be an invalid PDU itself. It could be
			// processed as follows:
			//     - as an unknown command_id again, which is fine; or
			//     - as an incomplete message, which is a problem, because it will
			//       then have the subsequent PDU tacked to the end of it, and
			//       that PDU will then be discarded as well (and almost certainly
			//       discarded via an UnknownCommandIdException again).
			throw e;
		}
		// [e-mail]: safer to catch all other PDU exceptions and force
		// force a check() here - some exception in parsing should not be allowed
		// to leave ghost data in the Unprocessed buffer (even though this is now
		// less likely after improvements to PDU.createPDU()):
		catch (PDUException e) {
			unprocessed.check();
			throw e;
		}

		if (pdu != null) {
			debug.write(DRXTX,"received complete pdu"+pdu.debugString());
			debug.write(DRXTX,"there is "+unprocBuffer.length()+
						" bytes left in unprocessed buffer");
		}
		// unprocessed.check();
		return pdu;
	}

	/**
	 * Sets the timeout for receiving the complete message.
	 * If no data are received for time longer then this timeout and there
	 * is still not completly received PDU in the internal buffer,
	 * <code>TimeoutException</code> is thrown.
	 *
	 * @param timeout the new timeout value
	 *
	 * @see #receivePDUFromConnection(Connection,Unprocessed)
	 * @see TimeoutException
	 */
	public void setReceiveTimeout(long timeout) { receiveTimeout = timeout; }

	/**
	 * Returns the current setting of the receiving timeout.
	 *
	 * @return the current timeout value
	 */
	public long getReceiveTimeout() { return receiveTimeout; }

	/**
	 * Depending on value of <code>timeout</code> and on <code>startTime</code>
	 * returns if it's still possible to continue in receiving of message.
	 * <code>timeout</code> can indicate either timeout in milliseconds
	 * (if > 0), or that there has to be only one attempt to receive
	 * a message (if = 0) or that the the receiving shuld continue until
	 * a PDU is received (if = Data.RECEIVE_BLOCKING).
	 *
	 * @param startTime when the receiving started
	 * @param timeout timeout indication
	 * @return if it's possible to continue receiving
	 */
	private boolean canContinueReceiving(long startTime, long timeout)
	{
		return timeout == Data.RECEIVE_BLOCKING ?
			   true :
			   Data.getCurrentTime() <= (startTime + timeout);
	}

}