sources/network/packetqueue.cpp

/*
	Copyright 2016 Teemu Piippo
	All rights reserved.

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions
	are met:

	1. Redistributions of source code must retain the above copyright
	   notice, this list of conditions and the following disclaimer.
	2. Redistributions in binary form must reproduce the above copyright
	   notice, this list of conditions and the following disclaimer in the
	   documentation and/or other materials provided with the distribution.
	3. Neither the name of the copyright holder nor the names of its
	   contributors may be used to endorse or promote products derived from
	   this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
	TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
	PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER
	OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
	LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
	NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
	SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <algorithm>
#include "packetqueue.h"
BEGIN_ZFC_NAMESPACE

/*!
 * \brief Constructs an empty packet queue.
 */
PacketQueue::PacketQueue() :
    m_currentSequenceNumber(0) {}

/*!
 * \brief Inserts the packet into the queue, unless the packet is the next packet to be processed.
 * \param sequenceNumber Sequence number of the packet.
 * \param data Payload of the packet.
 * \return True, if the packet was stored, false if the packet should be processed immediately.
 */
bool PacketQueue::addPacket(unsigned int sequenceNumber, const ByteArray& data)
{
	// Check whether this packet is the one we're supposed to process next.
	if (sequenceNumber != m_currentSequenceNumber)
	{
		// It is not, therefore store it for later.
		m_queue[sequenceNumber] = data;
		return true;
	}
	else
	{
		// It is, therefore the caller processes it, and we can advance to the next packet right away.
		m_currentSequenceNumber = getNextSequenceNumber();
		return false;
	}
}

/*!
 * \returns whether there are packets in queue that cannot be processed due to missing in-between packets. If true, the
 * \returns caller should initiate packet recovery protocol.
 */
bool PacketQueue::isStuck() const
{
	return m_queue.size() > 0  and  m_queue.find(m_currentSequenceNumber) == m_queue.end();
}

/*!
 * \returns whether or not there are packets awaiting processing.
 */
bool PacketQueue::hasPacketsToPop() const
{
	return m_queue.size() > 0  and  m_queue.find(m_currentSequenceNumber) != m_queue.end();
}

/*!
 * \brief Retrieves the next packet to be processed, and removes it from the queue.
 * \param packet Reference to a byte array to store the packet payload into.
 * \returns whether the next packet was successfully popped from the queue, or not.
 */
bool PacketQueue::popNextPacket(ByteArray& packet)
{
	// Find the packet matching our current sequence number.
	auto iterator = m_queue.find(m_currentSequenceNumber);

	if (iterator != m_queue.end())
	{
		// We found the packet we were looking for. Pass it to the caller.
		packet = iterator->second;
		// Remove the packet from the queue.
		m_queue.erase(iterator);
		// We can now advance to the next packet.
		m_currentSequenceNumber = getNextSequenceNumber();
		return true;
	}
	else
	{
		// We did not find the next packet.
		return false;
	}
}

/*!
 * \returns the sequence number for the next packet.
 */
int PacketQueue::getNextSequenceNumber() const
{
	return (m_currentSequenceNumber + 1) % 1024;
}

/*!
 * \returns a list of packets that have to be requested from the server.
 */
std::set<int> PacketQueue::getLostPackets() const
{
	std::set<int> packetsNeeded;
	std::set<int> packetsInQueue;

	// Build the set of packet numbers we currently have.
	for (auto pair : m_queue)
		packetsInQueue.insert(pair.first);

	// Build the set of packets we wish to process. To do this we need the smallest and largest numbers in
	// packetsInQueue.
	Range<int> packetRange(min(packetsInQueue), max(packetsInQueue));

	for (int i : packetRange)
		packetsNeeded.insert(i);

	// The set of lost packets is now the set of packets we want, minus the packets we have.
	std::set<int> packetsLost;
	std::set_difference(packetsNeeded.begin(), packetsNeeded.end(),
	                    packetsInQueue.begin(), packetsInQueue.end(),
	                    std::inserter(packetsLost, packetsLost.begin()));
	return packetsLost;
}

std::set<unsigned int> PacketQueue::getWaitingPackets() const
{
	std::set<unsigned int> packetsInQueue;

	// Build the set of packet numbers we currently have.
	for (auto pair : m_queue)
		packetsInQueue.insert(pair.first);

	return packetsInQueue;
}

END_ZFC_NAMESPACE