#include "link_layer.hpp" #include "mac_protocol.hpp" #include "physical_layer.hpp" const t_uint LinkLayer::m_LINK_LAYER_QUEUE_LENGTH = 1; LinkLayer::LinkLayer(NodePtr node, MacProtocolPtr macProtocol)    : CommunicationLayer(node), m_macProtocol(macProtocol) {    setMaxQueueLength(m_LINK_LAYER_QUEUE_LENGTH); } void LinkLayer::simulationEndHandler() { } bool LinkLayer::channelIsBusy() {    CommunicationLayer::Directions direction =       CommunicationLayer::Directions_Lower;    PhysicalLayerPtr physicalLayer =       boost::dynamic_pointer_cast<PhysicalLayer>       (getLayer(direction, getDefaultLayer(direction)));    assert(physicalLayer.get() != 0);    return physicalLayer->channelCarrierSensedBusy(); } bool LinkLayer::recvFromMacProtocol(    CommunicationLayer::Directions direction, PacketPtr packet) {    // Use the default function with packet passed back from    // the MAC.    return CommunicationLayer::sendToLayer(direction, packet); } bool LinkLayer::recvFromLayer(    CommunicationLayer::Directions direction, PacketPtr packet,    t_uint sendingLayerIdx) {    assert(m_macProtocol.get() != 0);    return m_macProtocol->recvFromLinkLayer(       direction, packet, sendingLayerIdx); }