<reponame>wangyang2013/TFM<filename>TFM/click-2.0.1/elements/standard/quicknotequeue.cc
// -*- c-basic-offset: 4 -*-
/*
 * quicknotequeue.{cc,hh} -- queue element that notifies quickly
 * <NAME>
 *
 * Copyright (c) 2009 Meraki, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, subject to the conditions
 * listed in the Click LICENSE file. These conditions include: you must
 * preserve this copyright notice, and you cannot mention the copyright
 * holders in advertising related to the Software without their permission.
 * The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
 * notice is a summary of the Click LICENSE file; the license in that file is
 * legally binding.
 */

#include <click/config.h>
#include "quicknotequeue.hh"
CLICK_DECLS

QuickNoteQueue::QuickNoteQueue()
{
}

QuickNoteQueue::~QuickNoteQueue()
{
}

void *
QuickNoteQueue::cast(const char *n)
{
    if (strcmp(n, "QuickNoteQueue") == 0)
	return (QuickNoteQueue *)this;
    else
	return FullNoteQueue::cast(n);
}

Packet *
QuickNoteQueue::pull(int)
{
    int h = _head, t = _tail;
    Packet *p;

    if (h != t) {
	p = _q[h];
	packet_memory_barrier(_q[h], _head);
	_head = h = next_i(h);
	_full_note.wake();
    } else
	p = 0;

    if (h == t) {
	_empty_note.sleep();
#if HAVE_MULTITHREAD
	// Work around race condition between push() and pull().
	// We might have just undone push()'s Notifier::wake() call.
	// Easiest lock-free solution: check whether we should wake again!
	if (size())
	    _empty_note.wake();
#endif
    }

    return p;
}

CLICK_ENDDECLS
ELEMENT_REQUIRES(FullNoteQueue)
EXPORT_ELEMENT(QuickNoteQueue)
