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/**
* @file llindexedqueue.h
* @brief An indexed FIFO queue, where only one element with each key
* can be in the queue.
*
* $LicenseInfo:firstyear=2003&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#ifndef LL_LLINDEXEDQUEUE_H
#define LL_LLINDEXEDQUEUE_H
// An indexed FIFO queue, where only one element with each key can be in the queue.
// This is ONLY used in the interest list, you'll probably want to review this code
// carefully if you want to use it elsewhere - Doug
template <typename Type>
class LLIndexedQueue
{
protected:
typedef std::deque<Type> type_deque;
type_deque mQueue;
std::set<Type> mKeySet;
public:
LLIndexedQueue() {}
// move_if_there is an O(n) operation
bool push_back(const Type &value, bool move_if_there = false)
{
if (mKeySet.find(value) != mKeySet.end())
{
// Already on the queue
if (move_if_there)
{
// Remove the existing entry.
typename type_deque::iterator it;
for (it = mQueue.begin(); it != mQueue.end(); ++it)
{
if (*it == value)
{
break;
}
}
// This HAS to succeed, otherwise there's a serious bug in the keyset implementation
// (although this isn't thread safe, at all)
mQueue.erase(it);
}
else
{
// We're not moving it, leave it alone
return false;
}
}
else
{
// Doesn't exist, add it to the key set
mKeySet.insert(value);
}
mQueue.push_back(value);
// We succeeded in adding the new element.
return true;
}
bool push_front(const Type &value, bool move_if_there = false)
{
if (mKeySet.find(value) != mKeySet.end())
{
// Already on the queue
if (move_if_there)
{
// Remove the existing entry.
typename type_deque::iterator it;
for (it = mQueue.begin(); it != mQueue.end(); ++it)
{
if (*it == value)
{
break;
}
}
// This HAS to succeed, otherwise there's a serious bug in the keyset implementation
// (although this isn't thread safe, at all)
mQueue.erase(it);
}
else
{
// We're not moving it, leave it alone
return false;
}
}
else
{
// Doesn't exist, add it to the key set
mKeySet.insert(value);
}
mQueue.push_front(value);
return true;
}
void pop()
{
Type value = mQueue.front();
mKeySet.erase(value);
mQueue.pop_front();
}
Type &front()
{
return mQueue.front();
}
S32 size() const
{
return mQueue.size();
}
bool empty() const
{
return mQueue.empty();
}
void clear()
{
// Clear out all elements on the queue
mQueue.clear();
mKeySet.clear();
}
};
#endif // LL_LLINDEXEDQUEUE_H
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