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//
// The MIT License
//
// Copyright (c) 2010 James E Beveridge
//
// 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, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// This sample code is for my blog entry titled, "Understanding ReadDirectoryChangesW"
// http://qualapps.blogspot.com/2010/05/understanding-readdirectorychangesw.html
// See ReadMe.txt for overview information.
#include <list>
template <typename C>
class CThreadSafeQueue : protected std::list<C>
{
public:
CThreadSafeQueue(int nMaxCount)
{
m_bOverflow = false;
m_hSemaphore = ::CreateSemaphore(
NULL, // no security attributes
0, // initial count
nMaxCount, // max count
NULL); // anonymous
}
~CThreadSafeQueue()
{
::CloseHandle(m_hSemaphore);
m_hSemaphore = NULL;
}
void push(C& c)
{
CComCritSecLock<CComAutoCriticalSection> lock( m_Crit, true );
push_back( c );
lock.Unlock();
if (!::ReleaseSemaphore(m_hSemaphore, 1, NULL))
{
// If the semaphore is full, then take back the entry.
lock.Lock();
pop_back();
if (GetLastError() == ERROR_TOO_MANY_POSTS)
{
m_bOverflow = true;
}
}
}
bool pop(C& c)
{
CComCritSecLock<CComAutoCriticalSection> lock( m_Crit, true );
// If the user calls pop() more than once after the
// semaphore is signaled, then the semaphore count will
// get out of sync. We fix that when the queue empties.
if (empty())
{
while (::WaitForSingleObject(m_hSemaphore, 0) != WAIT_TIMEOUT)
1;
return false;
}
c = front();
pop_front();
return true;
}
// If overflow, use this to clear the queue.
void clear()
{
CComCritSecLock<CComAutoCriticalSection> lock( m_Crit, true );
for (DWORD i=0; i<size(); i++)
WaitForSingleObject(m_hSemaphore, 0);
__super::clear();
m_bOverflow = false;
}
bool overflow()
{
return m_bOverflow;
}
HANDLE GetWaitHandle() { return m_hSemaphore; }
protected:
HANDLE m_hSemaphore;
CComAutoCriticalSection m_Crit;
bool m_bOverflow;
};