Condition Variable alternatives (c/c++ on windows xp) - winapi

Question

I want to write a thread which runs tasks from an unlimited-size container of tasks.
While the task-list is empty the thread trying to get a task should be blocked.
Coming from Linux I wanted to use condition variable which will be signaled on task adding and will be waited while the list is empty.
I found that CONDITION_VARIABLE is available only from windows Vista, so this is out of question.
Semaphores are problematic too due to the unlimited-size restriction.
Is there any apropriate subtitution?
Thanks

Answer 1

Why do you say that semaphores are problematic? Linux/Windows both have semaphores with a maximum count that can be realistically be described as 'Unlimited'.
Use James' suggestion on Windows - it will work fine. Init. your semaphore with zero count. Add a task to your big (thread-safe), container, then signal the semaphore. In the thread, wait on the semaphore, then get a task from your container and process it. You can pass the semaphore instance to multiple threads if you wish - that will work OK as well.
Rgds,
Martin

Answer 2

Sounds like you want a Win32 kernel event. See CreateEvent.

Answer 3

WaitForSingleObject and CreateSemaphore?

Answer 4

Thanks all,
thats my conclusion:
void ThreadPool::ThreadStartPoint(ThreadPool* tp)
{
while (1)
{
WaitForSingleObject(tp->m_taskCountSemaphore,INFINITE); // while (num of tasks==0) block; decreament num of tasks
BaseTask* current_task = 0;
// get top priority task
EnterCriticalSection (&tp->m_mutex);
{
current_task = tp->m_tasksQue.top();
tp->m_tasksQue.pop();
}
LeaveCriticalSection (&tp->m_mutex);
current_task->operator()(); // this is not critical section
current_task->PostExec();
}
}
void ThreadPool::AddTask(BaseTask& _task)
{
EnterCriticalSection (&m_mutex);
{
m_tasksQue.push(&_task);
_task.PrepareTask(m_mutex);
}
LeaveCriticalSection (&m_mutex);
if (!ReleaseSemaphore(m_taskCountSemaphore,
1, // increament num of tasks by 1
NULL // don't store previuos num of tasks value
))
{//if failed
throw ("semaphore release failed");
}
}