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#ifndef VPYTHON_UTIL_ATOMIC_QUEUE_HPP
#define VPYTHON_UTIL_ATOMIC_QUEUE_HPP
#include "util/thread.hpp"
#include <queue>
namespace cvisual {
// This class exists to separate out code that is not templated (and therefore
// doesn't need to be in a header file) from code that is. This prevents
// picking up the whole Python runtine throughout all of cvisual, thus making
// compilation faster.
class atomic_queue_impl
{
protected:
volatile bool waiting;
volatile bool empty;
condition ready;
mutable mutex barrier;
atomic_queue_impl()
: waiting(false), empty(true)
{}
void push_notify();
void py_pop_wait( lock& L);
};
template <typename T>
class atomic_queue : private atomic_queue_impl
{
private:
std::queue<T> data;
/**
* Precondition - the buggar is locked, at least one item is in data
*/
T pop_impl()
{
T ret = data.front();
data.pop();
if (data.empty())
empty = true;
return ret;
}
public:
atomic_queue() {}
void push( const T& item)
{
lock L(barrier);
data.push( item);
push_notify();
}
// It's assumed that the caller of py_pop() holds the Python GIL
T py_pop()
{
lock L(barrier);
py_pop_wait( L);
return pop_impl();
}
size_t size() const
{
lock L(barrier);
return data.size();
}
void clear()
{
lock L(barrier);
while (!data.empty())
data.pop();
empty = true;
}
};
} // !namespace cvisual
#endif // !defined VPYTHON_UTIL_ATOMIC_QUEUE_HPP
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