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#pragma once
#include <mutex>
#include <condition_variable>
#include <cassert>
namespace nix {
/* This template class ensures synchronized access to a value of type
T. It is used as follows:
struct Data { int x; ... };
Sync<Data> data;
{
auto data_(data.lock());
data_->x = 123;
}
Here, "data" is automatically unlocked when "data_" goes out of
scope.
*/
template<class T>
class Sync
{
private:
std::mutex mutex;
T data;
public:
Sync() { }
Sync(const T & data) : data(data) { }
class Lock
{
private:
Sync * s;
friend Sync;
Lock(Sync * s) : s(s) { s->mutex.lock(); }
public:
Lock(Lock && l) : s(l.s) { l.s = 0; }
Lock(const Lock & l) = delete;
~Lock() { if (s) s->mutex.unlock(); }
T * operator -> () { return &s->data; }
T & operator * () { return s->data; }
/* FIXME: performance impact of condition_variable_any? */
void wait(std::condition_variable_any & cv)
{
assert(s);
cv.wait(s->mutex);
}
template<class Rep, class Period, class Predicate>
bool wait_for(std::condition_variable_any & cv,
const std::chrono::duration<Rep, Period> & duration,
Predicate pred)
{
assert(s);
return cv.wait_for(s->mutex, duration, pred);
}
template<class Clock, class Duration>
std::cv_status wait_until(std::condition_variable_any & cv,
const std::chrono::time_point<Clock, Duration> & duration)
{
assert(s);
return cv.wait_until(s->mutex, duration);
}
};
Lock lock() { return Lock(this); }
};
}
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