mirror of
https://github.com/matrix-construct/construct
synced 2024-09-08 17:55:47 +02:00
161 lines
3.7 KiB
C++
161 lines
3.7 KiB
C++
/*
|
|
* Copyright (C) 2016 Charybdis Development Team
|
|
* Copyright (C) 2016 Jason Volk <jason@zemos.net>
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice is present in all copies.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
|
|
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
|
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
|
|
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
|
|
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_CTX_VIEW_H
|
|
|
|
namespace ircd::ctx
|
|
{
|
|
template<class T> class view;
|
|
}
|
|
|
|
/// Device for a context to share data on its stack with others while yielding
|
|
///
|
|
/// The view yields a context while other contexts examine the object pointed
|
|
/// to in the view. This allows a producing context to construct something
|
|
/// on its stack and then wait for the consuming contexts to do something with
|
|
/// that data before the producer resumes and potentially destroys the data.
|
|
/// This creates a very simple and lightweight single-producer/multi-consumer
|
|
/// queue mechanism using only context switching.
|
|
///
|
|
/// Consumers get one chance to safely view the data when a call to wait()
|
|
/// returns. Once the consumer context yields again for any reason the data is
|
|
/// potentially invalid. The data can only be viewed once by the consumer
|
|
/// because the second call to wait() will yield until the next data is
|
|
/// made available by the producer, not the same data.
|
|
///
|
|
/// Producers will share an object during the call to notify(). Once the call
|
|
/// to notify() returns all consumers have viewed the data and the producer is
|
|
/// free to destroy it.
|
|
///
|
|
template<class T>
|
|
class ircd::ctx::view
|
|
{
|
|
T *t {nullptr};
|
|
dock a, b;
|
|
|
|
bool ready() const;
|
|
|
|
public:
|
|
size_t waiting() const;
|
|
|
|
// Consumer interface;
|
|
template<class time_point> T &wait_until(time_point&&);
|
|
template<class duration> T &wait_for(const duration &);
|
|
T &wait();
|
|
|
|
// Producer interface;
|
|
void notify(T &);
|
|
|
|
view() = default;
|
|
~view() noexcept;
|
|
};
|
|
|
|
template<class T>
|
|
ircd::ctx::view<T>::~view()
|
|
noexcept
|
|
{
|
|
assert(!waiting());
|
|
}
|
|
|
|
template<class T>
|
|
void
|
|
ircd::ctx::view<T>::notify(T &t)
|
|
{
|
|
const unwind afterward{[this]
|
|
{
|
|
assert(a.empty());
|
|
this->t = nullptr;
|
|
if(!b.empty())
|
|
{
|
|
b.notify_all();
|
|
yield();
|
|
}
|
|
}};
|
|
|
|
assert(b.empty());
|
|
this->t = &t;
|
|
a.notify_all();
|
|
yield();
|
|
}
|
|
|
|
template<class T>
|
|
T &
|
|
ircd::ctx::view<T>::wait()
|
|
{
|
|
b.wait([this]
|
|
{
|
|
return !ready();
|
|
});
|
|
|
|
a.wait([this]
|
|
{
|
|
return ready();
|
|
});
|
|
|
|
assert(t != nullptr);
|
|
return *t;
|
|
}
|
|
|
|
template<class T>
|
|
template<class duration>
|
|
T &
|
|
ircd::ctx::view<T>::wait_for(const duration &dur)
|
|
{
|
|
return wait_until(now<steady_point>() + dur);
|
|
}
|
|
|
|
template<class T>
|
|
template<class time_point>
|
|
T &
|
|
ircd::ctx::view<T>::wait_until(time_point&& tp)
|
|
{
|
|
if(!b.wait_until(tp, [this]
|
|
{
|
|
return !ready();
|
|
}))
|
|
throw timeout();
|
|
|
|
if(!a.wait_until(tp, [this]
|
|
{
|
|
return ready();
|
|
}))
|
|
throw timeout();
|
|
|
|
assert(t != nullptr);
|
|
return *t;
|
|
}
|
|
|
|
template<class T>
|
|
size_t
|
|
ircd::ctx::view<T>::waiting()
|
|
const
|
|
{
|
|
return a.size() + b.size();
|
|
}
|
|
|
|
template<class T>
|
|
bool
|
|
ircd::ctx::view<T>::ready()
|
|
const
|
|
{
|
|
return t != nullptr;
|
|
}
|