mirror of
https://github.com/matrix-construct/construct
synced 2024-08-24 18:42:16 +02:00
143 lines
3.7 KiB
C++
143 lines
3.7 KiB
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2018 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. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_CTX_WHEN_H
|
|
|
|
namespace ircd::ctx
|
|
{
|
|
template<class it> future<void> when_all(it first, const it &last);
|
|
template<class it> future<it> when_any(it first, const it &last);
|
|
}
|
|
|
|
// Internal interface
|
|
namespace ircd::ctx::when
|
|
{
|
|
template<class T> auto &state(const future<T> &);
|
|
void all_then(promise<void> &p);
|
|
template<class it> void any_then(promise<it> &p, it &f);
|
|
template<class it> void set_all_then(promise<void> &p, it &f);
|
|
template<class it> void set_any_then(promise<it> &p, it &f);
|
|
}
|
|
|
|
/// Returns a future which becomes ready when any of the futures in the
|
|
/// iteration become ready or are already ready. The future that when_any()
|
|
/// eventually indicates is then considered "observed" which means you
|
|
/// are required to do nothing when including it in the next invocation of
|
|
/// when_any() and it won't be considered ready or pending again and the
|
|
/// collection does not have to be modified in any way.
|
|
///
|
|
/// The returned future's payload is an iterator into the collection as if
|
|
/// it were the result of an std::find() etc; thus to know its index an
|
|
/// std::distance is often satisfactory.
|
|
template<class it>
|
|
ircd::ctx::future<it>
|
|
ircd::ctx::when_any(it first,
|
|
const it &last)
|
|
{
|
|
promise<it> p;
|
|
future<it> ret(p);
|
|
for(auto f(first); f != last; ++f)
|
|
if(is(state(*f), future_state::READY))
|
|
{
|
|
set(when::state(*f), future_state::OBSERVED);
|
|
p.set_value(f);
|
|
return ret;
|
|
}
|
|
|
|
for(; first != last; ++first)
|
|
if(is(state(*first), future_state::PENDING))
|
|
when::set_any_then(p, first);
|
|
|
|
if(refcount(p.state()) <= 1)
|
|
p.set_value(first);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/// Returns a future which becomes ready when all of the futures in the
|
|
/// collection become ready. This future has a void payload to minimize
|
|
/// its cost since this indication is positively unate.
|
|
template<class it>
|
|
ircd::ctx::future<void>
|
|
ircd::ctx::when_all(it first,
|
|
const it &last)
|
|
{
|
|
promise<void> p;
|
|
future<void> ret(p);
|
|
for(; first != last; ++first)
|
|
if(is(state(*first), future_state::PENDING))
|
|
when::set_all_then(p, first);
|
|
|
|
if(refcount(p.state()) <= 1)
|
|
p.set_value();
|
|
|
|
return ret;
|
|
}
|
|
|
|
template<class it>
|
|
void
|
|
ircd::ctx::when::set_any_then(promise<it> &p,
|
|
it &f)
|
|
{
|
|
when::state(*f).then = [p, f] // TODO: quash this alloc
|
|
(shared_state_base &sb) mutable
|
|
{
|
|
if(sb.then)
|
|
any_then(p, f);
|
|
};
|
|
}
|
|
|
|
template<class it>
|
|
void
|
|
ircd::ctx::when::set_all_then(promise<void> &p,
|
|
it &f)
|
|
{
|
|
when::state(*f).then = [p] // TODO: quash this alloc
|
|
(shared_state_base &sb) mutable
|
|
{
|
|
if(sb.then)
|
|
all_then(p);
|
|
};
|
|
}
|
|
|
|
template<class it>
|
|
void
|
|
ircd::ctx::when::any_then(promise<it> &p,
|
|
it &f)
|
|
{
|
|
if(!p.valid())
|
|
return;
|
|
|
|
set(when::state(*f), future_state::OBSERVED);
|
|
p.set_value(f);
|
|
}
|
|
|
|
inline void
|
|
ircd::ctx::when::all_then(promise<void> &p)
|
|
{
|
|
if(!p.valid())
|
|
return;
|
|
|
|
if(refcount(p.state()) < 2)
|
|
return p.set_value();
|
|
|
|
return p.remove(p.state(), p);
|
|
}
|
|
|
|
/// In order for this template to be reusable with std::set iterations we
|
|
/// have to make a const_cast at some point; this internal function does that.
|
|
template<class T>
|
|
auto &
|
|
ircd::ctx::when::state(const future<T> &f)
|
|
{
|
|
return const_cast<future<T> &>(f).state();
|
|
}
|