tdlight/tdutils/td/utils/Closure.h

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//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2021
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#include "td/utils/common.h"
#include "td/utils/invoke.h"
#include "td/utils/logging.h"
#include <cstdlib>
#include <tuple>
#include <type_traits>
#include <utility>
//
// Essentially we have:
// (ActorT::func, arg1, arg2, ..., argn)
// We want to call:
// actor->func(arg1, arg2, ..., argn)
// And in some cases we would like to delay this call.
//
// First attempt would be
// [a1=arg1, a2=arg2, ..., an=argn](ActorT *actor) {
// actor->func(a1, a2, ..., an)
// }
//
// But there are some difficulties with elimitation on unnecessary copies.
// We want to use move constructor when it is possible
//
// We may pass
// Tmp. Temporary / rvalue reference
// Var. Variable / reference
// CnstRef. const reference
//
//
// Function may expect
// Val. Value
// CnstRef. const reference
// Ref. rvalue reverence / reference
//
// TODO:
// Immediate call / Delayed call
// Tmp->Val move / move->move
// Tmp->CnstRef + / move->+
// Tmp->Ref + / move->+
// Var->Val copy / copy->move
// Var->CnstRef + / copy->
// Var->Ref + / copy->+ // khm. It will complile, but won't work
//
// So I will use common idiom: forward references
// If delay is needed, just std::forward data to temporary storage, and std::move them when call is executed.
//
//
// create_immediate_closure(&ActorT::func, arg1, arg2, ..., argn).run(actor)
// to_delayed_closure(std::move(immediate)).run(actor)
namespace td {
template <class ActorT, class FunctionT, class... ArgsT>
class DelayedClosure;
template <class ActorT, class FunctionT, class... ArgsT>
class ImmediateClosure {
public:
using Delayed = DelayedClosure<ActorT, FunctionT, ArgsT...>;
friend Delayed;
using ActorType = ActorT;
// no &&. just save references as references.
explicit ImmediateClosure(FunctionT func, ArgsT... args) : args(func, std::forward<ArgsT>(args)...) {
}
private:
std::tuple<FunctionT, ArgsT...> args;
public:
auto run(ActorT *actor) -> decltype(mem_call_tuple(actor, std::move(args))) {
return mem_call_tuple(actor, std::move(args));
}
};
template <class ActorT, class ResultT, class... DestArgsT, class... SrcArgsT>
ImmediateClosure<ActorT, ResultT (ActorT::*)(DestArgsT...), SrcArgsT &&...> create_immediate_closure(
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ResultT (ActorT::*func)(DestArgsT...), SrcArgsT &&...args) {
return ImmediateClosure<ActorT, ResultT (ActorT::*)(DestArgsT...), SrcArgsT &&...>(func,
std::forward<SrcArgsT>(args)...);
}
template <class ActorT, class FunctionT, class... ArgsT>
class DelayedClosure {
public:
using ActorType = ActorT;
using Delayed = DelayedClosure<ActorT, FunctionT, ArgsT...>;
DelayedClosure clone() const {
return do_clone(*this);
}
explicit DelayedClosure(ImmediateClosure<ActorT, FunctionT, ArgsT...> &&other) : args(std::move(other.args)) {
}
explicit DelayedClosure(FunctionT func, ArgsT... args) : args(func, std::forward<ArgsT>(args)...) {
}
template <class F>
void for_each(const F &f) {
tuple_for_each(args, f);
}
private:
using ArgsStorageT = std::tuple<FunctionT, typename std::decay<ArgsT>::type...>;
ArgsStorageT args;
template <class FromActorT, class FromFunctionT, class... FromArgsT>
explicit DelayedClosure(const DelayedClosure<FromActorT, FromFunctionT, FromArgsT...> &other,
std::enable_if_t<LogicAnd<std::is_copy_constructible<FromArgsT>::value...>::value, int> = 0)
: args(other.args) {
}
template <class FromActorT, class FromFunctionT, class... FromArgsT>
explicit DelayedClosure(
const DelayedClosure<FromActorT, FromFunctionT, FromArgsT...> &other,
std::enable_if_t<!LogicAnd<std::is_copy_constructible<FromArgsT>::value...>::value, int> = 0) {
LOG(FATAL) << "Deleted constructor";
std::abort();
}
template <class FromActorT, class FromFunctionT, class... FromArgsT>
std::enable_if_t<!LogicAnd<std::is_copy_constructible<FromArgsT>::value...>::value,
DelayedClosure<FromActorT, FromFunctionT, FromArgsT...>>
do_clone(const DelayedClosure<FromActorT, FromFunctionT, FromArgsT...> &value) const {
LOG(FATAL) << "Trying to clone DelayedClosure that contains noncopyable elements";
std::abort();
}
template <class FromActorT, class FromFunctionT, class... FromArgsT>
std::enable_if_t<LogicAnd<std::is_copy_constructible<FromArgsT>::value...>::value,
DelayedClosure<FromActorT, FromFunctionT, FromArgsT...>>
do_clone(const DelayedClosure<FromActorT, FromFunctionT, FromArgsT...> &value) const {
return DelayedClosure<FromActorT, FromFunctionT, FromArgsT...>(value);
}
public:
auto run(ActorT *actor) -> decltype(mem_call_tuple(actor, std::move(args))) {
return mem_call_tuple(actor, std::move(args));
}
};
template <class... ArgsT>
typename ImmediateClosure<ArgsT...>::Delayed to_delayed_closure(ImmediateClosure<ArgsT...> &&other) {
return typename ImmediateClosure<ArgsT...>::Delayed(std::move(other));
}
template <class... ArgsT>
DelayedClosure<ArgsT...> to_delayed_closure(DelayedClosure<ArgsT...> &&other) {
return std::move(other);
}
template <class ActorT, class ResultT, class... DestArgsT, class... SrcArgsT>
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auto create_delayed_closure(ResultT (ActorT::*func)(DestArgsT...), SrcArgsT &&...args) {
return DelayedClosure<ActorT, ResultT (ActorT::*)(DestArgsT...), SrcArgsT &&...>(func,
std::forward<SrcArgsT>(args)...);
}
} // namespace td