tdlight/tdutils/td/utils/Promise.h
2023-01-01 00:28:08 +03:00

374 lines
10 KiB
C++

//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2023
//
// 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/CancellationToken.h"
#include "td/utils/common.h"
#include "td/utils/invoke.h"
#include "td/utils/MovableValue.h"
#include "td/utils/Status.h"
#include <tuple>
#include <type_traits>
#include <utility>
namespace td {
template <class T = Unit>
class PromiseInterface {
public:
PromiseInterface() = default;
PromiseInterface(const PromiseInterface &) = delete;
PromiseInterface &operator=(const PromiseInterface &) = delete;
PromiseInterface(PromiseInterface &&) = default;
PromiseInterface &operator=(PromiseInterface &&) = default;
virtual ~PromiseInterface() = default;
virtual void set_value(T &&value) {
set_result(std::move(value));
}
virtual void set_error(Status &&error) {
set_result(std::move(error));
}
virtual void set_result(Result<T> &&result) {
if (result.is_ok()) {
set_value(result.move_as_ok());
} else {
set_error(result.move_as_error());
}
}
virtual bool is_cancellable() const {
return false;
}
virtual bool is_canceled() const {
return false;
}
};
template <class T>
class SafePromise;
template <class T = Unit>
class Promise;
namespace detail {
template <typename T>
struct GetArg final : public GetArg<decltype(&T::operator())> {};
template <class C, class R, class Arg>
class GetArg<R (C::*)(Arg)> {
public:
using type = Arg;
};
template <class C, class R, class Arg>
class GetArg<R (C::*)(Arg) const> {
public:
using type = Arg;
};
template <class T>
using get_arg_t = std::decay_t<typename GetArg<T>::type>;
template <class T>
struct DropResult {
using type = T;
};
template <class T>
struct DropResult<Result<T>> {
using type = T;
};
template <class T>
using drop_result_t = typename DropResult<T>::type;
template <class ValueT, class FunctionT>
class LambdaPromise : public PromiseInterface<ValueT> {
enum class State : int32 { Empty, Ready, Complete };
public:
void set_value(ValueT &&value) override {
CHECK(state_.get() == State::Ready);
do_ok(std::move(value));
state_ = State::Complete;
}
void set_error(Status &&error) override {
if (state_.get() == State::Ready) {
do_error(std::move(error));
state_ = State::Complete;
}
}
LambdaPromise(const LambdaPromise &other) = delete;
LambdaPromise &operator=(const LambdaPromise &other) = delete;
LambdaPromise(LambdaPromise &&other) = default;
LambdaPromise &operator=(LambdaPromise &&other) = default;
~LambdaPromise() override {
if (state_.get() == State::Ready) {
do_error(Status::Error("Lost promise"));
}
}
template <class FromT>
explicit LambdaPromise(FromT &&func) : func_(std::forward<FromT>(func)), state_(State::Ready) {
}
private:
FunctionT func_;
MovableValue<State> state_{State::Empty};
template <class F = FunctionT>
std::enable_if_t<is_callable<F, Result<ValueT>>::value, void> do_error(Status &&status) {
func_(Result<ValueT>(std::move(status)));
}
template <class Y, class F = FunctionT>
std::enable_if_t<!is_callable<F, Result<ValueT>>::value, void> do_error(Y &&status) {
func_(Auto());
}
template <class F = FunctionT>
std::enable_if_t<is_callable<F, Result<ValueT>>::value, void> do_ok(ValueT &&value) {
func_(Result<ValueT>(std::move(value)));
}
template <class F = FunctionT>
std::enable_if_t<!is_callable<F, Result<ValueT>>::value, void> do_ok(ValueT &&value) {
func_(std::move(value));
}
};
template <class T>
struct is_promise_interface : std::false_type {};
template <class U>
struct is_promise_interface<PromiseInterface<U>> : std::true_type {};
template <class U>
struct is_promise_interface<Promise<U>> : std::true_type {};
template <class T>
struct is_promise_interface_ptr : std::false_type {};
template <class U>
struct is_promise_interface_ptr<unique_ptr<U>> : std::true_type {};
template <class T = void, class F = void, std::enable_if_t<std::is_same<T, void>::value, bool> has_t = false>
auto lambda_promise(F &&f) {
return LambdaPromise<drop_result_t<get_arg_t<std::decay_t<F>>>, std::decay_t<F>>(std::forward<F>(f));
}
template <class T = void, class F = void, std::enable_if_t<!std::is_same<T, void>::value, bool> has_t = true>
auto lambda_promise(F &&f) {
return LambdaPromise<T, std::decay_t<F>>(std::forward<F>(f));
}
template <class T, class F,
std::enable_if_t<is_promise_interface<std::decay_t<F>>::value, bool> from_promise_interface = true>
auto &&promise_interface(F &&f) {
return std::forward<F>(f);
}
template <class T, class F,
std::enable_if_t<!is_promise_interface<std::decay_t<F>>::value, bool> from_promise_interface = false>
auto promise_interface(F &&f) {
return lambda_promise<T>(std::forward<F>(f));
}
template <class T, class F,
std::enable_if_t<is_promise_interface_ptr<std::decay_t<F>>::value, bool> from_promise_interface = true>
auto promise_interface_ptr(F &&f) {
return std::forward<F>(f);
}
template <class T, class F,
std::enable_if_t<!is_promise_interface_ptr<std::decay_t<F>>::value, bool> from_promise_interface = false>
auto promise_interface_ptr(F &&f) {
return td::make_unique<std::decay_t<decltype(promise_interface<T>(std::forward<F>(f)))>>(
promise_interface<T>(std::forward<F>(f)));
}
} // namespace detail
template <class T>
class Promise {
public:
void set_value(T &&value) {
if (!promise_) {
return;
}
promise_->set_value(std::move(value));
promise_.reset();
}
void set_error(Status &&error) {
if (!promise_) {
return;
}
promise_->set_error(std::move(error));
promise_.reset();
}
void set_result(Result<T> &&result) {
if (!promise_) {
return;
}
promise_->set_result(std::move(result));
promise_.reset();
}
void reset() {
promise_.reset();
}
bool is_cancellable() const {
if (!promise_) {
return false;
}
return promise_->is_cancellable();
}
bool is_canceled() const {
if (!promise_) {
return false;
}
return promise_->is_canceled();
}
unique_ptr<PromiseInterface<T>> release() {
return std::move(promise_);
}
Promise() = default;
explicit Promise(unique_ptr<PromiseInterface<T>> promise) : promise_(std::move(promise)) {
}
Promise(Auto) {
}
Promise(SafePromise<T> &&other);
Promise &operator=(SafePromise<T> &&other);
template <class F, std::enable_if_t<!std::is_same<std::decay_t<F>, Promise>::value, int> = 0>
Promise(F &&f) : promise_(detail::promise_interface_ptr<T>(std::forward<F>(f))) {
}
explicit operator bool() const noexcept {
return static_cast<bool>(promise_);
}
private:
unique_ptr<PromiseInterface<T>> promise_;
};
template <class T = Unit>
class SafePromise {
public:
SafePromise(Promise<T> promise, Result<T> result) : promise_(std::move(promise)), result_(std::move(result)) {
}
SafePromise(const SafePromise &other) = delete;
SafePromise &operator=(const SafePromise &other) = delete;
SafePromise(SafePromise &&other) = default;
SafePromise &operator=(SafePromise &&other) = default;
~SafePromise() {
if (promise_) {
promise_.set_result(std::move(result_));
}
}
Promise<T> release() {
return std::move(promise_);
}
private:
Promise<T> promise_;
Result<T> result_;
};
template <class T>
Promise<T>::Promise(SafePromise<T> &&other) : Promise(other.release()) {
}
template <class T>
Promise<T> &Promise<T>::operator=(SafePromise<T> &&other) {
*this = other.release();
return *this;
}
namespace detail {
template <class PromiseT>
class CancellablePromise final : public PromiseT {
public:
template <class... ArgsT>
CancellablePromise(CancellationToken cancellation_token, ArgsT &&...args)
: PromiseT(std::forward<ArgsT>(args)...), cancellation_token_(std::move(cancellation_token)) {
}
bool is_cancellable() const final {
return true;
}
bool is_canceled() const final {
return static_cast<bool>(cancellation_token_);
}
private:
CancellationToken cancellation_token_;
};
template <class... ArgsT>
class JoinPromise final : public PromiseInterface<Unit> {
public:
explicit JoinPromise(ArgsT &&...arg) : promises_(std::forward<ArgsT>(arg)...) {
}
void set_value(Unit &&) final {
tuple_for_each(promises_, [](auto &promise) { promise.set_value(Unit()); });
}
void set_error(Status &&error) final {
tuple_for_each(promises_, [&error](auto &promise) { promise.set_error(error.clone()); });
}
private:
std::tuple<std::decay_t<ArgsT>...> promises_;
};
} // namespace detail
class PromiseCreator {
public:
template <class OkT, class ArgT = detail::drop_result_t<detail::get_arg_t<OkT>>>
static Promise<ArgT> lambda(OkT &&ok) {
return Promise<ArgT>(td::make_unique<detail::LambdaPromise<ArgT, std::decay_t<OkT>>>(std::forward<OkT>(ok)));
}
template <class OkT, class ArgT = detail::drop_result_t<detail::get_arg_t<OkT>>>
static auto cancellable_lambda(CancellationToken cancellation_token, OkT &&ok) {
return Promise<ArgT>(td::make_unique<detail::CancellablePromise<detail::LambdaPromise<ArgT, std::decay_t<OkT>>>>(
std::move(cancellation_token), std::forward<OkT>(ok)));
}
template <class... ArgsT>
static Promise<> join(ArgsT &&...args) {
return Promise<>(td::make_unique<detail::JoinPromise<ArgsT...>>(std::forward<ArgsT>(args)...));
}
};
inline void set_promises(vector<Promise<Unit>> &promises) {
auto moved_promises = std::move(promises);
promises.clear();
for (auto &promise : moved_promises) {
promise.set_value(Unit());
}
}
template <class T>
void fail_promises(vector<Promise<T>> &promises, Status &&error) {
CHECK(error.is_error());
auto moved_promises = std::move(promises);
promises.clear();
auto size = moved_promises.size();
if (size == 0) {
return;
}
size--;
for (size_t i = 0; i < size; i++) {
auto &promise = moved_promises[i];
if (promise) {
promise.set_error(error.clone());
}
}
moved_promises[size].set_error(std::move(error));
}
} // namespace td