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/*
* Copyright (C) 2024 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``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 APPLE INC. OR ITS CONTRIBUTORS
* 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
#include <concepts>
#include <wtf/CompletionHandler.h>
#include <wtf/TZoneMallocInlines.h>
#if __has_include(<coroutine>)
#include <coroutine>
#else
// FIXME: Remove this once all supported toolchains have non-experimental coroutine support.
#include <experimental/coroutine>
namespace std {
using std::experimental::coroutine_handle;
using std::experimental::suspend_never;
using std::experimental::suspend_always;
}
#endif
namespace WebKit {
template<typename PromiseType>
class CoroutineHandle {
public:
CoroutineHandle() = default;
CoroutineHandle(std::coroutine_handle<PromiseType>&& handle)
: m_handle(std::exchange(handle, nullptr)) { }
CoroutineHandle(CoroutineHandle&& other)
: m_handle(std::exchange(other.m_handle, nullptr)) { }
CoroutineHandle& operator=(CoroutineHandle&& other)
{
m_handle = std::exchange(other.m_handle, nullptr);
return *this;
}
CoroutineHandle(const CoroutineHandle&) = delete;
CoroutineHandle& operator=(const CoroutineHandle&) = delete;
~CoroutineHandle()
{
if (m_handle)
m_handle.destroy();
}
std::coroutine_handle<PromiseType> handle() const { return m_handle; }
private:
std::coroutine_handle<PromiseType> m_handle;
};
// Name based on https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1056r1.html
template<typename T>
class Lazy {
public:
class PromiseBase {
public:
struct final_awaitable {
bool await_ready() const noexcept { return false; }
template<typename Promise>
std::coroutine_handle<> await_suspend(std::coroutine_handle<Promise> coroutine) noexcept { return coroutine.promise().handle(); }
void await_resume() noexcept { }
};
std::suspend_always initial_suspend() { return { }; }
final_awaitable final_suspend() noexcept { return { }; }
template<typename Promise>
void unhandled_exception() { }
void setHandle(std::coroutine_handle<> handle) { m_handle = handle; }
std::coroutine_handle<> handle() { return m_handle; }
private:
std::coroutine_handle<> m_handle;
};
template<typename U>
class Promise final : public PromiseBase {
public:
Lazy<U> get_return_object() { return Lazy<U> { std::coroutine_handle<Promise>::from_promise(*this) }; }
void return_value(U&& value) { m_value = WTFMove(value); }
U result() && { return std::exchange(m_value, { }); }
private:
U m_value;
};
template<std::same_as<void> U>
class Promise<U> : public PromiseBase {
public:
Lazy<void> get_return_object() { return Lazy<void> { std::coroutine_handle<Promise>::from_promise(*this) }; }
void return_void() { }
void result() { }
};
using promise_type = Promise<T>;
class Awaitable {
public:
Awaitable(std::coroutine_handle<promise_type> coroutine)
: m_coroutine(coroutine) { }
bool await_ready() const { return m_coroutine.done(); }
std::coroutine_handle<> await_suspend(std::coroutine_handle<> handle)
{
m_coroutine.promise().setHandle(handle);
return m_coroutine;
}
T await_resume() { return WTFMove(this->m_coroutine.promise()).result(); }
private:
std::coroutine_handle<promise_type> m_coroutine;
};
Lazy(std::coroutine_handle<promise_type> coroutine)
: m_coroutine(std::exchange(coroutine, nullptr)) { }
Awaitable operator co_await() const { return { m_coroutine.handle() }; }
private:
CoroutineHandle<promise_type> m_coroutine;
};
struct Task {
struct promise_type {
Task get_return_object() { return { std::coroutine_handle<promise_type>::from_promise(*this) }; }
std::suspend_never initial_suspend() { return { }; }
std::suspend_always final_suspend() noexcept { return { }; }
void unhandled_exception() { }
void return_void() { }
};
std::coroutine_handle<promise_type> handle;
};
class CoroutineCaller {
WTF_MAKE_TZONE_ALLOCATED_INLINE(CoroutineCaller);
public:
CoroutineCaller() = default;
void setCoroutine(Function<Task()>&& coroutine)
{
m_coroutine = std::exchange(coroutine, { });
m_coroutine();
}
private:
Function<Task()> m_coroutine;
};
static void callCoroutine(auto coroutine)
{
CoroutineCaller* caller = new CoroutineCaller();
caller->setCoroutine([caller, coroutine = WTFMove(coroutine)] () mutable -> Task {
co_await coroutine();
delete caller;
});
}
template<typename T>
class AwaitableTaskWithCompletionHandler {
public:
using Task = CompletionHandler<void(CompletionHandler<void(T&&)>&&)>;
AwaitableTaskWithCompletionHandler(Task&& task)
: m_task(WTFMove(task)) { }
bool await_ready() { return !!m_result; }
void await_suspend(std::coroutine_handle<> handle)
{
m_task([this, handle] (T&& result) mutable {
m_result = WTFMove(result);
handle();
});
}
T await_resume() { return *std::exchange(m_result, { }); }
private:
Task m_task;
std::optional<T> m_result;
};
}
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