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#pragma once
#include <coroutine>
struct schedulable {
schedulable* next = nullptr;
std::coroutine_handle<> awaiter;
schedulable() {}
schedulable(std::coroutine_handle<> h) : awaiter(h) {}
};
struct scheduler_t {
schedulable* first = nullptr;
schedulable** last_next_p = &first;
void run() {
while(first) {
auto sch = pop_next();
sch.awaiter.resume();
}
}
schedulable& pop_next() {
critical_section lock;
auto sch = first;
first = first->next;
if(!first) {
last_next_p = &first;
}
return *sch;
}
void schedule(schedulable& sch) {
critical_section lock;
sch.next = nullptr;
*last_next_p = &sch;
last_next_p = &sch.next;
}
};
scheduler_t scheduler;
struct yield : public schedulable {
bool await_ready() {
return false;
}
bool await_suspend(std::coroutine_handle<> h) {
awaiter = h;
scheduler.schedule(*this);
return true;
}
void await_resume() {}
};
template <typename T = void>
struct future : public schedulable {
std::optional<T> value;
bool await_ready() {
return bool(value);
}
bool await_suspend(std::coroutine_handle<> h) {
if(value) {
return false;
} else {
awaiter = h;
return true;
}
}
T await_resume() {
return *value; // TODO: move?
}
bool done() {
return bool(value);
}
void set(T v) {
if(value) {
return;
}
value = v;
if(awaiter) {
scheduler.schedule(*this);
}
}
void reset() {
value.reset();
awaiter = nullptr;
}
};
template <>
struct future<void> : public schedulable {
bool ready;
future() : ready(false) {}
bool await_ready() {
return ready;
}
bool await_suspend(std::coroutine_handle<> h) {
if(ready) {
return false;
} else {
awaiter = h;
return true;
}
}
void await_resume() {
}
bool done() {
return ready;
}
void set() {
if(ready) {
return;
}
ready = true;
if(awaiter) {
scheduler.schedule(*this);
}
}
void reset() {
awaiter = nullptr;
ready = false;
}
};
struct task : public schedulable {
struct promise_type {
task get_return_object() {
auto handle = std::coroutine_handle<promise_type>::from_promise(*this);
return {handle};
}
std::suspend_always initial_suspend() { return {}; }
std::suspend_never final_suspend() { return {}; }
void return_void() {}
};
task(std::coroutine_handle<promise_type> h) : schedulable(h) {}
};
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