67 lines
1.6 KiB
C++
67 lines
1.6 KiB
C++
// https://www.scs.stanford.edu/~dm/blog/c++-coroutines.html#generic-generator-example
|
|
#include <exception>
|
|
#include <utility>
|
|
#ifdef __clang__
|
|
#include <experimental/coroutine>
|
|
namespace stdco = std::experimental;
|
|
#else
|
|
#include <coroutine>
|
|
namespace stdco = std;
|
|
#endif
|
|
|
|
template<typename T>
|
|
struct Generator
|
|
{
|
|
struct promise_type;
|
|
using handle_type = stdco::coroutine_handle<promise_type>;
|
|
|
|
struct promise_type
|
|
{
|
|
T value_;
|
|
std::exception_ptr exception_;
|
|
|
|
Generator get_return_object()
|
|
{
|
|
return Generator(handle_type::from_promise(*this));
|
|
}
|
|
stdco::suspend_always initial_suspend() { return {}; }
|
|
stdco::suspend_always final_suspend() noexcept { return {}; }
|
|
void unhandled_exception() { exception_ = std::current_exception(); }
|
|
template<std::convertible_to<T> From> // C++20 concept
|
|
stdco::suspend_always yield_value(From&& from)
|
|
{
|
|
value_ = std::forward<From>(from);
|
|
return {};
|
|
}
|
|
void return_void() {}
|
|
};
|
|
|
|
handle_type h_;
|
|
|
|
Generator(handle_type h) : h_(h) {}
|
|
~Generator() { h_.destroy(); }
|
|
explicit operator bool()
|
|
{
|
|
fill();
|
|
return !h_.done();
|
|
}
|
|
T operator()()
|
|
{
|
|
fill();
|
|
full_ = false;
|
|
return std::move(h_.promise().value_);
|
|
}
|
|
|
|
private:
|
|
bool full_ = false;
|
|
|
|
void fill()
|
|
{
|
|
if (!full_) {
|
|
h_();
|
|
if (h_.promise().exception_) std::rethrow_exception(h_.promise().exception_);
|
|
full_ = true;
|
|
}
|
|
}
|
|
};
|