C++ Coroutines
C++20 introduced coroutines, which provide a way to write asynchronous and cooperative code in a more sequential and readable manner. Coroutines allow you to suspend and resume the execution of a function, enabling the creation of asynchronous tasks and generators. Here's an example demonstrating the usage of coroutines:
#include <iostream>
#include <experimental/coroutine>
struct Generator {
struct promise_type {
int current_value;
Generator get_return_object() {
return Generator{std::experimental::coroutine_handle<promise_type>::from_promise(*this)};
}
std::experimental::suspend_always initial_suspend() {
return {};
}
std::experimental::suspend_always final_suspend() noexcept {
return {};
}
void return_void() {}
std::experimental::suspend_always yield_value(int value) {
current_value = value;
return {};
}
};
std::experimental::coroutine_handle<promise_type> coroutine_handle;
Generator(std::experimental::coroutine_handle<promise_type> handle)
: coroutine_handle(handle) {}
~Generator() {
if (coroutine_handle)
coroutine_handle.destroy();
}
int current() {
return coroutine_handle.promise().current_value;
}
bool move_next() {
coroutine_handle.resume();
return !coroutine_handle.done();
}
};
Generator generate_range(int start, int end) {
for (int i = start; i <= end; ++i) {
co_yield i;
}
}
int main() {
Generator generator = generate_range(1, 5);
while (generator.move_next()) {
std::cout << generator.current() << " ";
}
std::cout << std::endl;
return 0;
}
In the above code, we define a Generator struct that represents a coroutine generator. It has an inner promise_type struct that provides the necessary functions and suspend points for the coroutine. The promise_type defines the get_return_object, initial_suspend, final_suspend, return_void, and yield_value functions.
The Generator struct holds a coroutine handle and provides a current function to retrieve the current value and a move_next function to resume the coroutine and check if it is done.
We define a generate_range function that is a coroutine and uses the co_yield keyword to yield values from a range. It generates integers from start to end inclusively.
In the main() function, we create a Generator using generate_range and iterate over it using the move_next function. We print each value using the current function.
Coroutines provide a powerful mechanism to write asynchronous and cooperative code, making it easier to work with asynchronous operations, generators, and state machines.
If you have any more questions or would like to explore additional topics, please let me know!
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