Coroutines are a powerful feature in modern C++ that enable writing asynchronous and non-blocking code in a more intuitive and sequential manner. One of the key aspects of coroutines is their ability to suspend and resume execution at specific points, allowing for efficient resource usage and cooperative multitasking.

In C++, coroutine suspension and resumption is achieved through the use of the co_await keyword. When a coroutine function encounters a co_await expression, it will suspend its execution and transfer control back to the caller, allowing other tasks to be processed. Once the awaited operation completes, the coroutine resumes from where it left off.

Let’s see an example of how coroutine suspension and resumption can be used in C++:

#include <iostream>
#include <experimental/coroutine>

std::experimental::suspend_always suspend() {
    std::cout << "Suspending coroutine..." << std::endl;
    co_await std::experimental::suspend_always(); // Suspend coroutine
    std::cout << "Resuming coroutine..." << std::endl;
}

int main() {
    auto coro = suspend(); // Create coroutine
    std::cout << "Coroutine created" << std::endl;
    coro.resume(); // Resume coroutine
    return 0;
}

In this example, we define a coroutine function suspend() that prints a message, suspends itself using co_await std::experimental::suspend_always(), and then prints another message when resumed. In the main() function, we create an instance of the coroutine and invoke resume() to start its execution.

When we run the above code, it will output:

Suspending coroutine...
Coroutine created
Resuming coroutine...

As we can see, the execution of the coroutine is suspended after printing “Suspending coroutine…” and resumes after printing “Coroutine created” when coro.resume() is called.

Coroutine suspension and resumption is not limited to simple prints, but can also be used for I/O operations, networking, and other tasks that would traditionally block the execution flow. This allows for more efficient use of system resources and better responsiveness in asynchronous applications.

By leveraging the power of coroutines and their suspension and resumption mechanisms, developers can write more readable and maintainable code that is easy to reason about and offers better scalability in handling concurrent operations.

#C++ #coroutines