How Can I Implement Semaphore Functionality in C 0x Without Native Support?

C 0x Semaphore Replacement

While C 0x doesn't natively provide semaphores, there are alternative approaches to achieve synchronization between threads. One method is to utilize a mutex and a condition variable to create a custom semaphore.

Consider the following code snippet:

#include <mutex>
#include <condition_variable>

class semaphore {
    std::mutex mutex_;
    std::condition_variable condition_;
    unsigned long count_ = 0; // Initialized as locked.

public:
    void release() {
        std::lock_guard<decltype(mutex_)> lock(mutex_);
        ++count_;
        condition_.notify_one();
    }

    void acquire() {
        std::unique_lock<decltype(mutex_)> lock(mutex_);
        while(!count_) // Handle spurious wake-ups.
            condition_.wait(lock);
        --count_;
    }

    bool try_acquire() {
        std::lock_guard<decltype(mutex_)> lock(mutex_);
        if(count_) {
            --count_;
            return true;
        }
        return false;
    }
};

This custom semaphore provides similar functionality to POSIX semaphores, allowing threads to wait for and release events. The release method increments the count and notifies waiting threads, while the acquire method decrements the count and waits if necessary. The try_acquire method attempts to acquire the semaphore immediately without waiting.

By employing this technique, you can achieve semaphore-like functionality in C 0x, even in the absence of native semaphore support.

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