Question

Circular_buffer from boost library is not thread-safe. So I wrapped boost::circular_buffer object in a class as shown below. Mutual exclusion between the threads is achieved (I think) by using conditional variables, a mutex and a lock acquisition/release. Is this implementation thread safe?

#include <boost/thread/condition.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <boost/circular_buffer.hpp>

// Thread safe circular buffer 
template <typename T>
class circ_buffer : private boost::noncopyable
{
public:
    typedef boost::mutex::scoped_lock lock;
    circ_buffer() {}
    circ_buffer(int n) {cb.set_capacity(n);}
    void send (T imdata) {
        lock lk(monitor);
        cb.push_back(imdata);
        buffer_not_empty.notify_one();
    }
    T receive() {
        lock lk(monitor);
        while (cb.empty())
            buffer_not_empty.wait(lk);
        T imdata = cb.front();
        cb.pop_front();
        return imdata;
    }
    void clear() {
        lock lk(monitor);
        cb.clear();
    }
    int size() {
        lock lk(monitor);
        return cb.size();
    }
    void set_capacity(int capacity) {
        lock lk(monitor);
        cb.set_capacity(capacity);
    }
private:
    boost::condition buffer_not_empty;
    boost::mutex monitor;
    boost::circular_buffer<T> cb;
};

Edit This is now a template class, which accepts an object of any type (not just cv::Mat object).

Answer 1

Yes.
If you lock all the public methods with the same lock it will be threadsafe.

You could consider using read-write locks, which may have better performance if you have a lot of concurrent readers.

If you don’t have a lot of readers, it will just add overhead, but may be worth checking the option and testing.