stdsharedtimedmutex

stdsharedtimedmutex is a synchronization primitive in C++ that allows multiple threads to read a shared resource concurrently, but ensures exclusive access for writing. It is part of the C++14 standard library, found in the <mutex> header.

The core idea behind stdsharedtimedmutex is to manage access to a shared data structure. Multiple threads can acquire a shared lock on the mutex simultaneously, meaning they can all read the data without interfering with each other. However, if a thread wishes to modify the data, it must acquire an exclusive lock. Only one thread can hold an exclusive lock at a time, and no shared locks can be held while an exclusive lock is active. This prevents race conditions during write operations.

stdsharedtimedmutex offers both shared and exclusive locking mechanisms. The shared lock is acquired using lock_shared() and released with unlock_shared(). The exclusive lock is acquired using lock() and released with unlock(). For situations where threads might need to wait for a specified duration, timed versions of these operations are also available, such as try_lock_shared_for(), try_lock_shared_until(), try_lock_for(), and try_lock_until(). These timed operations return a boolean indicating whether the lock was acquired within the specified timeout.

This mutex is particularly useful in scenarios where read operations are much more frequent than write operations, such as in caching mechanisms or configuration data access. By allowing concurrent reads, it can significantly improve performance compared to a regular std::mutex, which would serialize all access, including reads. However, it introduces more complexity in usage due to the two distinct lock types.