Reader writer locks

The reader-writer lock (SRWLOCK) wrapper is defined in wil/resource.h as part of the RAII resource wrappers library.

The WIL srwlock RAII class manages an SRWLOCK exposing appropriate locking methods:

// declare a lock:
wil::srwlock m_lock;

// Locks and unlocks when the returned variable goes out of scope
auto lock = m_lock.lock_exclusive();        // or 'lock_shared' for a shared lock

// Attempt to lock. If successful, the lock is released when the returned variable goes out of scope.
auto lock = m_lock.try_lock_exclusive();    // or 'try_lock_shared' for a shared lock
if (lock)
{
    // lock was successfully acquired by try_lock_exclusive()...
}

// To release a lock before the returned variable goes out of scope use reset()
auto lock = m_lock.lock_exclusive();        // or 'lock_shared' for a shared lock
// My code...
lock.reset();

Though the need should be rare, if you have a raw SRWLOCK without the WIL class, you can use the same locking mechanisms (return of an RAII class) through methods named identically to the system counterparts in the wil namespace:

auto lock = wil::AcquireSRWLockExclusive(&rwlock);
auto lock = wil::AcquireSRWLockShared(&rwlock);
auto lock = wil::TryAcquireSRWLockExclusive(&rwlock);
auto lock = wil::TryAcquireSRWLockShared(&rwlock);

Gotchas

Lock guard object

There are some gotchas in the use of the lock guard object returned by the lock_xxx() and try_lock_xxx() methods, and by the AcquireXxx and TryAcquireXxx functions. See Lock guard object for details.