mutex.cpp

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#include <iostream>      // for cout
#include <rw/_mutex.h>   // for __rw::__rw_mutex
 
#include <examples.h>
 
 
#ifdef _RWSTD_REENTRANT
 
// An integer shared amongst multiple threads.
int shared;
 
// A mutex used to synchronize updates to shared.
__rw::__rw_mutex shared_mutex;
 
// Increment shared by one.  Uses a mutex directly.
void increment_shared ()
{
    shared_mutex._C_acquire();  // Lock the mutex.
    ++shared;
    shared_mutex._C_release();  // Unlock the mutex.
}
 
 
// Decrement shared by one.  Uses a mutex guard.
void decrement_shared ()
{
    _RWSTD_MT_GUARD (shared_mutex);  // Acquire the lock on shared_mutex.
    --shared;
    // The lock on shared is released when destructor is called on guard.
}
 
 
int exchange_shared ()
{
    int new_value = shared;
 
    new_value *= new_value;
 
    // atomically assign new_value to shared and return shared's old value
    int old_value = _RWSTD_ATOMIC_SWAP (shared, new_value, shared_mutex);
 
    return old_value;
}
 
#endif   // _RWSTD_REENTRANT
 
 
int main()
{
#ifdef _RWSTD_REENTRANT
 
    increment_shared();
    decrement_shared();
 
    std::cout << "Multi Threading enabled" << std::endl;
 
#else   // if !defined (_RWSTD_REENTRANT)
 
    std::cout << "Multi Threading not enabled" << std::endl;
 
#endif   // _RWSTD_REENTRANT
 
    return 0;
}