// class for mutual exclusion using the posix thread library #include <pthread.h>#include <errno.h>class leda_mutex {  leda_mutex(const leda_mutex& m) { pthread_mutex_init (&lock_, NULL); }   leda_mutex operator=(const leda_mutex& m)   { pthread_mutex_init (&lock_, NULL); return *this; }public:  leda_mutex() { pthread_mutex_init (&lock_, NULL); } ~leda_mutex() { pthread_mutex_destroy (&lock_); }  void acquire() { pthread_mutex_lock (&lock_); }  void lock()    { pthread_mutex_lock (&lock_); }  void enter()   { pthread_mutex_lock (&lock_); }  void release() { pthread_mutex_unlock (&lock_); }  void unlock()  { pthread_mutex_unlock (&lock_); }  void exit()    { pthread_mutex_unlock (&lock_); }  int trylock()  { return pthread_mutex_trylock (&lock_); }  int tryenter() { return pthread_mutex_trylock (&lock_); }  private:  pthread_mutex_t lock_;};