/*

  *

  *

  * Copyright (c) 1994

  * Hewlett-Packard Company

  *

  * Copyright (c) 1996,1997

  * Silicon Graphics Computer Systems, Inc.

  *

  * Copyright (c) 1997

  * Moscow Center for SPARC Technology

  *

  * Copyright (c) 1999 

  * Boris Fomitchev

  *

  * This material is provided "as is", with absolutely no warranty expressed

  * or implied. Any use is at your own risk.

  *

  * Permission to use or copy this software for any purpose is hereby granted 

  * without fee, provided the above notices are retained on all copies.

  * Permission to modify the code and to distribute modified code is granted,

  * provided the above notices are retained, and a notice that the code was

  * modified is included with the above copyright notice.

  *

  */

 #ifndef _STLP_THREADS_C

 #define _STLP_THREADS_C

 #ifndef _STLP_INTERNAL_THREADS_H

 # include <stl/_threads.h>

 #endif

 # if defined (_STLP_EXPOSE_GLOBALS_IMPLEMENTATION)

 # if defined(_STLP_SGI_THREADS)

 #  include <time.h>

 # elif defined (_STLP_UNIX)

 #  include <ctime>

 # if defined (_STLP_USE_NAMESPACES) && ! defined (_STLP_VENDOR_GLOBAL_CSTD)

 using _STLP_VENDOR_CSTD::time_t;

 # endif

 #  include <sys/time.h>

 # endif

 _STLP_BEGIN_NAMESPACE

 # if (_STLP_STATIC_TEMPLATE_DATA > 0)

 #  ifdef _STLP_THREADS

 #  if !defined(_STLP_ATOMIC_EXCHANGE) && (defined(_STLP_PTHREADS) || defined(_STLP_UITHREADS) || defined(_STLP_OS2THREADS) || defined(_STLP_USE_PTHREAD_SPINLOCK))

 template<int __dummy>

 _STLP_STATIC_MUTEX

 _Swap_lock_struct<__dummy>::_S_swap_lock _STLP_MUTEX_INITIALIZER;

 #  endif

 #  endif //_STLP_THREADS

 #  ifndef _STLP_USE_PTHREAD_SPINLOCK

 template <int __inst>

 unsigned _STLP_mutex_spin<__inst>::__max = _STLP_mutex_spin<__inst>::__low_max;

 template <int __inst>

 unsigned _STLP_mutex_spin<__inst>::__last = 0;

 #  endif // _STLP_USE_PTHREAD_SPINLOCK

 # else /* ( _STLP_STATIC_TEMPLATE_DATA > 0 ) */

 #  if defined(_STLP_PTHREADS) || defined(_STLP_UITHREADS) || defined(_STLP_OS2THREADS)

 __DECLARE_INSTANCE(_STLP_STATIC_MUTEX, _Swap_lock_struct<0>::_S_swap_lock, 

                    _STLP_MUTEX_INITIALIZER  );

 #  endif /* _STLP_PTHREADS */

 #  ifndef _STLP_USE_PTHREAD_SPINLOCK

 __DECLARE_INSTANCE(unsigned, _STLP_mutex_spin<0>::__max,  =30);

 __DECLARE_INSTANCE(unsigned, _STLP_mutex_spin<0>::__last, =0);

 #  endif // _STLP_USE_PTHREAD_SPINLOCK

 # endif /* ( _STLP_STATIC_TEMPLATE_DATA > 0 ) */

 #ifndef _STLP_USE_PTHREAD_SPINLOCK

 #ifdef _STLP_SPARC_SOLARIS_THREADS

 // underground function in libc.so; we do not want dependance on librt

 extern "C" int __nanosleep(const struct timespec*, struct timespec*);

 # define _STLP_NANOSLEEP __nanosleep

 #else

 # define _STLP_NANOSLEEP nanosleep

 #endif

 template <int __inst>

 void _STLP_CALL

 _STLP_mutex_spin<__inst>::_S_nsec_sleep(int __log_nsec) {

 #     if defined(_STLP_WIN32THREADS)

 	  if (__log_nsec <= 20) {

         // Note from boost (www.boost.org): 

         // Changed to Sleep(1) from Sleep(0).

         // According to MSDN, Sleep(0) will never yield

         // to a lower-priority thread, whereas Sleep(1)

         // will. Performance seems not to be affected.

 	      Sleep(1);

 	  } else {

 	      Sleep(1 << (__log_nsec - 20));

 	  }

 #    elif defined(_STLP_OS2THREADS)

       if (__log_nsec <= 20) {

          DosSleep(0);

       } else {

          DosSleep(1 << (__log_nsec - 20));

       }

 #     elif defined (_STLP_UNIX)

           timespec __ts;

           /* Max sleep is 2**27nsec ~ 60msec      */

           __ts.tv_sec = 0;

           __ts.tv_nsec = 1 << __log_nsec;

           _STLP_NANOSLEEP(&__ts, 0);

 #     endif

   }

 template <int __inst>

 void  _STLP_CALL

 _STLP_mutex_spin<__inst>::_M_do_lock(volatile __stl_atomic_t* __lock)

 {

 #if defined(_STLP_ATOMIC_EXCHANGE)

   if (_Atomic_swap(__lock, 1)) {

     unsigned __my_spin_max = _STLP_mutex_spin<0>::__max;

     unsigned __my_last_spins = _STLP_mutex_spin<0>::__last;

     volatile unsigned __junk = 17; 	// Value doesn't matter.

     unsigned  __i;

     for (__i = 0; __i < __my_spin_max; ++__i) {

       if (__i < __my_last_spins/2 || *__lock) {

         __junk *= __junk; __junk *= __junk;

         __junk *= __junk; __junk *= __junk;

       } else {

         if (!_Atomic_swap(__lock, 1)) {

           // got it!

           // Spinning worked.  Thus we're probably not being scheduled

           // against the other process with which we were contending.

           // Thus it makes sense to spin longer the next time.

           _STLP_mutex_spin<0>::__last = __i;

           _STLP_mutex_spin<0>::__max = _STLP_mutex_spin<0>::__high_max;

 	    return;

         }

       }

     }

     // We are probably being scheduled against the other process.  Sleep.

     _STLP_mutex_spin<0>::__max = _STLP_mutex_spin<0>::__low_max;

     for (__i = 0 ;; ++__i) {

       int __log_nsec = __i + 6;

       if (__log_nsec > 27) __log_nsec = 27;

       if (!_Atomic_swap(__lock, 1)) {

 	  break;

       }

       _S_nsec_sleep(__log_nsec);

     }

   } /* first _Atomic_swap */

 # endif

 }

 #endif // _STLP_USE_PTHREAD_SPINLOCK

 _STLP_END_NAMESPACE

 # endif /* BUILDING_STLPORT */

 #endif /*  _STLP_THREADS_C */

 // Local Variables:

 // mode:C++

 // End: