/*

 *

 *

 * 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 */

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