1 /*

     2     SDL - Simple DirectMedia Layer

     3     Copyright (C) 1997-2006 Sam Lantinga

     4 

     5     This library is free software; you can redistribute it and/or

     6     modify it under the terms of the GNU Lesser General Public

     7     License as published by the Free Software Foundation; either

     8     version 2.1 of the License, or (at your option) any later version.

     9 

    10     This library is distributed in the hope that it will be useful,

    11     but WITHOUT ANY WARRANTY; without even the implied warranty of

    12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    13     Lesser General Public License for more details.

    14 

    15     You should have received a copy of the GNU Lesser General Public

    16     License along with this library; if not, write to the Free Software

    17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    18 

    19     Sam Lantinga

    20     slouken@libsdl.org

    21 */

    22 

    23 #include <errno.h>

    24 

    25 #include "SDL_config.h"

    26 

    27 /* An implementation of semaphores using mutexes and condition variables */

    28 

    29 #include "SDL_timer.h"

    30 #include "SDL_thread.h"

    31 #include "SDL_systhread_c.h"

    32 

    33 

    34 #if SDL_THREADS_DISABLED

    35 

    36 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)

    37 {

    38 	SDL_SetError("SDL not configured with thread support");

    39 	return (SDL_sem *)0;

    40 }

    41 

    42 void SDL_DestroySemaphore(SDL_sem *sem)

    43 {

    44 	return;

    45 }

    46 

    47 int SDL_SemTryWait(SDL_sem *sem)

    48 {

    49 	SDL_SetError("SDL not configured with thread support");

    50 	return -1;

    51 }

    52 

    53 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)

    54 {

    55 	SDL_SetError("SDL not configured with thread support");

    56 	return -1;

    57 }

    58 

    59 int SDL_SemWait(SDL_sem *sem)

    60 {

    61 	SDL_SetError("SDL not configured with thread support");

    62 	return -1;

    63 }

    64 

    65 Uint32 SDL_SemValue(SDL_sem *sem)

    66 {

    67 	return 0;

    68 }

    69 

    70 int SDL_SemPost(SDL_sem *sem)

    71 {

    72 	SDL_SetError("SDL not configured with thread support");

    73 	return -1;

    74 }

    75 

    76 #else

    77 

    78 #include <kos/sem.h>

    79 

    80 struct SDL_semaphore

    81 {

    82 	semaphore_t sem;

    83 };

    84 

    85 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)

    86 {

    87 	return (SDL_sem *)sem_create(initial_value);

    88 }

    89 

    90 /* WARNING:

    91    You cannot call this function when another thread is using the semaphore.

    92 */

    93 void SDL_DestroySemaphore(SDL_sem *sem)

    94 {

    95 	if ( ! sem ) {

    96 		SDL_SetError("Passed a NULL semaphore");

    97 		return;

    98 	}

    99 

   100 	sem_destroy(&sem->sem);

   101 }

   102 

   103 int SDL_SemTryWait(SDL_sem *sem)

   104 {

   105 	int retval;

   106 

   107 	if ( ! sem ) {

   108 		SDL_SetError("Passed a NULL semaphore");

   109 		return -1;

   110 	}

   111 

   112 	retval = sem_trywait(&sem->sem);

   113 	if (retval==0) return 0;

   114 	else return SDL_MUTEX_TIMEDOUT;

   115 

   116 	return retval;

   117 }

   118 

   119 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)

   120 {

   121 	int retval;

   122 

   123 	if ( ! sem ) {

   124 		SDL_SetError("Passed a NULL semaphore");

   125 		return -1;

   126 	}

   127 

   128 	/* A timeout of 0 is an easy case */

   129 	if ( timeout == 0 ) {

   130 		return SDL_SemTryWait(sem);

   131 	}

   132 

   133 	retval = sem_wait_timed(&sem->sem,timeout);

   134 	if (retval==-1) retval= SDL_MUTEX_TIMEDOUT;

   135 

   136 	return retval;

   137 }

   138 

   139 int SDL_SemWait(SDL_sem *sem)

   140 {

   141 	int retval;

   142 

   143 	if ( ! sem ) {

   144 		SDL_SetError("Passed a NULL semaphore");

   145 		return -1;

   146 	}

   147 

   148 	while ( ((retval = sem_wait(&sem->sem)) == -1) && (errno == EINTR) ) {}

   149 	return retval;

   150 }

   151 

   152 Uint32 SDL_SemValue(SDL_sem *sem)

   153 {

   154 	if ( ! sem ) {

   155 		SDL_SetError("Passed a NULL semaphore");

   156 		return -1;

   157 	}

   158 

   159 	return sem_count(&sem->sem);

   160 }

   161 

   162 int SDL_SemPost(SDL_sem *sem)

   163 {

   164 	if ( ! sem ) {

   165 		SDL_SetError("Passed a NULL semaphore");

   166 		return -1;

   167 	}

   168 

   169 	sem_signal(&sem->sem);

   170 	return 0;

   171 }

   172 

   173 #endif /* SDL_THREADS_DISABLED */