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      1 /*
      2     SDL - Simple DirectMedia Layer
      3     Copyright (C) 1997-2012 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 (at) libsdl.org
     21 */
     22 #include "SDL_config.h"
     23 
     24 /* Semaphores in the BeOS environment */
     25 
     26 #include <be/kernel/OS.h>
     27 
     28 #include "SDL_thread.h"
     29 
     30 
     31 struct SDL_semaphore {
     32 	sem_id id;
     33 };
     34 
     35 /* Create a counting semaphore */
     36 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
     37 {
     38 	SDL_sem *sem;
     39 
     40 	sem = (SDL_sem *)SDL_malloc(sizeof(*sem));
     41 	if ( sem ) {
     42 		sem->id = create_sem(initial_value, "SDL semaphore");
     43 		if ( sem->id < B_NO_ERROR ) {
     44 			SDL_SetError("create_sem() failed");
     45 			SDL_free(sem);
     46 			sem = NULL;
     47 		}
     48 	} else {
     49 		SDL_OutOfMemory();
     50 	}
     51 	return(sem);
     52 }
     53 
     54 /* Free the semaphore */
     55 void SDL_DestroySemaphore(SDL_sem *sem)
     56 {
     57 	if ( sem ) {
     58 		if ( sem->id >= B_NO_ERROR ) {
     59 			delete_sem(sem->id);
     60 		}
     61 		SDL_free(sem);
     62 	}
     63 }
     64 
     65 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
     66 {
     67 	int32 val;
     68 	int retval;
     69 
     70 	if ( ! sem ) {
     71 		SDL_SetError("Passed a NULL semaphore");
     72 		return -1;
     73 	}
     74 
     75   tryagain:
     76 	if ( timeout == SDL_MUTEX_MAXWAIT ) {
     77 		val = acquire_sem(sem->id);
     78 	} else {
     79 		timeout *= 1000; /* BeOS uses a timeout in microseconds */
     80 		val = acquire_sem_etc(sem->id, 1, B_RELATIVE_TIMEOUT, timeout);
     81 	}
     82 	switch (val) {
     83 	    case B_INTERRUPTED:
     84 		goto tryagain;
     85 	    case B_NO_ERROR:
     86 		retval = 0;
     87 		break;
     88 	    case B_TIMED_OUT:
     89 		retval = SDL_MUTEX_TIMEDOUT;
     90 		break;
     91 	    case B_WOULD_BLOCK:
     92 		retval = SDL_MUTEX_TIMEDOUT;
     93 		break;
     94 	    default:
     95 		SDL_SetError("acquire_sem() failed");
     96 		retval = -1;
     97 		break;
     98 	}
     99 
    100 	return retval;
    101 }
    102 
    103 int SDL_SemTryWait(SDL_sem *sem)
    104 {
    105 	return SDL_SemWaitTimeout(sem, 0);
    106 }
    107 
    108 int SDL_SemWait(SDL_sem *sem)
    109 {
    110 	return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
    111 }
    112 
    113 /* Returns the current count of the semaphore */
    114 Uint32 SDL_SemValue(SDL_sem *sem)
    115 {
    116 	int32 count;
    117 	Uint32 value;
    118 
    119 	value = 0;
    120 	if ( sem ) {
    121 		get_sem_count(sem->id, &count);
    122 		if ( count > 0 ) {
    123 			value = (Uint32)count;
    124 		}
    125 	}
    126 	return value;
    127 }
    128 
    129 /* Atomically increases the semaphore's count (not blocking) */
    130 int SDL_SemPost(SDL_sem *sem)
    131 {
    132 	if ( ! sem ) {
    133 		SDL_SetError("Passed a NULL semaphore");
    134 		return -1;
    135 	}
    136 
    137 	if ( release_sem(sem->id) != B_NO_ERROR ) {
    138 		SDL_SetError("release_sem() failed");
    139 		return -1;
    140 	}
    141 	return 0;
    142 }
    143