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FORK: Simple Directmedia Layer
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SDL_syssem.c (3734B)

      1 /*
      2   Simple DirectMedia Layer
      3   Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>
      4 
      5   This software is provided 'as-is', without any express or implied
      6   warranty.  In no event will the authors be held liable for any damages
      7   arising from the use of this software.
      8 
      9   Permission is granted to anyone to use this software for any purpose,
     10   including commercial applications, and to alter it and redistribute it
     11   freely, subject to the following restrictions:
     12 
     13   1. The origin of this software must not be misrepresented; you must not
     14      claim that you wrote the original software. If you use this software
     15      in a product, an acknowledgment in the product documentation would be
     16      appreciated but is not required.
     17   2. Altered source versions must be plainly marked as such, and must not be
     18      misrepresented as being the original software.
     19   3. This notice may not be removed or altered from any source distribution.
     20 */
     21 #include "../../SDL_internal.h"
     22 
     23 #if SDL_THREAD_WINDOWS
     24 
     25 /* Semaphore functions using the Win32 API */
     26 
     27 #include "../../core/windows/SDL_windows.h"
     28 
     29 #include "SDL_thread.h"
     30 
     31 struct SDL_semaphore
     32 {
     33     HANDLE id;
     34     LONG count;
     35 };
     36 
     37 
     38 /* Create a semaphore */
     39 SDL_sem *
     40 SDL_CreateSemaphore(Uint32 initial_value)
     41 {
     42     SDL_sem *sem;
     43 
     44     /* Allocate sem memory */
     45     sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
     46     if (sem) {
     47         /* Create the semaphore, with max value 32K */
     48 #if __WINRT__
     49         sem->id = CreateSemaphoreEx(NULL, initial_value, 32 * 1024, NULL, 0, SEMAPHORE_ALL_ACCESS);
     50 #else
     51         sem->id = CreateSemaphore(NULL, initial_value, 32 * 1024, NULL);
     52 #endif
     53         sem->count = initial_value;
     54         if (!sem->id) {
     55             SDL_SetError("Couldn't create semaphore");
     56             SDL_free(sem);
     57             sem = NULL;
     58         }
     59     } else {
     60         SDL_OutOfMemory();
     61     }
     62     return (sem);
     63 }
     64 
     65 /* Free the semaphore */
     66 void
     67 SDL_DestroySemaphore(SDL_sem * sem)
     68 {
     69     if (sem) {
     70         if (sem->id) {
     71             CloseHandle(sem->id);
     72             sem->id = 0;
     73         }
     74         SDL_free(sem);
     75     }
     76 }
     77 
     78 int
     79 SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
     80 {
     81     int retval;
     82     DWORD dwMilliseconds;
     83 
     84     if (!sem) {
     85         return SDL_SetError("Passed a NULL sem");
     86     }
     87 
     88     if (timeout == SDL_MUTEX_MAXWAIT) {
     89         dwMilliseconds = INFINITE;
     90     } else {
     91         dwMilliseconds = (DWORD) timeout;
     92     }
     93     switch (WaitForSingleObjectEx(sem->id, dwMilliseconds, FALSE)) {
     94     case WAIT_OBJECT_0:
     95         InterlockedDecrement(&sem->count);
     96         retval = 0;
     97         break;
     98     case WAIT_TIMEOUT:
     99         retval = SDL_MUTEX_TIMEDOUT;
    100         break;
    101     default:
    102         retval = SDL_SetError("WaitForSingleObject() failed");
    103         break;
    104     }
    105     return retval;
    106 }
    107 
    108 int
    109 SDL_SemTryWait(SDL_sem * sem)
    110 {
    111     return SDL_SemWaitTimeout(sem, 0);
    112 }
    113 
    114 int
    115 SDL_SemWait(SDL_sem * sem)
    116 {
    117     return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
    118 }
    119 
    120 /* Returns the current count of the semaphore */
    121 Uint32
    122 SDL_SemValue(SDL_sem * sem)
    123 {
    124     if (!sem) {
    125         SDL_SetError("Passed a NULL sem");
    126         return 0;
    127     }
    128     return (Uint32)sem->count;
    129 }
    130 
    131 int
    132 SDL_SemPost(SDL_sem * sem)
    133 {
    134     if (!sem) {
    135         return SDL_SetError("Passed a NULL sem");
    136     }
    137     /* Increase the counter in the first place, because
    138      * after a successful release the semaphore may
    139      * immediately get destroyed by another thread which
    140      * is waiting for this semaphore.
    141      */
    142     InterlockedIncrement(&sem->count);
    143     if (ReleaseSemaphore(sem->id, 1, NULL) == FALSE) {
    144         InterlockedDecrement(&sem->count);      /* restore */
    145         return SDL_SetError("ReleaseSemaphore() failed");
    146     }
    147     return 0;
    148 }
    149 
    150 #endif /* SDL_THREAD_WINDOWS */
    151 
    152 /* vi: set ts=4 sw=4 expandtab: */