src/thread/windows/SDL_syssem.c
author Philipp Wiesemann <philipp.wiesemann@arcor.de>
Sun, 08 Jun 2014 12:51:02 +0200
changeset 8844 d35c1b1798c8
parent 8149 681eb46b8ac4
child 9619 b94b6d0bff0f
permissions -rw-r--r--
Fixed typo in source comment.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2014 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         sem->id = CreateSemaphore(NULL, initial_value, 32 * 1024, NULL);
    49         sem->count = initial_value;
    50         if (!sem->id) {
    51             SDL_SetError("Couldn't create semaphore");
    52             SDL_free(sem);
    53             sem = NULL;
    54         }
    55     } else {
    56         SDL_OutOfMemory();
    57     }
    58     return (sem);
    59 }
    60 
    61 /* Free the semaphore */
    62 void
    63 SDL_DestroySemaphore(SDL_sem * sem)
    64 {
    65     if (sem) {
    66         if (sem->id) {
    67             CloseHandle(sem->id);
    68             sem->id = 0;
    69         }
    70         SDL_free(sem);
    71     }
    72 }
    73 
    74 int
    75 SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
    76 {
    77     int retval;
    78     DWORD dwMilliseconds;
    79 
    80     if (!sem) {
    81         return SDL_SetError("Passed a NULL sem");
    82     }
    83 
    84     if (timeout == SDL_MUTEX_MAXWAIT) {
    85         dwMilliseconds = INFINITE;
    86     } else {
    87         dwMilliseconds = (DWORD) timeout;
    88     }
    89     switch (WaitForSingleObject(sem->id, dwMilliseconds)) {
    90     case WAIT_OBJECT_0:
    91         InterlockedDecrement(&sem->count);
    92         retval = 0;
    93         break;
    94     case WAIT_TIMEOUT:
    95         retval = SDL_MUTEX_TIMEDOUT;
    96         break;
    97     default:
    98         retval = SDL_SetError("WaitForSingleObject() failed");
    99         break;
   100     }
   101     return retval;
   102 }
   103 
   104 int
   105 SDL_SemTryWait(SDL_sem * sem)
   106 {
   107     return SDL_SemWaitTimeout(sem, 0);
   108 }
   109 
   110 int
   111 SDL_SemWait(SDL_sem * sem)
   112 {
   113     return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
   114 }
   115 
   116 /* Returns the current count of the semaphore */
   117 Uint32
   118 SDL_SemValue(SDL_sem * sem)
   119 {
   120     if (!sem) {
   121         SDL_SetError("Passed a NULL sem");
   122         return 0;
   123     }
   124     return (Uint32)sem->count;
   125 }
   126 
   127 int
   128 SDL_SemPost(SDL_sem * sem)
   129 {
   130     if (!sem) {
   131         return SDL_SetError("Passed a NULL sem");
   132     }
   133     /* Increase the counter in the first place, because
   134      * after a successful release the semaphore may
   135      * immediately get destroyed by another thread which
   136      * is waiting for this semaphore.
   137      */
   138     InterlockedIncrement(&sem->count);
   139     if (ReleaseSemaphore(sem->id, 1, NULL) == FALSE) {
   140         InterlockedDecrement(&sem->count);      /* restore */
   141         return SDL_SetError("ReleaseSemaphore() failed");
   142     }
   143     return 0;
   144 }
   145 
   146 #endif /* SDL_THREAD_WINDOWS */
   147 
   148 /* vi: set ts=4 sw=4 expandtab: */