src/thread/windows/SDL_syssem.c
author David Ludwig <dludwig@pobox.com>
Thu, 26 Nov 2015 13:51:03 -0500
changeset 9930 84285c1d8ca4
parent 9619 b94b6d0bff0f
child 9998 f67cf37e9cd4
permissions -rw-r--r--
WinRT: bug-fix - SDL_SetThreadPriority() didn't work on WinRT 8.x platforms

WinRT 8.0 (Phone and non-Phone) didn't offer an API to set an already-created
thread's priority. WinRT 8.1 offered this API, along with several other
Win32 thread functions that were previously unavailable (in WinRT).

This change makes WinRT 8.1+ platforms use SDL's Win32 backend.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2015 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 #if __WINRT__
    94     switch (WaitForSingleObjectEx(sem->id, dwMilliseconds, FALSE)) {
    95 #else
    96     switch (WaitForSingleObject(sem->id, dwMilliseconds)) {
    97 #endif
    98     case WAIT_OBJECT_0:
    99         InterlockedDecrement(&sem->count);
   100         retval = 0;
   101         break;
   102     case WAIT_TIMEOUT:
   103         retval = SDL_MUTEX_TIMEDOUT;
   104         break;
   105     default:
   106         retval = SDL_SetError("WaitForSingleObject() failed");
   107         break;
   108     }
   109     return retval;
   110 }
   111 
   112 int
   113 SDL_SemTryWait(SDL_sem * sem)
   114 {
   115     return SDL_SemWaitTimeout(sem, 0);
   116 }
   117 
   118 int
   119 SDL_SemWait(SDL_sem * sem)
   120 {
   121     return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
   122 }
   123 
   124 /* Returns the current count of the semaphore */
   125 Uint32
   126 SDL_SemValue(SDL_sem * sem)
   127 {
   128     if (!sem) {
   129         SDL_SetError("Passed a NULL sem");
   130         return 0;
   131     }
   132     return (Uint32)sem->count;
   133 }
   134 
   135 int
   136 SDL_SemPost(SDL_sem * sem)
   137 {
   138     if (!sem) {
   139         return SDL_SetError("Passed a NULL sem");
   140     }
   141     /* Increase the counter in the first place, because
   142      * after a successful release the semaphore may
   143      * immediately get destroyed by another thread which
   144      * is waiting for this semaphore.
   145      */
   146     InterlockedIncrement(&sem->count);
   147     if (ReleaseSemaphore(sem->id, 1, NULL) == FALSE) {
   148         InterlockedDecrement(&sem->count);      /* restore */
   149         return SDL_SetError("ReleaseSemaphore() failed");
   150     }
   151     return 0;
   152 }
   153 
   154 #endif /* SDL_THREAD_WINDOWS */
   155 
   156 /* vi: set ts=4 sw=4 expandtab: */