src/thread/psp/SDL_sysmutex.c
author Sam Lantinga <slouken@libsdl.org>
Sat, 02 Jan 2016 10:10:34 -0800
changeset 9998 f67cf37e9cd4
parent 9619 b94b6d0bff0f
child 10737 3406a0f8b041
permissions -rw-r--r--
Updated copyright to 2016
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2016 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_PSP
    24 
    25 /* An implementation of mutexes using semaphores */
    26 
    27 #include "SDL_thread.h"
    28 #include "SDL_systhread_c.h"
    29 
    30 
    31 struct SDL_mutex
    32 {
    33     int recursive;
    34     SDL_threadID owner;
    35     SDL_sem *sem;
    36 };
    37 
    38 /* Create a mutex */
    39 SDL_mutex *
    40 SDL_CreateMutex(void)
    41 {
    42     SDL_mutex *mutex;
    43 
    44     /* Allocate mutex memory */
    45     mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex));
    46     if (mutex) {
    47         /* Create the mutex semaphore, with initial value 1 */
    48         mutex->sem = SDL_CreateSemaphore(1);
    49         mutex->recursive = 0;
    50         mutex->owner = 0;
    51         if (!mutex->sem) {
    52             SDL_free(mutex);
    53             mutex = NULL;
    54         }
    55     } else {
    56         SDL_OutOfMemory();
    57     }
    58     return mutex;
    59 }
    60 
    61 /* Free the mutex */
    62 void
    63 SDL_DestroyMutex(SDL_mutex * mutex)
    64 {
    65     if (mutex) {
    66         if (mutex->sem) {
    67             SDL_DestroySemaphore(mutex->sem);
    68         }
    69         SDL_free(mutex);
    70     }
    71 }
    72 
    73 /* Lock the semaphore */
    74 int
    75 SDL_mutexP(SDL_mutex * mutex)
    76 {
    77 #if SDL_THREADS_DISABLED
    78     return 0;
    79 #else
    80     SDL_threadID this_thread;
    81 
    82     if (mutex == NULL) {
    83         return SDL_SetError("Passed a NULL mutex");
    84     }
    85 
    86     this_thread = SDL_ThreadID();
    87     if (mutex->owner == this_thread) {
    88         ++mutex->recursive;
    89     } else {
    90         /* The order of operations is important.
    91            We set the locking thread id after we obtain the lock
    92            so unlocks from other threads will fail.
    93          */
    94         SDL_SemWait(mutex->sem);
    95         mutex->owner = this_thread;
    96         mutex->recursive = 0;
    97     }
    98 
    99     return 0;
   100 #endif /* SDL_THREADS_DISABLED */
   101 }
   102 
   103 /* Unlock the mutex */
   104 int
   105 SDL_mutexV(SDL_mutex * mutex)
   106 {
   107 #if SDL_THREADS_DISABLED
   108     return 0;
   109 #else
   110     if (mutex == NULL) {
   111         return SDL_SetError("Passed a NULL mutex");
   112     }
   113 
   114     /* If we don't own the mutex, we can't unlock it */
   115     if (SDL_ThreadID() != mutex->owner) {
   116         return SDL_SetError("mutex not owned by this thread");
   117     }
   118 
   119     if (mutex->recursive) {
   120         --mutex->recursive;
   121     } else {
   122         /* The order of operations is important.
   123            First reset the owner so another thread doesn't lock
   124            the mutex and set the ownership before we reset it,
   125            then release the lock semaphore.
   126          */
   127         mutex->owner = 0;
   128         SDL_SemPost(mutex->sem);
   129     }
   130     return 0;
   131 #endif /* SDL_THREADS_DISABLED */
   132 }
   133 
   134 #endif /* SDL_THREAD_PSP */
   135 
   136 /* vi: set ts=4 sw=4 expandtab: */