SDL_sysmutex.c File Reference

#include "../../SDL_internal.h"
#include "SDL_thread.h"
#include "SDL_systhread_c.h"

Include dependency graph for SDL_sysmutex.c:

Go to the source code of this file.

Data Structures
struct	SDL_mutex

Functions
SDL_mutex *	SDL_CreateMutex (void)
void	SDL_DestroyMutex (SDL_mutex *mutex)
int	SDL_LockMutex (SDL_mutex *mutex)
int	SDL_TryLockMutex (SDL_mutex *mutex)
int	SDL_mutexV (SDL_mutex *mutex)

Function Documentation

SDL_CreateMutex()

SDL_mutex* SDL_CreateMutex

(

void

)

Create a mutex, initialized unlocked.

Definition at line 38 of file SDL_sysmutex.c.

{
    SDL_mutex *mutex;
 
    /* Allocate mutex memory */
    mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex));
    if (mutex) {
        /* Create the mutex semaphore, with initial value 1 */
        mutex->sem = SDL_CreateSemaphore(1);
        mutex->recursive = 0;
        mutex->owner = 0;
        if (!mutex->sem) {
            SDL_free(mutex);
            mutex = NULL;
        }
    } else {
        SDL_OutOfMemory();
    }
    return mutex;
}

SDL_DestroyMutex()

void SDL_DestroyMutex

(

SDL_mutex *

mutex

)

Destroy a mutex.

Definition at line 61 of file SDL_sysmutex.c.

{
    if (mutex) {
        if (mutex->sem) {
            SDL_DestroySemaphore(mutex->sem);
        }
        SDL_free(mutex);
    }
}

SDL_LockMutex()

int SDL_LockMutex

(

SDL_mutex *

mutex

)

Definition at line 73 of file SDL_sysmutex.c.

{
#if SDL_THREADS_DISABLED
    return 0;
#else
    SDL_threadID this_thread;
 
    if (mutex == NULL) {
        return SDL_SetError("Passed a NULL mutex");
    }
 
    this_thread = SDL_ThreadID();
    if (mutex->owner == this_thread) {
        ++mutex->recursive;
    } else {
        /* The order of operations is important.
           We set the locking thread id after we obtain the lock
           so unlocks from other threads will fail.
         */
        SDL_SemWait(mutex->sem);
        mutex->owner = this_thread;
        mutex->recursive = 0;
    }
 
    return 0;
#endif /* SDL_THREADS_DISABLED */
}

SDL_mutexV()

int SDL_mutexV

(

SDL_mutex *

mutex

)

Definition at line 136 of file SDL_sysmutex.c.

{
#if SDL_THREADS_DISABLED
    return 0;
#else
    if (mutex == NULL) {
        return SDL_SetError("Passed a NULL mutex");
    }
 
    /* If we don't own the mutex, we can't unlock it */
    if (SDL_ThreadID() != mutex->owner) {
        return SDL_SetError("mutex not owned by this thread");
    }
 
    if (mutex->recursive) {
        --mutex->recursive;
    } else {
        /* The order of operations is important.
           First reset the owner so another thread doesn't lock
           the mutex and set the ownership before we reset it,
           then release the lock semaphore.
         */
        mutex->owner = 0;
        SDL_SemPost(mutex->sem);
    }
    return 0;
#endif /* SDL_THREADS_DISABLED */
}

References mutex, NULL, SDL_mutex::owner, SDL_mutex::recursive, SDL_SemPost, SDL_SetError, SDL_ThreadID, and SDL_mutex::sem.

SDL_TryLockMutex()

int SDL_TryLockMutex

(

SDL_mutex *

mutex

)

Try to lock the mutex

Returns

0, SDL_MUTEX_TIMEDOUT, or -1 on error

Definition at line 103 of file SDL_sysmutex.c.

{
#if SDL_THREADS_DISABLED
    return 0;
#else
    int retval = 0;
    SDL_threadID this_thread;
 
    if (mutex == NULL) {
        return SDL_SetError("Passed a NULL mutex");
    }
 
    this_thread = SDL_ThreadID();
    if (mutex->owner == this_thread) {
        ++mutex->recursive;
    } else {
        /* The order of operations is important.
         We set the locking thread id after we obtain the lock
         so unlocks from other threads will fail.
         */
        retval = SDL_SemWait(mutex->sem);
        if (retval == 0) {
            mutex->owner = this_thread;
            mutex->recursive = 0;
        }
    }
 
    return retval;
#endif /* SDL_THREADS_DISABLED */
}