--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/thread/nds/SDL_sysmutex.c	Wed Aug 27 15:10:03 2008 +0000
@@ -0,0 +1,142 @@
+/*
+    SDL - Simple DirectMedia Layer
+    Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public
+    License along with this library; if not, write to the Free
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+    Sam Lantinga
+    slouken@devolution.com
+*/
+
+#ifdef SAVE_RCSID
+static char rcsid =
+    "@(#) $Id: SDL_sysmutex.c,v 1.2 2001/04/26 16:50:18 hercules Exp $";
+#endif
+
+/* An implementation of mutexes using semaphores */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "SDL_error.h"
+#include "SDL_thread.h"
+#include "SDL_systhread_c.h"
+
+
+struct SDL_mutex
+{
+    int recursive;
+    Uint32 owner;
+    SDL_sem *sem;
+};
+
+/* Create a mutex */
+SDL_mutex *
+SDL_CreateMutex(void)
+{
+    SDL_mutex *mutex;
+
+    /* Allocate mutex memory */
+    mutex = (SDL_mutex *) 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) {
+            free(mutex);
+            mutex = NULL;
+        }
+    } else {
+        SDL_OutOfMemory();
+    }
+    return mutex;
+}
+
+/* Free the mutex */
+void
+SDL_DestroyMutex(SDL_mutex * mutex)
+{
+    if (mutex) {
+        if (mutex->sem) {
+            SDL_DestroySemaphore(mutex->sem);
+        }
+        free(mutex);
+    }
+}
+
+/* Lock the semaphore */
+int
+SDL_mutexP(SDL_mutex * mutex)
+{
+#ifdef DISABLE_THREADS
+    return 0;
+#else
+    Uint32 this_thread;
+
+    if (mutex == NULL) {
+        SDL_SetError("Passed a NULL mutex");
+        return -1;
+    }
+
+    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 /* DISABLE_THREADS */
+}
+
+/* Unlock the mutex */
+int
+SDL_mutexV(SDL_mutex * mutex)
+{
+#ifdef DISABLE_THREADS
+    return 0;
+#else
+    if (mutex == NULL) {
+        SDL_SetError("Passed a NULL mutex");
+        return -1;
+    }
+
+    /* If we don't own the mutex, we can't unlock it */
+    if (SDL_ThreadID() != mutex->owner) {
+        SDL_SetError("mutex not owned by this thread");
+        return -1;
+    }
+
+    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 /* DISABLE_THREADS */
+}