--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/thread/nds/SDL_sysmutex.c	Tue Jun 10 06:57:57 2008 +0000
@@ -0,0 +1,137 @@
+/*
+    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 */
+}