N3DS port (squashed)

A dedicated renderer using Citro3D would likely allow for better
much better graphical performances.

src/thread/n3ds/SDL_sysmutex.c

@@ -0,0 +1,93 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "../../SDL_internal.h"
+
+#ifdef SDL_THREAD_N3DS
+
+/* An implementation of mutexes using libctru's RecursiveLock */
+
+#include "SDL_sysmutex_c.h"
+
+/* Create a mutex */
+SDL_mutex *
+SDL_CreateMutex(void)
+{
+    SDL_mutex *mutex;
+
+    /* Allocate mutex memory */
+    mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex));
+    if (mutex) {
+        RecursiveLock_Init(&mutex->lock);
+    } else {
+        SDL_OutOfMemory();
+    }
+    return mutex;
+}
+
+/* Free the mutex */
+void
+SDL_DestroyMutex(SDL_mutex *mutex)
+{
+    if (mutex) {
+        SDL_free(mutex);
+    }
+}
+
+/* Lock the mutex */
+int
+SDL_LockMutex(SDL_mutex *mutex)
+{
+    if (mutex == NULL) {
+        return SDL_SetError("Passed a NULL mutex");
+    }
+
+    RecursiveLock_Lock(&mutex->lock);
+
+    return 0;
+}
+
+/* try Lock the mutex */
+int
+SDL_TryLockMutex(SDL_mutex *mutex)
+{
+    if (mutex == NULL) {
+        return SDL_SetError("Passed a NULL mutex");
+    }
+
+    return RecursiveLock_TryLock(&mutex->lock);
+}
+
+/* Unlock the mutex */
+int
+SDL_mutexV(SDL_mutex *mutex)
+{
+    if (mutex == NULL) {
+        return SDL_SetError("Passed a NULL mutex");
+    }
+
+    RecursiveLock_Unlock(&mutex->lock);
+
+    return 0;
+}
+
+#endif /* SDL_THREAD_N3DS */
+
+/* vi: set sts=4 ts=4 sw=4 expandtab: */