N3DS port (squashed)

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

src/file/SDL_rwops.c

@@ -53,6 +53,10 @@
 #include "cocoa/SDL_rwopsbundlesupport.h"
 #endif /* __APPLE__ */
 
+#ifdef __3DS__
+#include "n3ds/SDL_rwopsromfs.h"
+#endif /* __3DS__ */
+
 #ifdef __ANDROID__
 #include "../core/android/SDL_android.h"
 #include "SDL_system.h"
@@ -601,6 +605,8 @@ SDL_RWFromFile(const char *file, const char *mode)
         #elif __WINRT__
         FILE *fp = NULL;
         fopen_s(&fp, file, mode);
+        #elif __3DS__
+        FILE *fp = N3DS_FileOpen(file, mode);
         #else
         FILE *fp = fopen(file, mode);
         #endif

src/file/n3ds/SDL_rwopsromfs.c

@@ -0,0 +1,56 @@
+/*
+  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_rwopsromfs.h"
+
+/* Nintendo 3DS applications may embed resources in the executable. The
+  resources are stored in a special read-only partition prefixed with
+  'romfs:/'. As such, when opening a file, we should first try the romfs
+  unless sdmc is specifically mentionned.
+*/
+FILE *
+N3DS_FileOpen(const char *file, const char *mode)
+{
+    FILE *fp = NULL;
+    char romfs_path[4096];
+
+    /* romfs are read-only */
+    if (SDL_strchr(mode, 'r') == NULL) {
+        return fopen(file, mode);
+    }
+
+    /* If the path has an explicit prefix, we skip the guess work */
+    if (SDL_strncmp("romfs:/", file, 7) == 0 ||
+        SDL_strncmp("sdmc:/", file, 6) == 0) {
+        return fopen(file, mode);
+    }
+
+    SDL_snprintf(romfs_path, 4096, "romfs:/%s", file);
+
+    fp = fopen(romfs_path, mode);
+    if (fp == NULL) {
+        fp = fopen(file, mode);
+    }
+
+    return fp;
+}
+
+/* vi: set sts=4 ts=4 sw=4 expandtab: */

src/file/n3ds/SDL_rwopsromfs.h

@@ -0,0 +1,30 @@
+/*
+  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"
+
+#ifndef SDL_rwopsromfs_h_
+#define SDL_rwopsromfs_h_
+
+FILE *N3DS_FileOpen(const char *file, const char *mode);
+
+#endif /* SDL_rwopsromfs_h_ */
+
+/* vi: set sts=4 ts=4 sw=4 expandtab: */