SDL

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/*
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  Simple DirectMedia Layer
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  Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely, subject to the following restrictions:
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  1. The origin of this software must not be misrepresented; you must not
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     claim that you wrote the original software. If you use this software
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     in a product, an acknowledgment in the product documentation would be
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     appreciated but is not required.
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  2. Altered source versions must be plainly marked as such, and must not be
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     misrepresented as being the original software.
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  3. This notice may not be removed or altered from any source distribution.
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*/
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#include "SDL_iostreamromfs.h"
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// Checks if the mode is a kind of reading
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static bool IsReadMode(const char *mode);
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// Checks if the file starts with the given prefix
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static bool HasPrefix(const char *file, const char *prefix);
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static FILE *TryOpenFile(const char *file, const char *mode);
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static FILE *TryOpenInRomfs(const char *file, const char *mode);
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/* Nintendo 3DS applications may embed resources in the executable. The
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  resources are stored in a special read-only partition prefixed with
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  'romfs:/'. As such, when opening a file, we should first try the romfs
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  unless sdmc is specifically mentioned.
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*/
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FILE *N3DS_FileOpen(const char *file, const char *mode)
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{
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    // romfs are read-only
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    if (!IsReadMode(mode)) {
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        return fopen(file, mode);
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    }
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    // If the path has an explicit prefix, we skip the guess work
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    if (HasPrefix(file, "romfs:/") || HasPrefix(file, "sdmc:/")) {
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        return fopen(file, mode);
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    }
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    return TryOpenFile(file, mode);
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}
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static bool IsReadMode(const char *mode)
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{
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    return SDL_strchr(mode, 'r') != NULL;
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}
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static bool HasPrefix(const char *file, const char *prefix)
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{
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    return SDL_strncmp(prefix, file, SDL_strlen(prefix)) == 0;
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}
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static FILE *TryOpenFile(const char *file, const char *mode)
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{
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    FILE *fp = NULL;
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    fp = TryOpenInRomfs(file, mode);
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    if (!fp) {
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        fp = fopen(file, mode);
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    }
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    return fp;
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}
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FILE *TryOpenInRomfs(const char *file, const char *mode)
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{
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    FILE *fp = NULL;
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    char *prefixed_filepath = NULL;
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    if (SDL_asprintf(&prefixed_filepath, "romfs:/%s", file) < 0) {
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        return NULL;
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    }
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    fp = fopen(prefixed_filepath, mode);
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    SDL_free(prefixed_filepath);
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    return fp;
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}
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