io.c

WiiFuse is a FUSE filesystem module for Linux and Mac OS X. It will let you mount a Wii disc ISO an

/*
 *  Copyright (C) 2008 dhewg, #wiidev efnet
 *
 *  this file is part of wiifuse
 *  http://wiibrew.org/index.php?title=Wiifuse
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdio.h>

#include "io.h"

int io_read (void *ptr, size_t size, struct image_file *image, u64 offset) {
        size_t bytes;

        if (fseeko (image->fp, offset, SEEK_SET)) {
                perror ("io_seek");
                return -1;
        }

        bytes = fread (ptr, 1, size, image->fp);

        if (bytes != size)
                perror ("io_read");

        return bytes;
}

int decrypt_block (struct image_file *image, u32 part, u32 block) {
        if (block == image->parts[part].cached_block)
                return 0;

        LOG (3, "decrypting part/block %u/%08x", part, block);

        if (io_read (image->parts[part].dec_buffer, 0x8000, image,
                     image->parts[part].offset +
                     image->parts[part].data_offset + 0x8000ull * block)
            != 0x8000) {
                perror ("decrypt read");
                return -1;
        }

        AES_cbc_encrypt (&image->parts[part].dec_buffer[0x400],
                         image->parts[part].cache, 0x7c00,
                         &image->parts[part].key,
                         &image->parts[part].dec_buffer[0x3d0], 0);

        image->parts[part].cached_block = block;

        return 0;
}

size_t io_read_part (void *ptr, size_t size, struct image_file *image,
                     u32 part, u64 offset) {
        u32 block = offset / 0x7c00;
        u32 cache_offset = offset % 0x7c00;
        u32 cache_size;
        void *dst = ptr;

        if (!image->parts[part].is_encrypted)
                return io_read (ptr, size, image,
                                image->parts[part].offset + offset);

        while (size) {
                if (decrypt_block (image, part, block))
                        return dst - ptr;

                cache_size = size;
                if (cache_size + cache_offset > 0x7c00)
                        cache_size = 0x7c00 - cache_offset;

                memcpy (dst, image->parts[part].cache + cache_offset,
                        cache_size);
                dst += cache_size;
                size -= cache_size;
                cache_offset = 0;

                block++;
        }

        return dst - ptr;
}