101 lines
3.5 KiB
C
101 lines
3.5 KiB
C
/* *****************************************************************************
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* libg1m/format.h -- the G1M format description.
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* Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
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*
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* This file is part of libg1m.
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* libg1m is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 3.0 of the License,
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* or (at your option) any later version.
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*
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* libg1m is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with libg1m; if not, see <http://www.gnu.org/licenses/>.
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* ************************************************************************** */
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#ifndef LIBG1M_FORMAT_H
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# define LIBG1M_FORMAT_H
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# include <stdint.h>
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# pragma pack(1)
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/* Welcome on this new episode of Monster Circus! Today we'll present to you
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* something that you might not be able to forget: the G1M format.
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*
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* This format is used by CASIO with its calculator for storing things
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* like add-ins (compiled programs), MCS (main memory saves), and others.
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* In fact, there is no name for the general format, only names for the
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* "subformats" based on this one.
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*
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* It all starts with a header, called Standard Header by Simon Lothar.
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* This Standard Header contains the total filesize, the G1M type (add-in,
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* MCS, e-acts), some data that will be useful for the MCS type, and some
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* magic and control bytes.
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*
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* For some reason, this StandardHeader is INVERTED on every file it's on,
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* you will have to apply a NOT operation on its bytes for it to make sense.
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*
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* Keep in mind that, everywhere in the header, multi-bytes integers
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* are BIG ENDIAN.
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*
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* The LSB is the Least Significant Byte: once adapted to the host endianness,
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* it can simply be obtained by bitwise-AND-ing with 0xff. */
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struct standard_header {
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/* the file identifier */
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uint8_t main_id[8];
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/* our subtype! */
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uint8_t subtype[6];
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/* first control byte: filesize LSB + 0x41 */
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uint8_t control;
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/* said to be 0x01, but doesn't need to */
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uint8_t align_one;
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/* total filesize */
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uint32_t filesize;
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/* second control byte: filesize LSB + 0xb8 */
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uint8_t control2;
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/* alignment */
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uint8_t align[8];
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/* is obfuscated - useful for G3P */
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uint8_t obfuscated;
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/* number of objects contained (useful for MCS filetype) */
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uint16_t number;
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};
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/* At the beginning, we thought "USBPower" was some magic sequence we would
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* systematically find in the "main_id" field. But counter examples came:
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* the G3L, whose main ID was "Ly755 ", and the C2P.
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*
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* We also thought the subtype was only one-byte long, but the C2P came along
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* with its "c2p\0\0\0" subtype.
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*
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* All main ID/types correspondances are in the `src/utils/type.c` file.
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* From a user program, you can use the functions
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* in `include/libg1m/formatutils.h`. */
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# pragma pack()
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/* After the Standard Header is read and the type is read, we have parts,
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* each with their own subheaders and their own subtilities.
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*
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* Where do you want to start? Pick your poison. */
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# include <libg1m/format/addin.h>
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# include <libg1m/format/eact.h>
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# include <libg1m/format/mcs.h>
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# include <libg1m/format/storage.h>
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# include <libg1m/format/picture.h>
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# include <libg1m/format/lang.h>
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# include <libg1m/format/fkey.h>
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#endif /* LIBG1M_FORMAT_H */
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