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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
/*
* Patches Myth C64 disk image
* Written by David Kinder, based on code by Niclas Karlsson
*/
#define D64_SIZE (174848L)
unsigned char image[D64_SIZE];
void ungarble(unsigned char *block, signed long key) {
unsigned char d;
int i, j;
d = (unsigned char)((key & 0x07) ^ 0xFF);
if (d < 0xFF) {
i = d;
j = d + 1;
while (j < 0x100)
block[j++] ^= block[i];
}
i = 0xFF;
j = d - 1;
while (j >= 0)
block[j--] ^= block[i--];
for (i = 0; i < 128; i++) {
d = block[i];
block[i] = block[255 - i];
block[255 - i] = d;
}
}
void garble(unsigned char *block, int i1, int j1, int i2) {
unsigned char d;
int i, j;
for (i = 0; i < 128; i++) {
d = block[i];
block[i] = block[255 - i];
block[255 - i] = d;
}
i = i1;
j = -1;
while (j < j1)
block[++j] ^= block[++i];
i = i2;
j = 0x100;
while (j > i2 + 1)
block[--j] ^= block[i];
}
/* This routine does the patching. */
void fixDiskImage(int code) {
unsigned char *block = NULL;
switch (code) {
case 0:
/* code[0x3056] = 0x60 */
block = image + 0x1600;
ungarble(block, 0x27L);
block[0x56] = 0x60;
garble(block, 0x07, 0xF7, 0xF8);
break;
case 1:
/* code[0x3148] = 0x60 */
/* code[0x314D] = 0x11 */
block = image + 0x1700;
ungarble(block, 0x28L);
block[0x48] = 0x60;
block[0x4D] = 0x11;
garble(block, 0x00, 0xFE, 0xFF);
break;
}
}
void readDiskImage(const char *filename) {
FILE *file = fopen(filename, "r+b");
if (file == NULL)
exit(1);
fread(image, 1, D64_SIZE, file);
}
void writeDiskImage(const char *filename) {
FILE *file = fopen(filename, "w+b");
if (file == NULL)
exit(1);
fwrite(image, 1, D64_SIZE, file);
}
int main(int argc, char **argv) {
if (argc == 4) {
int code = -1;
if (sscanf(argv[3], "%d", &code) == 1) {
if ((code >= 0) && (code <= 1)) {
readDiskImage(argv[1]);
fixDiskImage(code);
writeDiskImage(argv[2]);
printf("Myth patched.\n");
return 0;
}
}
}
printf("Removes password protection from Magnetic Scrolls' Myth.\n");
printf("Use: myth input.d64 output.d64 code\n");
printf("If code is 0, the password protection is completely removed.\n");
printf("If code is 1, any user name and password will be accepted.\n");
return 0;
}
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