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igs017.cpp: completed decryption of starzan's program ROM (nw)

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This commit is contained in:
Ivan Vangelista 2020-04-12 10:51:59 +02:00
parent 622763753c
commit e4319288dc
1 changed files with 24 additions and 46 deletions
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70
src/mame/drivers/igs017.cpp
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@ -603,7 +603,7 @@ private:
void tarzan_decrypt_tiles();
void tarzan_decrypt_program_rom();
void tarzana_decrypt_program_rom();
void starzan_decrypt(u8 *ROM, int size, bool isOpcode);
void starzan_decrypt_program_rom();
void lhzb2_patch_rom();
void lhzb2_decrypt_tiles();
void lhzb2_decrypt_sprites();
@ -946,7 +946,7 @@ void igs017_state::tarzana_decrypt_program_rom()
m_decrypted_opcodes[i] = x;
}
for (int i = 0; i < 0x40000; i++) // by iq132
for (int i = 0; i < 0x40000; i++) // by iq_132
{
u8 x = rom[i];
@ -963,49 +963,34 @@ void igs017_state::tarzana_decrypt_program_rom()
void igs017_state::init_tarzana()
{
tarzana_decrypt_program_rom();
// tarzana_decrypt_tiles(); // to do
// tarzana_decrypt_tiles(); // to do when dumped
}
// starzan
// decryption is incomplete: data decryption is correct but opcodes are encrypted differently.
void igs017_state::starzan_decrypt(u8 *ROM, int size, bool isOpcode)
void igs017_state::starzan_decrypt_program_rom()
{
for(int i=0; i<size; i++)
u8 *rom = memregion("maincpu")->base();
for (int i = 0; i < 0x40000; i++)
{
#if 1
u8 x = ROM[i];
u8 x = rom[i];
// this seems ok for opcodes too
if ((i & 0x10) && (i & 0x01))
{
if (!(!(i & 0x2000) && !(i & 0x100) && !(i & 0x80)))
x ^= 0x01;
}
else
{
if (!(i & 0x2000) && !(i & 0x100) && !(i & 0x80))
x ^= 0x01;
}
if ((i & 0x00011) == 0x00011) x ^= 0x01;
if ((i & 0x02180) == 0x00000) x ^= 0x01;
if ((i & 0x00020) != 0x00020) x ^= 0x20;
if ((i & 0x002a0) == 0x00220) x ^= 0x20;
if ((i & 0x00220) != 0x00200) x ^= 0x40;
if ((i & 0x001c0) != 0x00040) x ^= 0x80;
// 2x no xor (opcode)
// 3x no xor (opcode)
// 60-66 no xor (opcode)
if (!(i & 0x100) || (i & 0x80) || (i & 0x20))
x ^= 0x20;
m_decrypted_opcodes[i] = x;
}
// 2x needs xor (opcode)
// 3x needs xor (opcode)
if ((i & 0x200) || (i & 0x40) || !(i & 0x20))
x ^= 0x40;
for (int i = 0; i < 0x40000; i++) // by iq_132
{
u8 x = rom[i];
if ((!(i & 0x100) && (i & 0x80)) || (i & 0x20))
x ^= 0x80;
#else
// by iq_132
if ((i & 0x00011) == 0x00011) x ^= 0x01;
if ((i & 0x02180) == 0x00000) x ^= 0x01;
if ((i & 0x000a0) != 0x00000) x ^= 0x20;
@ -1014,23 +999,16 @@ void igs017_state::starzan_decrypt(u8 *ROM, int size, bool isOpcode)
if ((i & 0x00260) == 0x00220) x ^= 0x40;
if ((i & 0x00020) == 0x00020) x ^= 0x80;
if ((i & 0x001a0) == 0x00080) x ^= 0x80;
#endif
ROM[i] = x;
rom[i] = x;
}
}
void igs017_state::init_starzan()
{
int size = 0x040000;
u8 *data = memregion("maincpu")->base();
u8 *code = m_decrypted_opcodes;
memcpy(code, data, size);
starzan_decrypt(data, size, false); // data
starzan_decrypt(code, size, true); // opcodes
mgcs_flip_sprites();
starzan_decrypt_program_rom();
// starzan_decrypt_tiles(); // to do when dumped
mgcs_flip_sprites(); // ?
}