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Better detection of mapper numbers based on NES header version

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This commit is contained in:
negativeExponent
2020-03-01 23:17:30 +08:00
parent f9cc11c565
commit aee4669b8d
1 changed files with 15 additions and 3 deletions
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18
src/ines.c
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@@ -808,12 +808,24 @@ int iNESLoad(const char *name, FCEUFILE *fp) {
memset((char*)(&head) + 0xA, 0, 0x6);
}
subMapper = 0;
MapperNo = (head.ROM_type >> 4) | (head.ROM_type2 & 0xF0);
/* If byte 7 AND $0C = $08, and the size taking into account byte 9 does not exceed the actual size of the ROM image, then NES 2.0.
* If byte 7 AND $0C = $00, and bytes 12-15 are all 0, then iNES.
* Otherwise, archaic iNES. - nesdev*/
switch (head.ROM_type2 & 0x0C) {
case 0x08: /* header version is NES 2.0 */
iNES2 = 1;
/* fallthrough */
case 0x00: /* header version is iNES */
MapperNo = (head.ROM_type >> 4) | (head.ROM_type2 & 0xF0);
break;
default: /* any other value is Archaic iNes, byte 7-15 not used */
MapperNo = (head.ROM_type >> 4);
break;
}
Mirroring = (head.ROM_type & 8) ? 2 : (head.ROM_type & 1);
prgRom = head.ROM_size;
chrRom = head.VROM_size;
iNES2 = ((head.ROM_type2 & 0x0C) == 0x08) ? 1 : 0;
subMapper = 0;
if (iNES2) {
MapperNo |= ((uint32)head.ROM_type3 << 8) & 0xF00;