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Triforce: Check only first byte in region flag.

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In some Triforce games (e.g. _F-Zero AX_), the bytes that follow the
region flag in the `boot.id` file (at `0x38`) happen to be `0x00`.
However, in other games (e.g _Mario Kart Arcade GP 2_), it seems the
region flag is padded with `0xFF`.

_Mario Kart Arcade GP 2_ (`boot.id` in the USA version):
```
00000 0000:  42 54 49 44 00 00 01 E0  00 00 00 01 00 00 00 01  BTID.... ........
00000 0010:  FF FF FF FF FF FF FF FF  FF FF FF FF FF FF FF FF  ........ ........
00000 0020:  47 43 41 4D 00 00 01 C0  07 D3 05 0F 00 00 00 07  GCAM.... ........
00000 0030:  53 42 4E 4C 00 00 00 00  0E FF FF FF FF FF FF FF  SBNL.... ........
                                      -----------
                                           ^
                                           |
                                      region flag
```

When the region flag was tested in `switch` statements (where a single
byte was expected in the `case`s), the test would fail, depending
on the game.

This issue would lead to the wrong calculation of the country in
`VolumeDisc::GetCountry()`, which was then used to build the game ID in
`VolumeDisc::GetGameID()`.

The solution is to test using only the least meaningful byte in the
region flag.

Unexpected game IDs were first noticed with USA version of _Mario Kart
Arcade GP 2_, which was wrongly assigned the same game ID that is given
to the Japan version (i.e. `GNLJ82`). The correct game ID for the USA
version is `GNLE82`.
This commit is contained in:
cristian64 2026-03-15 18:14:43 +00:00
parent b6027da5db
commit 3eea3a90b5
2 changed files with 2 additions and 2 deletions
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2
Source/Core/DiscIO/VolumeDisc.cpp
View File

@ -67,7 +67,7 @@ Country VolumeDisc::GetCountry(const Partition& partition) const
{
const BootID* boot_id = static_cast<const VolumeGC*>(this)->GetTriforceBootID();
switch (boot_id->region_flags)
switch (boot_id->region_flags & 0x000000FF)
{
default:
case 0x02: // JAPAN

2
Source/Core/DiscIO/VolumeGC.cpp
View File

@ -92,7 +92,7 @@ Region VolumeGC::GetRegion() const
{
if (m_is_triforce)
{
switch (m_triforce_header.region_flags)
switch (m_triforce_header.region_flags & 0x000000FF)
{
default:
case 0x02: // JAPAN