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feat: Refactor RoomObject decoding logic to prioritize Type3 detection and update related unit tests

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scawful
2025-10-04 00:15:21 -04:00
parent c2dd6498e2
commit 9bfc95de37
3 changed files with 57 additions and 63 deletions
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82
src/app/zelda3/dungeon/room_object.cc
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@@ -271,31 +271,46 @@ int RoomObject::DetermineObjectType(uint8_t b1, uint8_t b3) {
RoomObject RoomObject::DecodeObjectFromBytes(uint8_t b1, uint8_t b2, uint8_t b3,
uint8_t layer) {
int type = DetermineObjectType(b1, b3);
uint8_t x = 0;
uint8_t y = 0;
uint8_t size = 0;
uint16_t id = 0;
switch (type) {
case 1: {
// Type1: xxxxxxss yyyyyyss iiiiiiii
// X position: bits 2-7 of byte 1
x = (b1 & 0xFC) >> 2;
// Y position: bits 2-7 of byte 2
y = (b2 & 0xFC) >> 2;
// Size: bits 0-1 of byte 1 (high), bits 0-1 of byte 2 (low)
size = ((b1 & 0x03) << 2) | (b2 & 0x03);
// ID: byte 3 (0x00-0xFF)
id = b3;
break;
}
// ZScream's approach: Check Type3 first, then decode as Type1,
// then override with Type2 if b1 >= 0xFC
// This is critical because Type1 objects can have b1 >= 0xFC when X is at max position
if (b3 >= 0xF8) {
// Type3: xxxxxxii yyyyyyii 11111iii
// X position: bits 2-7 of byte 1
x = (b1 & 0xFC) >> 2;
case 2: {
// Y position: bits 2-7 of byte 2
y = (b2 & 0xFC) >> 2;
// Size: Stored in same bits as ID lower bits
size = ((b1 & 0x03) << 2) | (b2 & 0x03);
// ID: Complex reconstruction (ZScream formula)
// Top 8 bits from byte 3 (shifted left by 4)
// OR'd with (0x80 + lower bits from b2 and b1)
id = ((b3 & 0xFF) << 4) | (0x80 + (((b2 & 0x03) << 2) + (b1 & 0x03)));
} else {
// Default decode as Type1: xxxxxxss yyyyyyss iiiiiiii
// X position: bits 2-7 of byte 1
x = (b1 & 0xFC) >> 2;
// Y position: bits 2-7 of byte 2
y = (b2 & 0xFC) >> 2;
// Size: bits 0-1 of byte 1 (high), bits 0-1 of byte 2 (low)
size = ((b1 & 0x03) << 2) | (b2 & 0x03);
// ID: byte 3 (0x00-0xFF)
id = b3;
// NOW check if this is actually Type2 and override
if (b1 >= 0xFC) {
// Type2: 111111xx xxxxyyyy yyiiiiii
// X position: bits 0-1 of byte 1 (high), bits 4-7 of byte 2 (low)
x = ((b1 & 0x03) << 4) | ((b2 & 0xF0) >> 4);
@@ -308,36 +323,7 @@ RoomObject RoomObject::DecodeObjectFromBytes(uint8_t b1, uint8_t b2, uint8_t b3,
// ID: bits 0-5 of byte 3, OR with 0x100 to mark as Type2
id = (b3 & 0x3F) | 0x100;
break;
}
case 3: {
// Type3: xxxxxxii yyyyyyii 11111iii
// X position: bits 2-7 of byte 1
x = (b1 & 0xFC) >> 2;
// Y position: bits 2-7 of byte 2
y = (b2 & 0xFC) >> 2;
// Size: 0 (Type3 objects don't use size parameter)
size = 0;
// ID: Complex reconstruction
// Top 8 bits from byte 3 (shifted left by 4)
// Bits 2-3 from byte 2
// Bits 0-1 from byte 1
// Plus 0x80 offset
id = ((b3 & 0xFF) << 4) | ((b2 & 0x03) << 2) | (b1 & 0x03) | 0x80;
break;
}
default:
// Should never happen, but default to Type1
id = b3;
x = (b1 & 0xFC) >> 2;
y = (b2 & 0xFC) >> 2;
size = ((b1 & 0x03) << 2) | (b2 & 0x03);
break;
}
return RoomObject(static_cast<int16_t>(id), x, y, size, layer);