SNES: Improved SPC file compatibility

Try to figure out which of the 100C0-100FF or 101C0-101FF sections contains the actual RAM
SourMesen · May 12, 2023 · 932c62f · 932c62f
1 parent da0825a
commit 932c62f
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Showing 2 changed files with 27 additions and 1 deletion.
diff --git a/Core/SNES/Spc.cpp b/Core/SNES/Spc.cpp
@@ -585,6 +585,28 @@ void Spc::LoadSpcFile(SpcFileData* data)
 {
 	memcpy(_ram, data->SpcRam, Spc::SpcRamSize);
 
+	if(data->HasExtraRam) {
+		bool extraRamContainsIpl = memcmp(data->SpcExtraRam, _spcBios, 0x40) == 0;
+		if(!extraRamContainsIpl) {
+			bool ramContainsIpl = memcmp(data->SpcRam + 0xFFC0, _spcBios, 0x40) == 0;
+			bool isSpcRamEmpty = true;
+			bool isExtraRamEmpty = true;
+			for(int i = 0; i < 0x40; i++) {
+				if(data->SpcExtraRam[i] != 0 && data->SpcExtraRam[i] != 0xFF) {
+					isExtraRamEmpty = false;
+				}
+				if(data->SpcRam[i+0xFFC0] != 0 && data->SpcRam[i + 0xFFC0] != 0xFF) {
+					isSpcRamEmpty = false;
+				}
+			}
+
+			if(ramContainsIpl || (isSpcRamEmpty && !isExtraRamEmpty)) {
+				//Use extra ram section only if the main spc FFC0-FFFF section is empty or contains the IPL code
+				memcpy(_ram + 0xFFC0, data->SpcExtraRam, 0x40);
+			}
+		}
+	}
+
 	_dsp->LoadSpcFileRegs(data->DspRegs);
 
 	_state.PC = data->PC;

diff --git a/Core/SNES/SpcFileData.h b/Core/SNES/SpcFileData.h
@@ -27,6 +27,9 @@ class SpcFileData
 	uint8_t DspRegs[128];
 	uint8_t SpcRam[0x10000];
 
+	bool HasExtraRam = false;
+	uint8_t SpcExtraRam[0x40] = {};
+
 	uint32_t TrackLength;
 	uint32_t FadeLength;
 
@@ -65,7 +68,8 @@ class SpcFileData
 		memcpy(SpcRam, spcData + 0x100, 0x10000);
 		if(size >= 0x10200) {
 			//Some SPC files don't have this data (0x10180 bytes instead of 0x10200 bytes)
-			memcpy(SpcRam + 0xFFC0, spcData + 0x101C0, 0x40);
+			memcpy(SpcExtraRam, spcData + 0x101C0, 0x40);
+			HasExtraRam = true;
 		}
 
 		memcpy(DspRegs, spcData + 0x10100, 128);