Fixed incorrect cycle calculation and removed floats entirely in drive loop

Replace incorrect cyclesLeft calculation with faster non-floating point error calculator. Replaced modulo calculation with faster size comparison.

src/Drive.cpp

@@ -487,7 +487,9 @@ bool Drive::Update()
 				DriveLoopReadNoCycles();
 			}
 			else
+			{
 				DriveLoopRead();
+			}
 		}
 #else
 		for (int cycles = 0; cycles < 16; ++cycles)
@@ -580,6 +582,7 @@ bool Drive::Update()
 	return dataReady;
 }
 
+
 #if defined(EXPERIMENTALZERO)
 #define min(a,b) (((a) < (b)) ? (a) : (b))
 #define max(a,b) (((a) > (b)) ? (a) : (b))
@@ -597,7 +600,6 @@ void Drive::DriveLoopReadNoFluxNoCycles()
 			cycles = 0;
 			return;
 		}
-
 		cycles -= UE7Counter;
 
 		UE7Counter = 16 - CLOCK_SEL_AB;	// A and B inputs of UE7 come from the VIA's CLOCK SEL A/B outputs (ie PB5/6) ie preload the encoder/decoder clock for the current density settings.
@@ -649,14 +651,8 @@ void Drive::DriveLoopReadNoFlux()
 
 		if (cyclesLeftForBit == 0)
 		{
-			//which is faster? single loop ceil check or the 3 lines below?
+			cyclesForBitErrorCounter -= cyclesPerBitErrorConstant;
-			float fn = 2.0f * cyclesPerBit - cyclesForBit;
+			cyclesLeftForBit = cyclesPerBitInt + (cyclesForBitErrorCounter < cyclesPerBitErrorConstant);
-			cyclesLeftForBit = (int)fn;
-			cyclesForBit = cyclesPerBit;
-			if (fn != (float)cyclesLeftForBit) {
-				++cyclesLeftForBit;
-				++cyclesForBit;
-			}
 
 			//cyclesForBit -= cyclesPerBit;
 			//cyclesLeftForBit = ceil(cyclesPerBit - cyclesForBit);
@@ -772,13 +768,8 @@ void Drive::DriveLoopRead()
 		if (cyclesLeftForBit == 0)
 		{
 			//which is faster? single loop ceil check or the 3 lines below?
-			float fn = 2.0f * cyclesPerBit - cyclesForBit;
+			cyclesForBitErrorCounter -= cyclesPerBitErrorConstant;
-			cyclesLeftForBit = (int)fn;
+			cyclesLeftForBit = cyclesPerBitInt + (cyclesForBitErrorCounter < cyclesPerBitErrorConstant);
-			cyclesForBit = cyclesPerBit;
-			if (fn != (float)cyclesLeftForBit) {
-				++cyclesLeftForBit;
-				++cyclesForBit;
-			}
 
 			//cyclesForBit -= cyclesPerBit;
 			//cyclesLeftForBit = ceil(cyclesPerBit - cyclesForBit);

src/Drive.h

@@ -96,6 +96,12 @@ private:
 		bitsInTrack = diskImage->BitsInTrack(headTrackPos);
 		headBitOffset %= bitsInTrack;
 		cyclesPerBit = CYCLES_16Mhz_PER_ROTATION / (float)bitsInTrack;
+#if defined(EXPERIMENTALZERO)
+		cyclesPerBitInt = cyclesPerBit;
+		cyclesPerBitErrorConstant = (unsigned int)((cyclesPerBit - ((float)cyclesPerBitInt)) * static_cast<float>(0xffffffff));
+		cyclesForBitErrorCounter = (unsigned int)(((cyclesForBit)-(int)(cyclesForBit)) * static_cast<float>(0xffffffff));
+#endif
+
 	}
 
 	inline void MoveHead(unsigned char headDirection)
@@ -118,6 +124,15 @@ private:
 
 	void DumpTrack(unsigned track); // Used for debugging disk images.
 
+#if defined(EXPERIMENTALZERO)
+	inline u32 AdvanceSectorPositionR(int& byteOffset)
+	{
+		if (++headBitOffset == bitsInTrack)
+			headBitOffset = 0;
+		byteOffset = headBitOffset >> 3;
+		return (~headBitOffset) & 7;
+	}
+#else
 	// No reason why I seperate these into individual read and write versions. I was just trying to get the bit stream to line up when rewriting over existing data.
 	inline u32 AdvanceSectorPositionR(int& byteOffset)
 	{
@@ -125,7 +140,7 @@ private:
 		byteOffset = headBitOffset >> 3;
 		return (~headBitOffset) & 7;
 	}
-
+#endif
 	inline u32 AdvanceSectorPositionW(int& byteOffset)
 	{
 		byteOffset = headBitOffset >> 3;
@@ -167,6 +182,9 @@ private:
 	unsigned int fluxReversalCyclesLeft;
 	unsigned int UE7Counter;
 	u32 writeShiftRegister;
+	unsigned int cyclesForBitErrorCounter;
+	unsigned int cyclesPerBitErrorConstant;
+	unsigned int cyclesPerBitInt;
 #else
 	int UE7Counter;
 	u8 writeShiftRegister;