X-Git-Url: http://shamusworld.gotdns.org/cgi-bin/gitweb.cgi?p=rmac;a=blobdiff_plain;f=fltpoint.c;h=2205a79f4c0d8d5a30d20216b8f08d17d84c7808;hp=1de5d0ac42a3cd5d53aae63beabf0e1eec17e9e8;hb=c59f7a33730dacf753e066a4002e2f749051a137;hpb=3b063cd8b11b5e868efec02f9e281a1e04f2707b

diff --git a/fltpoint.c b/fltpoint.c
index 1de5d0a..2205a79 100644
--- a/fltpoint.c
+++ b/fltpoint.c
@@ -2,7 +2,7 @@
 // Floating point to IEEE-754 conversion routines
 //
 // by James Hammons
-// (C) 2018 Underground Software
+// (C) 2019 Underground Software
 //
 // Since there are no guarantees vis-a-vis floating point numbers in C, we have
 // to utilize routines like the following in order to guarantee that the thing
@@ -14,6 +14,8 @@
 #include "fltpoint.h"
 #include <float.h>
 #include <math.h>
+#include <stdio.h>
+#include "error.h"
 
 //
 // Check for IEEE-754 conformance (C99 compilers should be OK here)
@@ -72,7 +74,7 @@ uint32_t FloatToIEEE754(float f)
 	// [+0.5, +1)) and base-2 exponent
 	// d = mantissa * (2 ^ exponent) *exactly* for FLT_RADIX=2
 	// Also, since we want the mantissa to be non-inverted (2's complemented),
-	// we make sure to pass in a positive number (floats/doubles are not 2's
+	// we make sure to pass in a positive number (floats/doubles are *not* 2's
 	// complemented) as we already captured the sign bit above.
 	int32_t exponent;
 	float mantissa = frexpf((f < 0 ? -f : f), &exponent);
@@ -111,7 +113,7 @@ uint64_t DoubleToIEEE754(double d)
 	// and base-2 exponent
 	// d = mantissa * (2 ^ exponent) *exactly* for FLT_RADIX=2
 	// Also, since we want the mantissa to be non-inverted (2's complemented),
-	// we make sure to pass in a positive number (floats/doubles are not 2's
+	// we make sure to pass in a positive number (floats/doubles are *not* 2's
 	// complemented) as we already captured the sign bit above.
 	double mantissa = frexp((d < 0 ? -d : d), &exponent);
 
@@ -169,3 +171,46 @@ void DoubleToExtended(double d, uint8_t out[])
 	out[11] = intMant & 0xFF;
 }
 
+
+//
+// Convert a double to a DSP56001 style fixed point float.
+// Seems to be 23 bits of float value with 1 bit (MSB) for the sign.
+//
+uint32_t DoubleToDSPFloat(double d)
+{
+	if (d >= 1)
+	{
+		warn("DSP value clamped to +1.");
+		return 0x7FFFFF;
+	}
+	else if (d <= -1)
+	{
+		warn("DSP value clamped to -1.");
+		return 0x800000;
+	}
+
+	return trunc(round(ldexp(d, 23)));
+}
+
+
+//
+// Convert a host native floating point number to a fixed point number.
+//
+uint64_t DoubleToFixedPoint(double d, int intBits, int fracBits)
+{
+	uint8_t signBit = (signbit(d) ? 1 : 0);
+
+	// Ensure what we're working on is positive...
+	if (d < 0)
+		d *= -1;
+
+	double scaleFactor = (double)(1 << fracBits);
+	uint64_t result = (uint64_t)(d * scaleFactor);
+
+	// Invert the result, if necessary
+	if (signBit == 1)
+		result = (result = 0xFFFFFFFFFFFFFFFFLL) + 1;
+
+	return result;
+}
+