Fix a small buglet in the last patch. :-)

[rmac] / fltpoint.c

diff --git a/fltpoint.c b/fltpoint.c
index 38bd0b59be21cd829b79cd8146c3d811caf587f3..7e516fbd360686985aa160bb45f7f38658c6a67a 100644 (file)
--- 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)
@@ -66,13 +68,13 @@
 
 uint32_t FloatToIEEE754(float f)
 {
-       uint32_t sign = (f < 0 ? 0x80000000 : 0);
+       uint32_t sign = (signbit(f) ? 0x80000000 : 0);
 
        // Split the float into normalized mantissa (range: (-1, -0.5], 0,
        // [+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);
@@ -104,14 +106,14 @@ uint32_t FloatToIEEE754(float f)
 
 uint64_t DoubleToIEEE754(double d)
 {
-       uint64_t sign = (d < 0 ? 0x8000000000000000LL : 0);
+       uint64_t sign = (signbit(d) ? 0x8000000000000000LL : 0);
        int32_t exponent;
 
        // Split double into normalized mantissa (range: (-1, -0.5], 0, [+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.
        double mantissa = frexp((d < 0 ? -d : d), &exponent);
 
@@ -141,9 +143,10 @@ uint64_t DoubleToIEEE754(double d)
 
 void DoubleToExtended(double d, uint8_t out[])
 {
+       int8_t sign = (signbit(d) ? 0x80 : 0);
        int32_t exponent;
        double mantissa = frexp((d < 0 ? -d : d), &exponent);
-       exponent += 0x3FFF;
+       exponent += 0x3FFE;
 
        if (d == 0)
                exponent = 0;
@@ -154,7 +157,7 @@ void DoubleToExtended(double d, uint8_t out[])
        // Motorola extended floating point is 96 bits, so we pack it into the
        // 12-byte array that's passed in. The format is as follows: 1 bit (sign),
        // 15 bits (exponent w/$3FFF bias), 16 bits of zero, 64 bits of mantissa.
-       out[0] = (d < 0 ? 0x80 : 0x00) | ((exponent >> 8) & 0x7F);
+       out[0] = sign | ((exponent >> 8) & 0x7F);
        out[1] = exponent & 0xFF;
        out[2] = 0;
        out[3] = 0;
@@ -168,3 +171,47 @@ 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;
+       }
+
+       // The casts are here because some compilers do weird shit.  See bug #149.
+       return (uint32_t)((int32_t)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;
+}
+