Implement rough versions of mod, remainder, copy_sign

1 files changed, 27 insertions, 88 deletions

diff --git a/gb_math.h b/gb_math.h
index c352644..41e17b8 100644
--- a/gb_math.h
+++ b/gb_math.h
@@ -1,9 +1,9 @@
-/* gb_math.h - v0.06 - public domain C math library - no warranty implied; use at your own risk */
-/* A C math library geared towards game development */
-/* use '#define GB_MATH_IMPLEMENTATION' before including to create the implementation in _ONE_ file */
+/* gb_math.h - v0.06a - public domain C math library - no warranty implied; use at your own risk
+   A C math library geared towards game development
+   use '#define GB_MATH_IMPLEMENTATION' before including to create the implementation in _ONE_ file
 
-/*
 Version History:
+	0.06a - Implement rough versions of mod, remainder, copy_sign
 	0.06  - Windows GCC Support and C90-ish Support
 	0.05  - Less/no dependencies or CRT
 	0.04d - License Update
@@ -205,6 +205,8 @@ GB_MATH_DEF float gb_angle_diff(float radians_a, float radians_b);
 #define gb_max(a, b) ((a) > (b) ? (a) : (b))
 #endif
 
+GB_MATH_DEF float gb_copy_sign(float x, float y);
+GB_MATH_DEF float gb_remainder(float x, float y);
 GB_MATH_DEF float gb_mod(float x, float y);
 GB_MATH_DEF float gb_sqrt(float a);
 GB_MATH_DEF float gb_rsqrt(float a);
@@ -771,95 +773,32 @@ gb_angle_diff(float radians_a, float radians_b)
 	return delta;
 }
 
-
 float
-gb_mod(float x, float y)
+gb_copy_sign(float x, float y)
 {
-	static float const gb__zero[] = {0, -0};
-
-	int n, hx, hy, hz, ix, iy, sx, i;
-
-	hx = *(int *)&x;
-	hy = *(int *)&y;
-	sx = hx & 0x80000000;
-	hx ^= sx;
-	hy &= 0x7fffffff;
-
-	/* NOTE(bill): Purge off exception values */
-	if (hy == 0||(hx >= 0x7f800000)|| /* NOTE(bill): Y=0,or x not finite */
-	    (hy > 0x7f800000))            /* NOTE(bill): Or y is NaN */
-		return (x*y)/(x*y);
-	if (hx < hy)  return x; /* NOTE(bill): |x|<|y| return x */
-	if (hx == hy) return gb__zero[(unsigned int)sx>>31]; /* NOTE(bill): |x|=|y| return x*0 */
-
-	/* NOTE(bill): Determine ix = ilogb(x) */
-	if (hx < 0x00800000) { /* NOTE(bill): Subnormal x */
-		for (ix = -126, i = (hx<<8); i > 0; i <<= 1)
-			ix -=1;
-	} else {
-		ix = (hx>>23)-127;
-	}
-
-	/* NOTE(bill): Determine iy = ilogb(y) */
-	if (hy < 0x00800000) { /* NOTE(bill): Subnormal y */
-		for (iy = -126, i = (hy<<8); i >= 0; i <<=1 )
-			iy -=1;
-	} else {
-		iy = (hy>>23)-127;
-	}
-
-	/* NOTE(bill): Set up {hx, lx}, {hy, ly} and align y to x */
-	if (ix >= -126) {
-		hx = 0x00800000|(0x007fffff&hx);
-	} else { /* NOTE(bill): Subnormal x, shift x to normal */
-		n = -126-ix;
-		hx = hx<<n;
-	}
-	if (iy >= -126) {
-		hy = 0x00800000|(0x007fffff&hy);
-	} else { /* NOTE(bill): Subnormal y, shift y to normal */
-		n = -126-iy;
-		hy = hy<<n;
-	}
+	int ix, iy;
+	ix = *(int *)&x;
+	iy = *(int *)&y;
 
-	/* NOTE(bill): Fix point fmod */
-	n = ix - iy;
-	while(n--) {
-		hz= hx-hy;
-		if (hz < 0) {
-			hx = hx+hx;
-		} else {
-			if (hz == 0) /* NOTE(bill): Return gb_sign(x)*0 */
-				return gb__zero[(unsigned int)sx>>31];
-			hx = hz+hz;
-		}
-	}
-	hz = hx-hy;
-	if (hz >= 0)
-		hx = hz;
+	ix &= 0x7fffffff;
+	ix |= iy & 0x80000000;
+	return *(float *)ix;
+}
 
-	/* NOTE(bill): Convert back to floating value and restore the sign */
-	if (hx == 0) /* NOTE(bill): Return sign(x)*0 */
-		return gb__zero[(unsigned int)sx>>31];
+float
+gb_remainder(float x, float y)
+{
+	return x - (gb_round(x/y)*y);
+}
 
-	while (hx < 0x00800000) { /* NOTE(bill): Normalize x */
-		hx = hx+hx;
-		iy -= 1;
-	}
-	if (iy >= -126) { /* NOTE(bill): Normalize output */
-		int t;
-		hx = ((hx-0x00800000) | ((iy + 127)<<23));
-		t = hx | sx;
-		x = *(float *)&t;
-	} else {
-		int t;
-		n = -126 - iy;
-		hx >>= n;
-		t = hx | sx;
-		x = *(float *)&t;
-		x *= 1.0f;
-	}
-	return x;
+float
+gb_mod(float x, float y)
+{
+	float result;
+	y = gb_abs(y);
+	result = gb_remainder(gb_abs(x), (y = gb_abs(y)));
+	if (gb_sign(result)) result += y;
+	return gb_copy_sign(result, x);
 }