From 7ce331c01ce6eb7b3f5c715a38a24359da9c6ee2 Mon Sep 17 00:00:00 2001
From: Eric Andersen <andersen@codepoet.org>
Date: Thu, 22 Nov 2001 14:04:29 +0000
Subject: Totally rework the math library, this time based on the MacOs X math
 library (which is itself based on the math lib from FreeBSD).  -Erik

---
 libm/e_fmod.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 libm/e_fmod.c

(limited to 'libm/e_fmod.c')

diff --git a/libm/e_fmod.c b/libm/e_fmod.c
new file mode 100644
index 000000000..2ce613574
--- /dev/null
+++ b/libm/e_fmod.c
@@ -0,0 +1,140 @@
+/* @(#)e_fmod.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: e_fmod.c,v 1.8 1995/05/10 20:45:07 jtc Exp $";
+#endif
+
+/* 
+ * __ieee754_fmod(x,y)
+ * Return x mod y in exact arithmetic
+ * Method: shift and subtract
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+static const double one = 1.0, Zero[] = {0.0, -0.0,};
+#else
+static double one = 1.0, Zero[] = {0.0, -0.0,};
+#endif
+
+#ifdef __STDC__
+	double __ieee754_fmod(double x, double y)
+#else
+	double __ieee754_fmod(x,y)
+	double x,y ;
+#endif
+{
+	int32_t n,hx,hy,hz,ix,iy,sx,i;
+	u_int32_t lx,ly,lz;
+
+	EXTRACT_WORDS(hx,lx,x);
+	EXTRACT_WORDS(hy,ly,y);
+	sx = hx&0x80000000;		/* sign of x */
+	hx ^=sx;		/* |x| */
+	hy &= 0x7fffffff;	/* |y| */
+
+    /* purge off exception values */
+	if((hy|ly)==0||(hx>=0x7ff00000)||	/* y=0,or x not finite */
+	  ((hy|((ly|-ly)>>31))>0x7ff00000))	/* or y is NaN */
+	    return (x*y)/(x*y);
+	if(hx<=hy) {
+	    if((hx<hy)||(lx<ly)) return x;	/* |x|<|y| return x */
+	    if(lx==ly) 
+		return Zero[(u_int32_t)sx>>31];	/* |x|=|y| return x*0*/
+	}
+
+    /* determine ix = ilogb(x) */
+	if(hx<0x00100000) {	/* subnormal x */
+	    if(hx==0) {
+		for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
+	    } else {
+		for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
+	    }
+	} else ix = (hx>>20)-1023;
+
+    /* determine iy = ilogb(y) */
+	if(hy<0x00100000) {	/* subnormal y */
+	    if(hy==0) {
+		for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
+	    } else {
+		for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
+	    }
+	} else iy = (hy>>20)-1023;
+
+    /* set up {hx,lx}, {hy,ly} and align y to x */
+	if(ix >= -1022) 
+	    hx = 0x00100000|(0x000fffff&hx);
+	else {		/* subnormal x, shift x to normal */
+	    n = -1022-ix;
+	    if(n<=31) {
+	        hx = (hx<<n)|(lx>>(32-n));
+	        lx <<= n;
+	    } else {
+		hx = lx<<(n-32);
+		lx = 0;
+	    }
+	}
+	if(iy >= -1022) 
+	    hy = 0x00100000|(0x000fffff&hy);
+	else {		/* subnormal y, shift y to normal */
+	    n = -1022-iy;
+	    if(n<=31) {
+	        hy = (hy<<n)|(ly>>(32-n));
+	        ly <<= n;
+	    } else {
+		hy = ly<<(n-32);
+		ly = 0;
+	    }
+	}
+
+    /* fix point fmod */
+	n = ix - iy;
+	while(n--) {
+	    hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
+	    if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
+	    else {
+	    	if((hz|lz)==0) 		/* return sign(x)*0 */
+		    return Zero[(u_int32_t)sx>>31];
+	    	hx = hz+hz+(lz>>31); lx = lz+lz;
+	    }
+	}
+	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
+	if(hz>=0) {hx=hz;lx=lz;}
+
+    /* convert back to floating value and restore the sign */
+	if((hx|lx)==0) 			/* return sign(x)*0 */
+	    return Zero[(u_int32_t)sx>>31];	
+	while(hx<0x00100000) {		/* normalize x */
+	    hx = hx+hx+(lx>>31); lx = lx+lx;
+	    iy -= 1;
+	}
+	if(iy>= -1022) {	/* normalize output */
+	    hx = ((hx-0x00100000)|((iy+1023)<<20));
+	    INSERT_WORDS(x,hx|sx,lx);
+	} else {		/* subnormal output */
+	    n = -1022 - iy;
+	    if(n<=20) {
+		lx = (lx>>n)|((u_int32_t)hx<<(32-n));
+		hx >>= n;
+	    } else if (n<=31) {
+		lx = (hx<<(32-n))|(lx>>n); hx = sx;
+	    } else {
+		lx = hx>>(n-32); hx = sx;
+	    }
+	    INSERT_WORDS(x,hx|sx,lx);
+	    x *= one;		/* create necessary signal */
+	}
+	return x;		/* exact output */
+}
-- 
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