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authorRich Felker <dalias@aerifal.cx>2011-02-12 00:22:29 -0500
committerRich Felker <dalias@aerifal.cx>2011-02-12 00:22:29 -0500
commit0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 (patch)
tree6eaef0d8a720fa3da580de87b647fff796fe80b3 /src/math/e_remainder.c
downloadmusl-0b44a0315b47dd8eced9f3b7f31580cf14bbfc01.tar.gz
initial check-in, version 0.5.0v0.5.0
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+
+/* @(#)e_remainder.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+/* remainder(x,p)
+ * Return :
+ * returns x REM p = x - [x/p]*p as if in infinite
+ * precise arithmetic, where [x/p] is the (infinite bit)
+ * integer nearest x/p (in half way case choose the even one).
+ * Method :
+ * Based on fmod() return x-[x/p]chopped*p exactlp.
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const double zero = 0.0;
+
+
+double
+remainder(double x, double p)
+{
+ int32_t hx,hp;
+ uint32_t sx,lx,lp;
+ double p_half;
+
+ EXTRACT_WORDS(hx,lx,x);
+ EXTRACT_WORDS(hp,lp,p);
+ sx = hx&0x80000000;
+ hp &= 0x7fffffff;
+ hx &= 0x7fffffff;
+
+ /* purge off exception values */
+ if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */
+ if((hx>=0x7ff00000)|| /* x not finite */
+ ((hp>=0x7ff00000)&& /* p is NaN */
+ (((hp-0x7ff00000)|lp)!=0)))
+ return (x*p)/(x*p);
+
+
+ if (hp<=0x7fdfffff) x = fmod(x,p+p); /* now x < 2p */
+ if (((hx-hp)|(lx-lp))==0) return zero*x;
+ x = fabs(x);
+ p = fabs(p);
+ if (hp<0x00200000) {
+ if(x+x>p) {
+ x-=p;
+ if(x+x>=p) x -= p;
+ }
+ } else {
+ p_half = 0.5*p;
+ if(x>p_half) {
+ x-=p;
+ if(x>=p_half) x -= p;
+ }
+ }
+ GET_HIGH_WORD(hx,x);
+ SET_HIGH_WORD(x,hx^sx);
+ return x;
+}