From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/e_fmod.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 src/math/e_fmod.c

(limited to 'src/math/e_fmod.c')

diff --git a/src/math/e_fmod.c b/src/math/e_fmod.c
new file mode 100644
index 00000000..99afe489
--- /dev/null
+++ b/src/math/e_fmod.c
@@ -0,0 +1,129 @@
+
+/* @(#)e_fmod.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.
+ * ====================================================
+ */
+
+/* 
+ * fmod(x,y)
+ * Return x mod y in exact arithmetic
+ * Method: shift and subtract
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const double one = 1.0, Zero[] = {0.0, -0.0,};
+
+double
+fmod(double x, double y)
+{
+        int32_t n,hx,hy,hz,ix,iy,sx,i;
+        uint32_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[(uint32_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[(uint32_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[(uint32_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)|((uint32_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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