1 /* @(#)e_remainder.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 /* remainder(x,p) 14 * Return : 15 * returns x REM p = x - [x/p]*p as if in infinite 16 * precise arithmetic, where [x/p] is the (infinite bit) 17 * integer nearest x/p (in half way case choose the even one). 18 * Method : 19 * Based on fmod() return x-[x/p]chopped*p exactlp. 20 */ 21 22 #include "math.h" 23 #include "math_private.h" 24 25 static const double zero = 0.0; 26 27 28 double 29 remainder(double x, double p) 30 { 31 int32_t hx,hp; 32 u_int32_t sx,lx,lp; 33 double p_half; 34 35 EXTRACT_WORDS(hx,lx,x); 36 EXTRACT_WORDS(hp,lp,p); 37 sx = hx&0x80000000; 38 hp &= 0x7fffffff; 39 hx &= 0x7fffffff; 40 41 /* purge off exception values */ 42 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ 43 if((hx>=0x7ff00000)|| /* x not finite */ 44 ((hp>=0x7ff00000)&& /* p is NaN */ 45 (((hp-0x7ff00000)|lp)!=0))) 46 return (x*p)/(x*p); 47 48 49 if (hp<=0x7fdfffff) x = fmod(x,p+p); /* now x < 2p */ 50 if (((hx-hp)|(lx-lp))==0) return zero*x; 51 x = fabs(x); 52 p = fabs(p); 53 if (hp<0x00200000) { 54 if(x+x>p) { 55 x-=p; 56 if(x+x>=p) x -= p; 57 } 58 } else { 59 p_half = 0.5*p; 60 if(x>p_half) { 61 x-=p; 62 if(x>=p_half) x -= p; 63 } 64 } 65 GET_HIGH_WORD(hx,x); 66 SET_HIGH_WORD(x,hx^sx); 67 return x; 68 } 69