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 #ifndef lint 14 static char rcsid[] = "$Id$"; 15 #endif 16 17 /* __ieee754_remainder(x,p) 18 * Return : 19 * returns x REM p = x - [x/p]*p as if in infinite 20 * precise arithmetic, where [x/p] is the (infinite bit) 21 * integer nearest x/p (in half way case choose the even one). 22 * Method : 23 * Based on fmod() return x-[x/p]chopped*p exactlp. 24 */ 25 26 #include "math.h" 27 #include "math_private.h" 28 29 #ifdef __STDC__ 30 static const double zero = 0.0; 31 #else 32 static double zero = 0.0; 33 #endif 34 35 36 #ifdef __STDC__ 37 double __generic___ieee754_remainder(double x, double p) 38 #else 39 double __generic___ieee754_remainder(x,p) 40 double x,p; 41 #endif 42 { 43 int32_t hx,hp; 44 u_int32_t sx,lx,lp; 45 double p_half; 46 47 EXTRACT_WORDS(hx,lx,x); 48 EXTRACT_WORDS(hp,lp,p); 49 sx = hx&0x80000000; 50 hp &= 0x7fffffff; 51 hx &= 0x7fffffff; 52 53 /* purge off exception values */ 54 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ 55 if((hx>=0x7ff00000)|| /* x not finite */ 56 ((hp>=0x7ff00000)&& /* p is NaN */ 57 (((hp-0x7ff00000)|lp)!=0))) 58 return (x*p)/(x*p); 59 60 61 if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ 62 if (((hx-hp)|(lx-lp))==0) return zero*x; 63 x = fabs(x); 64 p = fabs(p); 65 if (hp<0x00200000) { 66 if(x+x>p) { 67 x-=p; 68 if(x+x>=p) x -= p; 69 } 70 } else { 71 p_half = 0.5*p; 72 if(x>p_half) { 73 x-=p; 74 if(x>=p_half) x -= p; 75 } 76 } 77 GET_HIGH_WORD(hx,x); 78 SET_HIGH_WORD(x,hx^sx); 79 return x; 80 } 81