1 2 /* @(#)e_remainder.c 1.3 95/01/18 */ 3 /* 4 * ==================================================== 5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6 * 7 * Developed at SunSoft, a Sun Microsystems, Inc. business. 8 * Permission to use, copy, modify, and distribute this 9 * software is freely granted, provided that this notice 10 * is preserved. 11 * ==================================================== 12 */ 13 14 /* __ieee754_remainder(x,p) 15 * Return : 16 * returns x REM p = x - [x/p]*p as if in infinite 17 * precise arithmetic, where [x/p] is the (infinite bit) 18 * integer nearest x/p (in half way case choose the even one). 19 * Method : 20 * Based on ieee_fmod() return x-[x/p]chopped*p exactlp. 21 */ 22 23 #include "fdlibm.h" 24 25 #ifdef __STDC__ 26 static const double zero = 0.0; 27 #else 28 static double zero = 0.0; 29 #endif 30 31 32 #ifdef __STDC__ 33 double __ieee754_remainder(double x, double p) 34 #else 35 double __ieee754_remainder(x,p) 36 double x,p; 37 #endif 38 { 39 int hx,hp; 40 unsigned sx,lx,lp; 41 double p_half; 42 43 hx = __HI(x); /* high word of x */ 44 lx = __LO(x); /* low word of x */ 45 hp = __HI(p); /* high word of p */ 46 lp = __LO(p); /* low word of p */ 47 sx = hx&0x80000000; 48 hp &= 0x7fffffff; 49 hx &= 0x7fffffff; 50 51 /* purge off exception values */ 52 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ 53 if((hx>=0x7ff00000)|| /* x not finite */ 54 ((hp>=0x7ff00000)&& /* p is NaN */ 55 (((hp-0x7ff00000)|lp)!=0))) 56 return (x*p)/(x*p); 57 58 59 if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ 60 if (((hx-hp)|(lx-lp))==0) return zero*x; 61 x = ieee_fabs(x); 62 p = ieee_fabs(p); 63 if (hp<0x00200000) { 64 if(x+x>p) { 65 x-=p; 66 if(x+x>=p) x -= p; 67 } 68 } else { 69 p_half = 0.5*p; 70 if(x>p_half) { 71 x-=p; 72 if(x>=p_half) x -= p; 73 } 74 } 75 __HI(x) ^= sx; 76 return x; 77 } 78
