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 #include <sys/cdefs.h> 15 __FBSDID("$FreeBSD$"); 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 <float.h> 27 28 #include "math.h" 29 #include "math_private.h" 30 31 static const double zero = 0.0; 32 33 34 double 35 __ieee754_remainder(double x, double p) 36 { 37 int32_t hx,hp; 38 u_int32_t sx,lx,lp; 39 double p_half; 40 41 EXTRACT_WORDS(hx,lx,x); 42 EXTRACT_WORDS(hp,lp,p); 43 sx = hx&0x80000000; 44 hp &= 0x7fffffff; 45 hx &= 0x7fffffff; 46 47 /* purge off exception values */ 48 if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ 49 if((hx>=0x7ff00000)|| /* x not finite */ 50 ((hp>=0x7ff00000)&& /* p is NaN */ 51 (((hp-0x7ff00000)|lp)!=0))) 52 return ((long double)x*p)/((long double)x*p); 53 54 55 if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ 56 if (((hx-hp)|(lx-lp))==0) return zero*x; 57 x = fabs(x); 58 p = fabs(p); 59 if (hp<0x00200000) { 60 if(x+x>p) { 61 x-=p; 62 if(x+x>=p) x -= p; 63 } 64 } else { 65 p_half = 0.5*p; 66 if(x>p_half) { 67 x-=p; 68 if(x>=p_half) x -= p; 69 } 70 } 71 GET_HIGH_WORD(hx,x); 72 if ((hx&0x7fffffff)==0) hx = 0; 73 SET_HIGH_WORD(x,hx^sx); 74 return x; 75 } 76 77 #if LDBL_MANT_DIG == 53 78 __weak_reference(remainder, remainderl); 79 #endif 80