1 /* @(#)s_modf.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 #include <sys/cdefs.h> 14 #if defined(LIBM_SCCS) && !defined(lint) 15 __RCSID("$NetBSD: s_modf.c,v 1.9 1997/10/09 11:32:56 lukem Exp $"); 16 #endif 17 18 /* 19 * modf(double x, double *iptr) 20 * return fraction part of x, and return x's integral part in *iptr. 21 * Method: 22 * Bit twiddling. 23 * 24 * Exception: 25 * No exception. 26 */ 27 28 #include "math.h" 29 #include "math_private.h" 30 31 #ifdef __STDC__ 32 static const double one = 1.0; 33 #else 34 static double one = 1.0; 35 #endif 36 37 #ifdef __STDC__ 38 double modf(double x, double *iptr) 39 #else 40 double modf(x, iptr) 41 double x,*iptr; 42 #endif 43 { 44 int32_t i0,i1,j0; 45 u_int32_t i; 46 EXTRACT_WORDS(i0,i1,x); 47 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 48 if(j0<20) { /* integer part in high x */ 49 if(j0<0) { /* |x|<1 */ 50 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ 51 return x; 52 } else { 53 i = (0x000fffff)>>j0; 54 if(((i0&i)|i1)==0) { /* x is integral */ 55 u_int32_t high; 56 *iptr = x; 57 GET_HIGH_WORD(high,x); 58 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 59 return x; 60 } else { 61 INSERT_WORDS(*iptr,i0&(~i),0); 62 return x - *iptr; 63 } 64 } 65 } else if (j0>51) { /* no fraction part */ 66 u_int32_t high; 67 *iptr = x*one; 68 GET_HIGH_WORD(high,x); 69 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 70 return x; 71 } else { /* fraction part in low x */ 72 i = ((u_int32_t)(0xffffffff))>>(j0-20); 73 if((i1&i)==0) { /* x is integral */ 74 u_int32_t high; 75 *iptr = x; 76 GET_HIGH_WORD(high,x); 77 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 78 return x; 79 } else { 80 INSERT_WORDS(*iptr,i0,i1&(~i)); 81 return x - *iptr; 82 } 83 } 84 } 85