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 #ifndef lint 14 static char rcsid[] = "$FreeBSD$"; 15 #endif 16 17 /* 18 * modf(double x, double *iptr) 19 * return fraction part of x, and return x's integral part in *iptr. 20 * Method: 21 * Bit twiddling. 22 * 23 * Exception: 24 * No exception. 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 static const double one = 1.0; 31 32 double modf(double x, double *iptr) 33 { 34 int32_t i0,i1,j0; 35 u_int32_t i; 36 EXTRACT_WORDS(i0,i1,x); 37 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 38 if(j0<20) { /* integer part in high x */ 39 if(j0<0) { /* |x|<1 */ 40 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ 41 return x; 42 } else { 43 i = (0x000fffff)>>j0; 44 if(((i0&i)|i1)==0) { /* x is integral */ 45 u_int32_t high; 46 *iptr = x; 47 GET_HIGH_WORD(high,x); 48 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 49 return x; 50 } else { 51 INSERT_WORDS(*iptr,i0&(~i),0); 52 return x - *iptr; 53 } 54 } 55 } else if (j0>51) { /* no fraction part */ 56 u_int32_t high; 57 *iptr = x*one; 58 GET_HIGH_WORD(high,x); 59 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 60 return x; 61 } else { /* fraction part in low x */ 62 i = ((u_int32_t)(0xffffffff))>>(j0-20); 63 if((i1&i)==0) { /* x is integral */ 64 u_int32_t high; 65 *iptr = x; 66 GET_HIGH_WORD(high,x); 67 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 68 return x; 69 } else { 70 INSERT_WORDS(*iptr,i0,i1&(~i)); 71 return x - *iptr; 72 } 73 } 74 } 75