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 33 modf(double x, double *iptr) 34 { 35 int32_t i0,i1,j0; 36 u_int32_t i; 37 EXTRACT_WORDS(i0,i1,x); 38 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 39 if(j0<20) { /* integer part in high x */ 40 if(j0<0) { /* |x|<1 */ 41 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ 42 return x; 43 } else { 44 i = (0x000fffff)>>j0; 45 if(((i0&i)|i1)==0) { /* x is integral */ 46 u_int32_t high; 47 *iptr = x; 48 GET_HIGH_WORD(high,x); 49 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 50 return x; 51 } else { 52 INSERT_WORDS(*iptr,i0&(~i),0); 53 return x - *iptr; 54 } 55 } 56 } else if (j0>51) { /* no fraction part */ 57 u_int32_t high; 58 if (j0 == 0x400) { /* inf/NaN */ 59 *iptr = x; 60 return 0.0 / x; 61 } 62 *iptr = x*one; 63 GET_HIGH_WORD(high,x); 64 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 65 return x; 66 } else { /* fraction part in low x */ 67 i = ((u_int32_t)(0xffffffff))>>(j0-20); 68 if((i1&i)==0) { /* x is integral */ 69 u_int32_t high; 70 *iptr = x; 71 GET_HIGH_WORD(high,x); 72 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 73 return x; 74 } else { 75 INSERT_WORDS(*iptr,i0,i1&(~i)); 76 return x - *iptr; 77 } 78 } 79 } 80