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 /* 14 * modf(double x, double *iptr) 15 * return fraction part of x, and return x's integral part in *iptr. 16 * Method: 17 * Bit twiddling. 18 * 19 * Exception: 20 * No exception. 21 */ 22 23 #include <openlibm_math.h> 24 25 #include "math_private.h" 26 27 static const double one = 1.0; 28 29 OLM_DLLEXPORT double 30 modf(double x, double *iptr) 31 { 32 int32_t i0,i1,j0; 33 u_int32_t i; 34 EXTRACT_WORDS(i0,i1,x); 35 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 36 if(j0<20) { /* integer part in high x */ 37 if(j0<0) { /* |x|<1 */ 38 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ 39 return x; 40 } else { 41 i = (0x000fffff)>>j0; 42 if(((i0&i)|i1)==0) { /* x is integral */ 43 u_int32_t high; 44 *iptr = x; 45 GET_HIGH_WORD(high,x); 46 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 47 return x; 48 } else { 49 INSERT_WORDS(*iptr,i0&(~i),0); 50 return x - *iptr; 51 } 52 } 53 } else if (j0>51) { /* no fraction part */ 54 u_int32_t high; 55 if (j0 == 0x400) { /* inf/NaN */ 56 *iptr = x; 57 return 0.0 / x; 58 } 59 *iptr = x*one; 60 GET_HIGH_WORD(high,x); 61 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 62 return x; 63 } else { /* fraction part in low x */ 64 i = ((u_int32_t)(0xffffffff))>>(j0-20); 65 if((i1&i)==0) { /* x is integral */ 66 u_int32_t high; 67 *iptr = x; 68 GET_HIGH_WORD(high,x); 69 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 70 return x; 71 } else { 72 INSERT_WORDS(*iptr,i0,i1&(~i)); 73 return x - *iptr; 74 } 75 } 76 } 77