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