1 2 /* @(#)s_modf.c 1.3 95/01/18 */ 3 /* 4 * ==================================================== 5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6 * 7 * Developed at SunSoft, a Sun Microsystems, Inc. business. 8 * Permission to use, copy, modify, and distribute this 9 * software is freely granted, provided that this notice 10 * is preserved. 11 * ==================================================== 12 */ 13 14 /* 15 * ieee_modf(double x, double *iptr) 16 * return fraction part of x, and return x's integral part in *iptr. 17 * Method: 18 * Bit twiddling. 19 * 20 * Exception: 21 * No exception. 22 */ 23 24 #include "fdlibm.h" 25 26 #ifdef __STDC__ 27 static const double one = 1.0; 28 #else 29 static double one = 1.0; 30 #endif 31 32 #ifdef __STDC__ 33 double ieee_modf(double x, double *iptr) 34 #else 35 double ieee_modf(x, iptr) 36 double x,*iptr; 37 #endif 38 { 39 int i0,i1,j0; 40 unsigned i; 41 i0 = __HI(x); /* high x */ 42 i1 = __LO(x); /* low x */ 43 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 44 if(j0<20) { /* integer part in high x */ 45 if(j0<0) { /* |x|<1 */ 46 __HIp(iptr) = i0&0x80000000; 47 __LOp(iptr) = 0; /* *iptr = +-0 */ 48 return x; 49 } else { 50 i = (0x000fffff)>>j0; 51 if(((i0&i)|i1)==0) { /* x is integral */ 52 *iptr = x; 53 __HI(x) &= 0x80000000; 54 __LO(x) = 0; /* return +-0 */ 55 return x; 56 } else { 57 __HIp(iptr) = i0&(~i); 58 __LOp(iptr) = 0; 59 return x - *iptr; 60 } 61 } 62 } else if (j0>51) { /* no fraction part */ 63 *iptr = x*one; 64 __HI(x) &= 0x80000000; 65 __LO(x) = 0; /* return +-0 */ 66 return x; 67 } else { /* fraction part in low x */ 68 i = ((unsigned)(0xffffffff))>>(j0-20); 69 if((i1&i)==0) { /* x is integral */ 70 *iptr = x; 71 __HI(x) &= 0x80000000; 72 __LO(x) = 0; /* return +-0 */ 73 return x; 74 } else { 75 __HIp(iptr) = i0; 76 __LOp(iptr) = i1&(~i); 77 return x - *iptr; 78 } 79 } 80 } 81
