1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 /* 13 * modf(double x, double *iptr) 14 * return fraction part of x, and return x's integral part in *iptr. 15 * Method: 16 * Bit twiddling. 17 * 18 * Exception: 19 * No exception. 20 */ 21 22 #include "math.h" 23 #include "math_private.h" 24 25 static const double one = 1.0; 26 27 double 28 modf(double x, double *iptr) 29 { 30 int32_t i0,i1,j0; 31 u_int32_t i; 32 EXTRACT_WORDS(i0,i1,x); 33 j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ 34 if(j0<20) { /* integer part in high x */ 35 if(j0<0) { /* |x|<1 */ 36 INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ 37 return x; 38 } else { 39 i = (0x000fffff)>>j0; 40 if(((i0&i)|i1)==0) { /* x is integral */ 41 u_int32_t high; 42 *iptr = x; 43 GET_HIGH_WORD(high,x); 44 INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ 45 return x; 46 } else { 47 INSERT_WORDS(*iptr,i0&(~i),0); 48 return x - *iptr; 49 } 50 } 51 } else if (j0>51) { /* no fraction part */ 52 u_int32_t high; 53 if (j0 == 0x400) { /* inf/NaN */ 54 *iptr = x; 55 return 0.0 / x; 56 } 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