1 2 /* @(#)s_frexp.c 1.4 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 * for non-zero x 16 * x = ieee_frexp(arg,&exp); 17 * return a double fp quantity x such that 0.5 <= |x| <1.0 18 * and the corresponding binary exponent "exp". That is 19 * arg = x*2^exp. 20 * If arg is inf, 0.0, or NaN, then ieee_frexp(arg,&exp) returns arg 21 * with *exp=0. 22 */ 23 24 #include "fdlibm.h" 25 26 #ifdef __STDC__ 27 static const double 28 #else 29 static double 30 #endif 31 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ 32 33 #ifdef __STDC__ 34 double ieee_frexp(double x, int *eptr) 35 #else 36 double ieee_frexp(x, eptr) 37 double x; int *eptr; 38 #endif 39 { 40 int hx, ix, lx; 41 hx = __HI(x); 42 ix = 0x7fffffff&hx; 43 lx = __LO(x); 44 *eptr = 0; 45 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ 46 if (ix<0x00100000) { /* subnormal */ 47 x *= two54; 48 hx = __HI(x); 49 ix = hx&0x7fffffff; 50 *eptr = -54; 51 } 52 *eptr += (ix>>20)-1022; 53 hx = (hx&0x800fffff)|0x3fe00000; 54 __HI(x) = hx; 55 return x; 56 } 57
