s_frexp.c (1328B)
1 /* @(#)s_frexp.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 #ifndef lint 14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_frexp.c,v 1.8 2002/05/28 18:15:04 alfred Exp $"; 15 #endif 16 17 /* 18 * for non-zero x 19 * x = frexp(arg,&exp); 20 * return a double fp quantity x such that 0.5 <= |x| <1.0 21 * and the corresponding binary exponent "exp". That is 22 * arg = x*2^exp. 23 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg 24 * with *exp=0. 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 static const double 31 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ 32 33 double 34 frexp(double x, int *eptr) 35 { 36 int32_t hx, ix, lx; 37 EXTRACT_WORDS(hx,lx,x); 38 ix = 0x7fffffff&hx; 39 *eptr = 0; 40 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ 41 if (ix<0x00100000) { /* subnormal */ 42 x *= two54; 43 GET_HIGH_WORD(hx,x); 44 ix = hx&0x7fffffff; 45 *eptr = -54; 46 } 47 *eptr += (ix>>20)-1022; 48 hx = (hx&0x800fffff)|0x3fe00000; 49 SET_HIGH_WORD(x,hx); 50 return x; 51 }