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[] = "$FreeBSD$"; 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 <sys/cdefs.h> 28 #include <float.h> 29 30 #include "math.h" 31 #include "math_private.h" 32 33 static const double 34 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ 35 36 double 37 frexp(double x, int *eptr) 38 { 39 int32_t hx, ix, lx; 40 EXTRACT_WORDS(hx,lx,x); 41 ix = 0x7fffffff&hx; 42 *eptr = 0; 43 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ 44 if (ix<0x00100000) { /* subnormal */ 45 x *= two54; 46 GET_HIGH_WORD(hx,x); 47 ix = hx&0x7fffffff; 48 *eptr = -54; 49 } 50 *eptr += (ix>>20)-1022; 51 hx = (hx&0x800fffff)|0x3fe00000; 52 SET_HIGH_WORD(x,hx); 53 return x; 54 } 55 56 #if (LDBL_MANT_DIG == 53) 57 __weak_reference(frexp, frexpl); 58 #endif 59