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 #include <sys/cdefs.h> 14 //__FBSDID("$FreeBSD: src/lib/msun/src/s_frexp.c,v 1.11 2008/02/22 02:30:35 das Exp $"); 15 16 /* 17 * for non-zero x 18 * x = frexp(arg,&exp); 19 * return a double fp quantity x such that 0.5 <= |x| <1.0 20 * and the corresponding binary exponent "exp". That is 21 * arg = x*2^exp. 22 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg 23 * with *exp=0. 24 */ 25 26 #include <float.h> 27 28 #include "openlibm.h" 29 #include "math_private.h" 30 31 static const double 32 two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ 33 34 double 35 frexp(double x, int *eptr) 36 { 37 int32_t hx, ix, lx; 38 EXTRACT_WORDS(hx,lx,x); 39 ix = 0x7fffffff&hx; 40 *eptr = 0; 41 if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ 42 if (ix<0x00100000) { /* subnormal */ 43 x *= two54; 44 GET_HIGH_WORD(hx,x); 45 ix = hx&0x7fffffff; 46 *eptr = -54; 47 } 48 *eptr += (ix>>20)-1022; 49 hx = (hx&0x800fffff)|0x3fe00000; 50 SET_HIGH_WORD(x,hx); 51 return x; 52 } 53 54 #if (LDBL_MANT_DIG == 53) 55 __weak_reference(frexp, frexpl); 56 #endif 57