gonzui

    1: /*      $OpenBSD: frexp.c,v 1.7 2011/07/08 22:28:33 martynas Exp $   */
    2: 
    3: /*-
    4:  * Copyright (c) 2004 David Schultz <das@FreeBSD.ORG>
    5:  * All rights reserved.
    6:  *
    7:  * Redistribution and use in source and binary forms, with or without
    8:  * modification, are permitted provided that the following conditions
    9:  * are met:
   10:  * 1. Redistributions of source code must retain the above copyright
   11:  *    notice, this list of conditions and the following disclaimer.
   12:  * 2. Redistributions in binary form must reproduce the above copyright
   13:  *    notice, this list of conditions and the following disclaimer in the
   14:  *    documentation and/or other materials provided with the distribution.
   15:  *
   16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26:  * SUCH DAMAGE.
   27:  *
   28:  * $FreeBSD: frexp.c,v 1.1 2004/07/18 21:23:39 das Exp $
   29:  */
   30: 
   31: /* LINTLIBRARY */
   32: 
   33: #include <sys/types.h>
   34: #include <sys/cdefs.h>
   35: #include <machine/ieee.h>
   36: #include <float.h>
   37: #include <math.h>
   38: 
   39: double
   40: frexp(double v, int *ex)
   41: {
   42:         union  {
   43:                 double v;
   44:                 struct ieee_double s;
   45:         } u;
   46: 
   47:         u.v = v;
   48:         switch (u.s.dbl_exp) {
   49:         case 0:                /* 0 or subnormal */
   50:                 if ((u.s.dbl_fracl | u.s.dbl_frach) == 0) {
   51:                         *ex = 0;
   52:                 } else {
   53:                         /*
   54:                          * The power of 2 is arbitrary, any value from 54 to
   55:                          * 1024 will do.
   56:                          */
   57:                         u.v *= 0x1.0p514;
   58:                         *ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1 + 514);
   59:                         u.s.dbl_exp = DBL_EXP_BIAS - 1;
   60:                 }
   61:                 break;
   62:         case DBL_EXP_INFNAN:   /* Inf or NaN; value of *ex is unspecified */
   63:                 break;
   64:         default:       /* normal */
   65:                 *ex = u.s.dbl_exp - (DBL_EXP_BIAS - 1);
   66:                 u.s.dbl_exp = DBL_EXP_BIAS - 1;
   67:                 break;
   68:         }
   69:         return (u.v);
   70: }
   71: 
   72: #if     LDBL_MANT_DIG == 53
   73: #ifdef  lint
   74: /* PROTOLIB1 */
   75: long double frexpl(long double, int *);
   76: #else   /* lint */
   77: __weak_alias(frexpl, frexp);
   78: #endif  /* lint */
   79: #endif  /* LDBL_MANT_DIG == 53 */