lib/libc/quad/fixunsdfdi.c

   1 /*-
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This software was developed by the Computer Systems Engineering group
   6  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   7  * contributed to Berkeley.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)fixunsdfdi.c     8.1 (Berkeley) 6/4/93
  34  * $FreeBSD: src/lib/libc/quad/fixunsdfdi.c,v 1.3 2007/01/09 00:28:03 imp Exp $
  35  */
  36
  37 #include "quad.h"
  38
  39 #define ONE_FOURTH      (1 << (LONG_BITS - 2))
  40 #define ONE_HALF        (ONE_FOURTH * 2.0)
  41 #define ONE             (ONE_FOURTH * 4.0)
  42
  43 /*
  44  * Convert double to (unsigned) quad.
  45  * Not sure what to do with negative numbers---for now, anything out
  46  * of range becomes UQUAD_MAX.
  47  */
  48 u_quad_t
  49 __fixunsdfdi(double x)
  50 {
  51         double toppart;
  52         union uu t;
  53
  54         if (x < 0)
  55                 return (UQUAD_MAX);     /* ??? should be 0?  ERANGE??? */
  56 #ifdef notdef                           /* this falls afoul of a GCC bug */
  57         if (x >= UQUAD_MAX)
  58                 return (UQUAD_MAX);
  59 #else                                   /* so we wire in 2^64-1 instead */
  60         if (x >= 18446744073709551615.0)
  61                 return (UQUAD_MAX);
  62 #endif
  63         /*
  64          * Get the upper part of the result.  Note that the divide
  65          * may round up; we want to avoid this if possible, so we
  66          * subtract `1/2' first.
  67          */
  68         toppart = (x - ONE_HALF) / ONE;
  69         /*
  70          * Now build a u_quad_t out of the top part.  The difference
  71          * between x and this is the bottom part (this may introduce
  72          * a few fuzzy bits, but what the heck).  With any luck this
  73          * difference will be nonnegative: x should wind up in the
  74          * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
  75          * 2*ULONG_MAX] instead.
  76          */
  77         t.ul[H] = (unsigned long)toppart;
  78         t.ul[L] = 0;
  79         x -= (double)t.uq;
  80         if (x < 0) {
  81                 t.ul[H]--;
  82                 x += ULONG_MAX;
  83         }
  84         if (x > ULONG_MAX) {
  85                 t.ul[H]++;
  86                 x -= ULONG_MAX;
  87         }
  88         t.ul[L] = (u_long)x;
  89         return (t.uq);
  90 }