lib/libc/quad/fixunssfdi.c

   1 /*      $NetBSD: fixunssfdi.c,v 1.5 2002/10/20 10:15:47 scw Exp $       */
   2
   3 /*-
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This software was developed by the Computer Systems Engineering group
   8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   9  * contributed to Berkeley.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 #if 0
  39 static char sccsid[] = "@(#)fixunssfdi.c        8.1 (Berkeley) 6/4/93";
  40 #else
  41 __RCSID("$NetBSD: fixunssfdi.c,v 1.5 2002/10/20 10:15:47 scw Exp $");
  42 #endif
  43 #endif /* LIBC_SCCS and not lint */
  44
  45 #include "quad.h"
  46
  47 #define ONE_FOURTH      ((int)1 << (INT_BITS - 2))
  48 #define ONE_HALF        (ONE_FOURTH * 2.0)
  49 #define ONE             (ONE_FOURTH * 4.0)
  50
  51 /*
  52  * Convert float to (unsigned) quad.  We do most of our work in double,
  53  * out of sheer paranoia.
  54  *
  55  * Not sure what to do with negative numbers---for now, anything out
  56  * of range becomes UQUAD_MAX.
  57  *
  58  * N.B.: must use new ANSI syntax (sorry).
  59  */
  60 u_quad_t
  61 __fixunssfdi(float f)
  62 {
  63         double x, toppart;
  64         union uu t;
  65
  66         if (f < 0)
  67                 return (UQUAD_MAX);     /* ??? should be 0?  ERANGE??? */
  68 #ifdef notdef                           /* this falls afoul of a GCC bug */
  69         if (f >= UQUAD_MAX)
  70                 return (UQUAD_MAX);
  71 #else                                   /* so we wire in 2^64-1 instead */
  72         if (f >= 18446744073709551615.0)        /* XXX */
  73                 return (UQUAD_MAX);
  74 #endif
  75         x = f;
  76         /*
  77          * Get the upper part of the result.  Note that the divide
  78          * may round up; we want to avoid this if possible, so we
  79          * subtract `1/2' first.
  80          */
  81         toppart = (x - ONE_HALF) / ONE;
  82         /*
  83          * Now build a u_quad_t out of the top part.  The difference
  84          * between x and this is the bottom part (this may introduce
  85          * a few fuzzy bits, but what the heck).  With any luck this
  86          * difference will be nonnegative: x should wind up in the
  87          * range [0..UINT_MAX].  For paranoia, we assume [INT_MIN..
  88          * 2*UINT_MAX] instead.
  89          */
  90         t.ul[H] = (unsigned int)toppart;
  91         t.ul[L] = 0;
  92         x -= (double)t.uq;
  93         if (x < 0) {
  94                 t.ul[H]--;
  95                 x += UINT_MAX;
  96         }
  97         if (x > UINT_MAX) {
  98                 t.ul[H]++;
  99                 x -= UINT_MAX;
 100         }
 101         t.ul[L] = (u_int)x;
 102         return (t.uq);
 103 }