lib/libc/quad/fixunssfdi.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  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by the University of
  20  *      California, Berkeley and its contributors.
  21  * 4. Neither the name of the University nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  *
  37  * @(#)fixunssfdi.c     8.1 (Berkeley) 6/4/93
  38  */
  39
  40 #include "quad.h"
  41
  42 #define ONE_FOURTH      (1 << (LONG_BITS - 2))
  43 #define ONE_HALF        (ONE_FOURTH * 2.0)
  44 #define ONE             (ONE_FOURTH * 4.0)
  45
  46 /*
  47  * Convert float to (unsigned) quad.  We do most of our work in double,
  48  * out of sheer paranoia.
  49  *
  50  * Not sure what to do with negative numbers---for now, anything out
  51  * of range becomes UQUAD_MAX.
  52  *
  53  * N.B.: must use new ANSI syntax (sorry).
  54  */
  55 u_quad_t
  56 __fixunssfdi(float f)
  57 {
  58         double x, toppart;
  59         union uu t;
  60
  61         if (f < 0)
  62                 return (UQUAD_MAX);     /* ??? should be 0?  ERANGE??? */
  63 #ifdef notdef                           /* this falls afoul of a GCC bug */
  64         if (f >= UQUAD_MAX)
  65                 return (UQUAD_MAX);
  66 #else                                   /* so we wire in 2^64-1 instead */
  67         if (f >= 18446744073709551615.0)
  68                 return (UQUAD_MAX);
  69 #endif
  70         x = f;
  71         /*
  72          * Get the upper part of the result.  Note that the divide
  73          * may round up; we want to avoid this if possible, so we
  74          * subtract `1/2' first.
  75          */
  76         toppart = (x - ONE_HALF) / ONE;
  77         /*
  78          * Now build a u_quad_t out of the top part.  The difference
  79          * between x and this is the bottom part (this may introduce
  80          * a few fuzzy bits, but what the heck).  With any luck this
  81          * difference will be nonnegative: x should wind up in the
  82          * range [0..ULONG_MAX].  For paranoia, we assume [LONG_MIN..
  83          * 2*ULONG_MAX] instead.
  84          */
  85         t.ul[H] = (unsigned long)toppart;
  86         t.ul[L] = 0;
  87         x -= (double)t.uq;
  88         if (x < 0) {
  89                 t.ul[H]--;
  90                 x += ULONG_MAX;
  91         }
  92         if (x > ULONG_MAX) {
  93                 t.ul[H]++;
  94                 x -= ULONG_MAX;
  95         }
  96         t.ul[L] = (u_long)x;
  97         return (t.uq);
  98 }