source/libs/gmp/gmp-src/mpf/eq.c

   1 /* mpf_eq -- Compare two floats up to a specified bit #.
   2
   3 Copyright 1993, 1995, 1996, 2001, 2002, 2008, 2009, 2012 Free Software
   4 Foundation, Inc.
   5
   6 This file is part of the GNU MP Library.
   7
   8 The GNU MP Library is free software; you can redistribute it and/or modify
   9 it under the terms of either:
  10
  11   * the GNU Lesser General Public License as published by the Free
  12     Software Foundation; either version 3 of the License, or (at your
  13     option) any later version.
  14
  15 or
  16
  17   * the GNU General Public License as published by the Free Software
  18     Foundation; either version 2 of the License, or (at your option) any
  19     later version.
  20
  21 or both in parallel, as here.
  22
  23 The GNU MP Library is distributed in the hope that it will be useful, but
  24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  25 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  26 for more details.
  27
  28 You should have received copies of the GNU General Public License and the
  29 GNU Lesser General Public License along with the GNU MP Library.  If not,
  30 see https://www.gnu.org/licenses/.  */
  31
  32 #include "gmp.h"
  33 #include "gmp-impl.h"
  34 #include "longlong.h"
  35
  36 int
  37 mpf_eq (mpf_srcptr u, mpf_srcptr v, mp_bitcnt_t n_bits)
  38 {
  39   mp_srcptr up, vp, p;
  40   mp_size_t usize, vsize, minsize, maxsize, n_limbs, i, size;
  41   mp_exp_t uexp, vexp;
  42   mp_limb_t diff;
  43   int cnt;
  44
  45   uexp = u->_mp_exp;
  46   vexp = v->_mp_exp;
  47
  48   usize = u->_mp_size;
  49   vsize = v->_mp_size;
  50
  51   /* 1. Are the signs different?  */
  52   if ((usize ^ vsize) >= 0)
  53     {
  54       /* U and V are both non-negative or both negative.  */
  55       if (usize == 0)
  56         return vsize == 0;
  57       if (vsize == 0)
  58         return 0;
  59
  60       /* Fall out.  */
  61     }
  62   else
  63     {
  64       /* Either U or V is negative, but not both.  */
  65       return 0;
  66     }
  67
  68   /* U and V have the same sign and are both non-zero.  */
  69
  70   /* 2. Are the exponents different?  */
  71   if (uexp != vexp)
  72     return 0;
  73
  74   usize = ABS (usize);
  75   vsize = ABS (vsize);
  76
  77   up = u->_mp_d;
  78   vp = v->_mp_d;
  79
  80   up += usize;                  /* point just above most significant limb */
  81   vp += vsize;                  /* point just above most significant limb */
  82
  83   count_leading_zeros (cnt, up[-1]);
  84   if ((vp[-1] >> (GMP_LIMB_BITS - 1 - cnt)) != 1)
  85     return 0;                   /* msb positions different */
  86
  87   n_bits += cnt - GMP_NAIL_BITS;
  88   n_limbs = (n_bits + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS;
  89
  90   usize = MIN (usize, n_limbs);
  91   vsize = MIN (vsize, n_limbs);
  92
  93 #if 0
  94   /* Ignore zeros at the low end of U and V.  */
  95   while (up[0] == 0)
  96     up++, usize--;
  97   while (vp[0] == 0)
  98     vp++, vsize--;
  99 #endif
 100
 101   minsize = MIN (usize, vsize);
 102   maxsize = usize + vsize - minsize;
 103
 104   up -= minsize;                /* point at most significant common limb */
 105   vp -= minsize;                /* point at most significant common limb */
 106
 107   /* Compare the most significant part which has explicit limbs for U and V. */
 108   for (i = minsize - 1; i > 0; i--)
 109     {
 110       if (up[i] != vp[i])
 111         return 0;
 112     }
 113
 114   n_bits -= (maxsize - 1) * GMP_NUMB_BITS;
 115
 116   size = maxsize - minsize;
 117   if (size != 0)
 118     {
 119       if (up[0] != vp[0])
 120         return 0;
 121
 122       /* Now either U or V has its limbs consumed, i.e, continues with an
 123          infinite number of implicit zero limbs.  Check that the other operand
 124          has just zeros in the corresponding, relevant part.  */
 125
 126       if (usize > vsize)
 127         p = up - size;
 128       else
 129         p = vp - size;
 130
 131       for (i = size - 1; i > 0; i--)
 132         {
 133           if (p[i] != 0)
 134             return 0;
 135         }
 136
 137       diff = p[0];
 138     }
 139   else
 140     {
 141       /* Both U or V has its limbs consumed.  */
 142
 143       diff = up[0] ^ vp[0];
 144     }
 145
 146   if (n_bits < GMP_NUMB_BITS)
 147     diff >>= GMP_NUMB_BITS - n_bits;
 148
 149   return diff == 0;
 150 }