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/* mpf_eq -- Compare two floats up to a specified bit #.
Copyright 1993, 1995, 1996, 2001, 2002, 2008, 2009 Free Software Foundation,
Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
int
mpf_eq (mpf_srcptr u, mpf_srcptr v, unsigned long int n_bits)
{
mp_srcptr up, vp, p;
mp_size_t usize, vsize, minsize, maxsize, n_limbs, i;
mp_exp_t uexp, vexp;
mp_limb_t diff;
int cnt;
uexp = u->_mp_exp;
vexp = v->_mp_exp;
usize = u->_mp_size;
vsize = v->_mp_size;
/* 1. Are the signs different? */
if ((usize ^ vsize) >= 0)
{
/* U and V are both non-negative or both negative. */
if (usize == 0)
return vsize == 0;
if (vsize == 0)
return 0;
/* Fall out. */
}
else
{
/* Either U or V is negative, but not both. */
return 0;
}
/* U and V have the same sign and are both non-zero. */
/* 2. Are the exponents different? */
if (uexp != vexp)
return 0;
usize = ABS (usize);
vsize = ABS (vsize);
up = u->_mp_d;
vp = v->_mp_d;
up += usize; /* point just above most significant limb */
vp += vsize; /* point just above most significant limb */
count_leading_zeros (cnt, up[-1]);
if ((vp[-1] >> (GMP_LIMB_BITS - 1 - cnt)) != 1)
return 0; /* msb positions different */
n_bits += cnt - GMP_NAIL_BITS;
n_limbs = (n_bits + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS;
usize = MIN (usize, n_limbs);
vsize = MIN (vsize, n_limbs);
#if 0
/* Ignore zeros at the low end of U and V. */
while (up[0] == 0)
up++, usize--;
while (vp[0] == 0)
vp++, vsize--;
#endif
minsize = MIN (usize, vsize);
maxsize = usize + vsize - minsize;
up -= minsize; /* point at most significant common limb */
vp -= minsize; /* point at most significant common limb */
/* Compare the most significant part which has explicit limbs for U and V. */
for (i = minsize - 1; i > 0; i--)
{
if (up[i] != vp[i])
return 0;
}
if (minsize != maxsize)
{
if (up[0] != vp[0])
return 0;
}
/* Now either U or V has its limbs consumed. Check the the other operand
has just zeros in the corresponding, relevant part. */
if (usize > vsize)
p = up + minsize - maxsize;
else
p = vp + minsize - maxsize;
for (i = maxsize - minsize - 1; i > 0; i--)
{
if (p[i] != 0)
return 0;
}
n_bits -= (maxsize - 1) * GMP_NUMB_BITS;
if (minsize != maxsize)
diff = p[0];
else
diff = up[0] ^ vp[0];
if (n_bits < GMP_NUMB_BITS)
diff >>= GMP_NUMB_BITS - n_bits;
return diff == 0;
}
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