eq.c
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上传日期:2022-08-06
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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, mp_bitcnt_t n_bits)
- {
- mp_srcptr up, vp, p;
- mp_size_t usize, vsize, minsize, maxsize, n_limbs, i, size;
- 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;
- }
- n_bits -= (maxsize - 1) * GMP_NUMB_BITS;
- size = maxsize - minsize;
- if (size != 0)
- {
- if (up[0] != vp[0])
- return 0;
- /* Now either U or V has its limbs consumed, i.e, continues with an
- infinite number of implicit zero limbs. Check that the other operand
- has just zeros in the corresponding, relevant part. */
- if (usize > vsize)
- p = up - size;
- else
- p = vp - size;
- for (i = size - 1; i > 0; i--)
- {
- if (p[i] != 0)
- return 0;
- }
- diff = p[0];
- }
- else
- {
- /* Both U or V has its limbs consumed. */
- diff = up[0] ^ vp[0];
- }
- if (n_bits < GMP_NUMB_BITS)
- diff >>= GMP_NUMB_BITS - n_bits;
- return diff == 0;
- }