add.c
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上传日期:2022-08-06
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- /* mpf_add -- Add two floats.
- Copyright 1993, 1994, 1996, 2000, 2001, 2005 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"
- void
- mpf_add (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
- {
- mp_srcptr up, vp;
- mp_ptr rp, tp;
- mp_size_t usize, vsize, rsize;
- mp_size_t prec;
- mp_exp_t uexp;
- mp_size_t ediff;
- mp_limb_t cy;
- int negate;
- TMP_DECL;
- usize = u->_mp_size;
- vsize = v->_mp_size;
- /* Handle special cases that don't work in generic code below. */
- if (usize == 0)
- {
- set_r_v_maybe:
- if (r != v)
- mpf_set (r, v);
- return;
- }
- if (vsize == 0)
- {
- v = u;
- goto set_r_v_maybe;
- }
- /* If signs of U and V are different, perform subtraction. */
- if ((usize ^ vsize) < 0)
- {
- __mpf_struct v_negated;
- v_negated._mp_size = -vsize;
- v_negated._mp_exp = v->_mp_exp;
- v_negated._mp_d = v->_mp_d;
- mpf_sub (r, u, &v_negated);
- return;
- }
- TMP_MARK;
- /* Signs are now known to be the same. */
- negate = usize < 0;
- /* Make U be the operand with the largest exponent. */
- if (u->_mp_exp < v->_mp_exp)
- {
- mpf_srcptr t;
- t = u; u = v; v = t;
- usize = u->_mp_size;
- vsize = v->_mp_size;
- }
- usize = ABS (usize);
- vsize = ABS (vsize);
- up = u->_mp_d;
- vp = v->_mp_d;
- rp = r->_mp_d;
- prec = r->_mp_prec;
- uexp = u->_mp_exp;
- ediff = u->_mp_exp - v->_mp_exp;
- /* If U extends beyond PREC, ignore the part that does. */
- if (usize > prec)
- {
- up += usize - prec;
- usize = prec;
- }
- /* If V extends beyond PREC, ignore the part that does.
- Note that this may make vsize negative. */
- if (vsize + ediff > prec)
- {
- vp += vsize + ediff - prec;
- vsize = prec - ediff;
- }
- #if 0
- /* Locate the least significant non-zero limb in (the needed parts
- of) U and V, to simplify the code below. */
- while (up[0] == 0)
- up++, usize--;
- while (vp[0] == 0)
- vp++, vsize--;
- #endif
- /* Allocate temp space for the result. Allocate
- just vsize + ediff later??? */
- tp = TMP_ALLOC_LIMBS (prec);
- if (ediff >= prec)
- {
- /* V completely cancelled. */
- if (rp != up)
- MPN_COPY_INCR (rp, up, usize);
- rsize = usize;
- }
- else
- {
- /* uuuu | uuuu | uuuu | uuuu | uuuu */
- /* vvvvvvv | vv | vvvvv | v | vv */
- if (usize > ediff)
- {
- /* U and V partially overlaps. */
- if (vsize + ediff <= usize)
- {
- /* uuuu */
- /* v */
- mp_size_t size;
- size = usize - ediff - vsize;
- MPN_COPY (tp, up, size);
- cy = mpn_add (tp + size, up + size, usize - size, vp, vsize);
- rsize = usize;
- }
- else
- {
- /* uuuu */
- /* vvvvv */
- mp_size_t size;
- size = vsize + ediff - usize;
- MPN_COPY (tp, vp, size);
- cy = mpn_add (tp + size, up, usize, vp + size, usize - ediff);
- rsize = vsize + ediff;
- }
- }
- else
- {
- /* uuuu */
- /* vv */
- mp_size_t size;
- size = vsize + ediff - usize;
- MPN_COPY (tp, vp, vsize);
- MPN_ZERO (tp + vsize, ediff - usize);
- MPN_COPY (tp + size, up, usize);
- cy = 0;
- rsize = size + usize;
- }
- MPN_COPY (rp, tp, rsize);
- rp[rsize] = cy;
- rsize += cy;
- uexp += cy;
- }
- r->_mp_size = negate ? -rsize : rsize;
- r->_mp_exp = uexp;
- TMP_FREE;
- }