ui_sub.c
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上传日期:2022-08-06
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- /* mpz_ui_sub -- Subtract an unsigned one-word integer and an mpz_t.
- Copyright 2002, 2004 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
- mpz_ui_sub (mpz_ptr w, unsigned long int uval, mpz_srcptr v)
- {
- mp_ptr vp, wp;
- mp_size_t vn, wn;
- mp_limb_t cy;
- #if BITS_PER_ULONG > GMP_NUMB_BITS /* avoid warnings about shift amount */
- if (uval > GMP_NUMB_MAX)
- {
- mpz_t u;
- mp_limb_t ul[2];
- PTR(u) = ul;
- ul[0] = uval & GMP_NUMB_MASK;
- ul[1] = uval >> GMP_NUMB_BITS;
- SIZ(u) = 2;
- mpz_sub (w, u, v);
- return;
- }
- #endif
- vp = PTR(v);
- vn = SIZ(v);
- wp = PTR(w);
- if (vn > 1)
- {
- wp = MPZ_REALLOC (w, vn);
- vp = PTR(v);
- mpn_sub_1 (wp, vp, vn, (mp_limb_t) uval);
- wn = -(vn - (wp[vn - 1] == 0));
- }
- else if (vn == 1)
- {
- if (uval >= vp[0])
- {
- wp[0] = uval - vp[0];
- wn = wp[0] != 0;
- }
- else
- {
- wp[0] = vp[0] - uval;
- wn = -1;
- }
- }
- else if (vn == 0)
- {
- wp[0] = uval;
- wn = uval != 0;
- }
- else /* (vn < 0) */
- {
- vn = -vn;
- wp = MPZ_REALLOC (w, vn + 1);
- vp = PTR(v);
- cy = mpn_add_1 (wp, vp, vn, (mp_limb_t) uval);
- wp[vn] = cy;
- wn = vn + (cy != 0);
- }
- SIZ(w) = wn;
- }