88 lines
2.1 KiB
C
88 lines
2.1 KiB
C
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/* mpz_ui_sub -- Subtract an unsigned one-word integer and an mpz_t.
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Copyright 2002, 2004 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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void
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mpz_ui_sub (mpz_ptr w, unsigned long int uval, mpz_srcptr v)
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{
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mp_ptr vp, wp;
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mp_size_t vn, wn;
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mp_limb_t cy;
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#if BITS_PER_ULONG > GMP_NUMB_BITS /* avoid warnings about shift amount */
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if (uval > GMP_NUMB_MAX)
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{
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mpz_t u;
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mp_limb_t ul[2];
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PTR(u) = ul;
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ul[0] = uval & GMP_NUMB_MASK;
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ul[1] = uval >> GMP_NUMB_BITS;
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SIZ(u) = 2;
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mpz_sub (w, u, v);
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return;
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}
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#endif
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vp = PTR(v);
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vn = SIZ(v);
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wp = PTR(w);
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if (vn > 1)
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{
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wp = MPZ_REALLOC (w, vn);
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vp = PTR(v);
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mpn_sub_1 (wp, vp, vn, (mp_limb_t) uval);
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wn = -(vn - (wp[vn - 1] == 0));
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}
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else if (vn == 1)
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{
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if (uval >= vp[0])
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{
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wp[0] = uval - vp[0];
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wn = wp[0] != 0;
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}
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else
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{
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wp[0] = vp[0] - uval;
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wn = -1;
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}
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}
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else if (vn == 0)
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{
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wp[0] = uval;
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wn = uval != 0;
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}
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else /* (vn < 0) */
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{
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vn = -vn;
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wp = MPZ_REALLOC (w, vn + 1);
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vp = PTR(v);
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cy = mpn_add_1 (wp, vp, vn, (mp_limb_t) uval);
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wp[vn] = cy;
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wn = vn + (cy != 0);
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}
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SIZ(w) = wn;
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}
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