aa9bc17601
BMakefiles and other bits will follow. Requested by: Andrey Chernov Made world by: Chuck Robey
85 lines
2.1 KiB
C
85 lines
2.1 KiB
C
/* mpz_sub_ui -- Subtract an unsigned one-word integer from an MP_INT.
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Copyright (C) 1991, 1993, 1994, 1996 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 Library General Public License as published by
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the Free Software Foundation; either version 2 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 Library General Public
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License for more details.
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You should have received a copy of the GNU Library 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., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, 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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#if __STDC__
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mpz_sub_ui (mpz_ptr w, mpz_srcptr u, unsigned long int v)
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#else
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mpz_sub_ui (w, u, v)
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mpz_ptr w;
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mpz_srcptr u;
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unsigned long int v;
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#endif
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{
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mp_srcptr up;
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mp_ptr wp;
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mp_size_t usize, wsize;
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mp_size_t abs_usize;
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usize = u->_mp_size;
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abs_usize = ABS (usize);
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/* If not space for W (and possible carry), increase space. */
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wsize = abs_usize + 1;
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if (w->_mp_alloc < wsize)
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_mpz_realloc (w, wsize);
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/* These must be after realloc (U may be the same as W). */
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up = u->_mp_d;
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wp = w->_mp_d;
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if (abs_usize == 0)
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{
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wp[0] = v;
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w->_mp_size = -(v != 0);
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return;
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}
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if (usize < 0)
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{
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mp_limb_t cy;
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cy = mpn_add_1 (wp, up, abs_usize, v);
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wp[abs_usize] = cy;
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wsize = -(abs_usize + cy);
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}
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else
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{
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/* The signs are different. Need exact comparison to determine
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which operand to subtract from which. */
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if (abs_usize == 1 && up[0] < v)
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{
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wp[0] = v - up[0];
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wsize = -1;
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}
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else
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{
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mpn_sub_1 (wp, up, abs_usize, v);
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/* Size can decrease with at most one limb. */
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wsize = abs_usize - (wp[abs_usize - 1] == 0);
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}
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}
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w->_mp_size = wsize;
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}
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