54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
/* mpz_div_2exp -- Divide a bignum by 2**CNT
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Copyright (C) 1991 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 General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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The GNU MP Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with the GNU MP Library; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, 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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#ifdef __STDC__
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mpz_div_2exp (MP_INT *w, const MP_INT *u, unsigned long int cnt)
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#else
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mpz_div_2exp (w, u, cnt)
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MP_INT *w;
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const MP_INT *u;
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unsigned long int cnt;
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#endif
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{
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mp_size usize = u->size;
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mp_size wsize;
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mp_size abs_usize = ABS (usize);
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mp_size limb_cnt;
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limb_cnt = cnt / BITS_PER_MP_LIMB;
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wsize = abs_usize - limb_cnt;
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if (wsize <= 0)
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wsize = 0;
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else
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{
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if (w->alloc < wsize)
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_mpz_realloc (w, wsize);
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wsize = mpn_rshift (w->d, u->d + limb_cnt, abs_usize - limb_cnt,
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cnt % BITS_PER_MP_LIMB);
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}
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w->size = (usize >= 0) ? wsize : -wsize;
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}
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