73 lines
2.1 KiB
C
73 lines
2.1 KiB
C
/* mpz_tdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder.
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Copyright 1991, 1993, 1994, 1995, 2001, 2002 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_tdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt)
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{
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mp_size_t in_size = ABS (in->_mp_size);
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mp_size_t res_size;
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mp_size_t limb_cnt = cnt / GMP_NUMB_BITS;
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mp_srcptr in_ptr = in->_mp_d;
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if (in_size > limb_cnt)
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{
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/* The input operand is (probably) greater than 2**CNT. */
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mp_limb_t x;
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x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % GMP_NUMB_BITS) - 1);
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if (x != 0)
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{
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res_size = limb_cnt + 1;
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if (res->_mp_alloc < res_size)
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_mpz_realloc (res, res_size);
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res->_mp_d[limb_cnt] = x;
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}
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else
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{
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res_size = limb_cnt;
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MPN_NORMALIZE (in_ptr, res_size);
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if (res->_mp_alloc < res_size)
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_mpz_realloc (res, res_size);
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limb_cnt = res_size;
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}
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}
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else
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{
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/* The input operand is smaller than 2**CNT. We perform a no-op,
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apart from that we might need to copy IN to RES. */
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res_size = in_size;
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if (res->_mp_alloc < res_size)
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_mpz_realloc (res, res_size);
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limb_cnt = res_size;
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}
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if (res != in)
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MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt);
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res->_mp_size = in->_mp_size >= 0 ? res_size : -res_size;
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}
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