102 lines
3.0 KiB
C
102 lines
3.0 KiB
C
/* mpq_set_f -- set an mpq from an mpf.
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Copyright 2000, 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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#include "longlong.h"
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void
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mpq_set_f (mpq_ptr q, mpf_srcptr f)
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{
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mp_size_t fexp = EXP(f);
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mp_ptr fptr = PTR(f);
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mp_size_t fsize = SIZ(f);
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mp_size_t abs_fsize = ABS(fsize);
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mp_limb_t flow;
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if (fsize == 0)
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{
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/* set q=0 */
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q->_mp_num._mp_size = 0;
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q->_mp_den._mp_size = 1;
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q->_mp_den._mp_d[0] = 1;
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return;
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}
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/* strip low zero limbs from f */
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flow = *fptr;
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MPN_STRIP_LOW_ZEROS_NOT_ZERO (fptr, abs_fsize, flow);
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if (fexp >= abs_fsize)
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{
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/* radix point is to the right of the limbs, no denominator */
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mp_ptr num_ptr;
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MPZ_REALLOC (mpq_numref (q), fexp);
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num_ptr = q->_mp_num._mp_d;
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MPN_ZERO (num_ptr, fexp - abs_fsize);
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MPN_COPY (num_ptr + fexp - abs_fsize, fptr, abs_fsize);
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q->_mp_num._mp_size = fsize >= 0 ? fexp : -fexp;
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q->_mp_den._mp_size = 1;
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q->_mp_den._mp_d[0] = 1;
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}
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else
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{
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/* radix point is within or to the left of the limbs, use demominator */
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mp_ptr num_ptr, den_ptr;
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mp_size_t den_size;
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den_size = abs_fsize - fexp;
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MPZ_REALLOC (mpq_numref (q), abs_fsize);
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MPZ_REALLOC (mpq_denref (q), den_size+1);
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num_ptr = q->_mp_num._mp_d;
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den_ptr = q->_mp_den._mp_d;
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if (flow & 1)
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{
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/* no powers of two to strip from numerator */
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MPN_COPY (num_ptr, fptr, abs_fsize);
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MPN_ZERO (den_ptr, den_size);
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den_ptr[den_size] = 1;
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}
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else
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{
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/* right shift numerator, adjust denominator accordingly */
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int shift;
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den_size--;
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count_trailing_zeros (shift, flow);
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mpn_rshift (num_ptr, fptr, abs_fsize, shift);
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abs_fsize -= (num_ptr[abs_fsize-1] == 0);
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MPN_ZERO (den_ptr, den_size);
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den_ptr[den_size] = GMP_LIMB_HIGHBIT >> (shift-1);
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}
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q->_mp_num._mp_size = fsize >= 0 ? abs_fsize : -abs_fsize;
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q->_mp_den._mp_size = den_size + 1;
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}
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}
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