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/* mpq_set_f -- set an mpq from an mpf.
Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"
void
mpq_set_f (mpq_ptr q, mpf_srcptr f)
{
mp_size_t fexp = EXP(f);
mp_ptr fptr = PTR(f);
mp_size_t fsize = SIZ(f);
mp_size_t abs_fsize = ABS(fsize);
mp_limb_t flow;
if (fsize == 0)
{
/* set q=0 */
SIZ(NUM(q)) = 0;
SIZ(DEN(q)) = 1;
PTR(DEN(q))[0] = 1;
return;
}
/* strip low zero limbs from f */
flow = *fptr;
MPN_STRIP_LOW_ZEROS_NOT_ZERO (fptr, abs_fsize, flow);
if (fexp >= abs_fsize)
{
/* radix point is to the right of the limbs, no denominator */
mp_ptr num_ptr;
num_ptr = MPZ_NEWALLOC (mpq_numref (q), fexp);
MPN_ZERO (num_ptr, fexp - abs_fsize);
MPN_COPY (num_ptr + fexp - abs_fsize, fptr, abs_fsize);
SIZ(NUM(q)) = fsize >= 0 ? fexp : -fexp;
SIZ(DEN(q)) = 1;
PTR(DEN(q))[0] = 1;
}
else
{
/* radix point is within or to the left of the limbs, use denominator */
mp_ptr num_ptr, den_ptr;
mp_size_t den_size;
den_size = abs_fsize - fexp;
num_ptr = MPZ_NEWALLOC (mpq_numref (q), abs_fsize);
den_ptr = MPZ_NEWALLOC (mpq_denref (q), den_size+1);
if (flow & 1)
{
/* no powers of two to strip from numerator */
MPN_COPY (num_ptr, fptr, abs_fsize);
MPN_ZERO (den_ptr, den_size);
den_ptr[den_size] = 1;
}
else
{
/* right shift numerator, adjust denominator accordingly */
int shift;
den_size--;
count_trailing_zeros (shift, flow);
mpn_rshift (num_ptr, fptr, abs_fsize, shift);
abs_fsize -= (num_ptr[abs_fsize-1] == 0);
MPN_ZERO (den_ptr, den_size);
den_ptr[den_size] = GMP_LIMB_HIGHBIT >> (shift-1);
}
SIZ(NUM(q)) = fsize >= 0 ? abs_fsize : -abs_fsize;
SIZ(DEN(q)) = den_size + 1;
}
}
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