Blame mpz/fdiv_qr.c

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/* mpz_fdiv_qr -- Division rounding the quotient towards -infinity.
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   The remainder gets the same sign as the denominator.
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Copyright 1994-1996, 2000, 2001, 2005, 2012 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 either:
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  * the GNU Lesser General Public License as published by the Free
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    Software Foundation; either version 3 of the License, or (at your
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    option) any later version.
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or
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  * the GNU General Public License as published by the Free Software
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    Foundation; either version 2 of the License, or (at your option) any
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    later version.
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or both in parallel, as here.
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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 General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library.  If not,
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see https://www.gnu.org/licenses/.  */
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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_fdiv_qr (mpz_ptr quot, mpz_ptr rem, mpz_srcptr dividend, mpz_srcptr divisor)
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{
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  mp_size_t divisor_size = SIZ (divisor);
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  mp_size_t xsize;
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  mpz_t temp_divisor;		/* N.B.: lives until function returns! */
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  TMP_DECL;
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  TMP_MARK;
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  /* We need the original value of the divisor after the quotient and
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     remainder have been preliminary calculated.  We have to copy it to
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     temporary space if it's the same variable as either QUOT or REM.  */
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  if (quot == divisor || rem == divisor)
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    {
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      MPZ_TMP_INIT (temp_divisor, ABS (divisor_size));
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      mpz_set (temp_divisor, divisor);
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      divisor = temp_divisor;
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    }
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  xsize = SIZ (dividend) ^ divisor_size;;
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  mpz_tdiv_qr (quot, rem, dividend, divisor);
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  if (xsize < 0 && SIZ (rem) != 0)
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    {
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      mpz_sub_ui (quot, quot, 1L);
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      mpz_add (rem, rem, divisor);
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    }
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  TMP_FREE;
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}