gcc/gmp/mpz/mul_i.h

/* mpz_mul_ui/si (product, multiplier, small_multiplicand) -- Set PRODUCT to
   MULTIPLICATOR times SMALL_MULTIPLICAND.

Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2002, 2005, 2008 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"


#ifdef OPERATION_mul_si
#define FUNCTION               mpz_mul_si
#define MULTIPLICAND_UNSIGNED
#define MULTIPLICAND_ABS(x)    ((unsigned long) ABS(x))
#endif

#ifdef OPERATION_mul_ui
#define FUNCTION               mpz_mul_ui
#define MULTIPLICAND_UNSIGNED  unsigned
#define MULTIPLICAND_ABS(x)    x
#endif

#ifndef FUNCTION
Error, error, unrecognised OPERATION
#endif


void
FUNCTION (mpz_ptr prod, mpz_srcptr mult,
          MULTIPLICAND_UNSIGNED long int small_mult)
{
  mp_size_t size = SIZ(mult);
  mp_size_t sign_product = size;
  mp_limb_t sml;
  mp_limb_t cy;
  mp_ptr pp;

  if (size == 0 || small_mult == 0)
    {
      SIZ(prod) = 0;
      return;
    }

  size = ABS (size);

  sml = MULTIPLICAND_ABS (small_mult);

  if (sml <= GMP_NUMB_MAX)
    {
      MPZ_REALLOC (prod, size + 1);
      pp = PTR(prod);
      cy = mpn_mul_1 (pp, PTR(mult), size, sml & GMP_NUMB_MASK);
      pp[size] = cy;
      size += cy != 0;
    }
#if GMP_NAIL_BITS != 0
  else
    {
      /* Operand too large for the current nails size.  Use temporary for
	 intermediate products, to allow prod and mult being identical.  */
      mp_ptr tp;
      TMP_DECL;
      TMP_MARK;

      tp = TMP_ALLOC_LIMBS (size + 2);

      cy = mpn_mul_1 (tp, PTR(mult), size, sml & GMP_NUMB_MASK);
      tp[size] = cy;
      cy = mpn_addmul_1 (tp + 1, PTR(mult), size, sml >> GMP_NUMB_BITS);
      tp[size + 1] = cy;
      size += 2;
      MPN_NORMALIZE_NOT_ZERO (tp, size); /* too general, need to trim one or two limb */
      MPZ_REALLOC (prod, size);
      pp = PTR(prod);
      MPN_COPY (pp, tp, size);
      TMP_FREE;
    }
#endif

  SIZ(prod) = ((sign_product < 0) ^ (small_mult < 0)) ? -size : size;
}