gcc/gmp/mpz/sqrtrem.c

/* mpz_sqrtrem(root,rem,x) -- Set ROOT to floor(sqrt(X)) and REM
   to the remainder, i.e. X - ROOT**2.

Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2005 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 <stdio.h> /* for NULL */
#include "gmp.h"
#include "gmp-impl.h"
#ifdef BERKELEY_MP
#include "mp.h"
#endif

void
#ifndef BERKELEY_MP
mpz_sqrtrem (mpz_ptr root, mpz_ptr rem, mpz_srcptr op)
#else /* BERKELEY_MP */
msqrt (mpz_srcptr op, mpz_ptr root, mpz_ptr rem)
#endif /* BERKELEY_MP */
{
  mp_size_t op_size, root_size, rem_size;
  mp_ptr root_ptr, op_ptr;
  mp_ptr free_me = NULL;
  mp_size_t free_me_size;
  TMP_DECL;

  TMP_MARK;
  op_size = op->_mp_size;
  if (op_size <= 0)
    {
      if (op_size < 0)
        SQRT_OF_NEGATIVE;
      SIZ(root) = 0;
      SIZ(rem) = 0;
      return;
    }

  if (rem->_mp_alloc < op_size)
    _mpz_realloc (rem, op_size);

  /* The size of the root is accurate after this simple calculation.  */
  root_size = (op_size + 1) / 2;

  root_ptr = root->_mp_d;
  op_ptr = op->_mp_d;

  if (root->_mp_alloc < root_size)
    {
      if (root_ptr == op_ptr)
	{
	  free_me = root_ptr;
	  free_me_size = root->_mp_alloc;
	}
      else
	(*__gmp_free_func) (root_ptr, root->_mp_alloc * BYTES_PER_MP_LIMB);

      root->_mp_alloc = root_size;
      root_ptr = (mp_ptr) (*__gmp_allocate_func) (root_size * BYTES_PER_MP_LIMB);
      root->_mp_d = root_ptr;
    }
  else
    {
      /* Make OP not overlap with ROOT.  */
      if (root_ptr == op_ptr)
	{
	  /* ROOT and OP are identical.  Allocate temporary space for OP.  */
	  op_ptr = (mp_ptr) TMP_ALLOC (op_size * BYTES_PER_MP_LIMB);
	  /* Copy to the temporary space.  Hack: Avoid temporary variable
	     by using ROOT_PTR.  */
	  MPN_COPY (op_ptr, root_ptr, op_size);
	}
    }

  rem_size = mpn_sqrtrem (root_ptr, rem->_mp_d, op_ptr, op_size);

  root->_mp_size = root_size;

  /* Write remainder size last, to enable us to define this function to
     give only the square root remainder, if the user calls if with
     ROOT == REM.  */
  rem->_mp_size = rem_size;

  if (free_me != NULL)
    (*__gmp_free_func) (free_me, free_me_size * BYTES_PER_MP_LIMB);
  TMP_FREE;
}