src/gmp-6.1.0/mpz/xor.c

/* mpz_xor -- Logical xor.

Copyright 1991, 1993, 1994, 1996, 1997, 2000, 2001, 2005, 2012 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 either:

  * 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.

or

  * the GNU General Public License as published by the Free Software
    Foundation; either version 2 of the License, or (at your option) any
    later version.

or both in parallel, as here.

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 General Public License
for more details.

You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the GNU MP Library.  If not,
see https://www.gnu.org/licenses/.  */

#include "gmp.h"
#include "gmp-impl.h"

void
mpz_xor (mpz_ptr res, mpz_srcptr op1, mpz_srcptr op2)
{
  mp_srcptr op1_ptr, op2_ptr;
  mp_size_t op1_size, op2_size;
  mp_ptr res_ptr;
  mp_size_t res_size, res_alloc;
  TMP_DECL;

  TMP_MARK;
  op1_size = SIZ(op1);
  op2_size = SIZ(op2);

  op1_ptr = PTR(op1);
  op2_ptr = PTR(op2);
  res_ptr = PTR(res);

  if (op1_size >= 0)
    {
      if (op2_size >= 0)
	{
	  if (op1_size >= op2_size)
	    {
	      if (ALLOC(res) < op1_size)
		{
		  _mpz_realloc (res, op1_size);
		  /* No overlapping possible: op1_ptr = PTR(op1); */
		  op2_ptr = PTR(op2);
		  res_ptr = PTR(res);
		}

	      if (res_ptr != op1_ptr)
		MPN_COPY (res_ptr + op2_size, op1_ptr + op2_size,
			  op1_size - op2_size);
	      if (LIKELY (op2_size != 0))
		mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op2_size);
	      res_size = op1_size;
	    }
	  else
	    {
	      if (ALLOC(res) < op2_size)
		{
		  _mpz_realloc (res, op2_size);
		  op1_ptr = PTR(op1);
		  /* No overlapping possible: op2_ptr = PTR(op2); */
		  res_ptr = PTR(res);
		}

	      if (res_ptr != op2_ptr)
		MPN_COPY (res_ptr + op1_size, op2_ptr + op1_size,
			  op2_size - op1_size);
	      if (LIKELY (op1_size != 0))
		mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op1_size);
	      res_size = op2_size;
	    }

	  MPN_NORMALIZE (res_ptr, res_size);
	  SIZ(res) = res_size;
	  return;
	}
      else /* op2_size < 0 */
	{
	  /* Fall through to the code at the end of the function.  */
	}
    }
  else
    {
      if (op2_size < 0)
	{
	  mp_ptr opx, opy;

	  /* Both operands are negative, the result will be positive.
	      (-OP1) ^ (-OP2) =
	     = ~(OP1 - 1) ^ ~(OP2 - 1) =
	     = (OP1 - 1) ^ (OP2 - 1)  */

	  op1_size = -op1_size;
	  op2_size = -op2_size;

	  /* Possible optimization: Decrease mpn_sub precision,
	     as we won't use the entire res of both.  */
	  TMP_ALLOC_LIMBS_2 (opx, op1_size, opy, op2_size);
	  mpn_sub_1 (opx, op1_ptr, op1_size, (mp_limb_t) 1);
	  op1_ptr = opx;

	  mpn_sub_1 (opy, op2_ptr, op2_size, (mp_limb_t) 1);
	  op2_ptr = opy;

	  if (op1_size > op2_size)
	    MPN_SRCPTR_SWAP (op1_ptr,op1_size, op2_ptr,op2_size);

	  res_alloc = op2_size;
	  res_ptr = MPZ_REALLOC (res, res_alloc);

	  MPN_COPY (res_ptr + op1_size, op2_ptr + op1_size,
		    op2_size - op1_size);
	  mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op1_size);
	  res_size = op2_size;

	  MPN_NORMALIZE (res_ptr, res_size);
	  SIZ(res) = res_size;
	  TMP_FREE;
	  return;
	}
      else
	{
	  /* We should compute -OP1 ^ OP2.  Swap OP1 and OP2 and fall
	     through to the code that handles OP1 ^ -OP2.  */
	  MPZ_SRCPTR_SWAP (op1, op2);
	  MPN_SRCPTR_SWAP (op1_ptr,op1_size, op2_ptr,op2_size);
	}
    }

  {
    mp_ptr opx;
    mp_limb_t cy;

    /* Operand 2 negative, so will be the result.
       -(OP1 ^ (-OP2)) = -(OP1 ^ ~(OP2 - 1)) =
       = ~(OP1 ^ ~(OP2 - 1)) + 1 =
       = (OP1 ^ (OP2 - 1)) + 1      */

    op2_size = -op2_size;

    opx = TMP_ALLOC_LIMBS (op2_size);
    mpn_sub_1 (opx, op2_ptr, op2_size, (mp_limb_t) 1);
    op2_ptr = opx;

    res_alloc = MAX (op1_size, op2_size) + 1;
    if (ALLOC(res) < res_alloc)
      {
	_mpz_realloc (res, res_alloc);
	op1_ptr = PTR(op1);
	/* op2_ptr points to temporary space.  */
	res_ptr = PTR(res);
      }

    if (op1_size > op2_size)
      {
	MPN_COPY (res_ptr + op2_size, op1_ptr + op2_size, op1_size - op2_size);
	mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op2_size);
	res_size = op1_size;
      }
    else
      {
	MPN_COPY (res_ptr + op1_size, op2_ptr + op1_size, op2_size - op1_size);
	if (LIKELY (op1_size != 0))
	  mpn_xor_n (res_ptr, op1_ptr, op2_ptr, op1_size);
	res_size = op2_size;
      }

    cy = mpn_add_1 (res_ptr, res_ptr, res_size, (mp_limb_t) 1);
    res_ptr[res_size] = cy;
    res_size += (cy != 0);

    MPN_NORMALIZE (res_ptr, res_size);
    SIZ(res) = -res_size;
    TMP_FREE;
  }
}