/* mpn_popcount, mpn_hamdist -- mpn bit population count/hamming distance.

Copyright 1994, 1996, 2000-2002, 2005, 2011, 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"

#if OPERATION_popcount

#define FNAME mpn_popcount

#define POPHAM(u,v) u

#endif

#if OPERATION_hamdist

#define FNAME mpn_hamdist

#define POPHAM(u,v) u ^ v

#endif

mp_bitcnt_t

FNAME (mp_srcptr up,

#if OPERATION_hamdist

       mp_srcptr vp,

#endif

       mp_size_t n) __GMP_NOTHROW

{

  mp_bitcnt_t result = 0;

  mp_limb_t p0, p1, p2, p3, x, p01, p23;

  mp_size_t i;

  ASSERT (n >= 1);		/* Actually, this code handles any n, but some

				   assembly implementations do not.  */

  for (i = n >> 2; i != 0; i--)

    {

      p0 = POPHAM (up[0], vp[0]);

      p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */

      p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5);	/* 4 0-4 */

      p1 = POPHAM (up[1], vp[1]);

      p1 -= (p1 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */

      p1 = ((p1 >> 2) & MP_LIMB_T_MAX/5) + (p1 & MP_LIMB_T_MAX/5);	/* 4 0-4 */

      p01 = p0 + p1;							/* 8 0-8 */

      p01 = ((p01 >> 4) & MP_LIMB_T_MAX/17) + (p01 & MP_LIMB_T_MAX/17);	/* 8 0-16 */

      p2 = POPHAM (up[2], vp[2]);

      p2 -= (p2 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */

      p2 = ((p2 >> 2) & MP_LIMB_T_MAX/5) + (p2 & MP_LIMB_T_MAX/5);	/* 4 0-4 */

      p3 = POPHAM (up[3], vp[3]);

      p3 -= (p3 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */

      p3 = ((p3 >> 2) & MP_LIMB_T_MAX/5) + (p3 & MP_LIMB_T_MAX/5);	/* 4 0-4 */

      p23 = p2 + p3;							/* 8 0-8 */

      p23 = ((p23 >> 4) & MP_LIMB_T_MAX/17) + (p23 & MP_LIMB_T_MAX/17);	/* 8 0-16 */

      x = p01 + p23;							/* 8 0-32 */

      x = (x >> 8) + x;							/* 8 0-64 */

      x = (x >> 16) + x;						/* 8 0-128 */

#if GMP_LIMB_BITS > 32

      x = ((x >> 32) & 0xff) + (x & 0xff);				/* 8 0-256 */

      result += x;

#else

      result += x & 0xff;

#endif

      up += 4;

#if OPERATION_hamdist

      vp += 4;

#endif

    }

  n &= 3;

  if (n != 0)

    {

      x = 0;

      do

	{

	  p0 = POPHAM (up[0], vp[0]);

	  p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */

	  p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5);	/* 4 0-4 */

	  p0 = ((p0 >> 4) + p0) & MP_LIMB_T_MAX/17;			/* 8 0-8 */

	  x += p0;

	  up += 1;

#if OPERATION_hamdist

	  vp += 1;

#endif

	}

      while (--n);

      x = (x >> 8) + x;

      x = (x >> 16) + x;

#if GMP_LIMB_BITS > 32

      x = (x >> 32) + x;

#endif

      result += x & 0xff;

    }

  return result;

}