1  /* mpn_popcount, mpn_hamdist -- mpn bit population count/hamming distance.
       2  
       3  Copyright 1994, 1996, 2000-2002, 2005, 2011, 2012 Free Software Foundation,
       4  Inc.
       5  
       6  This file is part of the GNU MP Library.
       7  
       8  The GNU MP Library is free software; you can redistribute it and/or modify
       9  it under the terms of either:
      10  
      11    * the GNU Lesser General Public License as published by the Free
      12      Software Foundation; either version 3 of the License, or (at your
      13      option) any later version.
      14  
      15  or
      16  
      17    * the GNU General Public License as published by the Free Software
      18      Foundation; either version 2 of the License, or (at your option) any
      19      later version.
      20  
      21  or both in parallel, as here.
      22  
      23  The GNU MP Library is distributed in the hope that it will be useful, but
      24  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      25  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      26  for more details.
      27  
      28  You should have received copies of the GNU General Public License and the
      29  GNU Lesser General Public License along with the GNU MP Library.  If not,
      30  see https://www.gnu.org/licenses/.  */
      31  
      32  #include "gmp-impl.h"
      33  
      34  #if OPERATION_popcount
      35  #define FNAME mpn_popcount
      36  #define POPHAM(u,v) u
      37  #endif
      38  
      39  #if OPERATION_hamdist
      40  #define FNAME mpn_hamdist
      41  #define POPHAM(u,v) u ^ v
      42  #endif
      43  
      44  mp_bitcnt_t
      45  FNAME (mp_srcptr up,
      46  #if OPERATION_hamdist
      47         mp_srcptr vp,
      48  #endif
      49         mp_size_t n) __GMP_NOTHROW
      50  {
      51    mp_bitcnt_t result = 0;
      52    mp_limb_t p0, p1, p2, p3, x, p01, p23;
      53    mp_size_t i;
      54  
      55    ASSERT (n >= 1);		/* Actually, this code handles any n, but some
      56  				   assembly implementations do not.  */
      57  
      58    for (i = n >> 2; i != 0; i--)
      59      {
      60        p0 = POPHAM (up[0], vp[0]);
      61        p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
      62        p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
      63  
      64        p1 = POPHAM (up[1], vp[1]);
      65        p1 -= (p1 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
      66        p1 = ((p1 >> 2) & MP_LIMB_T_MAX/5) + (p1 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
      67  
      68        p01 = p0 + p1;							/* 8 0-8 */
      69        p01 = ((p01 >> 4) & MP_LIMB_T_MAX/17) + (p01 & MP_LIMB_T_MAX/17);	/* 8 0-16 */
      70  
      71        p2 = POPHAM (up[2], vp[2]);
      72        p2 -= (p2 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
      73        p2 = ((p2 >> 2) & MP_LIMB_T_MAX/5) + (p2 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
      74  
      75        p3 = POPHAM (up[3], vp[3]);
      76        p3 -= (p3 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
      77        p3 = ((p3 >> 2) & MP_LIMB_T_MAX/5) + (p3 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
      78  
      79        p23 = p2 + p3;							/* 8 0-8 */
      80        p23 = ((p23 >> 4) & MP_LIMB_T_MAX/17) + (p23 & MP_LIMB_T_MAX/17);	/* 8 0-16 */
      81  
      82        x = p01 + p23;							/* 8 0-32 */
      83        x = (x >> 8) + x;							/* 8 0-64 */
      84        x = (x >> 16) + x;						/* 8 0-128 */
      85  #if GMP_LIMB_BITS > 32
      86        x = ((x >> 32) & 0xff) + (x & 0xff);				/* 8 0-256 */
      87        result += x;
      88  #else
      89        result += x & 0xff;
      90  #endif
      91        up += 4;
      92  #if OPERATION_hamdist
      93        vp += 4;
      94  #endif
      95      }
      96  
      97    n &= 3;
      98    if (n != 0)
      99      {
     100        x = 0;
     101        do
     102  	{
     103  	  p0 = POPHAM (up[0], vp[0]);
     104  	  p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
     105  	  p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
     106  	  p0 = ((p0 >> 4) + p0) & MP_LIMB_T_MAX/17;			/* 8 0-8 */
     107  
     108  	  x += p0;
     109  	  up += 1;
     110  #if OPERATION_hamdist
     111  	  vp += 1;
     112  #endif
     113  	}
     114        while (--n);
     115  
     116        x = (x >> 8) + x;
     117        x = (x >> 16) + x;
     118  #if GMP_LIMB_BITS > 32
     119        x = (x >> 32) + x;
     120  #endif
     121        result += x & 0xff;
     122      }
     123  
     124    return result;
     125  }