/* -*- c++ -*- */
/*
 * Copyright 2012, 2014 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * GNU Radio 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 a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

/*!
 * \page volk_64u_popcnt
 *
 * \b Overview
 *
 * Computes the population count (popcnt), or Hamming distance of a
 * binary string. This kernel takes in a single unsigned 64-bit value
 * and returns the count of 1's that the value contains.
 *
 * <b>Dispatcher Prototype</b>
 * \code
 * void volk_64u_popcnt(uint64_t* ret, const uint64_t value)
 * \endcode
 *
 * \b Inputs
 * \li value: The input value.
 *
 * \b Outputs
 * \li ret: The return value containing the popcnt.
 *
 * \b Example
 * \code
 *   int N = 10;
 *   unsigned int alignment = volk_get_alignment();
 *
 *   uint64_t bitstring[] = {0x0, 0x1, 0xf, 0xffffffffffffffff,
 *       0x5555555555555555, 0xaaaaaaaaaaaaaaaa, 0x2a2a2a2a2a2a2a2a,
 *       0xffffffff, 0x32, 0x64};
 *   uint64_t hamming_distance = 0;
 *
 *   for(unsigned int ii=0; ii<N; ++ii){
 *       volk_64u_popcnt(&hamming_distance, bitstring[ii]);
 *       printf("hamming distance of %lx = %li\n", bitstring[ii], hamming_distance);
 *   }
 * \endcode
 */

#ifndef INCLUDED_volk_64u_popcnt_a_H
#define INCLUDED_volk_64u_popcnt_a_H

#include <stdio.h>
#include <inttypes.h>


#ifdef LV_HAVE_GENERIC


static inline void
volk_64u_popcnt_generic(uint64_t* ret, const uint64_t value)
{
  //const uint32_t* valueVector = (const uint32_t*)&value;

  // This is faster than a lookup table
  //uint32_t retVal = valueVector[0];
  uint32_t retVal = (uint32_t)(value & 0x00000000FFFFFFFFull);

  retVal = (retVal & 0x55555555) + (retVal >> 1 & 0x55555555);
  retVal = (retVal & 0x33333333) + (retVal >> 2 & 0x33333333);
  retVal = (retVal + (retVal >> 4)) & 0x0F0F0F0F;
  retVal = (retVal + (retVal >> 8));
  retVal = (retVal + (retVal >> 16)) & 0x0000003F;
  uint64_t retVal64  = retVal;

  //retVal = valueVector[1];
  retVal = (uint32_t)((value & 0xFFFFFFFF00000000ull) >> 31);
  retVal = (retVal & 0x55555555) + (retVal >> 1 & 0x55555555);
  retVal = (retVal & 0x33333333) + (retVal >> 2 & 0x33333333);
  retVal = (retVal + (retVal >> 4)) & 0x0F0F0F0F;
  retVal = (retVal + (retVal >> 8));
  retVal = (retVal + (retVal >> 16)) & 0x0000003F;
  retVal64 += retVal;

  *ret = retVal64;
}

#endif /*LV_HAVE_GENERIC*/


#if LV_HAVE_SSE4_2 && LV_HAVE_64

#include <nmmintrin.h>

static inline void volk_64u_popcnt_a_sse4_2(uint64_t* ret, const uint64_t value)
{
  *ret = _mm_popcnt_u64(value);
}

#endif /*LV_HAVE_SSE4_2*/


#if LV_HAVE_NEON
#include <arm_neon.h>
static inline void volk_64u_popcnt_neon(uint64_t* ret, const uint64_t value)
{
  uint8x8_t input_val, count8x8_val;
  uint16x4_t count16x4_val;
  uint32x2_t count32x2_val;
  uint64x1_t count64x1_val;

  input_val = vld1_u8((unsigned char *) &value);
  count8x8_val = vcnt_u8(input_val);
  count16x4_val = vpaddl_u8(count8x8_val);
  count32x2_val = vpaddl_u16(count16x4_val);
  count64x1_val = vpaddl_u32(count32x2_val);
  vst1_u64(ret, count64x1_val);

  //*ret = _mm_popcnt_u64(value);
}
#endif /*LV_HAVE_NEON*/


#endif /*INCLUDED_volk_64u_popcnt_a_H*/
