#ifndef INCLUDED_OP25_HAMMING_H
#define INCLUDED_OP25_HAMMING_H

#include <cstddef>
#include <stdint.h>
#include <assert.h>

/*
 * APCO Hamming(15,11,3) ecoder.
 *
 * \param val The 11-bit value to encode.
 * \return The encoded codeword.
 */
static inline uint16_t
hamming_15_encode(uint16_t code_word_in)
{
   static long int encoding[11] = {
      0x400f, 0x200e, 0x100d, 0x080c, 0x040b, 0x020a, 0x0109,
      0x0087, 0x0046, 0x0025, 0x0013
   };

   uint16_t code_word_out = 0u;
   for(uint8_t i = 0; i < 11; ++i) {
      if(code_word_in & (1u << (10 - i))) {
         code_word_out ^= encoding[i];
      }
   }
   return code_word_out;
}

/*
 * APCO Hamming(15,11,3) decoder.
 *
 * \param cw The 15-bit codeword to decode.
 * \return The number of errors detected.
 */
static inline size_t
hamming_15_decode(uint16_t& cw)
{
   static const int encoding[2048] = {
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11,
      5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2,
      6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1,
      15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8,
      7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0,
      14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9,
      13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10,
      4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3,
      0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7,
      9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14,
      10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13,
      3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4,
      11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12,
      2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5,
      1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6,
      8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15
   };

   static const int decoding[16] = {
      0, 0, 0, 1, 0, 2, 4, 8, 0, 16, 32, 64, 128, 256, 512, 1024
   };

   size_t errs = 0;
   uint16_t par = cw & 0xf;
   cw &= 0xffff;
   cw >>= 4;
   uint16_t correction = decoding[encoding[cw] ^ par];
   if(correction) {
      cw ^= correction;
      ++errs;
   }
   return errs;
}

static const uint32_t hmg1063EncTbl[64] = {
     0, 12, 3, 15, 7, 11, 4, 8, 11, 7, 8, 4, 12, 0, 15, 3, 
     13, 1, 14, 2, 10, 6, 9, 5, 6, 10, 5, 9, 1, 13, 2, 14, 
     14, 2, 13, 1, 9, 5, 10, 6, 5, 9, 6, 10, 2, 14, 1, 13, 
     3, 15, 0, 12, 4, 8, 7, 11, 8, 4, 11, 7, 15, 3, 12, 0 };

static const uint32_t hmg1063DecTbl[16] = {
     0, 0, 0, 2, 0, 0, 0, 4, 0, 0, 0, 8, 1, 16, 32, 0 };

static inline int hmg1063Dec (uint32_t Dat, uint32_t Par) {
     assert ((Dat < 64) && (Par < 16));
     return Dat ^ hmg1063DecTbl[hmg1063EncTbl[Dat] ^ Par];
}

#endif /* INCLUDED_OP25_HAMMING_H */