text: #include "des.h"
  #include "des_key.h"
  #include "des_data.h"
  #include "des_lookup.h"
  
  #include <memory>
  
  //#pragma GCC push_options
  #ifndef _MSC_VER
  #pragma GCC optimize ("unroll-loops")
  #endif
  
  DES::DES(ui64 key)
  {
      keygen(key);
  }
  
  DES::DES(ui64* sub_key)
  {
    set_sub_key(sub_key);
  }
  
  void DES::set_sub_key(ui64 *sub_key)
  {
    std::memcpy(this->sub_key, sub_key, 128);
  }
  
  ui64 DES::encrypt(ui64 block)
  {
      return des(block, false);
  }
  
  ui64 DES::decrypt(ui64 block)
  {
      return des(block, true);
  }
  
  ui64 DES::encrypt(ui64 block, ui64 key)
  {
      DES des(key);
      return des.des(block, false);
  }
  
  ui64 DES::decrypt(ui64 block, ui64 key)
  {
      DES des(key);
      return des.des(block, true);
  }
  
  void DES::keygen(ui64 key)
  {
      // initial key schedule calculation
      ui64 permuted_choice_1 = 0; // 56 bits
      for (ui8 i = 0; i < 56; i++)
      {
          permuted_choice_1 <<= 1;
          permuted_choice_1 |= (key >> (64-PC1[i])) & LB64_MASK;
      }
  
      // 28 bits
      ui32 C = (ui32) ((permuted_choice_1 >> 28) & 0x000000000fffffff);
      ui32 D = (ui32)  (permuted_choice_1 & 0x000000000fffffff);
  
      // Calculation of the 16 keys
      for (ui8 i = 0; i < 16; i++)
      {
          // key schedule, shifting Ci and Di
          for (ui8 j = 0; j < ITERATION_SHIFT[i]; j++)
          {
              C = (0x0fffffff & (C << 1)) | (0x00000001 & (C >> 27));
              D = (0x0fffffff & (D << 1)) | (0x00000001 & (D >> 27));
          }
  
          ui64 permuted_choice_2 = (((ui64) C) << 28) | (ui64) D;
  
          sub_key[i] = 0; // 48 bits (2*24)
          for (ui8 j = 0; j < 48; j++)
          {
              sub_key[i] <<= 1;
              sub_key[i] |= (permuted_choice_2 >> (56-PC2[j])) & LB64_MASK;
          }
      }
  }
  
  ui64 DES::des(ui64 block, bool mode)
  {
      // applying initial permutation
      block = ip(block);
  
      // dividing T' into two 32-bit parts
      ui32 L = (ui32) (block >> 32) & L64_MASK;
      ui32 R = (ui32) (block & L64_MASK);
  
      // 16 rounds
      for (ui8 i = 0; i < 16; i++)
      {
          ui32 F = mode ? f(R, sub_key[15-i]) : f(R, sub_key[i]);
          feistel(L, R, F);
      }
  
      // swapping the two parts
      block = (((ui64) R) << 32) | (ui64) L;
      // applying final permutation
      return fp(block);
  }
  
  ui64 DES::ip(ui64 block)
  {
      // initial permutation
      ui64 result = 0;
      for (ui8 i = 0; i < 64; i++)
      {
          result <<= 1;
          result |= (block >> (64-IP[i])) & LB64_MASK;
      }
      return result;
  }
  
  ui64 DES::fp(ui64 block)
  {
      // inverse initial permutation
      ui64 result = 0;
      for (ui8 i = 0; i < 64; i++)
      {
          result <<= 1;
          result |= (block >> (64-FP[i])) & LB64_MASK;
      }
      return result;
  }
  
  void DES::feistel(ui32 &L, ui32 &R, ui32 F)
  {
      ui32 temp = R;
      R = L ^ F;
      L = temp;
  }
  
  ui32 DES::f(ui32 R, ui64 k) // f(R,k) function
  {
      // applying expansion permutation and returning 48-bit data
      ui64 s_input = 0;
      for (ui8 i = 0; i < 48; i++)
      {
          s_input <<= 1;
          s_input |= (ui64) ((R >> (32-EXPANSION[i])) & LB32_MASK);
      }
  
      // XORing expanded Ri with Ki, the round key
      s_input = s_input ^ k;
  
      // applying S-Boxes function and returning 32-bit data
      ui32 s_output = 0;
      for (ui8 i = 0; i < 8; i++)
      {
          // Outer bits
          char row = (char) ((s_input & (0x0000840000000000 >> 6*i)) >> (42-6*i));
          row = (row >> 4) | (row & 0x01);
  
          // Middle 4 bits of input
          char column = (char) ((s_input & (0x0000780000000000 >> 6*i)) >> (43-6*i));
  
          s_output <<= 4;
          s_output |= (ui32) (SBOX[i][16*row + column] & 0x0f);
      }
  
      // applying the round permutation
      ui32 f_result = 0;
      for (ui8 i = 0; i < 32; i++)
      {
          f_result <<= 1;
          f_result |= (s_output >> (32 - PBOX[i])) & LB32_MASK;
      }
  
      return f_result;
  }
  
  //#pragma GCC pop_options
  