text: #include <string>
  #include <iostream>
  #include <cstring>
  #include <openssl/hmac.h>
  #include <openssl/sha.h>
  #include <openssl/evp.h>
  namespace utils { namespace crypto {
  
  inline std::string b2a_hex(char *byte_arr, int n) {
      const static std::string HexCodes = "0123456789abcdef";
      std::string HexString;
      for(int i = 0; i < n; ++i) {
          unsigned char BinValue = byte_arr[i];
          HexString += HexCodes[(BinValue >> 4) & 0x0F];
          HexString += HexCodes[BinValue & 0x0F];
      }
      return HexString;
  }
  
  inline std::string hmac_sha256( const char *key, const char *data) {
      unsigned char* digest;
      digest = HMAC(EVP_sha256(), key, strlen(key), (unsigned char*)(data), strlen(data), NULL, NULL);
      return b2a_hex((char *)digest, 32);
  }
  
  inline unsigned char* hmac_sha256_byte( const char *key, const char *data) {
      return HMAC(EVP_sha256(), key, strlen(key), (unsigned char*)(data), strlen(data), NULL, NULL);
  }
  
  inline std::string hmac_sha384( const char *key, const char *data) {
      unsigned char* digest;
      digest = HMAC(EVP_sha384(), key, strlen(key), (unsigned char*)(data), strlen(data), NULL, NULL);
      return b2a_hex((char *)digest, 48);
  }
  
  inline unsigned char* hmac_sha384_byte( const char *key, const char *data) {
      return HMAC(EVP_sha384(), key, strlen(key), (unsigned char*)(data), strlen(data), NULL, NULL);
  }
  
  inline std::string hmac_sha512( const char *key, const char *data) {
      unsigned char* digest;
      digest = HMAC(EVP_sha256(), key, strlen(key), (unsigned char*)(data), strlen(data), NULL, NULL);
      return b2a_hex((char *)digest, 64);
  }
  
  static const std::string base64_chars ="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                         "abcdefghijklmnopqrstuvwxyz"
                                         "0123456789+/";
  
  inline bool is_base64(unsigned char c) {
      return (isalnum(c) || (c == '+') || (c == '/'));
  }
  
  std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len) {
      std::string ret;
      int i = 0;
      int j = 0;
      unsigned char char_array_3[3];
      unsigned char char_array_4[4];
  
      while (in_len--) {
          char_array_3[i++] = *(bytes_to_encode++);
          if (i == 3) {
              char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
              char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
              char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
              char_array_4[3] = char_array_3[2] & 0x3f;
  
              for(i = 0; (i <4) ; i++)
                  ret += base64_chars[char_array_4[i]];
              i = 0;
          }
      }
  
      if (i)
      {
          for(j = i; j < 3; j++)
              char_array_3[j] = '\0';
  
          char_array_4[0] = ( char_array_3[0] & 0xfc) >> 2;
          char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
          char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
  
          for (j = 0; (j < i + 1); j++)
              ret += base64_chars[char_array_4[j]];
  
          while((i++ < 3))
              ret += '=';
  
      }
  
      return ret;
  
  }
  
  std::string base64_decode(std::string const& encoded_string) {
      int in_len = encoded_string.size();
      int i = 0;
      int j = 0;
      int in_ = 0;
      unsigned char char_array_4[4], char_array_3[3];
      std::string ret;
  
      while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) {
          char_array_4[i++] = encoded_string[in_]; in_++;
          if (i ==4) {
              for (i = 0; i <4; i++)
                  char_array_4[i] = base64_chars.find(char_array_4[i]);
  
              char_array_3[0] = ( char_array_4[0] << 2       ) + ((char_array_4[1] & 0x30) >> 4);
              char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
              char_array_3[2] = ((char_array_4[2] & 0x3) << 6) +   char_array_4[3];
  
              for (i = 0; (i < 3); i++)
                  ret += char_array_3[i];
              i = 0;
          }
      }
  
      if (i) {
          for (j = 0; j < i; j++)
              char_array_4[j] = base64_chars.find(char_array_4[j]);
  
          char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
          char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
  
          for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
      }
  
      return ret;
  }
  
  }}
  