Vigenere.hh

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#ifndef COSA_VIGENERE_HH
#define COSA_VIGENERE_HH

#include "Cosa/Types.h"

template<uint8_t N>
class Vigenere {
public:
  Vigenere(uint32_t seed, uint8_t n = N)
  {
    if (UNLIKELY(n > N)) n = N;
    srandom(seed);
    for (uint8_t i = 0; i < n; i++)
      m_key[i] = random();
    m_nr = 0;
    m_max = n;
    m_pos = n;
  }

  Vigenere(const char* password)
  {
    uint8_t i;
    for (i = 0; i < N && password[i]; i++)
      m_key[i] = password[i];
    m_nr = 0;
    m_max = i;
    m_pos = i;
  }

  void restart()
  {
    m_max = m_pos;
    m_nr = 0;
  }

  char encrypt(char c)
  {
    char res = c + m_key[m_nr++];
    if (m_max != N) m_key[m_max++] = c;
    if (m_nr == N) m_nr = 0;
    return (res);
  }

  void encrypt(void* buf, size_t n)
  {
    for (char* bp = (char*) buf; n--; bp++)
      *bp = encrypt(*bp);
  }

  void encrypt(void* dest, const void* src, size_t n)
  {
    char* dp = (char*) dest;
    const char* sp = (const char*) src;
    while (n--) *dp++ = encrypt(*sp++);
  }

  char decrypt(char c)
  {
    char res = c - m_key[m_nr++];
    if (m_max != N) m_key[m_max++] = res;
    if (m_nr == N) m_nr = 0;
    return (res);
  }

  void decrypt(void* buf, size_t n)
  {
    for (char* bp = (char*) buf; n--; bp++)
      *bp = decrypt(*bp);
  }

  void decrypt(void* dest, const void* src, size_t n)
  {
    char* dp = (char*) dest;
    const char* sp = (const char*) src;
    while (n--) *dp++ = decrypt(*sp++);
  }

private:
  char m_key[N];
  uint8_t m_nr;
  uint8_t m_max;
  uint8_t m_pos;
};

#endif