/*---------------------------------------------------------------------------*
 *                                   IT++			             *
 *---------------------------------------------------------------------------*
 * Copyright (c) 1995-2002 by Tony Ottosson, Thomas Eriksson, Pål Frenger,   *
 * Tobias Ringström, and Jonas Samuelsson.                                   *
 *                                                                           *
 * Permission to use, copy, modify, and distribute this software and its     *
 * documentation under the terms of the GNU General Public License is hereby *
 * granted. No representations are made about the suitability of this        *
 * software for any purpose. It is provided "as is" without expressed or     *
 * implied warranty. See the GNU General Public License for more details.    *
 *---------------------------------------------------------------------------*/

/*! 
  \file 
  \brief Definition of a CRC code class
  \author Tony Ottosson

  1.8 

  2003/05/22 08:55:17
*/

#ifndef __crc_h
#define __crc_h

#include "base/vec.h"
#include "base/mat.h"

namespace itpp {

  /*! 
    \ingroup fec 
    \brief Cyclic Redundancy Check Codes

    This class will add the CRC bits after each input word. With b(i) denoting the i-th input bit and
    p(i) the i-th parity check bit, the order of the outbut bits will be:
    \code [b(1), b(2), ..., b(k), p(1), p(2), ..., p(n-k)] \endcode

    When the WCDMA CRC polynomials are used, this class
    will reverse the order of the parity check bits in order to comply to the WCDMA standard. Thus for the
    polynomials WCDMA-8, WCDMA-12, WCDMA-16, and WCDMA-24 the output will be:
    \code [b(1), b(2), ..., b(k), p(n-k), ..., p(2), p(1)] \endcode

    Usage:
    \code
    CRC_Code crc(string("CRC-4"));
    bvec bits = randb(10), coded_bits, decoded_bits;
    bool error;

    coded_bits = crc.encode(bits);
    error = crc.decode(rec_bits, decoded_bits);
    \endcode
  */
  class CRC_Code {
  public:

    //! Default Constructor
    CRC_Code() { reverse_parity = false; }

    /*! 
      \brief Set CRC code to one of the standardpolynomials using the string value.
      \param code Possible values: CRC-4, CRC-7, CRC-8, CRC-12, CRC-24, CRC-32, CCITT-4, 
      CCITT-5, CCITT-6, CCITT-16, CCITT-32, WCDMA-8, WCDMA-12, WCDMA-16, WCDMA-24, ATM-8, ANSI-16, SDLC-16
    */
    CRC_Code(const std::string &code) { reverse_parity = false; set_code(code); }

    //! Set an arbitary polynomial in bvec form. Start with highest order terms.
    void set_generator(const bvec &poly);

    //! Set CRC code to one of the standardpolynomials using the string value.
    void set_code(const std::string &code);

    //! Calulate the parity bits
    void parity(const bvec &in_bits, bvec &out);

    //! Return true if parity checks OK otherwise flase
    bool check_parity(const bvec &coded_bits);

    //! Calculate and add parity to the in_bits.
    void encode(const bvec &in_bits, bvec &out);

    //! Returns the in_bits vector with parity added
    bvec encode(const bvec &in_bits);

    //! Return true if parity checks OK otherwise flase. Also returns the message part in out. 
    bool decode(const bvec &coded_bits, bvec &out);

    //! Return true if parity checks OK otherwise flase. Also returns the message part in bits.
    bool decode(bvec &bits);

  private:
    bool reverse_parity;
    bvec polynomial;
    int no_parity;
  };

} //namespace itpp

#endif // __crc_h