/******************************** MPEG Audio Encoder **************************

                       (C) copyright Fraunhofer-IIS (1999)
                               All Rights Reserved

    Please be advised that this software and/or program delivery is
    Confidential Information of Fraunhofer and subject to and covered by the

    Fraunhofer IIS Software Evaluation Agreement
    between Google Inc. and  Fraunhofer
    effective and in full force since March 1, 2012.

    You may use this software and/or program only under the terms and
    conditions described in the above mentioned Fraunhofer IIS Software
    Evaluation Agreement. Any other and/or further use requires a separate agreement.


   This software and/or program is protected by copyright law and international
   treaties. Any reproduction or distribution of this software and/or program,
   or any portion of it, may result in severe civil and criminal penalties, and
   will be prosecuted to the maximum extent possible under law.

   $Id$
   Initial author:
   contents/description: CRC calculation

******************************************************************************/

#ifndef FDK_CRC_H
#define FDK_CRC_H



#include "FDK_bitstream.h"


#define MAX_CRC_REGS 3    /*!< Maximal number of overlapping crc region in ADTS channel pair element is two.
                               Select three independent regions preventively. */

/**
 *  This structure describes single crc region used for crc calculation.
 */
typedef struct
{
  UCHAR isActive;
  INT   maxBits;
  UINT  bitBufCntBits;
  UINT  validBits;

} CCrcRegData;

/**
 *  CRC info structure.
 */
typedef struct
{
    CCrcRegData  crcRegData[MAX_CRC_REGS];   /*!< Multiple crc region description. */
    const USHORT       *pCrcLookup;          /*!< Pointer to lookup table filled in FDK_crcInit(). */

    USHORT              crcPoly;             /*!< CRC generator polynom. */
    USHORT              crcMask;             /*!< CRC mask. */
    USHORT              startValue;          /*!< CRC start value. */
    UCHAR               crcLen;              /*!< CRC length. */

    UINT                regStart;            /*!< Start region marker for synchronization. */
    UINT                regStop;             /*!< Stop region marker for synchronization. */

    USHORT              crcValue;            /*!< Crc value to be calculated. */

} FDK_CRCINFO;

/**
 *  CRC info handle.
 */
typedef FDK_CRCINFO* HANDLE_FDK_CRCINFO;


/**
 * \brief  Initialize CRC structure.
 *
 * The function initializes existing crc info structure with denoted configuration.
 *
 * \param hCrcInfo              Pointer to an outlying allocated crc info structure.
 * \param crcPoly               Configure crc polynom.
 * \param crcStartValue         Configure crc start value.
 * \param crcLen                Configure crc length.
 *
 * \return  none
 */
void FDKcrcInit(
        HANDLE_FDK_CRCINFO              hCrcInfo,
        const UINT                      crcPoly,
        const UINT                      crcStartValue,
        const UINT                      crcLen
        );

/**
 * \brief  Reset CRC info structure.
 *
 * This function clears all intern states of the crc structure.
 *
 * \param hCrcInfo              Pointer to crc info stucture.
 *
 * \return  none
 */
void FDKcrcReset(
        HANDLE_FDK_CRCINFO              hCrcInfo
        );


/**
 * \brief  Start CRC region with maximum number of bits.
 *
 * This function marks position in bitstream to be used as start point for crc calculation.
 * Bitstream range for crc calculation can be limited or kept dynamic depending on mBits parameter.
 * The crc region has to be terminated with FDKcrcEndReg() in each case.
 *
 * \param hCrcInfo              Pointer to crc info stucture.
 * \param hBs                   Pointer to current bit buffer structure.
 * \param mBits                 Number of bits in crc region to be calculated.
 *                              - mBits > 0: Zero padding will be used for CRC calculation, if there
 *                                           are less than mBits bits available.
 *                              - mBits < 0: No zero padding is done.
 *                              - mBits = 0: The number of bits used in crc calculation is dynamically,
 *                                           depending on bitstream position between FDKcrcStartReg() and
 *                                           FDKcrcEndReg() call.
 *
 * \return  ID for the created region, -1 in case of an error
 */
INT FDKcrcStartReg(
        HANDLE_FDK_CRCINFO              hCrcInfo,
        const HANDLE_FDK_BITSTREAM      hBs,
        const INT                       mBits
        );


/**
 * \brief  Ends CRC region.
 *
 * This function terminates crc region specified with FDKcrcStartReg(). The number of bits in crc region depends
 * on mBits parameter of FDKcrcStartReg().
 * This function calculates and updates crc in info structure.
 *
 * \param hCrcInfo              Pointer to crc info stucture.
 * \param hBs                   Pointer to current bit buffer structure.
 * \param reg                   Crc region ID created in FDKcrcStartReg().
 *
 * \return  0 on success
 */
INT FDKcrcEndReg(
        HANDLE_FDK_CRCINFO              hCrcInfo,
        const HANDLE_FDK_BITSTREAM      hBs,
        const INT                       reg
        );


/**
 * \brief  This function returns crc value from info struct.
 *
 * \param hCrcInfo              Pointer to crc info stucture.
 *
 * \return  CRC value masked with crc length.
 */
USHORT FDKcrcGetCRC(
        const HANDLE_FDK_CRCINFO        hCrcInfo
        );


#endif /* FDK_CRC_H */