gls_rle_decoder.h

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#ifndef _GLS_RLE_DECODER_H
#define _GLS_RLE_DECODER_H

/*! \file gls_rle_decoder.h

\brief  RLE ( Run Length Encoded compression ) decoder.  
        This decoder allows for incremental decoding of data in inline format in the
        GL Studio DO-178B Runtime Library.

\par Copyright Information
Copyright (C) 1999-2012 The DiSTI Corporation<br>
Orlando, FL USA<br>
All rights reserved.<br>

  This file is copyrighted software and contains proprietary trade secrets of
DiSTI, and embodies substantial creative efforts as well as confidential
information, ideas, and expressions.

  Permission to use, and copy this software and its documentation for any
purpose is hereby granted per the Distribution Agreement and/or the Licensing
Agreement signed with DiSTI. This permission is granted provided that:
    1.  The above copyright notice appears in all copies.
    2.  That both the copyright notice and this permission notice appear in
        the supporting documentation.
    3.  That the names DiSTI and GL Studio not be used in advertising or
        publicity pertaining to distribution of the software without specific,
        written prior permission of DiSTI.
 
  Permission to modify the software is granted, but not the right to
distribute the source code whether modified, or non-modified.  Modifying the
software might invalidate the DO-178B certification package.

  Permission to distribute binaries produced by compiling source code, or
modified source code is granted, provided you:
    1.  Provide your name and address as the primary contact for the support
        of your modified version.
    2.  Retain our contact information in regard to use of the base software. 

   DiSTI does not provide warranty for this software or guarantee that it
satisfies any specification or requirement unless otherwise stated in a
specific contractual arrangement between the customer and DiSTI.

*/

#include "gls_include.h"
#include "gls_types.h"
#include "gls_util.h"
#include "gls_class_invariant.h"

/** RLE ( Run Length Encoded compression ) decoder.  
  * This decoder allows for incremental decoding of RLE compressed data in inline format.
  * \invariant  _inlineReader invariant holds
  */
class GlsRLEDecoder
{
public:
    GLS_CLASS_INVARIANT_DECLARATION( GlsRLEDecoder )

    /** Constructor - create an instance
      * \param inlineData inline RLE data to decode
      * \param inlineDataLength length in bytes of inline RLE data to decode
      *        ( not including terminators at end of lines )
      * \param lineLength length (in bytes) of one line of data in the inline data
      *        (not including NULL terminator)
      * \pre inlineData != GLS_NULL, inlineDataLength > 1, lineLength > 0
      * \post instance created
      */
    GlsRLEDecoder( const GlsUChar* const inlineData[], const GlsUInt32 inlineDataLength,
                   const GlsUInt32 lineLength );

    /** Destructor - destroy instance
      * \pre none
      * \post instance destroyed
      */
    ~GlsRLEDecoder();

    /** Decode one byte of input
      * \return decoded byte
      * \pre there must be at least one more byte of input remaining
      * \post one byte is read from input
      */
    GlsUChar DecodeByte( void );

    /** Determine if decoder is finished decoding input data
      * \return GLS_TRUE if done else GLS_FALSE
      * \pre none
      * \post none
      */
    GlsBool IsDone( void ) const;

protected:
    static const GlsUChar TWO_BYTE_COUNT_FLAG = 0x80; /**< flag in input data that indicates
                                                        * a two byte repeat count */

    GlsUtil::InlineReader _inlineReader;      /**< inline data reader */
    GlsUChar              _markerByte;        /**< marker byte to signal run length */
    
    GlsUInt32             _sequenceRemaining; /**< number of repeated bytes remaining in sequence else 0 */
    GlsUChar              _repeatedByte;      /**< current repeated byte if _sequenceRemaining > 0 */

private:
    // Disable implicit generated Members
    GlsRLEDecoder& operator=( const GlsRLEDecoder &rhs );
    GlsRLEDecoder( const GlsRLEDecoder &src );
};

#endif // _GLS_RLE_DECODER_H