ebml/EbmlCrc32.h

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/****************************************************************************
** libebml : parse EBML files, see http://embl.sourceforge.net/
**
** <file/class description>
**
** Copyright (C) 2002-2010 Steve Lhomme.  All rights reserved.
**
** This file is part of libebml.
**
** This library is free software; you can redistribute it and/or
** modify it under the terms of the GNU Lesser General Public
** License as published by the Free Software Foundation; either
** version 2.1 of the License, or (at your option) any later version.
** 
** This library is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
** Lesser General Public License for more details.
** 
** You should have received a copy of the GNU Lesser General Public
** License along with this library; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
**
** See http://www.matroska.org/license/lgpl/ for LGPL licensing information.
**
** Contact license@matroska.org if any conditions of this licensing are
** not clear to you.
**
**********************************************************************/

#ifndef LIBEBML_CRC32_H
#define LIBEBML_CRC32_H

#include <cassert>

#include "EbmlTypes.h"
#include "EbmlBinary.h"

START_LIBEBML_NAMESPACE

const uint32 CRC32_NEGL = 0xffffffffL;

#ifdef WORDS_BIGENDIAN
# define CRC32_INDEX(c) (c >> 24)
# define CRC32_SHIFTED(c) (c << 8)
#else
# define CRC32_INDEX(c) (c & 0xff)
# define CRC32_SHIFTED(c) (c >> 8)
#endif

DECLARE_EBML_BINARY(EbmlCrc32)
        public:
                EbmlCrc32(const EbmlCrc32 & ElementToClone);
                virtual bool ValidateSize() const {return IsFiniteSize() && (GetSize() == 4);}
                filepos_t RenderData(IOCallback & output, bool bForceRender, bool bWithDefault = false);
                filepos_t ReadData(IOCallback & input, ScopeMode ReadFully = SCOPE_ALL_DATA);
//              filepos_t UpdateSize(bool bWithDefault = false);
                
                bool IsDefaultValue() const {
                        return false;
                }

                void AddElementCRC32(EbmlElement &ElementToCRC);
                bool CheckElementCRC32(EbmlElement &ElementToCRC);
                
                enum {DIGESTSIZE = 4};
                
                static bool CheckCRC(uint32 inputCRC, const binary *input, uint32 length);
                void FillCRC32(const binary *input, uint32 length);
                void Update(const binary *input, uint32 length);
                void Finalize();
                uint32 GetCrc32() const {
                        return m_crc_final;
                };
        
                void ForceCrc32(uint32 NewValue) { m_crc_final = NewValue; SetValueIsSet();}

#if defined(EBML_STRICT_API)
    private:
#else
    protected:
#endif
                void ResetCRC() {m_crc = CRC32_NEGL;}
                void UpdateByte(binary b) {m_crc = m_tab[CRC32_INDEX(m_crc) ^ b] ^ CRC32_SHIFTED(m_crc);}

                static const uint32 m_tab[256];
                uint32 m_crc;
                uint32 m_crc_final;
        
        EBML_CONCRETE_CLASS(EbmlCrc32)
};

template <class T>
inline unsigned int GetAlignment(T *dummy=NULL) // VC60 workaround
{
#if (_MSC_VER >= 1300)
        return __alignof(T);
#elif defined(__GNUC__)
        return __alignof__(T);
#else
        return sizeof(T);
#endif
}

template <class T>
inline bool IsPowerOf2(T n)
{
        return n > 0 && (n & (n-1)) == 0;
}

template <class T1, class T2>
inline T2 ModPowerOf2(T1 a, T2 b)
{
        assert(IsPowerOf2(b));
        return T2(a) & (b-1);
}

inline bool IsAlignedOn(const void *p, unsigned int alignment)
{
        return IsPowerOf2(alignment) ? ModPowerOf2((uintptr_t)p, alignment) == 0 : (uintptr_t)p % alignment == 0;
}

template <class T>
inline bool IsAligned(const void *p, T *dummy=NULL)     // VC60 workaround
{
        return IsAlignedOn(p, GetAlignment<T>());
}

END_LIBEBML_NAMESPACE

#endif // LIBEBML_CRC32_H

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