poddata.cpp

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/*
    This file is part of the Okteta Kasten module, made within the KDE community.

    Copyright 2007,2009 Friedrich W. H. Kossebau <kossebau@kde.org>

    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) version 3, or any
    later version accepted by the membership of KDE e.V. (or its
    successor approved by the membership of KDE e.V.), which shall
    act as a proxy defined in Section 6 of version 3 of the license.

    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, see <http://www.gnu.org/licenses/>.
*/

#include "poddata.h"


namespace Okteta
{

static inline void copyInvertedBytes( Byte* data, const Byte* sourceData, const int length )
{
    const int last = length-1;
    for( int i=0,j=last; i<length; ++i,--j )
        data[i] = sourceData[j];
}


PODData::PODData()
 : mCurrentOriginalData( 0 ),
   mCurrentEndiannessSetData( 0 ),
   mCurrentSize( 0 ),
   mByteOrder( thisMachineByteOrder )
{
}

const Byte* PODData::originalData()     const { return mCurrentOriginalData; }
const Byte* PODData::byteOrderSetData() const { return mCurrentEndiannessSetData; }
ByteOrder PODData::byteOrder()          const { return mByteOrder; }
int PODData::size()                     const { return mCurrentSize; }


Byte* PODData::rawData()    { return mOriginalAligned64Bit.mBytes; }

void PODData::setByteOrder( ByteOrder byteOrder )
{
    if( mByteOrder == byteOrder )
        return;

    mByteOrder = byteOrder;

    // swap data
    if( mCurrentOriginalData )
        copyInvertedBytes( mByteOrderSetAligned64Bit.mBytes, mOriginalAligned64Bit.mBytes, Size );
    else
        mByteOrderSetAligned64Bit = mOriginalAligned64Bit;
}

unsigned long PODData::bitValue( int noOfBitsToRead ) const
{
    static const int BitsPerByte = 8;
    static const unsigned char BitMask[9] =
    {
        0, 1<<7, 3<<6, 7<<5, 15<<4, 31<<3, 63<<2, 127<<1, 255
    };

    unsigned long result = 0;

    if( noOfBitsToRead < 1 )
        noOfBitsToRead = 1;

    // TODO: the cursor currently does not go into the byte
    int noOfUsedBits = 0;//7 - state.cell;

    const bool isReverse = ( mByteOrder != thisMachineByteOrder );
    const Byte* data = mByteOrderSetAligned64Bit.mBytes;
    if( isReverse )
        data += 7;

    while( noOfBitsToRead > 0 )
    {
        Byte byte = ( *data << noOfUsedBits );

        const int noOfNextBits =
            ( (BitsPerByte-noOfUsedBits) >= noOfBitsToRead ) ? noOfBitsToRead : (BitsPerByte-noOfUsedBits);

        byte &= BitMask[noOfNextBits];

        byte >>= BitsPerByte - noOfNextBits;

        result = (result<<noOfNextBits) | byte;

        noOfBitsToRead -= noOfNextBits;
        noOfUsedBits += noOfNextBits;

        if( noOfUsedBits >= BitsPerByte )
        {
            noOfUsedBits = 0;
            if( isReverse )
                --data;
            else
                ++data;
        }
    }

    return result;
}


bool PODData::updateRawData( int size )
{
    const Byte* oldCurrentOriginalData = mCurrentOriginalData;

    if( size > 0 )
    {
        if( mByteOrder != thisMachineByteOrder )
            copyInvertedBytes( mByteOrderSetAligned64Bit.mBytes, mOriginalAligned64Bit.mBytes, Size );
        else
            mByteOrderSetAligned64Bit = mOriginalAligned64Bit;

        mCurrentOriginalData = mOriginalAligned64Bit.mBytes;
        mCurrentEndiannessSetData = mByteOrderSetAligned64Bit.mBytes;
        mCurrentSize = size;
    }
    else
    {
        mCurrentOriginalData = 0;
        mCurrentEndiannessSetData = 0;
        mCurrentSize = 0;
    }

    return ( mCurrentOriginalData || oldCurrentOriginalData );
}

void PODData::getPointers( const void** P8Bit, const void** P16Bit, const void** P32Bit, const void** P64Bit ) const
{
    static const int MachineOffsets[4] = { 0, 0, 0, 0 };
    static const int ReversedOffsets[4] = { 7, 6, 4, 0 };

    const int* offsets = ( mByteOrder == thisMachineByteOrder ) ? MachineOffsets : ReversedOffsets;
    const Byte* data = mByteOrderSetAligned64Bit.mBytes;

    *P8Bit =  (mCurrentSize>=1) ? data + offsets[0] : 0;
    *P16Bit = (mCurrentSize>=2) ? data + offsets[1] : 0;
    *P32Bit = (mCurrentSize>=4) ? data + offsets[2] : 0;
    *P64Bit = (mCurrentSize>=8) ? data + offsets[3] : 0;
}

const void* PODData::pointer( int byteCount ) const
{
    if( byteCount > mCurrentSize )
        byteCount = 0;

    const int offset = ( mByteOrder == thisMachineByteOrder ) ? 0 : 8-byteCount;
    const Byte* data = mByteOrderSetAligned64Bit.mBytes;

    return (byteCount>0) ? data + offset : 0;
}

}