mitab_mapcoordblock.cpp

mitab,读取MapInfo的地图文件

    if ((!bCompressed && (WriteInt32(nX) != 0 || WriteInt32(nY) != 0 ) ) ||
        (bCompressed && (WriteInt16(nX - m_nComprOrgX) != 0 ||
                         WriteInt16(nY - m_nComprOrgY) != 0) ) )
    {
        return -1;
    }

    /*-----------------------------------------------------------------
     * Update block MBR
     *----------------------------------------------------------------*/
    //__TODO__ Do we still need to track the block MBR???
    if (nX < m_nMinX)
        m_nMinX = nX;
    if (nX > m_nMaxX)
        m_nMaxX = nX;
    
    if (nY < m_nMinY)
        m_nMinY = nY;
    if (nY > m_nMaxY)
        m_nMaxY = nY;
    
    /*-------------------------------------------------------------
     * Also keep track of current feature MBR.
     *------------------------------------------------------------*/
    if (nX < m_nFeatureXMin)
        m_nFeatureXMin = nX;
    if (nX > m_nFeatureXMax)
        m_nFeatureXMax = nX;

    if (nY < m_nFeatureYMin)
        m_nFeatureYMin = nY;
    if (nY > m_nFeatureYMax)
        m_nFeatureYMax = nY;

    return 0;
}

/**********************************************************************
 *                   TABMAPCoordBlock::SetMAPBlockManagerRef()
 *
 * Pass a reference to the block manager object for the file this 
 * block belongs to.  The block manager will be used by this object
 * when it needs to automatically allocate a new block.
 **********************************************************************/
void TABMAPCoordBlock::SetMAPBlockManagerRef(TABBinBlockManager *poBlockMgr)
{
    m_poBlockManagerRef = poBlockMgr;
};


/**********************************************************************
 *                   TABMAPCoordBlock::ReadBytes()
 *
 * Cover function for TABRawBinBlock::ReadBytes() that will automagically
 * load the next coordinate block in the chain before reading the 
 * requested bytes if we are at the end of the current block and if
 * m_nNextCoordBlock is a valid block.
 *
 * Then the control is passed to TABRawBinBlock::ReadBytes() to finish the
 * work:
 * Copy the number of bytes from the data block's internal buffer to
 * the user's buffer pointed by pabyDstBuf.
 *
 * Passing pabyDstBuf = NULL will only move the read pointer by the
 * specified number of bytes as if the copy had happened... but it 
 * won't crash.
 *
 * Returns 0 if succesful or -1 if an error happened, in which case 
 * CPLError() will have been called.
 **********************************************************************/
int     TABMAPCoordBlock::ReadBytes(int numBytes, GByte *pabyDstBuf)
{
    int nStatus;

    if (m_pabyBuf && 
        m_nCurPos >= (m_numDataBytes+MAP_COORD_HEADER_SIZE) && 
        m_nNextCoordBlock > 0)
    {
        // We're at end of current block... advance to next block.

        if ( (nStatus=GotoByteInFile(m_nNextCoordBlock, TRUE)) != 0)
        {
            // Failed.... an error has already been reported.
            return nStatus;
        }

        GotoByteInBlock(MAP_COORD_HEADER_SIZE); // Move pointer past header
        m_numBlocksInChain++;
    }

    if (m_pabyBuf && 
        m_nCurPos < (m_numDataBytes+MAP_COORD_HEADER_SIZE) && 
        m_nCurPos+numBytes > (m_numDataBytes+MAP_COORD_HEADER_SIZE) && 
        m_nNextCoordBlock > 0)
    {
        // Data overlaps on more than one block
        // Read until end of this block and then recursively call ReadBytes()
        // for the rest.
        int numBytesInThisBlock = 
                      (m_numDataBytes+MAP_COORD_HEADER_SIZE)-m_nCurPos;
        nStatus = TABRawBinBlock::ReadBytes(numBytesInThisBlock, pabyDstBuf);
        if (nStatus == 0)
            nStatus = TABMAPCoordBlock::ReadBytes(numBytes-numBytesInThisBlock,
                                               pabyDstBuf+numBytesInThisBlock);
        return nStatus;
    }


    return TABRawBinBlock::ReadBytes(numBytes, pabyDstBuf);
}


/**********************************************************************
 *                   TABMAPCoordBlock::WriteBytes()
 *
 * Cover function for TABRawBinBlock::WriteBytes() that will automagically
 * CommitToFile() the current block and create a new one if we are at 
 * the end of the current block.
 *
 * Then the control is passed to TABRawBinBlock::WriteBytes() to finish the
 * work.
 *
 * Passing pabySrcBuf = NULL will only move the write pointer by the
 * specified number of bytes as if the copy had happened... but it 
 * won't crash.
 *
 * Returns 0 if succesful or -1 if an error happened, in which case 
 * CPLError() will have been called.
 **********************************************************************/
int  TABMAPCoordBlock::WriteBytes(int nBytesToWrite, GByte *pabySrcBuf)
{
    if (m_eAccess != TABWrite && m_eAccess != TABReadWrite )
    {
        CPLError(CE_Failure, CPLE_AppDefined,
                 "WriteBytes(): Block does not support write operations.");
        return -1;
    }

    if (m_poBlockManagerRef && (m_nBlockSize - m_nCurPos) < nBytesToWrite)
    {
        if (nBytesToWrite <= (m_nBlockSize-MAP_COORD_HEADER_SIZE))
        {
            // Data won't fit in this block but can fit inside a single
            // block, so we'll allocate a new block for it.  This will 
            // prevent us from overlapping coordinate values on 2 blocks, but
            // still allows strings longer than one block (see 'else' below).
            //

            if ( m_nNextCoordBlock != 0 )
            {
                // We're in read/write mode and there is already an allocated
                // block following this one in the chain ... just reload it 
                // and continue writing to it

                CPLAssert( m_eAccess == TABReadWrite );

                if (CommitToFile() != 0 ||
                     ReadFromFile(m_fp, m_nNextCoordBlock, m_nBlockSize) != 0)
                {
                    // An error message should have already been reported.
                    return -1;
                }
            }
            else
            {
                // Need to alloc a new block.

                int nNewBlockOffset = m_poBlockManagerRef->AllocNewBlock();
                SetNextCoordBlock(nNewBlockOffset);

                if (CommitToFile() != 0 ||
                    InitNewBlock(m_fp, m_nBlockSize, nNewBlockOffset) != 0)
                {
                    // An error message should have already been reported.
                    return -1;
                }

                m_numBlocksInChain++;
            }
        }
        else
        {
            // Data to write is longer than one block... so we'll have to
            // split it over multiple block through multiple calls.
            //
            int nStatus = 0;
            while(nStatus == 0 && nBytesToWrite > 0)
            {
                int nBytes = m_nBlockSize-MAP_COORD_HEADER_SIZE;
                if ( (m_nBlockSize - m_nCurPos) > 0 )
                {
                    // Use free room in current block
                    nBytes = (m_nBlockSize - m_nCurPos);
                }

                nBytes = MIN(nBytes, nBytesToWrite);

                // The following call will result in a new block being 
                // allocated in the if() block above.
                nStatus = TABMAPCoordBlock::WriteBytes(nBytes, 
                                                       pabySrcBuf);

                nBytesToWrite -= nBytes;
                pabySrcBuf += nBytes;
            }
            return nStatus;
        }
    }

    if (m_nCurPos >= MAP_COORD_HEADER_SIZE)
    {
        // Keep track of Coordinate data... this means ignore header bytes
        // that could be written.
        m_nTotalDataSize += nBytesToWrite;
        m_nFeatureDataSize += nBytesToWrite;
    }

    return TABRawBinBlock::WriteBytes(nBytesToWrite, pabySrcBuf);
}

/**********************************************************************
 *                   TABMAPObjectBlock::SeekEnd()
 *
 * Move read/write pointer to end of used part of the block
 **********************************************************************/
void     TABMAPCoordBlock::SeekEnd()
{
    m_nCurPos = m_nSizeUsed;
}

/**********************************************************************
 *                   TABMAPCoordBlock::StartNewFeature()
 *
 * Reset all member vars that are used to keep track of data size
 * and MBR for the current feature.  This is info is not needed by
 * the coord blocks themselves, but it helps a lot the callers to
 * have this class take care of that for them.
 *
 * See Also: GetFeatureDataSize() and GetFeatureMBR()
 **********************************************************************/
void TABMAPCoordBlock::StartNewFeature()
{
    m_nFeatureDataSize = 0;

    m_nFeatureXMin = 1000000000;
    m_nFeatureYMin = 1000000000;
    m_nFeatureXMax = -1000000000;
    m_nFeatureYMax = -1000000000;
}

/**********************************************************************
 *                   TABMAPCoordBlock::GetFeatureMBR()
 *
 * Return the MBR of all the coords written using WriteIntCoord() since
 * the last call to StartNewFeature().
 **********************************************************************/
void TABMAPCoordBlock::GetFeatureMBR(GInt32 &nXMin, GInt32 &nYMin, 
                                     GInt32 &nXMax, GInt32 &nYMax)
{
    nXMin = m_nFeatureXMin;
    nYMin = m_nFeatureYMin;
    nXMax = m_nFeatureXMax;
    nYMax = m_nFeatureYMax; 
}


/**********************************************************************
 *                   TABMAPCoordBlock::Dump()
 *
 * Dump block contents... available only in DEBUG mode.
 **********************************************************************/
#ifdef DEBUG

void TABMAPCoordBlock::Dump(FILE *fpOut /*=NULL*/)
{
    if (fpOut == NULL)
        fpOut = stdout;

    fprintf(fpOut, "----- TABMAPCoordBlock::Dump() -----\n");
    if (m_pabyBuf == NULL)
    {
        fprintf(fpOut, "Block has not been initialized yet.");
    }
    else
    {
        fprintf(fpOut,"Coordinate Block (type %d) at offset %d.\n", 
                                                 m_nBlockType, m_nFileOffset);
        fprintf(fpOut,"  m_numDataBytes        = %d\n", m_numDataBytes);
        fprintf(fpOut,"  m_nNextCoordBlock     = %d\n", m_nNextCoordBlock);
    }

    fflush(fpOut);
}

#endif // DEBUG