mitab_maptoolblock.cpp

用于读取TAB、MIF、SHP文件的类

                                        int nFileOffset /* = 0*/)
{
    /*-----------------------------------------------------------------
     * Start with the default initialisation
     *----------------------------------------------------------------*/
    if ( TABRawBinBlock::InitNewBlock(fpSrc, nBlockSize, nFileOffset) != 0)
        return -1;

    /*-----------------------------------------------------------------
     * And then set default values for the block header.
     *----------------------------------------------------------------*/
    m_nNextToolBlock = 0;
 
    m_numDataBytes = 0;

    GotoByteInBlock(0x000);

    if (m_eAccess != TABRead)
    {
        WriteInt16(TABMAP_TOOL_BLOCK); // Block type code
        WriteInt16(0);                 // num. bytes used, excluding header
        WriteInt32(0);                 // Pointer to next tool block
    }

    if (CPLGetLastErrorNo() != 0)
        return -1;

    return 0;
}

/**********************************************************************
 *                   TABMAPToolBlock::SetNextToolBlock()
 *
 * Set the address (offset from beginning of file) of the drawing tool block
 * that follows the current one.
 **********************************************************************/
void     TABMAPToolBlock::SetNextToolBlock(GInt32 nNextToolBlockAddress)
{
    m_nNextToolBlock = nNextToolBlockAddress;
}

/**********************************************************************
 *                   TABMAPToolBlock::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 TABMAPToolBlock::SetMAPBlockManagerRef(TABBinBlockManager *poBlockMgr)
{
    m_poBlockManagerRef = poBlockMgr;
};


/**********************************************************************
 *                   TABMAPToolBlock::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_nNextToolBlock 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     TABMAPToolBlock::ReadBytes(int numBytes, GByte *pabyDstBuf)
{
    int nStatus;

    if (m_pabyBuf && 
        m_nCurPos >= (m_numDataBytes+MAP_TOOL_HEADER_SIZE) && 
        m_nNextToolBlock > 0)
    {
        if ( (nStatus=GotoByteInFile(m_nNextToolBlock)) != 0)
        {
            // Failed.... an error has already been reported.
            return nStatus;
        }

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

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

/**********************************************************************
 *                   TABMAPToolBlock::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  TABMAPToolBlock::WriteBytes(int nBytesToWrite, GByte *pabySrcBuf)
{
    if (m_eAccess == TABWrite && m_poBlockManagerRef &&
        (m_nBlockSize - m_nCurPos) < nBytesToWrite)
    {
        int nNewBlockOffset = m_poBlockManagerRef->AllocNewBlock();
        SetNextToolBlock(nNewBlockOffset);

        if (CommitToFile() != 0 ||
            InitNewBlock(m_fp, 512, nNewBlockOffset) != 0)
        {
            // An error message should have already been reported.
            return -1;
        }

        m_numBlocksInChain ++;
    }

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

/**********************************************************************
 *                   TABMAPToolBlock::CheckAvailableSpace()
 *
 * Check if an object of the specified type can fit in
 * current block.  If it can't fit then force committing current block 
 * and allocating a new one.
 *
 * Returns 0 if succesful or -1 if an error happened, in which case 
 * CPLError() will have been called.
 **********************************************************************/
int  TABMAPToolBlock::CheckAvailableSpace(int nToolType)
{
    int nBytesToWrite = 0;

    switch(nToolType)
    {
      case TABMAP_TOOL_PEN:
        nBytesToWrite = 11;
        break;
      case TABMAP_TOOL_BRUSH:
        nBytesToWrite = 13;
        break;
      case TABMAP_TOOL_FONT:
        nBytesToWrite = 37;
        break;
      case TABMAP_TOOL_SYMBOL:
        nBytesToWrite = 13;
        break;
      default:
        CPLAssert(FALSE);
    }

    if (GetNumUnusedBytes() < nBytesToWrite)
    {
        int nNewBlockOffset = m_poBlockManagerRef->AllocNewBlock();
        SetNextToolBlock(nNewBlockOffset);

        if (CommitToFile() != 0 ||
            InitNewBlock(m_fp, 512, nNewBlockOffset) != 0)
        {
            // An error message should have already been reported.
            return -1;
        }

        m_numBlocksInChain ++;
    }

    return 0;
}




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

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

    fprintf(fpOut, "----- TABMAPToolBlock::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_nNextToolBlock     = %d\n", m_nNextToolBlock);
    }

    fflush(fpOut);
}

#endif // DEBUG