avc_bin.c

GIS系统支持库Geospatial Data Abstraction Library代码.GDAL is a translator library for raster geospatial dat

 * Returns 0 on success or -1 on error.
 **********************************************************************/
int _AVCBinReadHeader(AVCRawBinFile *psFile, AVCBinHeader *psHeader,
                      AVCCoverType eCoverType)
{
    int nStatus = 0;

    /*-----------------------------------------------------------------
     * For AVCCoverPC coverages, there is a first 256 bytes header
     * that we just skip and that precedes the 100 bytes header block.
     *
     * In AVCCoverV7, we only have the 100 bytes header.
     *----------------------------------------------------------------*/
    if (eCoverType == AVCCoverPC)
        AVCRawBinFSeek(psFile, 256, SEEK_SET);
    else
        AVCRawBinFSeek(psFile, 0, SEEK_SET);

    psHeader->nSignature = AVCRawBinReadInt32(psFile);

    if (AVCRawBinEOF(psFile))
        nStatus = -1;

    psHeader->nPrecision = AVCRawBinReadInt32(psFile);
    psHeader->nRecordSize= AVCRawBinReadInt32(psFile);

    /* Jump to 24th byte in header */
    AVCRawBinFSeek(psFile, 12, SEEK_CUR);
    psHeader->nLength    = AVCRawBinReadInt32(psFile);

    /*-----------------------------------------------------------------
     * File length, in words (16 bits)... pass the info to the RawBinFile
     * to prevent it from trying to read junk bytes at the end of files...
     * this problem happens specially with PC Arc/Info files.
     *----------------------------------------------------------------*/
    if (eCoverType == AVCCoverPC)
        AVCRawBinSetFileDataSize(psFile, psHeader->nLength*2 + 256);
    else
        AVCRawBinSetFileDataSize(psFile, psHeader->nLength*2 );

    /* Move the pointer at the end of the 100 bytes header
     */
    AVCRawBinFSeek(psFile, 72, SEEK_CUR);

    return nStatus;
}


/**********************************************************************
 *                          AVCBinReadRewind()
 *
 * Rewind the read pointer, and read/skip the header if necessary so
 * that we are ready to read the data objects from the file after
 * this call.
 *
 * Returns 0 on success, -1 on error, and -2 if file has an invalid
 * signature and is possibly corrupted.
 **********************************************************************/
int AVCBinReadRewind(AVCBinFile *psFile)
{
    AVCBinHeader sHeader;
    int          nStatus=0;

    /*-----------------------------------------------------------------
     * For AVCCoverPC coverages, there is a first 256 bytes header
     * that we just skip and that precedes the 100 bytes header block.
     *
     * In AVCCoverV7 and AVCCoverWeird, we only find the 100 bytes header.
     *
     * Note: it is the call to _AVCBinReadHeader() that takes care
     * of skipping the first 256 bytes header if necessary.
     *----------------------------------------------------------------*/

    AVCRawBinFSeek(psFile->psRawBinFile, 0, SEEK_SET);

    if ( psFile->eFileType == AVCFileARC ||
         psFile->eFileType == AVCFilePAL ||
         psFile->eFileType == AVCFileRPL ||
         psFile->eFileType == AVCFileCNT ||
         psFile->eFileType == AVCFileLAB ||
         psFile->eFileType == AVCFileTXT ||
         psFile->eFileType == AVCFileTX6  )
    {   
        nStatus = _AVCBinReadHeader(psFile->psRawBinFile, &sHeader, 
                                    psFile->eCoverType);

        /* Store the precision information inside the file handle.
         *
         * Of course, there had to be an exception...
         * At least PAL and TXT files in PC Arc/Info coverages sometimes 
         * have a negative precision flag even if they contain single 
         * precision data... why is that????  A PC Arc bug?
         *
         * 2000-06-05: Found a double-precision PAL file with a signature
         *             of 1011 (should have been -11).  So we'll assume
         *             that signature > 1000 also means double precision.
         */
        if ((sHeader.nPrecision < 0 || sHeader.nPrecision > 1000) && 
            psFile->eCoverType != AVCCoverPC)
            psFile->nPrecision = AVC_DOUBLE_PREC;
        else
            psFile->nPrecision = AVC_SINGLE_PREC;

        /* Validate the signature value... this will allow us to detect
         * corrupted files or files that do not belong in the coverage.
         */
        if (sHeader.nSignature != 9993 && sHeader.nSignature != 9994)
        {
            CPLError(CE_Warning, CPLE_AssertionFailed,
                     "%s appears to have an invalid file header.",
                     psFile->pszFilename);
            return -2;
        }

        /* In Weird coverages, TXT files can be stored in the PC or the V7
         * format.  Look at the 'precision' field in the header to tell which
         * type we have.
         *   Weird TXT in PC format: nPrecision = 16
         *   Weird TXT in V7 format: nPrecision = +/-67
         * Use AVCFileTXT for PC type, and AVCFileTX6 for V7 type.
         */
        if (psFile->eCoverType == AVCCoverWeird &&
            psFile->eFileType == AVCFileTXT && ABS(sHeader.nPrecision) == 67)
        {
            /* TXT file will be processed as V7 TXT/TX6/TX7 */
            psFile->eFileType = AVCFileTX6;
        }
    }
    else if (psFile->eFileType == AVCFileTOL)
    {
        /*-------------------------------------------------------------
         * For some reason, the tolerance files do not follow the 
         * general rules!
         * Single precision "tol.adf" have no header
         * Double precision "par.adf" have the usual 100 bytes header,
         *  but the 3rd field, which usually defines the precision has
         *  a positive value, even if the file is double precision!
         *
         * Also, we have a problem with PC Arc/Info TOL files since they
         * do not contain the first 256 bytes header either... so we will
         * just assume that double precision TOL files cannot exist in
         * PC Arc/Info coverages... this should be OK.
         *------------------------------------------------------------*/
        int nSignature = 0;
        nSignature = AVCRawBinReadInt32(psFile->psRawBinFile);

        if (nSignature == 9993)
        {
            /* We have a double precision par.adf... read the 100 bytes 
             * header and set the precision information inside the file 
             * handle.
             */
            nStatus = _AVCBinReadHeader(psFile->psRawBinFile, &sHeader, 
                                        psFile->eCoverType);

            psFile->nPrecision = AVC_DOUBLE_PREC;
        }
        else
        {
            /* It's a single precision tol.adf ... just set the 
             * precision field.
             */
            AVCRawBinFSeek(psFile->psRawBinFile, 0, SEEK_SET);
            psFile->nPrecision = AVC_SINGLE_PREC;
        }
    }

    return nStatus;
}

/**********************************************************************
 *                          AVCBinReadObject()
 *
 * Read the object with a particular index.  For fixed length record
 * files we seek directly to the object.  For variable files we try to
 * get the offset from the corresponding index file.  
 *
 * NOTE: Currently only implemented for ARC, PAL and TABLE files.
 *
 * Returns the read object on success or NULL on error.
 **********************************************************************/
void *AVCBinReadObject(AVCBinFile *psFile, int iObjIndex )
{
    int	 bIndexed = FALSE;
    int  nObjectOffset, nRecordSize=0, nRecordStart = 0, nLen;
    char *pszExt = NULL;

    if( iObjIndex < 0 )
        return NULL;

    /*-----------------------------------------------------------------
     * Determine some information from based on the coverage type.    
     *----------------------------------------------------------------*/
    nLen = strlen(psFile->pszFilename);
    if( psFile->eFileType == AVCFileARC &&
        ((nLen>=3 && EQUALN((pszExt=psFile->pszFilename+nLen-3), "arc", 3)) ||
         (nLen>=7 && EQUALN((pszExt=psFile->pszFilename+nLen-7),"arc.adf",7))))
    {
        bIndexed = TRUE;
    }
    else if( psFile->eFileType == AVCFilePAL &&
        ((nLen>=3 && EQUALN((pszExt=psFile->pszFilename+nLen-3), "pal", 3)) ||
         (nLen>=7 && EQUALN((pszExt=psFile->pszFilename+nLen-7),"pal.adf",7))))
    {
        bIndexed = TRUE;
    }
    else if( psFile->eFileType == AVCFileTABLE )
    {
        bIndexed = FALSE;
        nRecordSize = psFile->hdr.psTableDef->nRecSize;
        nRecordStart = 0;
    }
    else
        return NULL;

    /*-----------------------------------------------------------------
     * Ensure the index file is opened if an index file is required.
     *----------------------------------------------------------------*/

    if( bIndexed && psFile->psIndexFile == NULL )
    {
        char chOrig;

        if( pszExt == NULL )
            return NULL;

        chOrig = pszExt[2];
        if( chOrig > 'A' && chOrig < 'Z' )
            pszExt[2] = 'X';
        else
            pszExt[2] = 'x';

        psFile->psIndexFile = 
            AVCRawBinOpen( psFile->pszFilename, "rb", 
                           psFile->psRawBinFile->eByteOrder, 
                           psFile->psRawBinFile->psDBCSInfo);
        pszExt[2] = chOrig;

        if( psFile->psIndexFile == NULL )
            return NULL;
    }

    /*-----------------------------------------------------------------
     * Establish the offset to read the object from.
     *----------------------------------------------------------------*/
    if( bIndexed )
    {
        int nIndexOffset;

        if (psFile->eCoverType == AVCCoverPC)
            nIndexOffset = 356 + (iObjIndex-1)*8;
        else
            nIndexOffset = 100 + (iObjIndex-1)*8;

        AVCRawBinFSeek( psFile->psIndexFile, nIndexOffset, SEEK_SET );
        if( AVCRawBinEOF( psFile->psIndexFile ) )
            return NULL;

        nObjectOffset = AVCRawBinReadInt32( psFile->psIndexFile );
        nObjectOffset *= 2;

        if (psFile->eCoverType == AVCCoverPC)
            nObjectOffset += 256;
    }
    else
        nObjectOffset = nRecordStart + nRecordSize * (iObjIndex-1);

    /*-----------------------------------------------------------------
     * Seek to the start of the object in the data file.
     *----------------------------------------------------------------*/
    AVCRawBinFSeek( psFile->psRawBinFile, nObjectOffset, SEEK_SET );
    if( AVCRawBinEOF( psFile->psRawBinFile ) )
        return NULL;

    /*-----------------------------------------------------------------
     * Read and return the object.
     *----------------------------------------------------------------*/
    return AVCBinReadNextObject( psFile );
}


/**********************************************************************
 *                          AVCBinReadNextObject()
 *
 * Read the next structure from the file.  This function is just a generic
 * cover on top of the AVCBinReadNextArc/Lab/Pal/Cnt() functions.
 *
 * Returns a (void*) to a static structure with the contents of the object
 * that was read.  The contents of the structure will be valid only until
 * the next call.  
 * If you use the returned value, then make sure that you cast it to
 * the right type for the current file! (AVCArc, AVCPal, AVCCnt, ...)
 *
 * Returns NULL if an error happened or if EOF was reached.  
 **********************************************************************/
void *AVCBinReadNextObject(AVCBinFile *psFile)
{
    void *psObj = NULL;

    switch(psFile->eFileType)
    {
      case AVCFileARC:
        psObj = (void*)AVCBinReadNextArc(psFile);
        break;
      case AVCFilePAL:
      case AVCFileRPL:
        psObj = (void*)AVCBinReadNextPal(psFile);
        break;
      case AVCFileCNT:
        psObj = (void*)AVCBinReadNextCnt(psFile);
        break;
      case AVCFileLAB:
        psObj = (void*)AVCBinReadNextLab(psFile);
        break;
      case AVCFileTOL:
        psObj = (void*)AVCBinReadNextTol(psFile);
        break;
      case AVCFileTXT:
      case AVCFileTX6:
        psObj = (void*)AVCBinReadNextTxt(psFile);
        break;
      case AVCFileRXP:
        psObj = (void*)AVCBinReadNextRxp(psFile);
        break;
      case AVCFileTABLE:
        psObj = (void*)AVCBinReadNextTableRec(psFile);
        break;
      default:
        CPLError(CE_Failure, CPLE_IllegalArg,
                 "AVCBinReadNextObject(): Unsupported file type!");
    }

    return psObj;
}



/**********************************************************************
 *                          AVCBinReadNextTableRec()
 *
 * Reads the next record from an attribute table.
 *
 * Returns a pointer to an array of static AVCField structure whose 
 * contents will be valid only until the next call,
 * or NULL if an error happened or if EOF was reached.  
 **********************************************************************/
AVCField *AVCBinReadNextTableRec(AVCBinFile *psFile)
{
    if (psFile->eCoverType != AVCCoverPC &&
        psFile->eFileType == AVCFileTABLE &&
        psFile->hdr.psTableDef->numRecords > 0 &&
        ! AVCRawBinEOF(psFile->psRawBinFile) &&
        _AVCBinReadNextTableRec(psFile->psRawBinFile, 
                                    psFile->hdr.psTableDef->numFields,
                                    psFile->hdr.psTableDef->pasFieldDef,
                                    psFile->cur.pasFields,
                                    psFile->hdr.psTableDef->nRecSize) == 0 )
    {
        return psFile->cur.pasFields;
    }
    else if (psFile->eCoverType == AVCCoverPC &&
             psFile->eFileType == AVCFileTABLE &&
             psFile->hdr.psTableDef->numRecords > 0 &&
             _AVCBinReadNextDBFTableRec(psFile->hDBFFile, 
                                        &(psFile->nCurDBFRecord),
                                        psFile->hdr.psTableDef->numFields,