root/trunk/gdal/frmts/iso8211/ddfrecord.cpp

/******************************************************************************
 * $Id$
 *
 * Project:  ISO 8211 Access
 * Purpose:  Implements the DDFRecord class.
 * Author:   Frank Warmerdam, warmerdam@pobox.com
 *
 ******************************************************************************
 * Copyright (c) 1999, Frank Warmerdam
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include "iso8211.h"
#include "cpl_conv.h"

CPL_CVSID("$Id$");

static const size_t nLeaderSize = 24;

/************************************************************************/
/*                             DDFRecord()                              */
/************************************************************************/

DDFRecord::DDFRecord( DDFModule * poModuleIn )

{
    poModule = poModuleIn;

    nReuseHeader = FALSE;

    nFieldOffset = 0;

    nDataSize = 0;
    pachData = NULL;

    nFieldCount = 0;
    paoFields = NULL;

    bIsClone = FALSE;

    _sizeFieldTag = 4;
    _sizeFieldPos = 0;
    _sizeFieldLength = 0;
}

/************************************************************************/
/*                             ~DDFRecord()                             */
/************************************************************************/

DDFRecord::~DDFRecord()

{
    Clear();

    if( bIsClone )
        poModule->RemoveCloneRecord( this );
}

/************************************************************************/
/*                                Dump()                                */
/************************************************************************/

/**
 * Write out record contents to debugging file.
 *
 * A variety of information about this record, and all it's fields and
 * subfields is written to the given debugging file handle.  Note that
 * field definition information (ala DDFFieldDefn) isn't written.
 *
 * @param fp The standard io file handle to write to.  ie. stderr
 */

void DDFRecord::Dump( FILE * fp )

{
    fprintf( fp, "DDFRecord:\n" );
    fprintf( fp, "    nReuseHeader = %d\n", nReuseHeader );
    fprintf( fp, "    nDataSize = %d\n", nDataSize );
    fprintf( fp, 
             "    _sizeFieldLength=%d, _sizeFieldPos=%d, _sizeFieldTag=%d\n",
             _sizeFieldLength, _sizeFieldPos, _sizeFieldTag );

    for( int i = 0; i < nFieldCount; i++ )
    {
        paoFields[i].Dump( fp );
    }
}

/************************************************************************/
/*                                Read()                                */
/*                                                                      */
/*      Read a record of data from the file, and parse the header to    */
/*      build a field list for the record (or reuse the existing one    */
/*      if reusing headers).  It is expected that the file pointer      */
/*      will be positioned at the beginning of a data record.  It is    */
/*      the DDFModule's responsibility to do so.                        */
/*                                                                      */
/*      This method should only be called by the DDFModule class.       */
/************************************************************************/

int DDFRecord::Read()

{
/* -------------------------------------------------------------------- */
/*      Redefine the record on the basis of the header if needed.       */
/*      As a side effect this will read the data for the record as well.*/
/* -------------------------------------------------------------------- */
    if( !nReuseHeader )
    {
        return( ReadHeader() );
    }

/* -------------------------------------------------------------------- */
/*      Otherwise we read just the data and carefully overlay it on     */
/*      the previous records data without disturbing the rest of the    */
/*      record.                                                         */
/* -------------------------------------------------------------------- */
    size_t      nReadBytes;

    nReadBytes = VSIFReadL( pachData + nFieldOffset, 1,
                            nDataSize - nFieldOffset,
                            poModule->GetFP() );
    if( nReadBytes != (size_t) (nDataSize - nFieldOffset)
        && nReadBytes == 0
        && VSIFEofL( poModule->GetFP() ) )
    {
        return FALSE;
    }
    else if( nReadBytes != (size_t) (nDataSize - nFieldOffset) )
    {
        CPLError( CE_Failure, CPLE_FileIO,
                  "Data record is short on DDF file.\n" );
        
        return FALSE;
    }

    // notdef: eventually we may have to do something at this point to 
    // notify the DDFField's that their data values have changed. 
    
    return TRUE;
}

/************************************************************************/
/*                               Write()                                */
/************************************************************************/

/**
 * Write record out to module.
 *
 * This method writes the current record to the module to which it is 
 * attached.  Normally this would be at the end of the file, and only used
 * for modules newly created with DDFModule::Create().  Rewriting existing
 * records is not supported at this time.  Calling Write() multiple times
 * on a DDFRecord will result it multiple copies being written at the end of
 * the module.
 *
 * @return TRUE on success or FALSE on failure.
 */

int DDFRecord::Write()

{
    if( !ResetDirectory() )
        return FALSE;
    
/* -------------------------------------------------------------------- */
/*      Prepare leader.                                                 */
/* -------------------------------------------------------------------- */
    char szLeader[nLeaderSize+1];

    memset( szLeader, ' ', nLeaderSize );

    sprintf( szLeader+0, "%05d", (int) (nDataSize + nLeaderSize) );
    szLeader[5] = ' ';
    szLeader[6] = 'D';
    
    sprintf( szLeader + 12, "%05d", (int) (nFieldOffset + nLeaderSize) );
    szLeader[17] = ' ';

    szLeader[20] = (char) ('0' + _sizeFieldLength);
    szLeader[21] = (char) ('0' + _sizeFieldPos);
    szLeader[22] = '0';
    szLeader[23] = (char) ('0' + _sizeFieldTag);

    /* notdef: lots of stuff missing */

/* -------------------------------------------------------------------- */
/*      Write the leader.                                               */
/* -------------------------------------------------------------------- */
    VSIFWriteL( szLeader, nLeaderSize, 1, poModule->GetFP() );

/* -------------------------------------------------------------------- */
/*      Write the remainder of the record.                              */
/* -------------------------------------------------------------------- */
    VSIFWriteL( pachData, nDataSize, 1, poModule->GetFP() );
    
    return TRUE;
}

/************************************************************************/
/*                               Clear()                                */
/*                                                                      */
/*      Clear any information associated with the last header in        */
/*      preparation for reading a new header.                           */
/************************************************************************/

void DDFRecord::Clear()

{
    if( paoFields != NULL )
        delete[] paoFields;

    paoFields = NULL;
    nFieldCount = 0;

    if( pachData != NULL )
        CPLFree( pachData );

    pachData = NULL;
    nDataSize = 0;
    nReuseHeader = FALSE;
}

/************************************************************************/
/*                             ReadHeader()                             */
/*                                                                      */
/*      This perform the header reading and parsing job for the         */
/*      Read() method.  It reads the header, and builds a field         */
/*      list.                                                           */
/************************************************************************/

int DDFRecord::ReadHeader()

{
/* -------------------------------------------------------------------- */
/*      Clear any existing information.                                 */
/* -------------------------------------------------------------------- */
    Clear();
    
/* -------------------------------------------------------------------- */
/*      Read the 24 byte leader.                                        */
/* -------------------------------------------------------------------- */
    char        achLeader[nLeaderSize];
    int         nReadBytes;

    nReadBytes = VSIFReadL(achLeader,1,nLeaderSize,poModule->GetFP());
    if( nReadBytes == 0 && VSIFEofL( poModule->GetFP() ) )
    {
        return FALSE;
    }
    else if( nReadBytes != (int) nLeaderSize )
    {
        CPLError( CE_Failure, CPLE_FileIO,
                  "Leader is short on DDF file." );
        
        return FALSE;
    }

/* -------------------------------------------------------------------- */
/*      Extract information from leader.                                */
/* -------------------------------------------------------------------- */
    int         _recLength, _fieldAreaStart;
    char        _leaderIden;
    
    _recLength                    = DDFScanInt( achLeader+0, 5 );
    _leaderIden                   = achLeader[6];
    _fieldAreaStart               = DDFScanInt(achLeader+12,5);
    
    _sizeFieldLength = achLeader[20] - '0';
    _sizeFieldPos = achLeader[21] - '0';
    _sizeFieldTag = achLeader[23] - '0';

    if( _sizeFieldLength < 0 || _sizeFieldLength > 9 
        || _sizeFieldPos < 0 || _sizeFieldPos > 9
        || _sizeFieldTag < 0 || _sizeFieldTag > 9 )
    {
        CPLError( CE_Failure, CPLE_AppDefined, 
                  "ISO8211 record leader appears to be corrupt." );
        return FALSE;
    }

    if( _leaderIden == 'R' )
        nReuseHeader = TRUE;

    nFieldOffset = _fieldAreaStart - nLeaderSize;

/* -------------------------------------------------------------------- */
/*      Is there anything seemly screwy about this record?              */
/* -------------------------------------------------------------------- */
    if(( _recLength < 24 || _recLength > 100000000
         || _fieldAreaStart < 24 || _fieldAreaStart > 100000 )
       && (_recLength != 0))
    {
        CPLError( CE_Failure, CPLE_FileIO, 
                  "Data record appears to be corrupt on DDF file.\n"
                  " -- ensure that the files were uncompressed without modifying\n"
                  "carriage return/linefeeds (by default WINZIP does this)." );
        
        return FALSE;
    }

/* ==================================================================== */
/*      Handle the normal case with the record length available.        */
/* ==================================================================== */
    if(_recLength != 0) {
/* -------------------------------------------------------------------- */
/*      Read the remainder of the record.                               */
/* -------------------------------------------------------------------- */
        nDataSize = _recLength - nLeaderSize;
        pachData = (char *) CPLMalloc(nDataSize);

        if( VSIFReadL( pachData, 1, nDataSize, poModule->GetFP()) !=
            (size_t) nDataSize )
        {
            CPLError( CE_Failure, CPLE_FileIO, 
                      "Data record is short on DDF file." );
          
            return FALSE;
        }

/* -------------------------------------------------------------------- */
/*      If we don't find a field terminator at the end of the record    */
/*      we will read extra bytes till we get to it.                     */
/* -------------------------------------------------------------------- */
        while( pachData[nDataSize-1] != DDF_FIELD_TERMINATOR 
               && (nDataSize == 0 || pachData[nDataSize-2] != DDF_FIELD_TERMINATOR) )
        {
            nDataSize++;
            pachData = (char *) CPLRealloc(pachData,nDataSize);
            
            if( VSIFReadL( pachData + nDataSize - 1, 1, 1, poModule->GetFP() )
                != 1 )
            {
                CPLError( CE_Failure, CPLE_FileIO, 
                          "Data record is short on DDF file." );
                
                return FALSE;
            }
            CPLDebug( "ISO8211", 
                      "Didn't find field terminator, read one more byte." );
        }

/* -------------------------------------------------------------------- */
/*      Loop over the directory entries, making a pass counting them.   */
/* -------------------------------------------------------------------- */
        int         i;
        int         nFieldEntryWidth;
      
        nFieldEntryWidth = _sizeFieldLength + _sizeFieldPos + _sizeFieldTag;
        nFieldCount = 0;
        for( i = 0; i < nDataSize; i += nFieldEntryWidth )
        {
            if( pachData[i] == DDF_FIELD_TERMINATOR )
                break;
          
            nFieldCount++;
        }
    
/* -------------------------------------------------------------------- */
/*      Allocate, and read field definitions.                           */
/* -------------------------------------------------------------------- */
        paoFields = new DDFField[nFieldCount];
    
        for( i = 0; i < nFieldCount; i++ )
        {
            char    szTag[128];
            int     nEntryOffset = i*nFieldEntryWidth;
            int     nFieldLength, nFieldPos;
          
/* -------------------------------------------------------------------- */
/*      Read the position information and tag.                          */
/* -------------------------------------------------------------------- */
            strncpy( szTag, pachData+nEntryOffset, _sizeFieldTag );
            szTag[_sizeFieldTag] = '\0';
          
            nEntryOffset += _sizeFieldTag;
            nFieldLength = DDFScanInt( pachData+nEntryOffset, _sizeFieldLength );
          
            nEntryOffset += _sizeFieldLength;
            nFieldPos = DDFScanInt( pachData+nEntryOffset, _sizeFieldPos );
          
/* -------------------------------------------------------------------- */
/*      Find the corresponding field in the module directory.           */
/* -------------------------------------------------------------------- */
            DDFFieldDefn    *poFieldDefn = poModule->FindFieldDefn( szTag );
          
            if( poFieldDefn == NULL )
            {
                CPLError( CE_Failure, CPLE_AppDefined,
                          "Undefined field `%s' encountered in data record.",
                          szTag );
                return FALSE;
            }

/* -------------------------------------------------------------------- */
/*      Assign info the DDFField.                                       */
/* -------------------------------------------------------------------- */
            paoFields[i].Initialize( poFieldDefn, 
                                     pachData + _fieldAreaStart + nFieldPos - nLeaderSize,
                                     nFieldLength );
        }
      
        return TRUE;
    }
/* ==================================================================== */
/*      Handle the exceptional case where the record length is          */
/*      zero.  In this case we have to read all the data based on       */
/*      the size of data items as per ISO8211 spec Annex C, 1.5.1.      */
/*                                                                      */
/*      See Bugzilla bug 181 and test with file US4CN21M.000.           */
/* ==================================================================== */
    else {
        CPLDebug( "ISO8211", 
                  "Record with zero length, use variant (C.1.5.1) logic." );

        /* ----------------------------------------------------------------- */
        /*   _recLength == 0, handle the large record.                       */
        /*                                                                   */
        /*   Read the remainder of the record.                               */
        /* ----------------------------------------------------------------- */
        nDataSize = 0;
        pachData = NULL;

        /* ----------------------------------------------------------------- */
        /*   Loop over the directory entries, making a pass counting them.   */
        /* ----------------------------------------------------------------- */
        int nFieldEntryWidth = _sizeFieldLength + _sizeFieldPos + _sizeFieldTag;
        nFieldCount = 0;
        int i=0;
        char *tmpBuf = (char*)VSIMalloc(nFieldEntryWidth);

        if( tmpBuf == NULL )
        {
            CPLError( CE_Failure, CPLE_OutOfMemory, 
                      "Attempt to allocate %d byte ISO8211 record buffer failed.", 
                      nFieldEntryWidth );
            return FALSE;
        }
      
        // while we're not at the end, store this entry,
        // and keep on reading...
        do {
            // read an Entry:
            if(nFieldEntryWidth != 
               (int) VSIFReadL(tmpBuf, 1, nFieldEntryWidth, poModule->GetFP())) {
                CPLError(CE_Failure, CPLE_FileIO,
                         "Data record is short on DDF file.");
                return FALSE;
            }
      
            // move this temp buffer into more permanent storage:
            char *newBuf = (char*)CPLMalloc(nDataSize+nFieldEntryWidth);
            if(pachData!=NULL) {
                memcpy(newBuf, pachData, nDataSize);
                CPLFree(pachData);
            }
            memcpy(&newBuf[nDataSize], tmpBuf, nFieldEntryWidth);
            pachData = newBuf;
            nDataSize += nFieldEntryWidth;

            if(DDF_FIELD_TERMINATOR != tmpBuf[0]) {
                nFieldCount++;
            }
        }
        while(DDF_FIELD_TERMINATOR != tmpBuf[0]);

        // --------------------------------------------------------------------
        // Now, rewind a little.  Only the TERMINATOR should have been read
        // --------------------------------------------------------------------
        int rewindSize = nFieldEntryWidth - 1;
        FILE *fp = poModule->GetFP();
        vsi_l_offset pos = VSIFTellL(fp) - rewindSize;
        VSIFSeekL(fp, pos, SEEK_SET);
        nDataSize -= rewindSize;

        // --------------------------------------------------------------------
        // Okay, now let's populate the heck out of pachData...
        // --------------------------------------------------------------------
        for(i=0; i<nFieldCount; i++) {
            int nEntryOffset = (i*nFieldEntryWidth) + _sizeFieldTag;
            int nFieldLength = DDFScanInt(pachData + nEntryOffset,
                                          _sizeFieldLength);
            char *tmpBuf = (char*)CPLMalloc(nFieldLength);

            // read an Entry:
            if(nFieldLength != 
               (int) VSIFReadL(tmpBuf, 1, nFieldLength, poModule->GetFP())) {
                CPLError(CE_Failure, CPLE_FileIO,
                         "Data record is short on DDF file.");
                return FALSE;
            }
      
            // move this temp buffer into more permanent storage:
            char *newBuf = (char*)CPLMalloc(nDataSize+nFieldLength);
            memcpy(newBuf, pachData, nDataSize);
            CPLFree(pachData);
            memcpy(&newBuf[nDataSize], tmpBuf, nFieldLength);
            CPLFree(tmpBuf);
            pachData = newBuf;
            nDataSize += nFieldLength;
        }
    
        /* ----------------------------------------------------------------- */
        /*     Allocate, and read field definitions.                         */
        /* ----------------------------------------------------------------- */
        paoFields = new DDFField[nFieldCount];
      
        for( i = 0; i < nFieldCount; i++ )
        {
            char    szTag[128];
            int     nEntryOffset = i*nFieldEntryWidth;
            int     nFieldLength, nFieldPos;
          
            /* ------------------------------------------------------------- */
            /* Read the position information and tag.                        */
            /* ------------------------------------------------------------- */
            strncpy( szTag, pachData+nEntryOffset, _sizeFieldTag );
            szTag[_sizeFieldTag] = '\0';
          
            nEntryOffset += _sizeFieldTag;
            nFieldLength = DDFScanInt( pachData+nEntryOffset, _sizeFieldLength );
          
            nEntryOffset += _sizeFieldLength;
            nFieldPos = DDFScanInt( pachData+nEntryOffset, _sizeFieldPos );
          
            /* ------------------------------------------------------------- */
            /* Find the corresponding field in the module directory.         */
            /* ------------------------------------------------------------- */
            DDFFieldDefn    *poFieldDefn = poModule->FindFieldDefn( szTag );
          
            if( poFieldDefn == NULL )
            {
                CPLError( CE_Failure, CPLE_AppDefined,
                          "Undefined field `%s' encountered in data record.",
                          szTag );
                return FALSE;
            }

            /* ------------------------------------------------------------- */
            /* Assign info the DDFField.                                     */
            /* ------------------------------------------------------------- */

            paoFields[i].Initialize( poFieldDefn, 
                                     pachData + _fieldAreaStart
                                     + nFieldPos - nLeaderSize,
                                     nFieldLength );
        }
      
        return TRUE;
    }
}

/************************************************************************/
/*                             FindField()                              */
/************************************************************************/

/**
 * Find the named field within this record.
 *
 * @param pszName The name of the field to fetch.  The comparison is
 * case insensitive.
 * @param iFieldIndex The instance of this field to fetch.  Use zero (the
 * default) for the first instance.
 *
 * @return Pointer to the requested DDFField.  This pointer is to an
 * internal object, and should not be freed.  It remains valid until
 * the next record read. 
 */

DDFField * DDFRecord::FindField( const char * pszName, int iFieldIndex )

{
    for( int i = 0; i < nFieldCount; i++ )
    {
        if( EQUAL(paoFields[i].GetFieldDefn()->GetName(),pszName) )
        {
            if( iFieldIndex == 0 )
                return paoFields + i;
            else
                iFieldIndex--;
        }
    }

    return NULL;
}

/************************************************************************/
/*                              GetField()                              */
/************************************************************************/

/**
 * Fetch field object based on index.
 *
 * @param i The index of the field to fetch.  Between 0 and GetFieldCount()-1.
 *
 * @return A DDFField pointer, or NULL if the index is out of range.
 */

DDFField *DDFRecord::GetField( int i )

{
    if( i < 0 || i >= nFieldCount )
        return NULL;
    else
        return paoFields + i;
}

/************************************************************************/
/*                           GetIntSubfield()                           */
/************************************************************************/

/**
 * Fetch value of a subfield as an integer.  This is a convenience
 * function for fetching a subfield of a field within this record.
 *
 * @param pszField The name of the field containing the subfield.
 * @param iFieldIndex The instance of this field within the record.  Use
 * zero for the first instance of this field.
 * @param pszSubfield The name of the subfield within the selected field.
 * @param iSubfieldIndex The instance of this subfield within the record.
 * Use zero for the first instance.
 * @param pnSuccess Pointer to an int which will be set to TRUE if the fetch
 * succeeds, or FALSE if it fails.  Use NULL if you don't want to check
 * success.
 * @return The value of the subfield, or zero if it failed for some reason.
 */

int DDFRecord::GetIntSubfield( const char * pszField, int iFieldIndex,
                               const char * pszSubfield, int iSubfieldIndex,
                               int * pnSuccess )

{
    DDFField    *poField;
    int         nDummyErr;

    if( pnSuccess == NULL )
        pnSuccess = &nDummyErr;

    *pnSuccess = FALSE;
            
/* -------------------------------------------------------------------- */
/*      Fetch the field. If this fails, return zero.                    */
/* -------------------------------------------------------------------- */
    poField = FindField( pszField, iFieldIndex );
    if( poField == NULL )
        return 0;

/* -------------------------------------------------------------------- */
/*      Get the subfield definition                                     */
/* -------------------------------------------------------------------- */
    DDFSubfieldDefn     *poSFDefn;

    poSFDefn = poField->GetFieldDefn()->FindSubfieldDefn( pszSubfield );
    if( poSFDefn == NULL )
        return 0;

/* -------------------------------------------------------------------- */
/*      Get a pointer to the data.                                      */
/* -------------------------------------------------------------------- */
    int         nBytesRemaining;
    
    const char *pachData = poField->GetSubfieldData(poSFDefn,
                                                    &nBytesRemaining,
                                                    iSubfieldIndex);

/* -------------------------------------------------------------------- */
/*      Return the extracted value.                                     */
/* -------------------------------------------------------------------- */
    *pnSuccess = TRUE;

    return( poSFDefn->ExtractIntData( pachData, nBytesRemaining, NULL ) );
}

/************************************************************************/
/*                          GetFloatSubfield()                          */
/************************************************************************/

/**
 * Fetch value of a subfield as a float (double).  This is a convenience
 * function for fetching a subfield of a field within this record.
 *
 * @param pszField The name of the field containing the subfield.
 * @param iFieldIndex The instance of this field within the record.  Use
 * zero for the first instance of this field.
 * @param pszSubfield The name of the subfield within the selected field.
 * @param iSubfieldIndex The instance of this subfield within the record.
 * Use zero for the first instance.
 * @param pnSuccess Pointer to an int which will be set to TRUE if the fetch
 * succeeds, or FALSE if it fails.  Use NULL if you don't want to check
 * success.
 * @return The value of the subfield, or zero if it failed for some reason.
 */

double DDFRecord::GetFloatSubfield( const char * pszField, int iFieldIndex,
                                 const char * pszSubfield, int iSubfieldIndex,
                                    int * pnSuccess )

{
    DDFField    *poField;
    int         nDummyErr;

    if( pnSuccess == NULL )
        pnSuccess = &nDummyErr;

    *pnSuccess = FALSE;
            
/* -------------------------------------------------------------------- */
/*      Fetch the field. If this fails, return zero.                    */
/* -------------------------------------------------------------------- */
    poField = FindField( pszField, iFieldIndex );
    if( poField == NULL )
        return 0;

/* -------------------------------------------------------------------- */
/*      Get the subfield definition                                     */
/* -------------------------------------------------------------------- */
    DDFSubfieldDefn     *poSFDefn;

    poSFDefn = poField->GetFieldDefn()->FindSubfieldDefn( pszSubfield );
    if( poSFDefn == NULL )
        return 0;

/* -------------------------------------------------------------------- */
/*      Get a pointer to the data.                                      */
/* -------------------------------------------------------------------- */
    int         nBytesRemaining;
    
    const char *pachData = poField->GetSubfieldData(poSFDefn,
                                                    &nBytesRemaining,
                                                    iSubfieldIndex);

/* -------------------------------------------------------------------- */
/*      Return the extracted value.                                     */
/* -------------------------------------------------------------------- */
    *pnSuccess = TRUE;

    return( poSFDefn->ExtractFloatData( pachData, nBytesRemaining, NULL ) );
}

/************************************************************************/
/*                         GetStringSubfield()                          */
/************************************************************************/

/**
 * Fetch value of a subfield as a string.  This is a convenience
 * function for fetching a subfield of a field within this record.
 *
 * @param pszField The name of the field containing the subfield.
 * @param iFieldIndex The instance of this field within the record.  Use
 * zero for the first instance of this field.
 * @param pszSubfield The name of the subfield within the selected field.
 * @param iSubfieldIndex The instance of this subfield within the record.
 * Use zero for the first instance.
 * @param pnSuccess Pointer to an int which will be set to TRUE if the fetch
 * succeeds, or FALSE if it fails.  Use NULL if you don't want to check
 * success.
 * @return The value of the subfield, or NULL if it failed for some reason.
 * The returned pointer is to internal data and should not be modified or
 * freed by the application.
 */

const char *
DDFRecord::GetStringSubfield( const char * pszField, int iFieldIndex,
                              const char * pszSubfield, int iSubfieldIndex,
                              int * pnSuccess )

{
    DDFField    *poField;
    int         nDummyErr;

    if( pnSuccess == NULL )
        pnSuccess = &nDummyErr;

    *pnSuccess = FALSE;
            
/* -------------------------------------------------------------------- */
/*      Fetch the field. If this fails, return zero.                    */
/* -------------------------------------------------------------------- */
    poField = FindField( pszField, iFieldIndex );
    if( poField == NULL )
        return NULL;

/* -------------------------------------------------------------------- */
/*      Get the subfield definition                                     */
/* -------------------------------------------------------------------- */
    DDFSubfieldDefn     *poSFDefn;

    poSFDefn = poField->GetFieldDefn()->FindSubfieldDefn( pszSubfield );
    if( poSFDefn == NULL )
        return NULL;

/* -------------------------------------------------------------------- */
/*      Get a pointer to the data.                                      */
/* -------------------------------------------------------------------- */
    int         nBytesRemaining;
    
    const char *pachData = poField->GetSubfieldData(poSFDefn,
                                                    &nBytesRemaining,
                                                    iSubfieldIndex);

/* -------------------------------------------------------------------- */
/*      Return the extracted value.                                     */
/* -------------------------------------------------------------------- */
    *pnSuccess = TRUE;

    return( poSFDefn->ExtractStringData( pachData, nBytesRemaining, NULL ) );
}

/************************************************************************/
/*                               Clone()                                */
/************************************************************************/

/**
 * Make a copy of a record.
 *
 * This method is used to make a copy of a record that will become (mostly)
 * the properly of application.  However, it is automatically destroyed if
 * the DDFModule it was created relative to is destroyed, as it's field
 * and subfield definitions relate to that DDFModule.  However, it does
 * persist even when the record returned by DDFModule::ReadRecord() is
 * invalidated, such as when reading a new record.  This allows an application
 * to cache whole DDFRecords.
 *
 * @return A new copy of the DDFRecord.  This can be delete'd by the
 * application when no longer needed, otherwise it will be cleaned up when