pihmLIBS/dbfopen.c

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/******************************************************************************
 * $Id: dbfopen.c,v 1.48 2003/03/10 14:51:27 warmerda Exp $
 *
 * Project:  Shapelib
 * Purpose:  Implementation of .dbf access API documented in dbf_api.html.
 * Author:   Frank Warmerdam, warmerdam@pobox.com
 *
 ******************************************************************************
 * Copyright (c) 1999, Frank Warmerdam
 *
 * This software is available under the following "MIT Style" license,
 * or at the option of the licensee under the LGPL (see LICENSE.LGPL).  This
 * option is discussed in more detail in shapelib.html.
 *
 * --
 * 
 * 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.
 ******************************************************************************
 *
 * $Log: dbfopen.c,v $
 * Revision 1.48  2003/03/10 14:51:27  warmerda
 * DBFWrite* calls now return FALSE if they have to truncate
 *
 * Revision 1.47  2002/11/20 03:32:22  warmerda
 * Ensure field name in DBFGetFieldIndex() is properly terminated.
 *
 * Revision 1.46  2002/10/09 13:10:21  warmerda
 * Added check that width is positive.
 *
 * Revision 1.45  2002/09/29 00:00:08  warmerda
 * added FTLogical and logical attribute read/write calls
 *
 * Revision 1.44  2002/05/07 13:46:11  warmerda
 * Added DBFWriteAttributeDirectly().
 *
 * Revision 1.43  2002/02/13 19:39:21  warmerda
 * Fix casting issues in DBFCloneEmpty().
 *
 * Revision 1.42  2002/01/15 14:36:07  warmerda
 * updated email address
 *
 * Revision 1.41  2002/01/15 14:31:49  warmerda
 * compute rather than copying nHeaderLength in DBFCloneEmpty()
 *
 * Revision 1.40  2002/01/09 04:32:35  warmerda
 * fixed to read correct amount of header
 *
 * Revision 1.39  2001/12/11 22:41:03  warmerda
 * improve io related error checking when reading header
 *
 * Revision 1.38  2001/11/28 16:07:31  warmerda
 * Cleanup to avoid compiler warnings as suggested by Richard Hash.
 *
 * Revision 1.37  2001/07/04 05:18:09  warmerda
 * do last fix properly
 *
 * Revision 1.36  2001/07/04 05:16:09  warmerda
 * fixed fieldname comparison in DBFGetFieldIndex
 *
 * Revision 1.35  2001/06/22 02:10:06  warmerda
 * fixed NULL shape support with help from Jim Matthews
 *
 * Revision 1.33  2001/05/31 19:20:13  warmerda
 * added DBFGetFieldIndex()
 *
 * Revision 1.32  2001/05/31 18:15:40  warmerda
 * Added support for NULL fields in DBF files
 *
 * Revision 1.31  2001/05/23 13:36:52  warmerda
 * added use of SHPAPI_CALL
 *
 * Revision 1.30  2000/12/05 14:43:38  warmerda
 * DBReadAttribute() white space trimming bug fix
 *
 * Revision 1.29  2000/10/05 14:36:44  warmerda
 * fix bug with writing very wide numeric fields
 *
 * Revision 1.28  2000/09/25 14:18:07  warmerda
 * Added some casts of strlen() return result to fix warnings on some
 * systems, as submitted by Daniel.
 *
 * Revision 1.27  2000/09/25 14:15:51  warmerda
 * added DBFGetNativeFieldType()
 *
 * Revision 1.26  2000/07/07 13:39:45  warmerda
 * removed unused variables, and added system include files
 *
 * Revision 1.25  2000/05/29 18:19:13  warmerda
 * avoid use of uchar, and adding casting fix
 *
 * Revision 1.24  2000/05/23 13:38:27  warmerda
 * Added error checks on return results of fread() and fseek().
 *
 * Revision 1.23  2000/05/23 13:25:49  warmerda
 * Avoid crashing if field or record are out of range in dbfread*attribute().
 *
 * Revision 1.22  1999/12/15 13:47:24  warmerda
 * Added stdlib.h to ensure that atof() is prototyped.
 *
 * Revision 1.21  1999/12/13 17:25:46  warmerda
 * Added support for upper case .DBF extention.
 *
 * Revision 1.20  1999/11/30 16:32:11  warmerda
 * Use atof() instead of sscanf().
 *
 * Revision 1.19  1999/11/05 14:12:04  warmerda
 * updated license terms
 *
 * Revision 1.18  1999/07/27 00:53:28  warmerda
 * ensure that whole old field value clear on write of string
 *
 * Revision 1.1  1999/07/05 18:58:07  warmerda
 * New
 *
 * Revision 1.17  1999/06/11 19:14:12  warmerda
 * Fixed some memory leaks.
 *
 * Revision 1.16  1999/06/11 19:04:11  warmerda
 * Remoted some unused variables.
 *
 * Revision 1.15  1999/05/11 03:19:28  warmerda
 * added new Tuple api, and improved extension handling - add from candrsn
 *
 * Revision 1.14  1999/05/04 15:01:48  warmerda
 * Added 'F' support.
 *
 * Revision 1.13  1999/03/23 17:38:59  warmerda
 * DBFAddField() now actually does return the new field number, or -1 if
 * it fails.
 *
 * Revision 1.12  1999/03/06 02:54:46  warmerda
 * Added logic to convert shapefile name to dbf filename in DBFOpen()
 * for convenience.
 *
 * Revision 1.11  1998/12/31 15:30:34  warmerda
 * Improved the interchangability of numeric and string attributes.  Add
 * white space trimming option for attributes.
 *
 * Revision 1.10  1998/12/03 16:36:44  warmerda
 * Use r+b instead of rb+ for binary access.
 *
 * Revision 1.9  1998/12/03 15:34:23  warmerda
 * Updated copyright message.
 *
 * Revision 1.8  1997/12/04 15:40:15  warmerda
 * Added newline character after field definitions.
 *
 * Revision 1.7  1997/03/06 14:02:10  warmerda
 * Ensure bUpdated is initialized.
 *
 * Revision 1.6  1996/02/12 04:54:41  warmerda
 * Ensure that DBFWriteAttribute() returns TRUE if it succeeds.
 *
 * Revision 1.5  1995/10/21  03:15:12  warmerda
 * Changed to use binary file access, and ensure that the
 * field name field is zero filled, and limited to 10 chars.
 *
 * Revision 1.4  1995/08/24  18:10:42  warmerda
 * Added use of SfRealloc() to avoid pre-ANSI realloc() functions such
 * as on the Sun.
 *
 * Revision 1.3  1995/08/04  03:15:16  warmerda
 * Fixed up header.
 *
 * Revision 1.2  1995/08/04  03:14:43  warmerda
 * Added header.
 */

static char rcsid[] = 
  "$Id: dbfopen.c,v 1.48 2003/03/10 14:51:27 warmerda Exp $";

#include "shapefil.h"

#include <math.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

#ifndef FALSE
#  define FALSE         0
#  define TRUE          1
#endif

static int      nStringFieldLen = 0;
static char * pszStringField = NULL;

/************************************************************************/
/*                             SfRealloc()                              */
/*                                                                      */
/*      A realloc cover function that will access a NULL pointer as     */
/*      a valid input.                                                  */
/************************************************************************/

static void * SfRealloc( void * pMem, int nNewSize )

{
    if( pMem == NULL )
        return( (void *) malloc(nNewSize) );
    else
        return( (void *) realloc(pMem,nNewSize) );
}

/************************************************************************/
/*                           DBFWriteHeader()                           */
/*                                                                      */
/*      This is called to write out the file header, and field          */
/*      descriptions before writing any actual data records.  This      */
/*      also computes all the DBFDataSet field offset/size/decimals     */
/*      and so forth values.                                            */
/************************************************************************/

static void DBFWriteHeader(DBFHandle psDBF)

{
    unsigned char       abyHeader[XBASE_FLDHDR_SZ];
    int         i;

    if( !psDBF->bNoHeader )
        return;

    psDBF->bNoHeader = FALSE;

/* -------------------------------------------------------------------- */
/*      Initialize the file header information.                         */
/* -------------------------------------------------------------------- */
    for( i = 0; i < XBASE_FLDHDR_SZ; i++ )
        abyHeader[i] = 0;

    abyHeader[0] = 0x03;                /* memo field? - just copying   */

    /* date updated on close, record count preset at zero */

    abyHeader[8] = psDBF->nHeaderLength % 256;
    abyHeader[9] = psDBF->nHeaderLength / 256;
    
    abyHeader[10] = psDBF->nRecordLength % 256;
    abyHeader[11] = psDBF->nRecordLength / 256;

/* -------------------------------------------------------------------- */
/*      Write the initial 32 byte file header, and all the field        */
/*      descriptions.                                                   */
/* -------------------------------------------------------------------- */
    fseek( psDBF->fp, 0, 0 );
    fwrite( abyHeader, XBASE_FLDHDR_SZ, 1, psDBF->fp );
    fwrite( psDBF->pszHeader, XBASE_FLDHDR_SZ, psDBF->nFields, psDBF->fp );

/* -------------------------------------------------------------------- */
/*      Write out the newline character if there is room for it.        */
/* -------------------------------------------------------------------- */
    if( psDBF->nHeaderLength > 32*psDBF->nFields + 32 )
    {
        char    cNewline;

        cNewline = 0x0d;
        fwrite( &cNewline, 1, 1, psDBF->fp );
    }
}

/************************************************************************/
/*                           DBFFlushRecord()                           */
/*                                                                      */
/*      Write out the current record if there is one.                   */
/************************************************************************/

static void DBFFlushRecord( DBFHandle psDBF )

{
    int         nRecordOffset;

    if( psDBF->bCurrentRecordModified && psDBF->nCurrentRecord > -1 )
    {
        psDBF->bCurrentRecordModified = FALSE;

        nRecordOffset = psDBF->nRecordLength * psDBF->nCurrentRecord 
                                                     + psDBF->nHeaderLength;

        fseek( psDBF->fp, nRecordOffset, 0 );
        fwrite( psDBF->pszCurrentRecord, psDBF->nRecordLength, 1, psDBF->fp );
    }
}

/************************************************************************/
/*                              DBFOpen()                               */
/*                                                                      */
/*      Open a .dbf file.                                               */
/************************************************************************/
   
DBFHandle SHPAPI_CALL
DBFOpen( const char * pszFilename, const char * pszAccess )

{
    DBFHandle           psDBF;
    unsigned char               *pabyBuf;
    int                 nFields, nHeadLen, nRecLen, iField, i;
    char                *pszBasename, *pszFullname;

/* -------------------------------------------------------------------- */
/*      We only allow the access strings "rb" and "r+".                  */
/* -------------------------------------------------------------------- */
    if( strcmp(pszAccess,"r") != 0 && strcmp(pszAccess,"r+") != 0 
        && strcmp(pszAccess,"rb") != 0 && strcmp(pszAccess,"rb+") != 0
        && strcmp(pszAccess,"r+b") != 0 )
        return( NULL );

    if( strcmp(pszAccess,"r") == 0 )
        pszAccess = "rb";
 
    if( strcmp(pszAccess,"r+") == 0 )
        pszAccess = "rb+";

/* -------------------------------------------------------------------- */
/*      Compute the base (layer) name.  If there is any extension       */
/*      on the passed in filename we will strip it off.                 */
/* -------------------------------------------------------------------- */
    pszBasename = (char *) malloc(strlen(pszFilename)+5);
    strcpy( pszBasename, pszFilename );
    for( i = strlen(pszBasename)-1; 
         i > 0 && pszBasename[i] != '.' && pszBasename[i] != '/'
               && pszBasename[i] != '\\';
         i-- ) {}

    if( pszBasename[i] == '.' )
        pszBasename[i] = '\0';

    pszFullname = (char *) malloc(strlen(pszBasename) + 5);
    sprintf( pszFullname, "%s.dbf", pszBasename );
        
    psDBF = (DBFHandle) calloc( 1, sizeof(DBFInfo) );
    psDBF->fp = fopen( pszFullname, pszAccess );

    if( psDBF->fp == NULL )
    {
        sprintf( pszFullname, "%s.DBF", pszBasename );
        psDBF->fp = fopen(pszFullname, pszAccess );
    }
    
    free( pszBasename );
    free( pszFullname );
    
    if( psDBF->fp == NULL )
    {
        free( psDBF );
        return( NULL );
    }

    psDBF->bNoHeader = FALSE;
    psDBF->nCurrentRecord = -1;
    psDBF->bCurrentRecordModified = FALSE;

/* -------------------------------------------------------------------- */
/*  Read Table Header info                                              */
/* -------------------------------------------------------------------- */
    pabyBuf = (unsigned char *) malloc(500);
    if( fread( pabyBuf, 32, 1, psDBF->fp ) != 1 )
    {
        fclose( psDBF->fp );
        free( pabyBuf );
        free( psDBF );
        return NULL;
    }

    psDBF->nRecords = 
     pabyBuf[4] + pabyBuf[5]*256 + pabyBuf[6]*256*256 + pabyBuf[7]*256*256*256;

    psDBF->nHeaderLength = nHeadLen = pabyBuf[8] + pabyBuf[9]*256;
    psDBF->nRecordLength = nRecLen = pabyBuf[10] + pabyBuf[11]*256;
    
    psDBF->nFields = nFields = (nHeadLen - 32) / 32;

    psDBF->pszCurrentRecord = (char *) malloc(nRecLen);

/* -------------------------------------------------------------------- */
/*  Read in Field Definitions                                           */
/* -------------------------------------------------------------------- */
    
    pabyBuf = (unsigned char *) SfRealloc(pabyBuf,nHeadLen);
    psDBF->pszHeader = (char *) pabyBuf;

    fseek( psDBF->fp, 32, 0 );
    if( fread( pabyBuf, nHeadLen-32, 1, psDBF->fp ) != 1 )
    {
        fclose( psDBF->fp );
        free( pabyBuf );
        free( psDBF );
        return NULL;
    }

    psDBF->panFieldOffset = (int *) malloc(sizeof(int) * nFields);
    psDBF->panFieldSize = (int *) malloc(sizeof(int) * nFields);
    psDBF->panFieldDecimals = (int *) malloc(sizeof(int) * nFields);
    psDBF->pachFieldType = (char *) malloc(sizeof(char) * nFields);

    for( iField = 0; iField < nFields; iField++ )
    {
        unsigned char           *pabyFInfo;

        pabyFInfo = pabyBuf+iField*32;

        if( pabyFInfo[11] == 'N' || pabyFInfo[11] == 'F' )
        {
            psDBF->panFieldSize[iField] = pabyFInfo[16];
            psDBF->panFieldDecimals[iField] = pabyFInfo[17];
        }
        else
        {
            psDBF->panFieldSize[iField] = pabyFInfo[16] + pabyFInfo[17]*256;
            psDBF->panFieldDecimals[iField] = 0;
        }

        psDBF->pachFieldType[iField] = (char) pabyFInfo[11];
        if( iField == 0 )
            psDBF->panFieldOffset[iField] = 1;
        else
            psDBF->panFieldOffset[iField] = 
              psDBF->panFieldOffset[iField-1] + psDBF->panFieldSize[iField-1];
    }

    return( psDBF );
}

/************************************************************************/
/*                              DBFClose()                              */
/************************************************************************/

void SHPAPI_CALL
DBFClose(DBFHandle psDBF)
{
/* -------------------------------------------------------------------- */
/*      Write out header if not already written.                        */
/* -------------------------------------------------------------------- */
    if( psDBF->bNoHeader )
        DBFWriteHeader( psDBF );

    DBFFlushRecord( psDBF );

/* -------------------------------------------------------------------- */
/*      Update last access date, and number of records if we have       */
/*      write access.                                                   */
/* -------------------------------------------------------------------- */
    if( psDBF->bUpdated )
    {
        unsigned char           abyFileHeader[32];

        fseek( psDBF->fp, 0, 0 );
        fread( abyFileHeader, 32, 1, psDBF->fp );

        abyFileHeader[1] = 95;                  /* YY */
        abyFileHeader[2] = 7;                   /* MM */
        abyFileHeader[3] = 26;                  /* DD */

        abyFileHeader[4] = psDBF->nRecords % 256;
        abyFileHeader[5] = (psDBF->nRecords/256) % 256;
        abyFileHeader[6] = (psDBF->nRecords/(256*256)) % 256;
        abyFileHeader[7] = (psDBF->nRecords/(256*256*256)) % 256;

        fseek( psDBF->fp, 0, 0 );
        fwrite( abyFileHeader, 32, 1, psDBF->fp );
    }

/* -------------------------------------------------------------------- */
/*      Close, and free resources.                                      */
/* -------------------------------------------------------------------- */
    fclose( psDBF->fp );

    if( psDBF->panFieldOffset != NULL )
    {
        free( psDBF->panFieldOffset );
        free( psDBF->panFieldSize );
        free( psDBF->panFieldDecimals );
        free( psDBF->pachFieldType );
    }

    free( psDBF->pszHeader );
    free( psDBF->pszCurrentRecord );

    free( psDBF );

    if( pszStringField != NULL )
    {
        free( pszStringField );
        pszStringField = NULL;
        nStringFieldLen = 0;
    }
}

/************************************************************************/
/*                             DBFCreate()                              */
/*                                                                      */
/*      Create a new .dbf file.                                         */
/************************************************************************/

DBFHandle SHPAPI_CALL
DBFCreate( const char * pszFilename )

{
    DBFHandle   psDBF;
    FILE        *fp;
    char        *pszFullname, *pszBasename;
    int         i;

/* -------------------------------------------------------------------- */
/*      Compute the base (layer) name.  If there is any extension       */
/*      on the passed in filename we will strip it off.                 */
/* -------------------------------------------------------------------- */
    pszBasename = (char *) malloc(strlen(pszFilename)+5);
    strcpy( pszBasename, pszFilename );
    for( i = strlen(pszBasename)-1; 
         i > 0 && pszBasename[i] != '.' && pszBasename[i] != '/'
               && pszBasename[i] != '\\';
         i-- ) {}

    if( pszBasename[i] == '.' )
        pszBasename[i] = '\0';

    pszFullname = (char *) malloc(strlen(pszBasename) + 5);
    sprintf( pszFullname, "%s.dbf", pszBasename );
    free( pszBasename );

/* -------------------------------------------------------------------- */
/*      Create the file.                                                */
/* -------------------------------------------------------------------- */
    fp = fopen( pszFullname, "wb" );
    if( fp == NULL )
        return( NULL );

    fputc( 0, fp );
    fclose( fp );

    fp = fopen( pszFullname, "rb+" );
    if( fp == NULL )
        return( NULL );

    free( pszFullname );

/* -------------------------------------------------------------------- */
/*      Create the info structure.                                      */
/* -------------------------------------------------------------------- */
    psDBF = (DBFHandle) malloc(sizeof(DBFInfo));

    psDBF->fp = fp;
    psDBF->nRecords = 0;
    psDBF->nFields = 0;
    psDBF->nRecordLength = 1;
    psDBF->nHeaderLength = 33;
    
    psDBF->panFieldOffset = NULL;
    psDBF->panFieldSize = NULL;
    psDBF->panFieldDecimals = NULL;
    psDBF->pachFieldType = NULL;
    psDBF->pszHeader = NULL;

    psDBF->nCurrentRecord = -1;
    psDBF->bCurrentRecordModified = FALSE;
    psDBF->pszCurrentRecord = NULL;

    psDBF->bNoHeader = TRUE;

    return( psDBF );
}

/************************************************************************/
/*                            DBFAddField()                             */
/*                                                                      */
/*      Add a field to a newly created .dbf file before any records     */
/*      are written.                                                    */
/************************************************************************/

int SHPAPI_CALL
DBFAddField(DBFHandle psDBF, const char * pszFieldName, 
            DBFFieldType eType, int nWidth, int nDecimals )

{
    char        *pszFInfo;
    int         i;

/* -------------------------------------------------------------------- */
/*      Do some checking to ensure we can add records to this file.     */
/* -------------------------------------------------------------------- */
    if( psDBF->nRecords > 0 )
        return( -1 );

    if( !psDBF->bNoHeader )
        return( -1 );

    if( eType != FTDouble && nDecimals != 0 )
        return( -1 );

    if( nWidth < 1 )
        return -1;

/* -------------------------------------------------------------------- */
/*      SfRealloc all the arrays larger to hold the additional field      */
/*      information.                                                    */
/* -------------------------------------------------------------------- */
    psDBF->nFields++;

    psDBF->panFieldOffset = (int *) 
      SfRealloc( psDBF->panFieldOffset, sizeof(int) * psDBF->nFields );

    psDBF->panFieldSize = (int *) 
      SfRealloc( psDBF->panFieldSize, sizeof(int) * psDBF->nFields );

    psDBF->panFieldDecimals = (int *) 
      SfRealloc( psDBF->panFieldDecimals, sizeof(int) * psDBF->nFields );

    psDBF->pachFieldType = (char *) 
      SfRealloc( psDBF->pachFieldType, sizeof(char) * psDBF->nFields );

/* -------------------------------------------------------------------- */
/*      Assign the new field information fields.                        */
/* -------------------------------------------------------------------- */
    psDBF->panFieldOffset[psDBF->nFields-1] = psDBF->nRecordLength;
    psDBF->nRecordLength += nWidth;
    psDBF->panFieldSize[psDBF->nFields-1] = nWidth;
    psDBF->panFieldDecimals[psDBF->nFields-1] = nDecimals;

    if( eType == FTLogical )
        psDBF->pachFieldType[psDBF->nFields-1] = 'L';
    else if( eType == FTString )
        psDBF->pachFieldType[psDBF->nFields-1] = 'C';
    else
        psDBF->pachFieldType[psDBF->nFields-1] = 'N';

/* -------------------------------------------------------------------- */
/*      Extend the required header information.                         */
/* -------------------------------------------------------------------- */
    psDBF->nHeaderLength += 32;
    psDBF->bUpdated = FALSE;

    psDBF->pszHeader = (char *) SfRealloc(psDBF->pszHeader,psDBF->nFields*32);

    pszFInfo = psDBF->pszHeader + 32 * (psDBF->nFields-1);

    for( i = 0; i < 32; i++ )
        pszFInfo[i] = '\0';

    if( (int) strlen(pszFieldName) < 10 )
        strncpy( pszFInfo, pszFieldName, strlen(pszFieldName));
    else
        strncpy( pszFInfo, pszFieldName, 10);

    pszFInfo[11] = psDBF->pachFieldType[psDBF->nFields-1];

    if( eType == FTString )
    {
        pszFInfo[16] = nWidth % 256;
        pszFInfo[17] = nWidth / 256;
    }
    else
    {
        pszFInfo[16] = nWidth;
        pszFInfo[17] = nDecimals;
    }
    
/* -------------------------------------------------------------------- */
/*      Make the current record buffer appropriately larger.            */
/* -------------------------------------------------------------------- */
    psDBF->pszCurrentRecord = (char *) SfRealloc(psDBF->pszCurrentRecord,
                                               psDBF->nRecordLength);

    return( psDBF->nFields-1 );
}

/************************************************************************/
/*                          DBFReadAttribute()                          */
/*                                                                      */
/*      Read one of the attribute fields of a record.                   */
/************************************************************************/

static void *DBFReadAttribute(DBFHandle psDBF, int hEntity, int iField,
                              char chReqType )

{
    int         nRecordOffset;
    unsigned char       *pabyRec;
    void        *pReturnField = NULL;

    static double dDoubleField;

/* -------------------------------------------------------------------- */
/*      Verify selection.                                               */
/* -------------------------------------------------------------------- */
    if( hEntity < 0 || hEntity >= psDBF->nRecords )
        return( NULL );

    if( iField < 0 || iField >= psDBF->nFields )
        return( NULL );

/* -------------------------------------------------------------------- */
/*      Have we read the record?                                        */
/* -------------------------------------------------------------------- */
    if( psDBF->nCurrentRecord != hEntity )
    {
        DBFFlushRecord( psDBF );

        nRecordOffset = psDBF->nRecordLength * hEntity + psDBF->nHeaderLength;

        if( fseek( psDBF->fp, nRecordOffset, 0 ) != 0 )
        {
            fprintf( stderr, "fseek(%d) failed on DBF file.\n",
                     nRecordOffset );
            return NULL;
        }

        if( fread( psDBF->pszCurrentRecord, psDBF->nRecordLength, 
                   1, psDBF->fp ) != 1 )
        {
            fprintf( stderr, "fread(%d) failed on DBF file.\n",
                     psDBF->nRecordLength );
            return NULL;
        }

        psDBF->nCurrentRecord = hEntity;
    }

    pabyRec = (unsigned char *) psDBF->pszCurrentRecord;

/* -------------------------------------------------------------------- */
/*      Ensure our field buffer is large enough to hold this buffer.    */
/* -------------------------------------------------------------------- */
    if( psDBF->panFieldSize[iField]+1 > nStringFieldLen )
    {
        nStringFieldLen = psDBF->panFieldSize[iField]*2 + 10;
        pszStringField = (char *) SfRealloc(pszStringField,nStringFieldLen);
    }

/* -------------------------------------------------------------------- */
/*      Extract the requested field.                                    */
/* -------------------------------------------------------------------- */
    strncpy( pszStringField, 
             ((const char *) pabyRec) + psDBF->panFieldOffset[iField],
             psDBF->panFieldSize[iField] );
    pszStringField[psDBF->panFieldSize[iField]] = '\0';

    pReturnField = pszStringField;

/* -------------------------------------------------------------------- */
/*      Decode the field.                                               */
/* -------------------------------------------------------------------- */
    if( chReqType == 'N' )
    {
        dDoubleField = atof(pszStringField);

        pReturnField = &dDoubleField;
    }

/* -------------------------------------------------------------------- */
/*      Should we trim white space off the string attribute value?      */
/* -------------------------------------------------------------------- */
#ifdef TRIM_DBF_WHITESPACE
    else
    {
        char    *pchSrc, *pchDst;

        pchDst = pchSrc = pszStringField;
        while( *pchSrc == ' ' )
            pchSrc++;

        while( *pchSrc != '\0' )
            *(pchDst++) = *(pchSrc++);
        *pchDst = '\0';

        while( pchDst != pszStringField && *(--pchDst) == ' ' )
            *pchDst = '\0';
    }
#endif
    
    return( pReturnField );
}

/************************************************************************/
/*                        DBFReadIntAttribute()                         */
/*                                                                      */
/*      Read an integer attribute.                                      */
/************************************************************************/

int SHPAPI_CALL
DBFReadIntegerAttribute( DBFHandle psDBF, int iRecord, int iField )

{
    double      *pdValue;

    pdValue = (double *) DBFReadAttribute( psDBF, iRecord, iField, 'N' );

    if( pdValue == NULL )
        return 0;
    else
        return( (int) *pdValue );
}

/************************************************************************/
/*                        DBFReadDoubleAttribute()                      */
/*                                                                      */
/*      Read a double attribute.                                        */
/************************************************************************/

double SHPAPI_CALL
DBFReadDoubleAttribute( DBFHandle psDBF, int iRecord, int iField )

{
    double      *pdValue;

    pdValue = (double *) DBFReadAttribute( psDBF, iRecord, iField, 'N' );

    if( pdValue == NULL )
        return 0.0;
    else
        return( *pdValue );
}

/************************************************************************/
/*                        DBFReadStringAttribute()                      */
/*                                                                      */
/*      Read a string attribute.                                        */
/************************************************************************/

const char SHPAPI_CALL1(*)
DBFReadStringAttribute( DBFHandle psDBF, int iRecord, int iField )

{
    return( (const char *) DBFReadAttribute( psDBF, iRecord, iField, 'C' ) );
}

/************************************************************************/
/*                        DBFReadLogicalAttribute()                     */
/*                                                                      */
/*      Read a logical attribute.                                       */
/************************************************************************/

const char SHPAPI_CALL1(*)
DBFReadLogicalAttribute( DBFHandle psDBF, int iRecord, int iField )

{
    return( (const char *) DBFReadAttribute( psDBF, iRecord, iField, 'L' ) );
}

/************************************************************************/
/*                         DBFIsAttributeNULL()                         */
/*                                                                      */
/*      Return TRUE if value for field is NULL.                         */
/*                                                                      */
/*      Contributed by Jim Matthews.                                    */
/************************************************************************/

int SHPAPI_CALL
DBFIsAttributeNULL( DBFHandle psDBF, int iRecord, int iField )

{
    const char  *pszValue;

    pszValue = DBFReadStringAttribute( psDBF, iRecord, iField );

    switch(psDBF->pachFieldType[iField])
    {
      case 'N':
      case 'F':
        /* NULL numeric fields have value "****************" */
        return pszValue[0] == '*';

      case 'D':
        /* NULL date fields have value "00000000" */
        return strncmp(pszValue,"00000000",8) == 0;

      case 'L':
        /* NULL boolean fields have value "?" */ 
        return pszValue[0] == '?';

      default:
        /* empty string fields are considered NULL */
        return strlen(pszValue) == 0;
    }
}

/************************************************************************/
/*                          DBFGetFieldCount()                          */
/*                                                                      */
/*      Return the number of fields in this table.                      */
/************************************************************************/

int SHPAPI_CALL
DBFGetFieldCount( DBFHandle psDBF )

{
    return( psDBF->nFields );
}

/************************************************************************/
/*                         DBFGetRecordCount()                          */
/*                                                                      */
/*      Return the number of records in this table.                     */
/************************************************************************/

int SHPAPI_CALL
DBFGetRecordCount( DBFHandle psDBF )

{
    return( psDBF->nRecords );
}

/************************************************************************/
/*                          DBFGetFieldInfo()                           */
/*                                                                      */
/*      Return any requested information about the field.               */
/************************************************************************/

DBFFieldType SHPAPI_CALL
DBFGetFieldInfo( DBFHandle psDBF, int iField, char * pszFieldName,
                 int * pnWidth, int * pnDecimals )

{
    if( iField < 0 || iField >= psDBF->nFields )
        return( FTInvalid );

    if( pnWidth != NULL )
        *pnWidth = psDBF->panFieldSize[iField];

    if( pnDecimals != NULL )
        *pnDecimals = psDBF->panFieldDecimals[iField];

    if( pszFieldName != NULL )
    {
        int     i;

        strncpy( pszFieldName, (char *) psDBF->pszHeader+iField*32, 11 );
        pszFieldName[11] = '\0';
        for( i = 10; i > 0 && pszFieldName[i] == ' '; i-- )
            pszFieldName[i] = '\0';
    }

    if ( psDBF->pachFieldType[iField] == 'L' )
        return( FTLogical);

    else if( psDBF->pachFieldType[iField] == 'N' 
             || psDBF->pachFieldType[iField] == 'F'
             || psDBF->pachFieldType[iField] == 'D' )
    {
        if( psDBF->panFieldDecimals[iField] > 0 )
            return( FTDouble );
        else
            return( FTInteger );
    }
    else
    {
        return( FTString );
    }
}

/************************************************************************/
/*                         DBFWriteAttribute()                          */
/*                                                                      */
/*      Write an attribute record to the file.                          */
/************************************************************************/

static int DBFWriteAttribute(DBFHandle psDBF, int hEntity, int iField,
                             void * pValue )

{
    int         nRecordOffset, i, j, nRetResult = TRUE;
    unsigned char       *pabyRec;
    char        szSField[400], szFormat[20];

/* -------------------------------------------------------------------- */
/*      Is this a valid record?                                         */
/* -------------------------------------------------------------------- */
    if( hEntity < 0 || hEntity > psDBF->nRecords )
        return( FALSE );

    if( psDBF->bNoHeader )
        DBFWriteHeader(psDBF);

/* -------------------------------------------------------------------- */
/*      Is this a brand new record?                                     */
/* -------------------------------------------------------------------- */
    if( hEntity == psDBF->nRecords )
    {
        DBFFlushRecord( psDBF );

        psDBF->nRecords++;
        for( i = 0; i < psDBF->nRecordLength; i++ )
            psDBF->pszCurrentRecord[i] = ' ';

        psDBF->nCurrentRecord = hEntity;
    }

/* -------------------------------------------------------------------- */
/*      Is this an existing record, but different than the last one     */
/*      we accessed?                                                    */
/* -------------------------------------------------------------------- */
    if( psDBF->nCurrentRecord != hEntity )
    {
        DBFFlushRecord( psDBF );

        nRecordOffset = psDBF->nRecordLength * hEntity + psDBF->nHeaderLength;

        fseek( psDBF->fp, nRecordOffset, 0 );
        fread( psDBF->pszCurrentRecord, psDBF->nRecordLength, 1, psDBF->fp );

        psDBF->nCurrentRecord = hEntity;
    }

    pabyRec = (unsigned char *) psDBF->pszCurrentRecord;

    psDBF->bCurrentRecordModified = TRUE;
    psDBF->bUpdated = TRUE;

/* -------------------------------------------------------------------- */
/*      Translate NULL value to valid DBF file representation.          */
/*                                                                      */
/*      Contributed by Jim Matthews.                                    */
/* -------------------------------------------------------------------- */
    if( pValue == NULL )
    {
        switch(psDBF->pachFieldType[iField])
        {
          case 'N':
          case 'F':
            /* NULL numeric fields have value "****************" */
            memset( (char *) (pabyRec+psDBF->panFieldOffset[iField]), '*', 
                    psDBF->panFieldSize[iField] );
            break;

          case 'D':
            /* NULL date fields have value "00000000" */
            memset( (char *) (pabyRec+psDBF->panFieldOffset[iField]), '0', 
                    psDBF->panFieldSize[iField] );
            break;

          case 'L':
            /* NULL boolean fields have value "?" */ 
            memset( (char *) (pabyRec+psDBF->panFieldOffset[iField]), '?', 
                    psDBF->panFieldSize[iField] );
            break;

          default:
            /* empty string fields are considered NULL */
            memset( (char *) (pabyRec+psDBF->panFieldOffset[iField]), '\0', 
                    psDBF->panFieldSize[iField] );
            break;
        }
        return TRUE;
    }

/* -------------------------------------------------------------------- */
/*      Assign all the record fields.                                   */
/* -------------------------------------------------------------------- */
    switch( psDBF->pachFieldType[iField] )
    {
      case 'D':
      case 'N':
      case 'F':
        if( psDBF->panFieldDecimals[iField] == 0 )
        {
            int         nWidth = psDBF->panFieldSize[iField];

            if( sizeof(szSField)-2 < nWidth )
                nWidth = sizeof(szSField)-2;

            sprintf( szFormat, "%%%dd", nWidth );
            sprintf(szSField, szFormat, (int) *((double *) pValue) );
            if( (int)strlen(szSField) > psDBF->panFieldSize[iField] )
            {
                szSField[psDBF->panFieldSize[iField]] = '\0';
                nRetResult = FALSE;
            }

            strncpy((char *) (pabyRec+psDBF->panFieldOffset[iField]),
                    szSField, strlen(szSField) );
        }
        else
        {
            int         nWidth = psDBF->panFieldSize[iField];

            if( sizeof(szSField)-2 < nWidth )
                nWidth = sizeof(szSField)-2;

            sprintf( szFormat, "%%%d.%df", 
                     nWidth, psDBF->panFieldDecimals[iField] );
            sprintf(szSField, szFormat, *((double *) pValue) );
            if( (int) strlen(szSField) > psDBF->panFieldSize[iField] )
            {
                szSField[psDBF->panFieldSize[iField]] = '\0';
                nRetResult = FALSE;
            }
            strncpy((char *) (pabyRec+psDBF->panFieldOffset[iField]),
                    szSField, strlen(szSField) );
        }
        break;

      case 'L':
        if (psDBF->panFieldSize[iField] >= 1  && 
            (*(char*)pValue == 'F' || *(char*)pValue == 'T'))
            *(pabyRec+psDBF->panFieldOffset[iField]) = *(char*)pValue;
        break;

      default:
        if( (int) strlen((char *) pValue) > psDBF->panFieldSize[iField] )
        {
            j = psDBF->panFieldSize[iField];
            nRetResult = FALSE;
        }
        else
        {
            memset( pabyRec+psDBF->panFieldOffset[iField], ' ',
                    psDBF->panFieldSize[iField] );
            j = strlen((char *) pValue);
        }

        strncpy((char *) (pabyRec+psDBF->panFieldOffset[iField]),
                (char *) pValue, j );
        break;
    }

    return( nRetResult );
}

/************************************************************************/
/*                     DBFWriteAttributeDirectly()                      */
/*                                                                      */
/*      Write an attribute record to the file, but without any          */
/*      reformatting based on type.  The provided buffer is written     */
/*      as is to the field position in the record.                      */
/************************************************************************/

int DBFWriteAttributeDirectly(DBFHandle psDBF, int hEntity, int iField,
                              void * pValue )

{
    int         nRecordOffset, i, j;
    unsigned char       *pabyRec;

/* -------------------------------------------------------------------- */
/*      Is this a valid record?                                         */
/* -------------------------------------------------------------------- */
    if( hEntity < 0 || hEntity > psDBF->nRecords )
        return( FALSE );

    if( psDBF->bNoHeader )
        DBFWriteHeader(psDBF);

/* -------------------------------------------------------------------- */
/*      Is this a brand new record?                                     */
/* -------------------------------------------------------------------- */
    if( hEntity == psDBF->nRecords )
    {
        DBFFlushRecord( psDBF );

        psDBF->nRecords++;
        for( i = 0; i < psDBF->nRecordLength; i++ )
            psDBF->pszCurrentRecord[i] = ' ';

        psDBF->nCurrentRecord = hEntity;
    }

/* -------------------------------------------------------------------- */
/*      Is this an existing record, but different than the last one     */
/*      we accessed?                                                    */
/* -------------------------------------------------------------------- */
    if( psDBF->nCurrentRecord != hEntity )
    {
        DBFFlushRecord( psDBF );

        nRecordOffset = psDBF->nRecordLength * hEntity + psDBF->nHeaderLength;

        fseek( psDBF->fp, nRecordOffset, 0 );
        fread( psDBF->pszCurrentRecord, psDBF->nRecordLength, 1, psDBF->fp );

        psDBF->nCurrentRecord = hEntity;
    }

    pabyRec = (unsigned char *) psDBF->pszCurrentRecord;

/* -------------------------------------------------------------------- */
/*      Assign all the record fields.                                   */
/* -------------------------------------------------------------------- */
    if( (int)strlen((char *) pValue) > psDBF->panFieldSize[iField] )
        j = psDBF->panFieldSize[iField];
    else
    {
        memset( pabyRec+psDBF->panFieldOffset[iField], ' ',
                psDBF->panFieldSize[iField] );
        j = strlen((char *) pValue);
    }

    strncpy((char *) (pabyRec+psDBF->panFieldOffset[iField]),
            (char *) pValue, j );

    psDBF->bCurrentRecordModified = TRUE;
    psDBF->bUpdated = TRUE;

    return( TRUE );
}

/************************************************************************/
/*                      DBFWriteDoubleAttribute()                       */
/*                                                                      */
/*      Write a double attribute.                                       */
/************************************************************************/

int SHPAPI_CALL
DBFWriteDoubleAttribute( DBFHandle psDBF, int iRecord, int iField,
                         double dValue )

{
    return( DBFWriteAttribute( psDBF, iRecord, iField, (void *) &dValue ) );
}

/************************************************************************/
/*                      DBFWriteIntegerAttribute()                      */
/*                                                                      */
/*      Write a integer attribute.                                      */
/************************************************************************/

int SHPAPI_CALL
DBFWriteIntegerAttribute( DBFHandle psDBF, int iRecord, int iField,
                          int nValue )

{
    double      dValue = nValue;

    return( DBFWriteAttribute( psDBF, iRecord, iField, (void *) &dValue ) );
}

/************************************************************************/
/*                      DBFWriteStringAttribute()                       */
/*                                                                      */
/*      Write a string attribute.                                       */
/************************************************************************/

int SHPAPI_CALL
DBFWriteStringAttribute( DBFHandle psDBF, int iRecord, int iField,
                         const char * pszValue )

{
    return( DBFWriteAttribute( psDBF, iRecord, iField, (void *) pszValue ) );
}

/************************************************************************/
/*                      DBFWriteNULLAttribute()                         */
/*                                                                      */
/*      Write a string attribute.                                       */
/************************************************************************/

int SHPAPI_CALL
DBFWriteNULLAttribute( DBFHandle psDBF, int iRecord, int iField )

{
    return( DBFWriteAttribute( psDBF, iRecord, iField, NULL ) );
}

/************************************************************************/
/*                      DBFWriteLogicalAttribute()                      */
/*                                                                      */
/*      Write a logical attribute.                                      */
/************************************************************************/

int SHPAPI_CALL
DBFWriteLogicalAttribute( DBFHandle psDBF, int iRecord, int iField,
                       const char lValue)

{
    return( DBFWriteAttribute( psDBF, iRecord, iField, (void *) (&lValue) ) );
}

/************************************************************************/
/*                         DBFWriteTuple()                              */
/*                                                                      */
/*      Write an attribute record to the file.                          */
/************************************************************************/

int SHPAPI_CALL
DBFWriteTuple(DBFHandle psDBF, int hEntity, void * pRawTuple )

{
    int         nRecordOffset, i;
    unsigned char       *pabyRec;

/* -------------------------------------------------------------------- */
/*      Is this a valid record?                                         */
/* -------------------------------------------------------------------- */
    if( hEntity < 0 || hEntity > psDBF->nRecords )
        return( FALSE );

    if( psDBF->bNoHeader )
        DBFWriteHeader(psDBF);

/* -------------------------------------------------------------------- */
/*      Is this a brand new record?                                     */
/* -------------------------------------------------------------------- */
    if( hEntity == psDBF->nRecords )
    {
        DBFFlushRecord( psDBF );

        psDBF->nRecords++;
        for( i = 0; i < psDBF->nRecordLength; i++ )
            psDBF->pszCurrentRecord[i] = ' ';

        psDBF->nCurrentRecord = hEntity;
    }

/* -------------------------------------------------------------------- */
/*      Is this an existing record, but different than the last one     */
/*      we accessed?                                                    */
/* -------------------------------------------------------------------- */
    if( psDBF->nCurrentRecord != hEntity )
    {
        DBFFlushRecord( psDBF );

        nRecordOffset = psDBF->nRecordLength * hEntity + psDBF->nHeaderLength;

        fseek( psDBF->fp, nRecordOffset, 0 );
        fread( psDBF->pszCurrentRecord, psDBF->nRecordLength, 1, psDBF->fp );

        psDBF->nCurrentRecord = hEntity;
    }

    pabyRec = (unsigned char *) psDBF->pszCurrentRecord;

    memcpy ( pabyRec, pRawTuple,  psDBF->nRecordLength );

    psDBF->bCurrentRecordModified = TRUE;
    psDBF->bUpdated = TRUE;

    return( TRUE );
}

/************************************************************************/
/*                          DBFReadTuple()                              */
/*                                                                      */
/*      Read one of the attribute fields of a record.                   */
/************************************************************************/

const char SHPAPI_CALL1(*)
DBFReadTuple(DBFHandle psDBF, int hEntity )

{
    int         nRecordOffset;
    unsigned char       *pabyRec;
    static char *pReturnTuple = NULL;

    static int  nTupleLen = 0;

/* -------------------------------------------------------------------- */
/*      Have we read the record?                                        */
/* -------------------------------------------------------------------- */
    if( hEntity < 0 || hEntity >= psDBF->nRecords )
        return( NULL );

    if( psDBF->nCurrentRecord != hEntity )
    {
        DBFFlushRecord( psDBF );

        nRecordOffset = psDBF->nRecordLength * hEntity + psDBF->nHeaderLength;

        fseek( psDBF->fp, nRecordOffset, 0 );
        fread( psDBF->pszCurrentRecord, psDBF->nRecordLength, 1, psDBF->fp );

        psDBF->nCurrentRecord = hEntity;
    }

    pabyRec = (unsigned char *) psDBF->pszCurrentRecord;

    if ( nTupleLen < psDBF->nRecordLength) {
      nTupleLen = psDBF->nRecordLength;
      pReturnTuple = (char *) SfRealloc(pReturnTuple, psDBF->nRecordLength);
    }
    
    memcpy ( pReturnTuple, pabyRec, psDBF->nRecordLength );
        
    return( pReturnTuple );
}

/************************************************************************/
/*                          DBFCloneEmpty()                              */
/*                                                                      */
/*      Read one of the attribute fields of a record.                   */
/************************************************************************/

DBFHandle SHPAPI_CALL
DBFCloneEmpty(DBFHandle psDBF, const char * pszFilename ) 
{
    DBFHandle   newDBF;

   newDBF = DBFCreate ( pszFilename );
   if ( newDBF == NULL ) return ( NULL ); 
   
   newDBF->pszHeader = (char *) malloc ( 32 * psDBF->nFields );
   memcpy ( newDBF->pszHeader, psDBF->pszHeader, 32 * psDBF->nFields );
   
   newDBF->nFields = psDBF->nFields;
   newDBF->nRecordLength = psDBF->nRecordLength;
   newDBF->nHeaderLength = 32 * (psDBF->nFields+1);
    
   newDBF->panFieldOffset = (int *) malloc ( sizeof(int) * psDBF->nFields ); 
   memcpy ( newDBF->panFieldOffset, psDBF->panFieldOffset, sizeof(int) * psDBF->nFields );
   newDBF->panFieldSize = (int *) malloc ( sizeof(int) * psDBF->nFields );
   memcpy ( newDBF->panFieldSize, psDBF->panFieldSize, sizeof(int) * psDBF->nFields );
   newDBF->panFieldDecimals = (int *) malloc ( sizeof(int) * psDBF->nFields );
   memcpy ( newDBF->panFieldDecimals, psDBF->panFieldDecimals, sizeof(int) * psDBF->nFields );
   newDBF->pachFieldType = (char *) malloc ( sizeof(int) * psDBF->nFields );
   memcpy ( newDBF->pachFieldType, psDBF->pachFieldType, sizeof(int) * psDBF->nFields );

   newDBF->bNoHeader = TRUE;
   newDBF->bUpdated = TRUE;
   
   DBFWriteHeader ( newDBF );
   DBFClose ( newDBF );
   
   newDBF = DBFOpen ( pszFilename, "rb+" );

   return ( newDBF );
}

/************************************************************************/
/*                       DBFGetNativeFieldType()                        */
/*                                                                      */
/*      Return the DBase field type for the specified field.            */
/*                                                                      */
/*      Value can be one of: 'C' (String), 'D' (Date), 'F' (Float),     */
/*                           'N' (Numeric, with or without decimal),    */
/*                           'L' (Logical),                             */
/*                           'M' (Memo: 10 digits .DBT block ptr)       */
/************************************************************************/

char SHPAPI_CALL
DBFGetNativeFieldType( DBFHandle psDBF, int iField )

{
    if( iField >=0 && iField < psDBF->nFields )
        return psDBF->pachFieldType[iField];

    return  ' ';
}

/************************************************************************/
/*                            str_to_upper()                            */
/************************************************************************/

static void str_to_upper (char *string)
{
    int len;
    short i = -1;

    len = strlen (string);

    while (++i < len)
        if (isalpha(string[i]) && islower(string[i]))
            string[i] = toupper ((int)string[i]);
}

/************************************************************************/
/*                          DBFGetFieldIndex()                          */
/*                                                                      */
/*      Get the index number for a field in a .dbf file.                */
/*                                                                      */
/*      Contributed by Jim Matthews.                                    */
/************************************************************************/

int SHPAPI_CALL
DBFGetFieldIndex(DBFHandle psDBF, const char *pszFieldName)

{
    char          name[12], name1[12], name2[12];
    int           i;

    strncpy(name1, pszFieldName,11);
    name1[11] = '\0';
    str_to_upper(name1);

    for( i = 0; i < DBFGetFieldCount(psDBF); i++ )
    {
        DBFGetFieldInfo( psDBF, i, name, NULL, NULL );
        strncpy(name2,name,11);
        str_to_upper(name2);

        if(!strncmp(name1,name2,10))
            return(i);
    }
    return(-1);
}

---