dbfopen.c

ESRI SHAPE文件读/写源代码。SHAPE是GIS中的重要文件格式

/*	write access.                					*/
/* -------------------------------------------------------------------- */
    if( psDBF->bUpdated )
    {
	uchar		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 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	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 );

/* -------------------------------------------------------------------- */
/*      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 == 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( 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;
    uchar	*pabyRec;
    void	*pReturnField = NULL;

    static double dDoubleField;

/* -------------------------------------------------------------------- */
/*	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 = (uchar *) 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, 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) == ' ' && pchDst != pszStringField )
            *pchDst = '\0';

    }
#endif
    
    return( pReturnField );
}

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

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

{
    double	*pdValue;

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

    return( (int) *pdValue );
}

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

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

{
    double	*pdValue;

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

    return( *pdValue );
}

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

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

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

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