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BLOBDirectExport Function

Export the contents of a binary large object (BLOB) pointer to a file. Note:  A BLOB file (.DBV or .FPT) is used for storing memo field information, as an alternative to the standard .DBT file mechanism supported by some RDDs.  It is a more powerful and efficient mechanism for storing and retrieving large amounts of data than using .DBT files.  X# supplies the DBFCDX driver, which uses the BLOB file storage mechanism by default, and the DBFBLOB driver, which you can use as an inherited driver with other RDDs.  Refer to the "RDD Specifics" appendix in the Programmer's Guide for further information on using this driver.

Namespace:  XSharp.RT
Assembly:  XSharp.RT (in XSharp.RT.dll) Version: 2.08
Syntax
 FUNCTION BLOBDirectExport(
	 nPointer AS USUAL,
	 cTargetFile AS USUAL,
	 kMode AS USUAL
) AS LOGIC
View Source

Parameters

nPointer
Type: Usual
A pointer to the BLOB data.  This pointer can be obtained using BLOBDirectPut(), BLOBDirectExport(), or DBFieldInfo(DBS_BLOB_POINTER, <nFieldPos>).
cTargetFile
Type: Usual
The name of the target file where the BLOB data will be written, including an optional drive, directory, and extension.  See SetDefault() and SetPath() for file searching and creation rules.  No default extension is assumed.
If <cTargetFile> does not exist, it is created.  If it exists, this function attempts to open the file in exclusive mode and, if successful, the file is written to without warning or error.  If access is denied because, for example, another process is using the file, NetErr() is set to TRUE.  Refer to the "Concurrency Control" chapter in the Programmer's Guide for more information on resolving concurrency conflicts.
kMode
Type: Usual
A constant defining the copy mode, as shown in the table below:
Constant Description
BLOB_EXPORT_APPEND Appends to the file
BLOB_EXPORT_OVERWRITE Overwrites the file — this is the default

Return Value

Type: Boolean
TRUE if successful; otherwise, FALSE.
Remarks
By default, this function operates on the currently selected work area.  It can be made to operate on an unselected work area by specifying it within an aliased expression.
Examples
This example extracts an array of pointers from the BLOB file's root area, then uses one of the pointers to export a picture to a file:
X#
FUNCTION PutPix()
        LOCAL cPixFile AS STRING
        LOCAL nPointer
        LOCAL aBLOBPtrs AS ARRAY
        cPixFile := "picture.gif"
        // Customer database with a picture of
        // each customer stored in a field called Pix
        USE customer NEW VIA "DBFCDX"
        // Assumes that the program previously
        // stored an array of direct BLOB pointers
        // into the root area of the BLOB file.
        // The picture that we want is assumed to
        // be the second array element.
        aBLOBPtrs := BLOBRootGet()
        nPointer := aBLOBPtrs[2]
        // Export picture pointed to by nPointer to a file
        IF !BLOBDirectExport(nPointer, cPixFile, ;
                BLOB_EXPORT_OVERWRITE)
                        Alert("Export of picture " + cPixFile + ";
                                failed!")
        ELSE
                // Code for displaying picture would go here
        ENDIF
See Also