AppendChunk and GetChunk Methods Example

This example uses the AppendChunk and GetChunk methods to fill an OLE object field with data from another record, 32K at a time. In a real application, one might use a procedure like this to copy an employee record (including the employee's photo) from one table to another. In this example, the record is simply being copied back to same table. Note that all the chunk manipulation takes place within a single AddNew-Update sequence.

Sub AppendChunkX()

    Dim dbsNorthwind As Database
    Dim rstEmployees As Recordset
    Dim rstEmployees2 As Recordset

    Set dbsNorthwind = OpenDatabase("Northwind.mdb")

    ' Open two recordsets from the Employees table.
    Set rstEmployees = _
        dbsNorthwind.OpenRecordset("Employees", _
        dbOpenDynaset)
    Set rstEmployees2 = rstEmployees.Clone

    ' Add a new record to the first Recordset and copy the 
    ' data from a record in the second Recordset.
    With rstEmployees
        .AddNew
        !FirstName = rstEmployees2!FirstName
        !LastName = rstEmployees2!LastName
        CopyLargeField rstEmployees2!Photo, !Photo
        .Update

        ' Delete new record because this is a demonstration.
        .Bookmark = .LastModified
        .Delete
        .Close
    End With

    rstEmployees2.Close
    dbsNorthwind.Close

End Sub

Function CopyLargeField(fldSource As Field, _
    fldDestination As Field)

    ' Set size of chunk in bytes.
    Const conChunkSize = 32768

    Dim lngOffset As Long
    Dim lngTotalSize As Long
    Dim strChunk As String

    ' Copy the photo from one Recordset to the other in 32K 
    ' chunks until the entire field is copied.
    lngTotalSize = fldSource.FieldSize
    Do While lngOffset < lngTotalSize
        strChunk = fldSource.GetChunk(lngOffset, conChunkSize)
        fldDestination.AppendChunk strChunk
        lngOffset = lngOffset + conChunkSize
    Loop

End Function