SecureBlackbox 16: How to Resolve OutOfMemory Errors when Loading Large PDF Documents
Note: This article applies only to SecureBlackbox Legacy. For future development please consider using the latest version.
In this case you should handle the TElPDFDocument.OnCreateTemporaryStream and/or TElPDFDocument.PDFFile.OnCreateTemporaryStream events, create a temporary file on the disk inside the handler, and then return the corresponding FileStream/TFileStream object back to the component. If the event is not handled, a memory stream is internally created and used. This can lead to out-of-memory exceptions on large files.
The TElPDFDocument.OnCreateTemporaryStream event handler is fired when the document is loaded, and the TElPDFDocument.PDFFile.OnCreateTemporaryStream event handler is fired on saving the document when the document is reassembled (for example during document encryption).
PDFDocument.OnCreateTemporaryStream := DoCreateTemporaryStream; PDFDocument.PDFFile.OnCreateTemporaryStream := DoCreateTemporaryStream; procedure TfrmMain.DoCreateTemporaryStream(Sender: TObject; var Stream: TStream; var FreeOnClose : boolean); begin Stream := TFileStream.Create(GenerateTempFilename, fmOpenReadWrite or fmShareDenyWrite) FreeOnClose := True; end;
AddHandler PDFDocument.OnCreateTemporaryStream, AddressOf HandleCreateTemporaryStream ' on opening document AddHandler PDFDocument.PDFFile.OnCreateTemporaryStream, AddressOf HandleCreateTemporaryStream ' on saving Private Sub HandleCreateTemporaryStream(sender As Object, ByRef stream As IO.Stream, ByRef freeOnClose As Boolean) stream = New FileStream(IO.Path.GetTempFileName, FileMode.Create) freeOnClose = True End Sub
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