BdpDataReader.GetBytes always returns 0

Thread View: borland.public.delphi.database.bdp

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3 total messages Started by David Clegg Tue, 03 Apr 2007 09:28

#224

Author: David Clegg
Date: Tue, 03 Apr 2007 09:28

66 lines
2909 bytes

I am trying to read data from an Interbase blob field in small chunks,
but my attempts are falling flat because calls to
BdpDataReader.GetBytes always return 0 even though bytes are
successfully read from the database.

I can reproduce the problem with a more contrived example, and below is
the code I'm using for this :-

procedure TWinForm2.Button1_Click(sender: System.Object; e:
System.EventArgs);
var
  lCon: BdpConnection;
  lCmd: BdpCommand;
  lReader: BdpDataReader;
  lBuff: array of byte;
  lRead: Int64;
begin
  lCon := BdpConnection.Create;
  lCon.ConnectionString := 'assembly=Borland.Data.Interbase,
Version=2.5' +
  '.0.0, Culture=neutral,
PublicKeyToken=91d62ebb5b0d1b1b;vendorclient=gds32' +
  '.dll;pooling=True;grow on
demand=True;database=localhost:D:\IBData\BLOBTEST' +
  '.IB;username=SYSDBA;max pool
size=100;password=masterkey;provider=In' +
  'terbase;min pool size=0';

  lCmd := BdpCommand.Create('SELECT BLOB_FIELD FROM BLOB_TABLE WHERE ID
= 1', lCon);
  lCon.Open;
  try
    lReader := lCmd.ExecuteReader(CommandBehavior.SequentialAccess);
    try
      SetLength(lBuff, 16384);
      if lReader.Read then
      begin
        lRead := lReader.GetBytes(0, 0, lBuff, 0, Length(lBuff));
        MessageBox.Show(lRead.ToString);
      end;
    finally
      lReader.Close;
    end;
  finally
    lCon.Close;
  end;
end;


Is there anything obviously wrong with the above code, or are there any
known issues with BdpDataReader.GetBytes not correctly returning the
number of bytes read? I did a quick search in QC, but didn't find any
existing bug reports.



-- 
Cheers,
David Clegg
dclegg@gmail.com
http://cc.borland.com/Author.aspx?ID=72299

QualityCentral. The best way to bug Borland about bugs.
http://qc.borland.com

"Pffft. Who needs English? I'm never going to England." - Homer Simpson

Re: BdpDataReader.GetBytes always returns 0

#227

Author: David Wilcockson
Date: Tue, 10 Apr 2007 19:20

18 lines
1513 bytes

>      if lReader.Read then
>      begin
>        lRead := lReader.GetBytes(0, 0, lBuff, 0, Length(lBuff));
>        MessageBox.Show(lRead.ToString);
>      end;
>    finally
>      lReader.Close;
>    end;


Try calling it separately with a nil to get the size first. This is the code 
I use (and I believe it worked when I used to use BDP):

           BlobSize := SQLReader.GetChars(0, 0, nil, 0, 0);
           SetLength(BlobArray, BlobSize);
           if BlobSize <> 0 then SQLReader.GetChars(0, 0, BlobArray, 0, 
BlobSize);

Re: BdpDataReader.GetBytes always returns 0

#228

Author: David Clegg
Date: Tue, 10 Apr 2007 20:40

17 lines
1395 bytes

David Wilcockson wrote:

> Try calling it separately with a nil to get the size first. This is
> the code I use (and I believe it worked when I used to use BDP):

This is what the original code is currently doing, so I am dubious as
to whether this will solve the problem. However, I'll add it to my test
app so I can know for sure that nothing else is causing this behaviour.

-- 
Cheers,
David Clegg
dclegg@gmail.com
http://cc.codegear.com/Author/72299

QualityCentral. The best way to bug CodeGear about bugs.
http://qc.codegear.com

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