Save a file to a TBlobStream and read it back

Spread the love

If you develop a database related software, then a very popular task is to
save some files (documents/images/reports/etc) in some BLOB field of table
and use these saved data later.
In this tip I want to show how this task could be solved.

To save a file to BLOB:

procedure TForm1.Button1Click(Sender: TObject);
var
  blob: TBlobStream;
begin
  blob := yourDataset.CreateBlobStream(yourDataset.FieldByName('YOUR_BLOB'), bmWrite);
  try
    blob.Seek(0, soFromBeginning);
    fs := TFileStream.Create('c:\your_name.doc', fmOpenRead or
      fmShareDenyWrite);
    try
      blob.CopyFrom(fs, fs.Size)
    finally
      fs.Free
    end;
  finally
    blob.Free
  end;
end;
  // To load from BLOB:

procedure TForm1.Button1Click(Sender: TObject);
var
  blob: TBlobStream;
begin
  blob := yourDataset.CreateBlobStream(yourDataset.FieldByName('YOUR_BLOB'), bmRead);
  try
    blob.Seek(0, soFromBeginning);

    with TFileStream.Create('c:\your_name.doc', fmCreate) do
      try
        CopyFrom(blob, blob.Size)
      finally
        Free
      end;
  finally
    blob.Free
  end;
end;

Using this code you can work with any database engine (BDE/ADO/DAO/ODBC/etc)
and any file format (document of MS Word, spreadsheet of MS Excel, bitmap or
jpeg pictures, wav-files etc)