Any specific difference between TCSVStream and TMemoryStream?
lazarus / 21-General

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egsuh · 2025-04-09 11:08

Hello,

I've written a procedure that converts datasets to TMemoryStream.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
Taq_r_5.SetDataSet(querydef, fieldname, filename:
string;DataSet:TDataSet): Boolean;var   turl, tfn : string;   AStrm:
TMemoryStream;   AStrl : TStringList;begin   Result:= false; 
 DataSet.First;   AStrl := TStringList.Create;   AStrm :=
TMemoryStream.Create;   try      if DataSet <> nil then begin       
 if uppercase(fieldname) = 'SAMPLELIST'            then (DataSet as
TCSVDataSet).SaveToCSVStream(AStrm)   // <==== This is not Freed
completely            else (DataSet as
TBufDataSet).SaveToStream(AStrm);         tfn := filename;        
 Astrm.Position:= 0;          turl := url + Format('e/SetDataSet?%s',
[querydef]);         Result :=  HttpPostFile(tURL, fieldname, tfn,
AStrm, AStrl);         Result:= uppercase(trim(astrl.Text)) =
uppercase(BoolToStr(true, true));      end;    finally     
AStrl.Free;      AStrm.Free;    // <--- it should be freed finally 
 end;end; 
SaveToStream to a MemoryStream variable works ok.  But SaveToCSVStream
to a MemoryStream variable is not cleared at free.
Even though it is not completely freed, it operates correctly.

Any reasons?

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Zoran · 2025-04-09 19:20

Quote from: egsuh on April 09, 2025, 01:08:47 pmHello,

I've written a procedure that converts datasets to TMemoryStream.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
Taq_r_5.SetDataSet(querydef, fieldname, filename:
string;DataSet:TDataSet): Boolean;var   turl, tfn : string;   AStrm:
TMemoryStream;   AStrl : TStringList;begin   Result:= false; 
 DataSet.First;   AStrl := TStringList.Create;   AStrm :=
TMemoryStream.Create;   try      if DataSet <> nil then begin       
 if uppercase(fieldname) = 'SAMPLELIST'            then (DataSet as
TCSVDataSet).SaveToCSVStream(AStrm)   // <==== This is not Freed
completely            else (DataSet as
TBufDataSet).SaveToStream(AStrm);         tfn := filename;        
 Astrm.Position:= 0;          turl := url + Format('e/SetDataSet?%s',
[querydef]);         Result :=  HttpPostFile(tURL, fieldname, tfn,
AStrm, AStrl);         Result:= uppercase(trim(astrl.Text)) =
uppercase(BoolToStr(true, true));      end;    finally     
AStrl.Free;      AStrm.Free;    // <--- it should be freed finally 
 end;end; 
SaveToStream to a MemoryStream variable works ok.  But SaveToCSVStream
to a MemoryStream variable is not cleared at free.
Even though it is not completely freed, it operates correctly.

Any reasons?

What do you mean? This code does not do anything after calling
AStrm.Free, so it doesn't try to access this object after it was freed
(and of course it shouldn't try). So how can you tell that the
variable operates correctly and that it is not completely freed?

Please try to explain better what you mean.

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egsuh · 2025-04-10 02:49

QuoteSo how can you tell that the variable operates correctly and that
it is not completely freed?
Heaptrack says some memories are not freed.