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Slow tfilestream.EndOfData  Bottom

  • kif
    • Registered: Oct 30, 2008
    • Last visit: Mar 18, 2009
    • Posts: 10
    Link to this post Posted: Mar 09, 2009 - 08:54 PM
    Hi

    I have found the following code to be very slow (this also is the principle used in tstringlist.loadfromfile) :

    Code

    var

    f : tfilestream;



    ....



    while not f.endofdata do

    begin

    s := f.readln;

    .....

    end;


    I have made some experiments and found the problem to be the way EodOfData works.

    Whenever EndOfData is called, it tests weather current position is >= size, only problem with that is that size is a property hiding a seek to end of file and then back to current position.

    Cut fron ustream :

    Code

    Function TStream.GetSize:LongInt;



    Var OldPos:LongInt;



    Begin

    OldPos:=GetPosition;

    Result:=Seek(0,Seek_End);

    SetPosition(OldPos);

    End;



    Function TStream.EndOfData: Boolean;

    Begin

    Result := (Position >= Size);

    End;


    A solution to this could be to make tstream.GetSize virtual, and add the following to tfilestream :

    interface :

    Code

    TFileStream = class(tstream)

    Private

    ...

    Function GetSize:LongInt; Override;


    Implementation :

    Code

    Function TFileStream.GetSize:LongInt;

    begin

    result := filesize(PStreamFile);

    end;


    In a test, the original GetSize resulted in tstringlist.loadfromfile using several minutes reading a 600 kb text file, the corrected one used seconds reading the same file !

    Kim

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