How can I download a huge file via TIdHTTP?

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TMemoryStream provides an in-memory buffer, so if you download into one, you need to have enough memory to hold everything you receive. It's not the only kind of stream, though. You can pass the Get method any kind of stream you want, including one that writes its contents to disk as it receives it. Use TFileStream, for example.

var
  s: TStream;

s := TFileStream.Create('myfile.zip', fmCreate);
try
  IdHttp1.Get(..., s);
finally
  s.Free;
end;

Anywhere you call LoadFromFile or SaveToFile on a TMemoryStream, it's possible that TFileStream is a better choice.

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Red October
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Red October

Updated on June 04, 2022

Comments

  • Red October
    Red October over 1 year

    I use this code to download small files:

    Var
     ms:TMemoryStream;
    begin
      ms:=TMemoryStream.Create;
      Idhttp1.get('http://mydomain.com/myfile.zip',ms);
      ms.SaveToFile('myfile.zip');
      ms.Free;
    end;
    

    But file is saved in RAM before storing to disk, so it may be difficult to download files >1Gb, for example. Is there a way to download a file by its parts? Or do I need to use the WinInet? Thanks in advance!

    • Ken White
      Ken White over 10 years
      The easiest option is to just use a TFileStream instead of a TMemoryStream, which would write to disk directly as the file is downloaded. IdHTTP.Get just asks for a TStream, which means you can provide any type of stream to it.
    • TLama
      TLama over 10 years
      It's like @Ken says, simply replace TMemoryStream with the TFileStream. And anyway, don't forget to ensecure the stream to be released by using try..finally block. Your code might be finally modified to something like this.
  • Red October
    Red October over 10 years
    Thanks, exactly what I need.
  • Remy Lebeau
    Remy Lebeau over 10 years
    I would go a step further by using an extra try/except to delete the file after calling s.Free() if Get() failed. With the code you showed, the file is not deleted if the download fails. Unless you want to support resuming broken downloads, in which case don't delete the file.