Delphi HTTP App raising error when loading files into streams

Question

I've been working on an HTTP Web Server Application (via TIdHTTPWebBrokerBridge) and have a little issue when it comes to loading files into streams (TFileStream) to be sent back to the client. It doesn't happen every time, but quite randomly... I keep getting an exception...

Cannot open file "C:\SomePath\SomeFile.html". The process cannot access the file because it is being used by another process

It happens on this line:

Str:= TFileStream.Create('C:\SomePath\SomeFile.html', fmOpenRead);

(Str being a TFileStream)

I'm assuming the message speaks for its self, but I absolutely need to avoid it. This exception only happens in debug mode, but I need to debug this thing without worrying about getting this message all the time.

Strangely, most of the time, the file is loaded and sent back anyway.

How could I go about avoiding this? And why might it not allow me to open it more than once, even if its read only?

Well, you don't use the share mode in your code... perhaps using `fmShareDenyWrite` or `fmShareDenyNone` is all thats needed to fix your problem, see http://docwiki.embarcadero.com/Libraries/en/System.Classes.TFileStream.Create — ain, Mar 24 '12 at 17:38

score 6 · Accepted Answer · answered Mar 24 '12 at 17:51

6

As @ain stated in the comment - you are missing the share mode in your Constructor.

Change this

Str:= TFileStream.Create('C:\SomePath\SomeFile.html', fmOpenRead);

to this

Str:= TFileStream.Create('C:\SomePath\SomeFile.html', fmOpenRead or fmShareDenyNone);

answered Mar 24 '12 at 17:51

Darian Miller

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Yup, that did it! That goes to point out to never completely trust any sample source code you find on the internet :P – Jerry Dodge Mar 24 '12 at 18:49
I wish the default open+share mode in Delphi was fmOpenRead + fmShareDenyWrite that would solve so many issues that starters have. – Jeroen Wiert Pluimers Mar 24 '12 at 21:34

Delphi HTTP App raising error when loading files into streams

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