Is it possible to modify an already loaded resource?

Question

I'm using the TResourceStream class to read a resource, know I want to modify the resource in memory, but the documentation of the Write method of the above class says:

Applications should not use a TResourceStream to write the resources of the running application. Write overrides the inherited method to raise an EStreamError exception when an application tries to write to the application's resources.

As all other data-writing methods of TResourceStream (WriteBuffer, WriteComponent) call Write to do the actual writing, calling any of the data-writing methods of TResourceStream will raise an exception.

The question is, is there a way to modify a resource in my running application using any WinApi funcion? or are the resources stictly read-only?

Why don't you load the resource into some Delphi component and change the copy inside the component before further processing, sounds much simpler than the deep WinApi magic you'll have to pull off. — Johan, Dec 17 '11 at 13:33

score 8 · Accepted Answer · edited May 23 '17 at 12:20

8

Resources are just pointers to some executable part mapped in memory.

So you may be able to change this memory by using VirtualProtectEx, just as you can patch any part of the code.

See Ok to use VirtualProtect to change resource in Delphi? about this technique (here about resourcestring, but the same API can be used over any locked resource).

edited May 23 '17 at 12:20

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answered Dec 16 '11 at 16:44

Arnaud Bouchez

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Out of interest, do you know what happens if you write to a page that is shared between two processes? Presumably the OS unshares it and there makes a copy. – David Heffernan Dec 16 '11 at 17:38
[That's exactly what happens](http://msdn.microsoft.com/en-us/library/windows/desktop/aa366785.aspx), @David. – Rob Kennedy Dec 16 '11 at 18:08
@RobKennedy, does the OS require PAGE_WRITECOPY flag to do that? – Free Consulting Dec 08 '14 at 05:24
I don't know, @Free. That would seem to make sense, though, wouldn't it? – Rob Kennedy Dec 08 '14 at 06:06

Is it possible to modify an already loaded resource?

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