Question

I need to create a patching routine for my application,
it’s really small but I need to update it daily or weekly
how does the xdelta and the others work?
i’ve read around about those but I didn’t understand much of it
the user shouldn’t be prompted at all

Answer 1

Ok this post got flagged on meta for the answers given, so I’m going to weigh in on this.

xdelta is a binary difference program that, rather than providing you with a full image, only gives you what has changed and where. An example of a text diff will have + and – signs before lines of text showing you that these have been added or removed in the new version.

There are two ways to update a binary image: replace it using your own program or replace it using some form of package management. For example, Linux Systems use rpm etc to push out updates to packages. In a windows environment your options are limited by what is installed if you’re not on a corporate network. If you are, try WSUS and MSI packaging. That’ll give you an easier life, or ClickOnce as someone has mentioned.

If you’re not however, you will need to bear in mind the following:

• You need to be an administrator to update anything in certain folders as others have said. I would strongly encourage you to accept this behaviour.
• If the user is an administrator, you can offer to check for updates. Then, you can do one of two things. You can download a whole new version of your application and write it over the image on the hard disk (i.e. the file – remember images are loaded into memory so you can re-write your own program file). You then need to tell the user the update has succeeded and reload the program as the new image will be different.
• Or, you can apply a diff if bandwidth is a concern. Probably not in your case but you will need to know from the client program the two versions to diff between so that the update server gives you the correct patch. Otherwise, the diff might not succeed.

I don’t think for your purposes xdelta is going to give you much gain anyway. Just replace the entire image.

Edit if the user must not be prompted at all, just reload the app. However, I would strongly encourage informing the user you are talking on their network and ask permission to do so / enable a manual update mode, otherwise people like me will block it.