 Hey everybody, this is Brian and welcome to the 70 second Qt tutorial with C++ and GUI programming This is going to be another user feedback. I get to ask the question, Brian How do you compile and use a third-party DLL? So we're going to do this and maybe Split it into two parts depending on how big this gets. This is a fairly advanced topic So well, we'll see. All right first thing you need to do is go to the Qt website and go to downloads And you're going to want to download The Qt creator source That's right the actual source code for Qt creator this IDE that we've been working with all this time And the reason why you're going to do that is because it uses a library called botan or botan I think it's called botan. Anyways very very powerful library and what this library does is it allows for Another user feedback, which I wanted to cover encryption Brian. How do you encrypt a file? Well, we're going to cover that too So rather than have you go out and look for these arcane libraries We're going to use something that you already have the source code and the project file and everything set up matter of fact After you've downloaded these and let's say you've downloaded the Qt creator source code You can just go into the source slash lib slash third-party slash botan and open botan dot pro And you have the actual source code for botan set up and ready to go All you have to do is compile it Now after you've compiled it you are going to have a few libraries and You notice how it's, you know, Libs third-party botan build desktop lib slash Qt creator You're gonna have botan DLL bot and D dot DLL bot and a bot and a what are these? well These a files right here are just basically files that the linker can attach to So that it knows you have this specific DLL you want to bind to and the DLL on files are dynamic link libraries That's how you distribute code so someone else can use it Now botan comes with DLLs, but they're compiled with Microsoft Visual Studio And if you remember from any of our previous videos anything you compile in Qt creator uses the main W compiler So you have to recompile this library for these tutorials to work Otherwise you're going to get all sorts of unresolved reference errors So go ahead download the source Open up botan dot pro and just hit build once you're done You'll be able to find these DLLs under Third-party and then whatever your build directory was mine is botan build desktop source slash lib slash Qt creator and then actually go out and download the botan source and Then you should actually Hmm I'm not used to IE 8 here. I'm going to actually walk you through installing the botan Botan DLLs you just hit next you're gonna want to put these somewhere where you're going to be able to find them Because you're gonna have to link to these So I just do C drive button. You can put them wherever you want Make sure you include the import library include files and development documentation Next next install fairly straightforward fairly easy process And then go back to these DLLs that you made And then we're just going to go Into the botan directory where we just installed I put it C drive button You know so it's our there's already a DLL and there's a lib file those are generated by visual studio, which we're not using We're just going to right-click and paste and then we're going to copy and replace those files That way we now have our working files that are compiled with the main W compiler Like I said if you skip that step you're going to have nothing but problems You're going to get unresolved reference errors and just all sorts of little gremlins in your code You're not going to be able to figure out what in the world is going on here Now I'm not going to lie to you botan is in Extremely complex library. It has a very good reference manual And you should actually go through this and read this and it'll talk very in-depth Hopefully on how to do certain things with this library So that is a little bit of homework you're going to have to do before we step into the next tutorial That being said This is an extremely easy library to work with and we're going to show that in our next tutorial I'm going to chunk these up into two parts simply because there is a bit of Preliminary overhead you're going to have to understand in order to work with encryption encryption is a science in itself And you have to know the difference between like a block cipher and a stream cipher We're going to cover those things in a very briefly very simply All right. Well, that's Pretty much all for this tutorial. I'm going to call this one part one of two how to compile the botan library And the next one we are going to actually use the botan library So thank you for watching. This is Brian. I hope you found this educational and entertaining