Hi guys
In my experience i have never written code that controls the allowed amount of running instances of a program.
I suppose we only want to have the game running once at a time, but there is no code yet that makes sure this happens.
Since we're still on the Win(32) platform layer, maybe Mr. Muratori wants to talk about code that blocks additional instances from running?
I for sure would be interested in a professional implementation of such a concept.
Bert
In my experience i have never written code that controls the allowed amount of running instances of a program.
I suppose we only want to have the game running once at a time, but there is no code yet that makes sure this happens.
Since we're still on the Win(32) platform layer, maybe Mr. Muratori wants to talk about code that blocks additional instances from running?
I for sure would be interested in a professional implementation of such a concept.
Bert
Why would you want somebody to prevent running two instances of game simultaneously? Sometimes it actually could be useful, for example, to test some networking functionality.
Anyways, if you really want to disable second instance, you need to know that there is one already running. You need to have something in system that you can check. On Windows it can be one of several things:
1) Named mutex - create it with CreateMutex
2) Named event - use CreateEvent
3) Named pipe - use CreateNamedPipe
4) Memory mapped file - use CreateFileMapping (with handle = -1)
5) ... probably something else that has name
All these methods accept some string as name and can return status if object with such name existed before or not.
If you open pipe you can even communicate between instances you open later and first instance (by passing strings around).
Alternative way would be to enumerate process list with EnumProcesses function and check executable location if it is same as ours. But with this method you must be a bit careful so both processes don't think they are second instance and both think that they need to exit - you could for example make process with lowest process identifier (PID) as "first" process, and don't exit if your process id is less that other process id.
Anyways, if you really want to disable second instance, you need to know that there is one already running. You need to have something in system that you can check. On Windows it can be one of several things:
1) Named mutex - create it with CreateMutex
2) Named event - use CreateEvent
3) Named pipe - use CreateNamedPipe
4) Memory mapped file - use CreateFileMapping (with handle = -1)
5) ... probably something else that has name
All these methods accept some string as name and can return status if object with such name existed before or not.
If you open pipe you can even communicate between instances you open later and first instance (by passing strings around).
Alternative way would be to enumerate process list with EnumProcesses function and check executable location if it is same as ours. But with this method you must be a bit careful so both processes don't think they are second instance and both think that they need to exit - you could for example make process with lowest process identifier (PID) as "first" process, and don't exit if your process id is less that other process id.
Typically what people do is just look for a window of the window class they registered. If they find it, they switch to it and call ExitProcess.
- Casey
- Casey