Forum > Beginners

Record Locking

(1/1)

Andy Anderson:

I've read all the references I
could find but couldn't find an
example to put it all together.

Can someone supply a link to an
example of non OOP record/region
locking?

Thanks in advance.

Andy Anderson:
Well, I guess there is no way in Free Pascal
to lock/unlock records/regions for Windows
OS's.

My workaround will be to use the LOCKFILEEX/UNLOCKFILEEX API's.

Laksen:
It depends on what you need.

If you need to lock a shared variable you can use critical sections, mutexes, semaphores, or events.

Critical sections are probably by far the simplest to understand. You can take a look at the syncobjs unit to see some easy to use object oriented classes for this.

Edit: Ah, if you need non-OOP code you can also take a look at that unit. It uses the standard platform independent interface in the RTL to do the different things.

For example, a critical section:


--- Code: ---var cs: TRTLCriticalSection;

   // Call this to initialize
   InitCriticalSection(cs);

   // And this when you are done with it
   DoneCriticalSection(cs);

   // And to lock some resource
   EnterCriticalSection(cs);
   ... do stuff with whatever needs locking
   LeaveCriticalSection(cs);

--- End code ---

The CS variable would be a single lock that only prevents others from entering the same. So you will want one for each thing that you are locking.

Andy Anderson:
Thanks, Laksen. I'll take a look at the critical sections material. Curiously, the Windows API's I mentioned require a type specification almost identical to the Unix based FLock type for the FpFcntl call.
 

Navigation

[0] Message Index