Re: Thread safe 'global' variable
I'd suggest you get rid of the global concept altogether. You
have a class - you can tell it what its callback is. While you
are at it - get rid of the callback function as well. In C++
you have pure virtual methods for that purpose:
struct IMyCallback {
void callback(params) = 0;
};
Derive from this C++ interface class to provide the handler,
then pass an IMyCallback* pointer into your engine class for
it to use when delivering callbacks.
More sophisticated code might use Boost smart pointers to
manage the lifetime of the callback object as well. Check out
boost::shared_ptr<>.
--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://vcfaq.mvps.org
=====================================
"Bart Simpson" <123evergreen@terrace.com> wrote in message
news:j-2dnUnrPq6-FqTbnZ2dnUVZ8tOmnZ2d@bt.com...
Bart Simpson wrote:
I am writing a class which is an analytic engine that traverses a MxN
matrix space and makes calculations at each point in the matrix. The
calculations involve calling "exposed" functions via callbacks.
In a nutshell, I need to be able to pass the current position in the grid
to the callback function, so I have somehing like this:
//'global' vars
namespace
{
Point mypoint ;
}
class MyEngine
{
public:
void WriteCurrentPointValue();
//...
};
//"registered" functions
int foo()
{
Point point = ReadCurrentPointValue();
return DoSomething(point);
}
However, this soln is not thread safe in that if I have multiple
instances of the engine running in different threads, all bets are off.
My question is this:
How can I provide threadsafe 'global' variable for use as discussed
above?
Further clarification/correction - what I need is actually, a thread-local
'global' variable. The architecture of the program means that thread
safety is not an issue here ... (once I have thread-local global variables
sorted out)