A New Home for Kingler
Today, well more like last night, my hermit crab finally changed shells. Its been in the default one I bought it in for about 2 years, which is quite a long time now that I think about it.
I had a picture of it in its old shell but I can't seem to find it.
I'll post some code that I have been doing the past month. I've played around the evil uses for pointers again.
I've also upgraded my XCode to the new version, which caused some problems when moving from Mac OS X 10.5 libraries to Mac OS X 10.6, most of them just being deprecated functions.
Mutable and Volatile Keywords
I've seen mutable used only a few times, and not thought much about it until recently went I was reading about what it does on MSDN. This keyword makes a variable ignore whether a function is const or not within a class.
Below is an example of one way it could be used.
class MyClass
{
//
// Functions
public:
//
MyClass()
:
m_value( 10 ),
m_valueGetCount( 0 )
{
}
//
int GetValue() const
{
// Class variable can be changed despite function being declared const
++m_valueGetCount;
return m_value;
}
//
unsigned int ValueGetCount() const
{
return m_valueGetCount;
}
//
// Attributes
private:
int m_value;
mutable unsigned int m_valueGetCount;
};
My experiences with it have been for thread synchronization objects I use such as my Semaphore class. For some reason the MacOSX implementation of the semaphore doesn't allow me to get the count, so I had to add a variable myself.
The mutable keyword allowed me to keep the class usable within a const scope, which the use of const_cast().
Another keyword I seem to use with threads a lot is volatile. It prevents variable value being cached, forcing it be read from memory every single time it is access.
//
//
namespace
{
volatile bool l_myBoolean = true;
}
//
//
void main()
{
//
createSomeOtherThread();
//
while( l_myBoolean )
{
// do nothing
}
}
//
//
int someOtherThread( void * inParam )
{
l_myBoolean = false;
return 0;
}
In the case of a while loop that relies on a boolean that gets updated in another thread, this has the potentially that the compiler will cache it and thus the loop will never end.