Re: code pattern for locking & unlocking
On 25.11.2010 23:48, Daniel Anderson wrote:
Hi!
I often have to acquire locks and release them after I'm finished with
them.
I use constructor/destructor to acquire& release locks. everything
works fine.
sometime I must acquire a lock for few instructions, then release it
in the middle of a big function. I use braces to get timely
destructors, but I find the "middle of nowhere" braces kind of
embarrassing.
something like:
struct Lock
{
Lock(Mutex& mtx) mtx_(mtx) { mtx.lock(); }
~Lock() { mtx_.unlock(); }
operator bool() { return true;}
};
This is incomplete! You should never be able to copy a lock object.
void someFunc()
{
// do some stuff
...
// now time to update share data
{
Lock myLock(data_mutex);
//use locked data
....
} // destructor called
// do more stuff
...
}
So do I. I do not know of another way. Sometime I have considered this:
//...
{ Lock myLock(data_mutex);
// use locked data ...
}
But I don't find it much better. It save a line but potentially confuses pothers.
I would like to have something like the using keyword in c#.
Is there a way to fake it in C++ ?
I do not know of a way - but maybe you can find some code examples for the new C++0x threading features that provide a "better" way.
for now I'm using an if to do it.
void someFunc()
{
// do some stuff
...
// now time to update share data
if (Lock myLock = Lock(data_mutex))
And this will break down if you have a proper lock class that is non-copyable.
It is also confusing, because a lock will always evaluate to true (which is the whole point, I know), so there is no need for an if.
cheers,
Martin
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