Re: wrapping synchronization in objects?

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 1 Apr 2009 13:09:28 -0700 (PDT)
Message-ID:
<778d1dd9-7f03-4c79-98c2-a17634327196@l13g2000vba.googlegroups.com>
On Apr 1, 5:47 pm, "Gernot Frisch" <m...@privacy.net> wrote:

is it possible (win32, *nix, only) to create a template class
that locks/unlocks a mutex every time the value of an object
is used?

Like:

template <typename T> class wrapper
{
public:
    wrapper() :m_t() {}
    wrapper(const T& t) :m_t(t) {}
    operator T() const
    {
       T t;
       lock();
       t=m_t;
       unlock();
       return t;
    }
    T operator = (const T& t)
    {
       lock();
       m_t = t;
       unlock();
       return t;
    }
private:
    T m_t;
    void lock()const {/*EnterCricitcalSection...whatever*/}
    void unlock()const{/*LeaveCriticalSection...*/}
};

int main()
{
    wrapper<int> i = 13;
 return i;
}


Doubtlessly, but I doubt that it would be very useful.
Individual accesses rarely have the right granularity for
locking. (There are exceptions, of course, but they're rare
enough to probably not justify a generic solution.) Of course,
you'd want a scoped lock in the two functions, in case the
assignment threw an exception.

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