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digitalmars.D.learn - Is synchronized(mutex) == mutex.lock()?

reply Heywood Floyd <soul8o8 gmail.com> writes:
Hi!

Breakfast toast: Is there any chance a) and b) below are identical in what they
do?


auto mutex = new Mutex();
auto cond = new Condition(mutex);

// a)
synchronized(mutex){
   cond.wait();
}

// b)
mutex.lock();
   cond.wait();
mutex.unlock();


I was sprinkling my code with mutex.lock/unlock (for fun) when suddenly I
realized that, hey, maybe synchronized would work just as well, and be even
more fun? (If that's even possible.)

BR
/HF
Jul 14 2010
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 14 Jul 2010 23:22:20 -0400, Heywood Floyd <soul8o8 gmail.com>  
wrote:


 Hi!

 Breakfast toast: Is there any chance a) and b) below are identical in  
 what they do?


 auto mutex = new Mutex();
 auto cond = new Condition(mutex);

 // a)
 synchronized(mutex){
    cond.wait();
 }

 // b)
 mutex.lock();
    cond.wait();
 mutex.unlock();


Almost, this is more equivalent:

{
   mutex.lock();
   scope(exit) mutex.unlock();
   cond.wait();
}

But yes, the mutex object implements the monitor interface, and replaces  
its own monitor object with a pointer to itself.

For something really nifty, you can tell mutex to be the monitor object of  
*any* other object :)  Unfortunately, I can't point you at the docs, cause  
they dont exist yet, but this will do it:

class C{}

auto c = new C;
auto m = new Mutex(c); // now synchronizing on c is the same as locking m

-Steve
Jul 15 2010
parent Heywood Floyd <soul8o8 gmail.com> writes:
Steven Schveighoffer Wrote:


 On Wed, 14 Jul 2010 23:22:20 -0400, Heywood Floyd <soul8o8 gmail.com>  
 wrote:
 

 Hi!

 Breakfast toast: Is there any chance a) and b) below are identical in  
 what they do?


 auto mutex = new Mutex();
 auto cond = new Condition(mutex);

 // a)
 synchronized(mutex){
    cond.wait();
 }

 // b)
 mutex.lock();
    cond.wait();
 mutex.unlock();


 
 Almost, this is more equivalent:
 
 {
    mutex.lock();
    scope(exit) mutex.unlock();
    cond.wait();
 }
 
 But yes, the mutex object implements the monitor interface, and replaces  
 its own monitor object with a pointer to itself.
 
 For something really nifty, you can tell mutex to be the monitor object of  
 *any* other object :)  Unfortunately, I can't point you at the docs, cause  
 they dont exist yet, but this will do it:
 
 class C{}
 
 auto c = new C;
 auto m = new Mutex(c); // now synchronizing on c is the same as locking m
 
 -Steve


Cool, love it! Thanks!

/HF
Jul 15 2010