What sync object should i use?

[Juan Manuel Cabo]

On Monday, 13 May 2013 at 20:44:37 UTC, Heinz wrote:
> Ok, here's a summary in case someone else is in the same need:
>
> 1) Want to know what "mutex/condition" are, how do they work 
> and when to use them? Here's a good resource: 
> http://stackoverflow.com/a/4742236
>
> 2) If you come to the question "Why a condition needs a 
> mutex?": 
> http://stackoverflow.com/questions/2763714/why-do-pthreads-condition-variable-functions-require-a-mutex
>
> 3) Need a working example in D? (by Steven Schveighoffer): 
> http://forum.dlang.org/thread/j7sdte$25qm$1@digitalmars.com


Here is the absolute minimum of code I could think to try 
Condition. I tested it on linux 64bits and windows 32bits. There 
is one thing that should definitely added to the documentation, 
and that is what happens when one issues a notify while the 
thread hasn't yet called Condition.wait().

I seem to recall (though I might be wrong) that win32 events can 
be signalled before the thread calls WaitForSingleObject (or 
WaitForMultipleObjects), and if it was signalled, the call 
returns immediately. I think this was very useful.


import std.stdio, core.thread, core.sync.condition, 
core.sync.mutex;

//Note: The condition must be __gshared:
__gshared Condition condition;
__gshared Mutex mutex;

private void myThread() {
     writeln("Started");
     synchronized(mutex) {
         condition.wait();
     }
     writeln("Notified");
}

void main() {
     mutex = new Mutex();
     condition = new Condition(mutex);

     Thread theThread = new Thread(&myThread);
     theThread.start();

     //Note: if one doesn't wait for the thread to
     //get to condition.wait(), before calling notify(),
     //the thread is not awaken. (ie: commenting the
     //sleep makes the thread stuck).
     Thread.sleep(dur!"msecs"(100));
     synchronized(mutex) {
         condition.notify();
     }

     theThread.join();
     writeln("main finished");
}