base库中的BarrierClosure

说明说得很明白，就是等侍num_closures 为零的时候回调done_closure,代码也很简单，不加详述

#ifndef BASE_BARRIER_CLOSURE_H_

#define BASE_BARRIER_CLOSURE_H_

 

#include "base/base_export.h"

#include "base/callback_forward.h"

 

namespace base {

 

// BarrierClosure executes |done_closure| after it has been invoked

// |num_closures| times.

//

// If |num_closures| is 0, |done_closure| is executed immediately.

//

// BarrierClosure is thread-safe - the count of remaining closures is

// maintained as a base::AtomicRefCount. |done_closure| will be run on

// the thread that calls the final Run() on the returned closures.

//

// |done_closure| is also Reset() on the final calling thread but due to the

// refcounted nature of callbacks, it is hard to know what thread resources

// will be released on.

BASE_EXPORT base::Closure BarrierClosure(int num_closures,

const base::Closure& done_closure);

 

} // namespace base

 

#endif // BASE_BARRIER_CLOSURE_H_