Mailbox wouldBlock primitive.

Atomic/Mailbox.h

@@ -197,6 +197,8 @@ namespace Alepha::Hydrogen::Atomic  ::detail::  Mailbox_m
 				return std::move( *pos++ );
 			}
 
+			bool pushWouldBlock() const noexcept { return weight > boxLimit; }
+
 			/*!
 			 * @brief      This function will add mail to the mailbox.
 			 *
@@ -210,7 +212,7 @@ namespace Alepha::Hydrogen::Atomic  ::detail::  Mailbox_m
 			void
 			push( Item item )
 			{
-				if( weight > boxLimit )
+				if( pushWouldBlock() )
 				{
 					[[unlikely]];
 					Alepha::unique_lock lock( access );