Added onSize() method to DeferredGet

include/callbacks.h

@@ -24,6 +24,7 @@ using EmptyCallback     =   std::function<void()>;
 using MessageCallback   =   std::function<void(const Message &message, uint64_t deliveryTag, bool redelivered)>;
 using QueueCallback     =   std::function<void(const std::string &name, uint32_t messagecount, uint32_t consumercount)>;
 using DeleteCallback    =   std::function<void(uint32_t deletedmessages)>;
+using SizeCallback      =   std::function<void(uint32_t messagecount)>;
 using ConsumeCallback   =   std::function<void(const std::string &consumer)>;
 using CancelCallback    =   std::function<void(const std::string &consumer)>;
 

include/deferredget.h

@@ -34,6 +34,12 @@ private:
      */
     EmptyCallback _emptyCallback;
     
+    /**
+     *  Callback with the number of messages still in the queue
+     *  @var    SizeCallback
+     */
+    SizeCallback _sizeCallback;
+
     /**
      *  Report success when a message is indeed expected
      *  @param  count           number of messages in the queue
@@ -121,6 +127,19 @@ public:
         // allow chaining
         return *this;
     }
+    
+    /**
+     *  Register a function to be called when size information is known
+     *  @param  callback    the callback to execute
+     */
+    DeferredGet &onSize(const SizeCallback &callback)
+    {
+        // store callback
+        _sizeCallback = callback;
+        
+        // allow chaining
+        return *this;
+    }
 };
     
 /**

src/deferredget.cpp

@@ -29,6 +29,12 @@ Deferred *DeferredGet::reportSuccess(uint32_t messageCount) const
     auto finalizeCallback = _finalizeCallback;
     auto *channel = _channel;
 
+    // install a monitor because the channel could be destructed
+    Monitor monitor(channel);
+
+    // report the size (technically, the channel object could be destructed now, but we ignore that case)
+    if (_sizeCallback) _sizeCallback(messageCount);
+    
     // we now know the name, so we can install the message callback on the channel
     _channel->install("", [channel, messageCallback, finalizeCallback](const Message &message, uint64_t deliveryTag, bool redelivered) {
 
@@ -54,6 +60,9 @@ Deferred *DeferredGet::reportSuccess(uint32_t messageCount) const
  */
 Deferred *DeferredGet::reportSuccess() const
 {
+    // report the size
+    if (_sizeCallback) _sizeCallback(0);
+
     // check if a callback was set
     if (_emptyCallback) _emptyCallback();