add adjustment report to overloaded Buffer::AddAtEnd method

src/common/buffer.cc

@@ -434,9 +434,10 @@ Buffer::AddAtEnd (uint32_t end)
   return delta;
 }
 
-void 
+int32_t
 Buffer::AddAtEnd (const Buffer &o)
 {
+  int32_t orgStart = m_start;
   if (m_end == m_zeroAreaEnd &&
       o.m_start == o.m_zeroAreaStart &&
       o.m_zeroAreaEnd - o.m_zeroAreaStart > 0)
@@ -456,7 +457,7 @@ Buffer::AddAtEnd (const Buffer &o)
       Buffer::Iterator src = o.End ();
       src.Prev (endData);
       dst.Write (src, o.End ());
-      return;
+      return m_start - orgStart;
     }
   Buffer dst = CreateFullCopy ();
   Buffer src = o.CreateFullCopy ();
@@ -466,6 +467,7 @@ Buffer::AddAtEnd (const Buffer &o)
   destStart.Prev (src.GetSize ());
   destStart.Write (src.Begin (), src.End ());
   *this = dst;
+  return m_start - orgStart;
 }
 
 void 

src/common/buffer.h

@@ -423,7 +423,20 @@ public:
    */
   int32_t AddAtEnd (uint32_t end);
 
-  void AddAtEnd (const Buffer &o);
+  /**
+   * \param o the buffer to append to the end of this buffer.
+   * \returns the adjustment delta.
+   *
+   * Add bytes at the end of the Buffer.
+   * Any call to this method invalidates any Iterator
+   * pointing to this Buffer.
+   *
+   * The value returned by this method indicates how the internal
+   * buffer was modified to handle the user request to reserve space.
+   * If that value is zero, the buffer was not modified: the user
+   * request was completed without further memory allocation.
+   */
+  int32_t AddAtEnd (const Buffer &o);
   /**
    * \param start size to remove
    *