add API to get bytes out of a packet without calling PeekData

src/common/packet.cc

@@ -296,6 +296,19 @@ Packet::PeekData (void) const
   return m_buffer.PeekData ();
 }
 
+uint32_t 
+Packet::CopyData (uint8_t *buffer, uint32_t size) const
+{
+  Buffer::Iterator i = m_buffer.Begin ();
+  uint32_t cur = 0;
+  while (!i.IsEnd () && cur < size)
+    {
+      buffer[cur] = i.ReadU8 ();
+      cur++;
+    }
+  return cur;
+}
+
 uint32_t 
 Packet::GetUid (void) const
 {

src/common/packet.h

@@ -280,6 +280,16 @@ public:
    */
   uint8_t const *PeekData (void) const;
 
+  /**
+   * \param buffer a pointer to a byte buffer where the packet data 
+   *        should be copied.
+   * \param size the size of the byte buffer. 
+   * \returns the number of bytes read from the packet
+   *
+   * No more than \b size bytes will be copied by this function.
+   */
+  uint32_t CopyData (uint8_t *buffer, uint32_t size) const;
+
   /**
    * A packet is allocated a new uid when it is created
    * empty or with zero-filled payload.
@@ -437,6 +447,7 @@ std::ostream& operator<< (std::ostream& os, const Packet &packet);
  *   - ns3::Packet::CreateFragment
  *   - ns3::Packet::RemoveAtStart
  *   - ns3::Packet::RemoveAtEnd
+ *   - ns3::Packet::CopyData
  *
  * Dirty operations will always be slower than non-dirty operations,
  * sometimes by several orders of magnitude. However, even the