Adding enet library for future replacement of tcp

Externals/enet/callbacks.c

@@ -0,0 +1,53 @@
+/** 
+ @file callbacks.c
+ @brief ENet callback functions
+*/
+#define ENET_BUILDING_LIB 1
+#include "enet/enet.h"
+
+static ENetCallbacks callbacks = { malloc, free, abort };
+
+int
+enet_initialize_with_callbacks (ENetVersion version, const ENetCallbacks * inits)
+{
+   if (version < ENET_VERSION_CREATE (1, 3, 0))
+     return -1;
+
+   if (inits -> malloc != NULL || inits -> free != NULL)
+   {
+      if (inits -> malloc == NULL || inits -> free == NULL)
+        return -1;
+
+      callbacks.malloc = inits -> malloc;
+      callbacks.free = inits -> free;
+   }
+      
+   if (inits -> no_memory != NULL)
+     callbacks.no_memory = inits -> no_memory;
+
+   return enet_initialize ();
+}
+
+ENetVersion
+enet_linked_version (void)
+{
+    return ENET_VERSION;
+}
+           
+void *
+enet_malloc (size_t size)
+{
+   void * memory = callbacks.malloc (size);
+
+   if (memory == NULL)
+     callbacks.no_memory ();
+
+   return memory;
+}
+
+void
+enet_free (void * memory)
+{
+   callbacks.free (memory);
+}
+