core: Reuse a global hasher instance

src/core/model/hash.cc

@@ -32,6 +32,13 @@ namespace ns3 {
 
 NS_LOG_COMPONENT_DEFINE ("Hash");
 
+Hasher& GetStaticHash (void)
+{
+  static Hasher g_hasher = Hasher ();
+  g_hasher.clear();
+  return g_hasher;
+}
+
 Hasher::Hasher ()
 {
   m_impl = Create <Hash::Function::Murmur3> ();

src/core/model/hash.h

@@ -271,32 +271,38 @@ Hasher::GetHash64  (const std::string s)
   Global hash functions, inlined for rvo
 */
 
+/**
+  * \brief Get a reference to the static global hasher at g_hasher
+  * \return Reference to the static Hasher instance.
+  */
+Hasher& GetStaticHash (void);
+
 inline
 uint32_t
 Hash32 (const char * buffer, const std::size_t size)
 {
-  return Hasher ().GetHash32 (buffer, size);
+  return GetStaticHash ().GetHash32 (buffer, size);
 }
 
 inline
 uint64_t
 Hash64 (const char * buffer, const std::size_t size)
 {
-  return Hasher ().GetHash64 (buffer, size);
+  return GetStaticHash ().GetHash64 (buffer, size);
 }
 
 inline
 uint32_t
 Hash32 (const std::string s)
 {
-  return Hasher ().GetHash32 (s);
+  return GetStaticHash ().GetHash32 (s);
 }
 
 inline
 uint64_t
 Hash64 (const std::string s)
 {
-  return Hasher ().GetHash64 (s);
+  return GetStaticHash ().GetHash64 (s);
 }