network: (fixes #372) Remove std::unary_function

Remove `std::unary_function` usage from `Ipv*AddressHash`.
Use std::hash instead of class Hash (in ns-3). This is because
speed is more important than cryptographic robustness.

Signed-off-by: Ameya Deshpande <ameyanrd@outlook.com>

src/network/utils/ipv4-address.cc

@@ -422,7 +422,7 @@ Ipv4Address::GetLoopback (void)
 
 size_t Ipv4AddressHash::operator() (Ipv4Address const &x) const
 { 
-  return x.Get ();
+  return std::hash<uint32_t>()(x.Get ());
 }
 
 std::ostream& operator<< (std::ostream& os, Ipv4Address const& address)

src/network/utils/ipv4-address.h

@@ -435,12 +435,15 @@ inline bool operator < (const Ipv4Address &a, const Ipv4Address &b)
  *
  * \brief Class providing an hash for IPv4 addresses
  */
-class Ipv4AddressHash : public std::unary_function<Ipv4Address, size_t> {
+class Ipv4AddressHash {
 public:
   /**
-   * Returns the hash of the address
+   * \brief Returns the hash of an IPv4 address.
    * \param x the address
    * \return the hash
+   *
+   * This method uses std::hash rather than class Hash
+   * as speed is more important than cryptographic robustness.
    */
   size_t operator() (Ipv4Address const &x) const;
 };

src/network/utils/ipv6-address.h

@@ -697,11 +697,11 @@ inline bool operator != (const Ipv6Prefix& a, const Ipv6Prefix& b)
  * \class Ipv6AddressHash
  * \brief Hash function class for IPv6 addresses.
  */
-class Ipv6AddressHash : public std::unary_function<Ipv6Address, size_t>
+class Ipv6AddressHash
 {
 public:
   /**
-   * \brief Unary operator to hash IPv6 address.
+   * \brief Returns the hash of an IPv6 address.
    * \param x IPv6 address to hash
    * \returns the hash of the address
    */