[2491] Added function to get a single option definition using a code.

src/lib/dhcp/libdhcp++.cc

@@ -45,7 +45,7 @@ OptionDefContainer LibDHCP::v4option_defs_;
 OptionDefContainer LibDHCP::v6option_defs_;
 
 const OptionDefContainer&
-LibDHCP::getOptionDefs(Option::Universe u) {
+LibDHCP::getOptionDefs(const Option::Universe u) {
     switch (u) {
     case Option::V4:
         initStdOptionDefs4();
@@ -60,6 +60,17 @@ LibDHCP::getOptionDefs(Option::Universe u) {
     }
 }
 
+OptionDefinitionPtr
+LibDHCP::getOptionDef(const Option::Universe u, const uint16_t code) {
+    const OptionDefContainer& defs = getOptionDefs(u);
+    const OptionDefContainerTypeIndex& idx = defs.get<1>();
+    const OptionDefContainerTypeRange& range = idx.equal_range(code);
+    if (range.first != range.second) {
+        return (*range.first);
+    }
+    return (OptionDefinitionPtr());
+}
+
 OptionPtr
 LibDHCP::optionFactory(Option::Universe u,
                        uint16_t type,

src/lib/dhcp/libdhcp++.h

@@ -42,7 +42,18 @@ public:
     /// @param u universe of the options (V4 or V6).
     ///
     /// @return collection of option definitions.
-    static const OptionDefContainer& getOptionDefs(Option::Universe u);
+    static const OptionDefContainer& getOptionDefs(const Option::Universe u);
+
+    /// @brief Return the first option definition matching a
+    /// particular option code.
+    ///
+    /// @param u universe (V4 or V6)
+    /// @param code option code.
+    ///
+    /// @return reference to an option definition being requested
+    /// or NULL pointer if option definition has not been found.
+    static OptionDefinitionPtr getOptionDef(const Option::Universe u,
+                                            const uint16_t code);
 
     /// @brief Factory function to create instance of option.
     ///