[libzmq] const string p -> const string& p (#860)

src/mechanism.cpp

@@ -133,7 +133,7 @@ int zmq::mechanism_t::parse_metadata (const unsigned char *ptr_,
     return 0;
 }
 
-int zmq::mechanism_t::property (const std::string /* name_ */,
+int zmq::mechanism_t::property (const std::string& /* name_ */,
                                 const void * /* value_ */, size_t /* length_ */)
 {
     //  Default implementation does not check
@@ -141,7 +141,7 @@ int zmq::mechanism_t::property (const std::string /* name_ */,
     return 0;
 }
 
-bool zmq::mechanism_t::check_socket_type (const std::string type_) const
+bool zmq::mechanism_t::check_socket_type (const std::string& type_) const
 {
     switch (options.type) {
         case ZMQ_REQ:

src/mechanism.hpp

@@ -86,7 +86,7 @@ namespace zmq
         //  parsing remaining data.
         //  Derived classes are supposed to override this
         //  method to handle custom processing.
-        virtual int property (const std::string name_,
+        virtual int property (const std::string& name_,
                               const void *value_, size_t length_);
 
         options_t options;
@@ -99,7 +99,7 @@ namespace zmq
 
         //  Returns true iff socket associated with the mechanism
         //  is compatible with a given socket type 'type_'.
-        bool check_socket_type (const std::string type_) const;
+        bool check_socket_type (const std::string& type_) const;
     };
 
 }