Merge pull request bitcoin#27 from laanwj/2016_09_const_refs

Return const references from getKeys, getValues, get_str

Author: jgarzik

include/univalue.h

@@ -142,10 +142,10 @@ class UniValue {
 public:
     // Strict type-specific getters, these throw std::runtime_error if the
     // value is of unexpected type
-    std::vector<std::string> getKeys() const;
-    std::vector<UniValue> getValues() const;
+    const std::vector<std::string>& getKeys() const;
+    const std::vector<UniValue>& getValues() const;
     bool get_bool() const;
-    std::string get_str() const;
+    const std::string& get_str() const;
     int get_int() const;
     int64_t get_int64() const;
     double get_real() const;

lib/univalue.cpp

@@ -283,14 +283,14 @@ const UniValue& find_value(const UniValue& obj, const std::string& name)
     return NullUniValue;
 }
 
-std::vector<std::string> UniValue::getKeys() const
+const std::vector<std::string>& UniValue::getKeys() const
 {
     if (typ != VOBJ)
         throw std::runtime_error("JSON value is not an object as expected");
     return keys;
 }
 
-std::vector<UniValue> UniValue::getValues() const
+const std::vector<UniValue>& UniValue::getValues() const
 {
     if (typ != VOBJ && typ != VARR)
         throw std::runtime_error("JSON value is not an object or array as expected");
@@ -304,7 +304,7 @@ bool UniValue::get_bool() const
     return getBool();
 }
 
-std::string UniValue::get_str() const
+const std::string& UniValue::get_str() const
 {
     if (typ != VSTR)
         throw std::runtime_error("JSON value is not a string as expected");