Merge pull request #635 from Dark-Passenger/master

Add move assignment operator for Json::Value class and overload append member function for RValue references

resolves #621

Author: cdunn2001

include/json/value.h

@@ -23,7 +23,7 @@
 #endif
 
 //Conditional NORETURN attribute on the throw functions would:
-// a) suppress false positives from static code analysis 
+// a) suppress false positives from static code analysis
 // b) possibly improve optimization opportunities.
 #if !defined(JSONCPP_NORETURN)
 #  if defined(_MSC_VER)
@@ -64,7 +64,7 @@ class JSON_API Exception : public std::exception {
 /** Exceptions which the user cannot easily avoid.
  *
  * E.g. out-of-memory (when we use malloc), stack-overflow, malicious input
- * 
+ *
  * \remark derived from Json::Exception
  */
 class JSON_API RuntimeError : public Exception {
@@ -75,7 +75,7 @@ class JSON_API RuntimeError : public Exception {
 /** Exceptions thrown by JSON_ASSERT/JSON_FAIL macros.
  *
  * These are precondition-violations (user bugs) and internal errors (our bugs).
- * 
+ *
  * \remark derived from Json::Exception
  */
 class JSON_API LogicError : public Exception {
@@ -233,7 +233,12 @@ class JSON_API Value {
     CZString(CZString&& other);
 #endif
     ~CZString();
-    CZString& operator=(CZString other);
+    CZString& operator=(const CZString& other);
+
+#if JSON_HAS_RVALUE_REFERENCES
+    CZString& operator=(CZString&& other);
+#endif
+
     bool operator<(CZString const& other) const;
     bool operator==(CZString const& other) const;
     ArrayIndex index() const;
@@ -322,12 +327,21 @@ Json::Value obj_value(Json::objectValue); // {}
 
   /// Deep copy, then swap(other).
   /// \note Over-write existing comments. To preserve comments, use #swapPayload().
-  Value& operator=(Value other);
+  Value& operator=(const Value& other);
+#if JSON_HAS_RVALUE_REFERENCES
+  Value& operator=(Value&& other);
+#endif
+
   /// Swap everything.
   void swap(Value& other);
   /// Swap values but leave comments and source offsets in place.
   void swapPayload(Value& other);
 
+  /// copy everything.
+  void copy(const Value& other);
+  /// copy values but leave comments and source offsets in place.
+  void copyPayload(const Value& other);
+
   ValueType type() const;
 
   /// Compare payload only, not comments etc.
@@ -438,6 +452,10 @@ Json::Value obj_value(Json::objectValue); // {}
   /// Equivalent to jsonvalue[jsonvalue.size()] = value;
   Value& append(const Value& value);
 
+#if JSON_HAS_RVALUE_REFERENCES
+  Value& append(Value&& value);
+#endif
+
   /// Access an object value by name, create a null member if it does not exist.
   /// \note Because of our implementation, keys are limited to 2^30 -1 chars.
   ///  Exceeding that will cause an exception.

src/lib_json/json_value.cpp

@@ -292,11 +292,21 @@ void Value::CZString::swap(CZString& other) {
   std::swap(index_, other.index_);
 }
 
-Value::CZString& Value::CZString::operator=(CZString other) {
-  swap(other);
+Value::CZString& Value::CZString::operator=(const CZString& other) {
+  cstr_ = other.cstr_;
+  index_ = other.index_;
   return *this;
 }
 
+#if JSON_HAS_RVALUE_REFERENCES
+Value::CZString& Value::CZString::operator=(CZString&& other) {
+  cstr_ = other.cstr_;
+  index_ = other.index_;
+  other.cstr_ = nullptr;
+  return *this;
+}
+#endif
+
 bool Value::CZString::operator<(const CZString& other) const {
   if (!cstr_) return index_ < other.index_;
   //return strcmp(cstr_, other.cstr_) < 0;
@@ -398,7 +408,7 @@ Value::Value(double value) {
 
 Value::Value(const char* value) {
   initBasic(stringValue, true);
-  JSON_ASSERT_MESSAGE(value != NULL, "Null Value Passed to Value Constructor");	
+  JSON_ASSERT_MESSAGE(value != NULL, "Null Value Passed to Value Constructor");
   value_.string_ = duplicateAndPrefixStringValue(value, static_cast<unsigned>(strlen(value)));
 }
 
@@ -508,10 +518,18 @@ Value::~Value() {
   value_.uint_ = 0;
 }
 
-Value& Value::operator=(Value other) {
+Value& Value::operator=(const Value& other) {
+  swap(const_cast<Value&>(other));
+  return *this;
+}
+
+#if JSON_HAS_RVALUE_REFERENCES
+Value& Value::operator=(Value&& other) {
+  initBasic(nullValue);
   swap(other);
   return *this;
 }
+#endif
 
 void Value::swapPayload(Value& other) {
   ValueType temp = type_;
@@ -523,13 +541,26 @@ void Value::swapPayload(Value& other) {
   other.allocated_ = temp2 & 0x1;
 }
 
+void Value::copyPayload(const Value& other) {
+  type_ = other.type_;
+  value_ = other.value_;
+  allocated_ = other.allocated_;
+}
+
 void Value::swap(Value& other) {
   swapPayload(other);
   std::swap(comments_, other.comments_);
   std::swap(start_, other.start_);
   std::swap(limit_, other.limit_);
 }
 
+void Value::copy(const Value& other) {
+  copyPayload(other);
+  comments_ = other.comments_;
+  start_ = other.start_;
+  limit_ = other.limit_;
+}
+
 ValueType Value::type() const { return type_; }
 
 int Value::compare(const Value& other) const {
@@ -1124,6 +1155,10 @@ Value const& Value::operator[](CppTL::ConstString const& key) const
 
 Value& Value::append(const Value& value) { return (*this)[size()] = value; }
 
+#if JSON_HAS_RVALUE_REFERENCES
+  Value& Value::append(Value&& value) { return (*this)[size()] = value; }
+#endif
+
 Value Value::get(char const* key, char const* cend, Value const& defaultValue) const
 {
   Value const* found = find(key, cend);