add a new method to insert a new value in an array at specific index.

include/json/value.h

@@ -463,7 +463,12 @@ Json::Value obj_value(Json::objectValue); // {}
   ///
   /// Equivalent to jsonvalue[jsonvalue.size()] = value;
   Value& append(const Value& value);
+  /// \brief Insert value in array at specific index
+  bool insert(ArrayIndex index, const Value& newValue);
+#if JSON_HAS_RVALUE_REFERENCES
   Value& append(Value&& value);
+  bool insert(ArrayIndex index, const Value&& newValue);
+#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.

src/lib_json/json_value.cpp

@@ -1170,11 +1170,48 @@ Value const& Value::operator[](CppTL::ConstString const& key) const {
 #endif
 
 Value& Value::append(const Value& value) { return (*this)[size()] = value; }
-
-Value& Value::append(Value&& value) {
-  return (*this)[size()] = std::move(value);
+/// \brief Insert value in array at specific index
+bool Value::insert(ArrayIndex index, const Value& newValue) {
+  if(type() != arrayValue) {
+    return false;
+  }
+  if(!isValidIndex(index)) {
+    return false;
+  }
+  ArrayIndex oldsize = size();
+  resize(oldsize+1);
+  ArrayIndex length = size();
+  if(length != oldsize +1) {
+    return false;
+  }
+  for(ArrayIndex i = length ; i> index ; i--) {
+    (*this)[i] = (*this)[i-1];
+  }
+  (*this)[index]= newValue;
+  return true;
 }
-
+#if JSON_HAS_RVALUE_REFERENCES
+Value& Value::append(Value&& value) { return (*this)[size()] = std::move(value); }
+bool Value::insert(ArrayIndex index, const Value&& newValue) {
+  if(type() != arrayValue) {
+    return false;
+  }
+  if(!isValidIndex(index)) {
+    return false;
+  }
+  ArrayIndex oldsize = size();
+  resize(oldsize+1);
+  ArrayIndex length = size();
+  if(length != oldsize +1) {
+    return false;
+  }
+  for(ArrayIndex i = length ; i> index ; i--) {
+    (*this)[i] = (*this)[i-1];
+  }
+  (*this)[index]= std::move(newValue);
+  return true;
+}
+#endif
 Value Value::get(char const* begin,
                  char const* end,
                  Value const& defaultValue) const {

src/test_lib_json/main.cpp

@@ -307,7 +307,21 @@ JSONTEST_FIXTURE(ValueTest, arrayIssue252) {
   }
   // JSONTEST_ASSERT_EQUAL(5, root["array"].size());
 }
+JSONTEST_FIXTURE(ValueTest, arrayIssue691) {
+  Json::Value array2;
+  array2.append(10);  // index 0
+  array2.append(20);  // index 1
+  array2.append(30);  // index 2
+  array2.append(50);  // index 3
 
+  JSONTEST_ASSERT_EQUAL(Json::Value(50),array2[3]);
+
+  array2.insert(3,40); // index 3
+  // After updating, index 3 should be changed from 50 to 40, and 50 moved to 
+  // index 4.
+  JSONTEST_ASSERT_EQUAL(Json::Value(40),array2[3]);
+  JSONTEST_ASSERT_EQUAL(Json::Value(50),array2[4]);    
+}
 JSONTEST_FIXTURE(ValueTest, null) {
   JSONTEST_ASSERT_EQUAL(Json::nullValue, null_.type());
 
@@ -2535,6 +2549,7 @@ int main(int argc, const char* argv[]) {
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, objects);
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, arrays);
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, arrayIssue252);
+  JSONTEST_REGISTER_FIXTURE(runner, ValueTest, arrayIssue691);
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, null);
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, strings);
   JSONTEST_REGISTER_FIXTURE(runner, ValueTest, bools);