According to code review results, adding new web::json::value constructor overloads with additional has_escaped_chars parameter. New overlods have O(1) performance since they do not try to search for to-be-escaped-characters in provided string.

Author: kolomiets

Release/include/cpprest/json.h

@@ -131,16 +131,56 @@ namespace web { namespace json
         /// Constructor creating a JSON string value
         /// </summary>
         /// <param name="value">The C++ value to create a JSON value from, a C++ STL string of the platform-native character width</param>
-        _ASYNCRTIMP explicit value(utility::string_t);
+        /// <remarks>
+        /// This constructor has O(n) performance because it tries to determine if
+        /// specified string has characters that should be properly escaped in JSON. 
+        /// <remarks>
+        _ASYNCRTIMP explicit value(utility::string_t value);
+
+        /// <summary>
+        /// Constructor creating a JSON string value specifying if the string contains characters to escape
+        /// </summary>
+        /// <param name="value">The C++ value to create a JSON value from, a C++ STL string of the platform-native character width</param>
+        /// <param name="has_escape_chars">Whether <paramref name="value" /> contains characters 
+        /// that should be escaped in JSON value</param>
+        /// <remarks>
+        /// This constructor has O(1) performance.
+        /// </remarks>
+        _ASYNCRTIMP explicit value(utility::string_t value, bool has_escape_chars);
+
+        /// <summary>
+        /// Constructor creating a JSON string value
+        /// </summary>
+        /// <param name="value">The C++ value to create a JSON value from, a C++ STL string of the platform-native character width</param>
+        /// <remarks>
+        /// <para>
+        /// This constructor has O(n) performance because it tries to determine if
+        /// specified string has characters that should be properly escaped in JSON. 
+        /// </para>
+        /// <para>
+        /// This constructor exists in order to avoid string literals matching another constructor,
+        /// as is very likely. For example, conversion to bool does not require a user-defined conversion,
+        /// and will therefore match first, which means that the JSON value turns up as a boolean.
+        /// </para>
+        /// </remarks>
+        _ASYNCRTIMP explicit value(const utility::char_t* value);
 
         /// <summary>
         /// Constructor creating a JSON string value
         /// </summary>
         /// <param name="value">The C++ value to create a JSON value from, a C++ STL string of the platform-native character width</param>
-        /// <remarks>This constructor exists in order to avoid string literals matching another constructor,
+        /// <param name="has_escape_chars">Whether <paramref name="value" /> contains characters 
+        /// <remarks>
+        /// <para>
+        /// This overload has O(1) performance.
+        /// </para>
+        /// <para>
+        /// This constructor exists in order to avoid string literals matching another constructor,
         /// as is very likely. For example, conversion to bool does not require a user-defined conversion,
-        /// and will therefore match first, which means that the JSON value turns up as a boolean.</remarks>
-        _ASYNCRTIMP explicit value(const utility::char_t *);
+        /// and will therefore match first, which means that the JSON value turns up as a boolean.
+        /// </para>
+        /// </remarks>
+        _ASYNCRTIMP explicit value(const utility::char_t* value, bool has_escape_chars);
 
         /// <summary>
         /// Copy constructor

Release/src/json/json.cpp

@@ -105,13 +105,27 @@ web::json::value::value(utility::string_t value) :
 #endif
     { }
 
+web::json::value::value(utility::string_t value, bool has_escape_chars) :
+m_value(utility::details::make_unique<web::json::details::_String>(std::move(value), has_escape_chars))
+#ifdef ENABLE_JSON_VALUE_VISUALIZER
+, m_kind(value::String)
+#endif
+{ }
+
 web::json::value::value(const utility::char_t* value) : 
     m_value(utility::details::make_unique<web::json::details::_String>(utility::string_t(value)))
 #ifdef ENABLE_JSON_VALUE_VISUALIZER
     ,m_kind(value::String)
 #endif
     { }
 
+web::json::value::value(const utility::char_t* value, bool has_escape_chars) :
+m_value(utility::details::make_unique<web::json::details::_String>(utility::string_t(value), has_escape_chars))
+#ifdef ENABLE_JSON_VALUE_VISUALIZER
+, m_kind(value::String)
+#endif
+{ }
+
 web::json::value::value(const value &other) : 
     m_value(other.m_value->_copy_value())
 #ifdef ENABLE_JSON_VALUE_VISUALIZER

Release/tests/Functional/json/construction_tests.cpp

@@ -153,6 +153,10 @@ TEST(constructor_overloads)
     json::value v5(U("Hello Again!"));
     json::value v6(U("YES YOU KNOW IT"));
     json::value v7(U("HERE ID IS"));
+    json::value v8(U("Hello not-escaped!"), true);
+
+    const utility::char_t* p9 = U("Hello not-escaped!");
+    json::value v9(p9, false);
 
     VERIFY_ARE_EQUAL(v0.type(), json::value::Null);
     VERIFY_IS_TRUE(v0.is_null());
@@ -174,6 +178,10 @@ TEST(constructor_overloads)
     VERIFY_IS_TRUE(v6.is_string());
     VERIFY_ARE_EQUAL(v7.type(), json::value::String);
     VERIFY_IS_TRUE(v7.is_string());
+    VERIFY_ARE_EQUAL(v8.type(), json::value::String);
+    VERIFY_IS_TRUE(v8.is_string());
+    VERIFY_ARE_EQUAL(v9.type(), json::value::String);
+    VERIFY_IS_TRUE(v9.is_string());
 }
 
 TEST(factory_overloads)