-Improve performance and memory usage when serializing Unicode characters

Src/Newtonsoft.Json.Tests/PerformanceTests.cs

@@ -94,6 +94,7 @@ namespace Newtonsoft.Json.Tests
       JsonNetWithIsoConverter,
       JsonNetBinary,
       JsonNetLinq,
+      JsonNetManual,
       BinaryFormatter,
       JavaScriptSerializer,
       DataContractSerializer,
@@ -132,6 +133,7 @@ namespace Newtonsoft.Json.Tests
       BenchmarkSerializeMethod(SerializeMethod.DataContractJsonSerializer, value);
       BenchmarkSerializeMethod(SerializeMethod.JsonNet, value);
       BenchmarkSerializeMethod(SerializeMethod.JsonNetLinq, value);
+      BenchmarkSerializeMethod(SerializeMethod.JsonNetManual, value);
       BenchmarkSerializeMethod(SerializeMethod.JsonNetWithIsoConverter, value);
       BenchmarkSerializeMethod(SerializeMethod.JsonNetBinary, value);
     }
@@ -513,6 +515,69 @@ namespace Newtonsoft.Json.Tests
             }
             break;
           }
+        case SerializeMethod.JsonNetManual:
+          {
+            TestClass c = value as TestClass;
+            if (c != null)
+            {
+              StringWriter sw = new StringWriter();
+              JsonTextWriter writer = new JsonTextWriter(sw);
+              writer.WriteStartObject();
+              writer.WritePropertyName("strings");
+              writer.WriteStartArray();
+              foreach (string s in c.strings)
+              {
+                writer.WriteValue(s);
+              }
+              writer.WriteEndArray();
+              writer.WritePropertyName("dictionary");
+              writer.WriteStartObject();
+              foreach (KeyValuePair<string, int> keyValuePair in c.dictionary)
+              {
+                writer.WritePropertyName(keyValuePair.Key);
+                writer.WriteValue(keyValuePair.Value);
+              }
+              writer.WriteEndObject();
+              writer.WritePropertyName("Name");
+              writer.WriteValue(c.Name);
+              writer.WritePropertyName("Now");
+              writer.WriteValue(c.Now);
+              writer.WritePropertyName("BigNumber");
+              writer.WriteValue(c.BigNumber);
+              writer.WritePropertyName("Address1");
+              writer.WriteStartObject();
+              writer.WritePropertyName("Street");
+              writer.WriteValue(c.BigNumber);
+              writer.WritePropertyName("Street");
+              writer.WriteValue(c.BigNumber);
+              writer.WritePropertyName("Street");
+              writer.WriteValue(c.BigNumber);
+              writer.WriteEndObject();
+              writer.WritePropertyName("Addresses");
+              writer.WriteStartArray();
+              foreach (Address address in c.Addresses)
+              {
+                writer.WriteStartObject();
+                writer.WritePropertyName("Street");
+                writer.WriteValue(address.Street);
+                writer.WritePropertyName("Phone");
+                writer.WriteValue(address.Phone);
+                writer.WritePropertyName("Entered");
+                writer.WriteValue(address.Entered);
+                writer.WriteEndObject();
+              }
+              writer.WriteEndArray();
+              writer.WriteEndObject();
+
+              writer.Flush();
+              json = sw.ToString();
+            }
+            else
+            {
+              json = string.Empty;
+            }
+            break;
+          }
         case SerializeMethod.JsonNetBinary:
           {
             MemoryStream ms = new MemoryStream(Buffer);
@@ -695,6 +760,14 @@ namespace Newtonsoft.Json.Tests
       BenchmarkSerializeMethod(SerializeMethod.JsonNetBinary, rootValue);
     }
 
+    [Test]
+    public void SerializeUnicodeChars()
+    {
+      string s = (new string('\0', 30));
+
+      BenchmarkSerializeMethod(SerializeMethod.JsonNet, s);
+    }
+
     [Test]
     public void JObjectToString()
     {

Src/Newtonsoft.Json/Utilities/JavaScriptUtils.cs

@@ -35,6 +35,8 @@ namespace Newtonsoft.Json.Utilities
 {
   internal static class JavaScriptUtils
   {
+    private const string EscapedUnicodeText = "!";
+
     public static void WriteEscapedJavaScriptString(TextWriter writer, string s, char delimiter, bool appendDelimiters)
     {
       // leading delimiter
@@ -44,6 +46,7 @@ namespace Newtonsoft.Json.Utilities
       if (s != null)
       {
         char[] chars = null;
+        char[] unicodeBuffer = null;
         int lastWritePosition = 0;
 
         for (int i = 0; i < s.Length; i++)
@@ -94,7 +97,20 @@ namespace Newtonsoft.Json.Utilities
               escapedValue = "\\\"";
               break;
             default:
-              escapedValue = (c <= '\u001f') ? StringUtils.ToCharAsUnicode(c) : null;
+              if (c <= '\u001f')
+              {
+                if (unicodeBuffer == null)
+                  unicodeBuffer = new char[6];
+
+                StringUtils.ToCharAsUnicode(c, unicodeBuffer);
+
+                // slightly hacky but it saves multiple conditions in if test
+                escapedValue = EscapedUnicodeText;
+              }
+              else
+              {
+                escapedValue = null;
+              }
               break;
           }
 
@@ -111,7 +127,10 @@ namespace Newtonsoft.Json.Utilities
           }
 
           lastWritePosition = i + 1;
-          writer.Write(escapedValue);
+          if (!string.Equals(escapedValue, EscapedUnicodeText))
+            writer.Write(escapedValue);
+          else
+            writer.Write(unicodeBuffer);
         }
 
         if (lastWritePosition == 0)

Src/Newtonsoft.Json/Utilities/MathUtils.cs

@@ -45,9 +45,8 @@ namespace Newtonsoft.Json.Utilities
     public static char IntToHex(int n)
     {
       if (n <= 9)
-      {
         return (char)(n + 48);
-      }
+
       return (char)((n - 10) + 97);
     }
 

Src/Newtonsoft.Json/Utilities/StringUtils.cs

@@ -117,14 +117,14 @@ namespace Newtonsoft.Json.Utilities
         return value.Length;
     }
 
-    public static string ToCharAsUnicode(char c)
+    public static void ToCharAsUnicode(char c, char[] buffer)
     {
-      char h1 = MathUtils.IntToHex((c >> 12) & '\x000f');
-      char h2 = MathUtils.IntToHex((c >> 8) & '\x000f');
-      char h3 = MathUtils.IntToHex((c >> 4) & '\x000f');
-      char h4 = MathUtils.IntToHex(c & '\x000f');
-
-      return new string(new[] { '\\', 'u', h1, h2, h3, h4 });
+      buffer[0] = '\\';
+      buffer[1] = 'u';
+      buffer[2] = MathUtils.IntToHex((c >> 12) & '\x000f');
+      buffer[3] = MathUtils.IntToHex((c >> 8) & '\x000f');
+      buffer[4] = MathUtils.IntToHex((c >> 4) & '\x000f');
+      buffer[5] = MathUtils.IntToHex(c & '\x000f');
     }
 
     public static TSource ForgivingCaseSensitiveFind<TSource>(this IEnumerable<TSource> source, Func<TSource, string> valueSelector, string testValue)