CSHARP-1972: Optimize BsonUtils.ToHexString and ObjectId.ToString.

Author: rstam

src/MongoDB.Bson/BsonUtils.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2016 MongoDB Inc.
+/* Copyright 2010-2017 MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -26,7 +26,6 @@ namespace MongoDB.Bson
     /// </summary>
     public static class BsonUtils
     {
-
         // public static methods
         /// <summary>
         /// Gets a friendly class name suitable for use in error messages.
@@ -120,6 +119,16 @@ public static DateTime ToDateTimeFromMillisecondsSinceEpoch(long millisecondsSin
             }
         }
 
+        /// <summary>
+        /// Converts a value to a hex character.
+        /// </summary>
+        /// <param name="value">The value (assumed to be between 0 and 15).</param>
+        /// <returns>The hex character.</returns>
+        public static char ToHexChar(int value)
+        {
+            return (char)(value + (value < 10 ? '0' : 'a' - 10));
+        }
+
         /// <summary>
         /// Converts a byte array to a hex string.
         /// </summary>
@@ -131,12 +140,18 @@ public static string ToHexString(byte[] bytes)
             {
                 throw new ArgumentNullException("bytes");
             }
-            var sb = new StringBuilder(bytes.Length * 2);
-            foreach (var b in bytes)
+
+            var length = bytes.Length;
+            var c = new char[length * 2];
+
+            for (int i = 0, j = 0; i < length; i++)
             {
-                sb.AppendFormat("{0:x2}", b);
+                var b = bytes[i];
+                c[j++] = ToHexChar(b >> 4);
+                c[j++] = ToHexChar(b & 0x0f);
             }
-            return sb.ToString();
+
+            return new string(c);
         }
 
         /// <summary>

src/MongoDB.Bson/IO/JsonWriter.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2016 MongoDB Inc.
+/* Copyright 2010-2017 MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -491,18 +491,16 @@ public override void WriteObjectId(ObjectId objectId)
                 ThrowInvalidState("WriteObjectId", BsonWriterState.Value, BsonWriterState.Initial);
             }
 
-            var bytes = objectId.ToByteArray();
-
             WriteNameHelper(Name);
             switch (_jsonWriterSettings.OutputMode)
             {
                 case JsonOutputMode.Strict:
-                    _textWriter.Write("{{ \"$oid\" : \"{0}\" }}", BsonUtils.ToHexString(bytes));
+                    _textWriter.Write("{{ \"$oid\" : \"{0}\" }}", objectId.ToString());
                     break;
 
                 case JsonOutputMode.Shell:
                 default:
-                    _textWriter.Write("ObjectId(\"{0}\")", BsonUtils.ToHexString(bytes));
+                    _textWriter.Write("ObjectId(\"{0}\")", objectId.ToString());
                     break;
             }
 

src/MongoDB.Bson/ObjectModel/ObjectId.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2016 MongoDB Inc.
+/* Copyright 2010-2017 MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -541,7 +541,32 @@ public void ToByteArray(byte[] destination, int offset)
         /// <returns>A string representation of the value.</returns>
         public override string ToString()
         {
-            return BsonUtils.ToHexString(ToByteArray());
+            var c = new char[24];
+            c[0] = BsonUtils.ToHexChar((_a >> 28) & 0x0f);
+            c[1] = BsonUtils.ToHexChar((_a >> 24) & 0x0f);
+            c[2] = BsonUtils.ToHexChar((_a >> 20) & 0x0f);
+            c[3] = BsonUtils.ToHexChar((_a >> 16) & 0x0f);
+            c[4] = BsonUtils.ToHexChar((_a >> 12) & 0x0f);
+            c[5] = BsonUtils.ToHexChar((_a >> 8) & 0x0f);
+            c[6] = BsonUtils.ToHexChar((_a >> 4) & 0x0f);
+            c[7] = BsonUtils.ToHexChar(_a & 0x0f);
+            c[8] = BsonUtils.ToHexChar((_b >> 28) & 0x0f);
+            c[9] = BsonUtils.ToHexChar((_b >> 24) & 0x0f);
+            c[10] = BsonUtils.ToHexChar((_b >> 20) & 0x0f);
+            c[11] = BsonUtils.ToHexChar((_b >> 16) & 0x0f);
+            c[12] = BsonUtils.ToHexChar((_b >> 12) & 0x0f);
+            c[13] = BsonUtils.ToHexChar((_b >> 8) & 0x0f);
+            c[14] = BsonUtils.ToHexChar((_b >> 4) & 0x0f);
+            c[15] = BsonUtils.ToHexChar(_b & 0x0f);
+            c[16] = BsonUtils.ToHexChar((_c >> 28) & 0x0f);
+            c[17] = BsonUtils.ToHexChar((_c >> 24) & 0x0f);
+            c[18] = BsonUtils.ToHexChar((_c >> 20) & 0x0f);
+            c[19] = BsonUtils.ToHexChar((_c >> 16) & 0x0f);
+            c[20] = BsonUtils.ToHexChar((_c >> 12) & 0x0f);
+            c[21] = BsonUtils.ToHexChar((_c >> 8) & 0x0f);
+            c[22] = BsonUtils.ToHexChar((_c >> 4) & 0x0f);
+            c[23] = BsonUtils.ToHexChar(_c & 0x0f);
+            return new string(c);
         }
 
         // explicit IConvertible implementation

src/MongoDB.Bson/Serialization/Serializers/ByteArraySerializer.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2015 MongoDB Inc.
+/* Copyright 2010-2017 MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -124,12 +124,7 @@ protected override void SerializeValue(BsonSerializationContext context, BsonSer
                     break;
 
                 case BsonType.String:
-                    var sb = new StringBuilder(value.Length * 2);
-                    for (int i = 0; i < value.Length; i++)
-                    {
-                        sb.Append(string.Format("{0:x2}", value[i]));
-                    }
-                    bsonWriter.WriteString(sb.ToString());
+                    bsonWriter.WriteString(BsonUtils.ToHexString(value));
                     break;
 
                 default: