add StringBuilder extension methods to allow garbage-free number appends

Blarg.GameFramework/Blarg.GameFramework.csproj

@@ -134,6 +134,7 @@
     <Compile Include="Graphics\BillboardSpriteBatch.cs" />
     <Compile Include="Graphics\Helpers\FlatWireframeGrid.cs" />
     <Compile Include="Support\FreeMovementCamera.cs" />
+    <Compile Include="Support\StringBuilderExtensions.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <ItemGroup>

Blarg.GameFramework/Support/StringBuilderExtensions.cs

@@ -0,0 +1,198 @@
+#region File Description
+//-----------------------------------------------------------------------------
+// StringBuilderExtensions.cs
+//
+// Microsoft XNA Community Game Platform
+// Copyright (C) Microsoft Corporation. All rights reserved.
+//-----------------------------------------------------------------------------
+#endregion
+
+#region Using Statements
+
+using System;
+using System.Globalization;
+using System.Text;
+
+#endregion
+
+namespace Blarg.GameFramework.Support
+{
+	/// <summary>
+	/// Options for StringBuilder extension methods.
+	/// </summary>
+	[Flags]
+	public enum AppendNumberOptions
+	{
+		// Normal format.
+		None = 0,
+
+		// Added "+" sign for positive value.
+		PositiveSign = 1,
+
+		// Insert Number group separation characters.
+		// In Use, added "," for every 3 digits.
+		NumberGroup = 2,
+	}
+
+	/// <summary>
+	/// Static class for string builder extension methods.
+	/// </summary>
+	/// <remarks>
+	/// You can specified StringBuilder for SpriteFont.DrawString from XNA GS 3.0.
+	/// And you can save unwanted memory allocations.
+	/// 
+	/// But there are still problems for adding numerical value to StringBuilder.
+	/// One of them is boxing occurred when you use StringBuilder.AppendFormat method.
+	/// Another issue is memory allocation occurred when you specify int or float for
+	/// StringBuild.Append method.
+	/// 
+	/// This class provides solution for those issue.
+	/// 
+	/// All methods are defined as extension methods as StringBuilder. So, you can use
+	/// those method like below.
+	/// 
+	/// stringBuilder.AppendNumber(12345);
+	/// 
+	/// </remarks>
+	public static class StringBuilderExtensions
+	{
+		#region Fields
+
+		/// <summary>
+		/// Cache for NumberGroupSizes of NumberFormat class.
+		/// </summary>
+		static int[] numberGroupSizes = CultureInfo.CurrentCulture.NumberFormat.NumberGroupSizes;
+
+		/// <summary>
+		/// string conversion buffer.
+		/// </summary>
+		static char[] numberString = new char[32];
+
+		#endregion
+
+		/// <summary>
+		/// Convert integer to string and add to string builder.
+		/// </summary>
+		public static StringBuilder AppendNumber(this StringBuilder builder, int number)
+		{
+			return AppendNumberInternal(builder, number, 0, AppendNumberOptions.None);
+		}
+
+		/// <summary>
+		/// Convert integer to string and add to string builder.
+		/// </summary>
+		/// <param name="number"></param>
+		/// <param name="options">Format options</param>
+		public static StringBuilder AppendNumber(this StringBuilder builder, int number, AppendNumberOptions options)
+		{
+			return AppendNumberInternal(builder, number, 0, options);
+		}
+
+		/// <summary>
+		/// Convert float to string and add to string builder.
+		/// </summary>
+		/// <remarks>It shows 2 decimal digits.</remarks>
+		public static StringBuilder AppendNumber(this StringBuilder builder, float number)
+		{
+			return AppendNumber(builder, number, 2, AppendNumberOptions.None);
+		}
+
+		/// <summary>
+		/// Convert float to string and add to string builder.
+		/// </summary>
+		/// <remarks>It shows 2 decimal digits.</remarks>
+		public static StringBuilder AppendNumber(this StringBuilder builder, float number, AppendNumberOptions options)
+		{
+			return AppendNumber(builder, number, 2, options);
+		}
+
+		/// <summary>
+		/// Convert float to string and add to string builder.
+		/// </summary>
+		public static StringBuilder AppendNumber(this StringBuilder builder, float number, int decimalCount, AppendNumberOptions options = AppendNumberOptions.None)
+		{
+			// Handle NaN, Infinity cases.
+			if (float.IsNaN(number))
+			{
+				return builder.Append("NaN");
+			}
+			else if (float.IsNegativeInfinity(number))
+			{
+				return builder.Append("-Infinity");
+			}
+			else if (float.IsPositiveInfinity(number))
+			{
+				return builder.Append("+Infinity");
+			}
+			else
+			{
+				int intNumber =
+					(int)(number * (float)Math.Pow(10, decimalCount) + 0.5f);
+
+				return AppendNumberInternal(builder, intNumber, decimalCount, options);
+			}
+		}
+
+
+		static StringBuilder AppendNumberInternal(StringBuilder builder, int number, int decimalCount, AppendNumberOptions options)
+		{
+			// Initialize variables for conversion.
+			NumberFormatInfo nfi = CultureInfo.CurrentCulture.NumberFormat;
+
+			int idx = numberString.Length;
+			int decimalPos = idx - decimalCount;
+
+			if (decimalPos == idx)
+				decimalPos = idx + 1;
+
+			int numberGroupIdx = 0;
+			int numberGroupCount = numberGroupSizes[numberGroupIdx] + decimalCount;
+
+			bool showNumberGroup = (options & AppendNumberOptions.NumberGroup) != 0;
+			bool showPositiveSign = (options & AppendNumberOptions.PositiveSign) != 0;
+
+			bool isNegative = number < 0;
+			number = Math.Abs(number);
+
+			// Converting from smallest digit.
+			do
+			{
+				// Add decimal separator ("." in US).
+				if (idx == decimalPos)
+				{
+					numberString[--idx] = nfi.NumberDecimalSeparator[0];
+				}
+
+				// Added number group separator ("," in US).
+				if (--numberGroupCount < 0 && showNumberGroup)
+				{
+					numberString[--idx] = nfi.NumberGroupSeparator[0];
+
+					if (numberGroupIdx < numberGroupSizes.Length - 1)
+						numberGroupIdx++;
+
+					numberGroupCount = numberGroupSizes[numberGroupIdx] - 1;
+				}
+
+				// Convert current digit to character and add to buffer.
+				numberString[--idx] = (char)('0' + (number % 10));
+				number /= 10;
+
+			} while (number > 0 || decimalPos <= idx);
+
+
+			// Added sign character if needed.
+			if (isNegative)
+			{
+				numberString[--idx] = nfi.NegativeSign[0];
+			}
+			else if (showPositiveSign)
+			{
+				numberString[--idx] = nfi.PositiveSign[0];
+			}
+
+			// Added converted string to StringBuilder.
+			return builder.Append(numberString, idx, numberString.Length - idx);
+		}
+	}
+}