Added overloads for the StringBuilderHelper.Append() method to limit the number of decimal places being displayed; wrote unit tests for the new functionality

git-svn-id: file:///srv/devel/repo-conversion/nusu@190 d2e56fa2-650e-0410-a79f-9358c0239efd

Source/StringBuilderHelper.Test.cs

@@ -166,6 +166,26 @@ namespace Nuclex.Support {
       Assert.AreEqual("1000000000.0", builder.ToString());
     }
 
+    /// <summary>Tests whether the number of decimal places can be restricted</summary>
+    [Test]
+    public void TestAppendFloatLimitDecimalPlaces() {
+      StringBuilder builder = new StringBuilder();
+      StringBuilderHelper.Append(builder, 0.00390625f, 3);
+
+      Assert.AreEqual("0.003", builder.ToString());
+    }
+
+    /// <summary>
+    ///   Verifies that a float with no decimal places is correctly appended
+    /// </summary>
+    [Test]
+    public void TestAppendFloatWithoutDecimalPlaces() {
+      StringBuilder builder = new StringBuilder();
+      StringBuilderHelper.Append(builder, 0.00390625f, 0);
+
+      Assert.AreEqual("0", builder.ToString()); // Note: no rounding!
+    }
+
     /// <summary>
     ///   Verifies the behavior of the helper with unsupported floating point values
     /// </summary>
@@ -226,6 +246,26 @@ namespace Nuclex.Support {
       Assert.AreEqual("1000000000000000000.0", builder.ToString());
     }
 
+    /// <summary>Tests whether the number of decimal places can be restricted</summary>
+    [Test]
+    public void TestAppendDoubleLimitDecimalPlaces() {
+      StringBuilder builder = new StringBuilder();
+      StringBuilderHelper.Append(builder, 0.00390625, 3);
+
+      Assert.AreEqual("0.003", builder.ToString()); // Note: no rounding!
+    }
+
+    /// <summary>
+    ///   Verifies that a double with no decimal places is correctly appended
+    /// </summary>
+    [Test]
+    public void TestAppendDoubleWithoutDecimalPlaces() {
+      StringBuilder builder = new StringBuilder();
+      StringBuilderHelper.Append(builder, 0.00390625, 0);
+
+      Assert.AreEqual("0", builder.ToString());
+    }
+
     /// <summary>
     ///   Verifies the behavior of the helper with unsupported double precision
     ///   floating point values

Source/StringBuilderHelper.cs

@@ -103,6 +103,22 @@ namespace Nuclex.Support {
     ///   is returned and the traditional double.ToString() method can be used.
     /// </remarks>
     public static bool Append(StringBuilder builder, float value) {
+      return Append(builder, value, int.MaxValue);
+    }
+
+    /// <summary>
+    ///   Appends a floating point value to a string builder without generating garbage
+    /// </summary>
+    /// <param name="builder">String builder the value will be appended to</param>
+    /// <param name="value">Value that will be appended to the string builder</param>
+    /// <param name="decimalPlaces">Maximum number of decimal places to display</param>
+    /// <returns>Whether the value was inside the algorithm's supported range</returns>
+    /// <remarks>
+    ///   Uses an algorithm that covers the sane range of possible values but will
+    ///   fail to render extreme values, NaNs and infinity. In these cases, false
+    ///   is returned and the traditional double.ToString() method can be used.
+    /// </remarks>
+    public static bool Append(StringBuilder builder, float value, int decimalPlaces) {
       const int ExponentBits = 0xFF; // Bit mask for the exponent bits
       const int FractionalBitCount = 23; // Number of bits for fractional part
       const int ExponentBias = 127; // Bias subtraced from exponent
@@ -148,6 +164,7 @@ namespace Nuclex.Support {
         recursiveAppend(builder, integral);
       }
 
+      if(decimalPlaces > 0) {
         builder.Append('.');
 
         // Build the fractional part
@@ -159,6 +176,12 @@ namespace Nuclex.Support {
             int digit = (fractional >> FractionalBitCountPlusOne);
             builder.Append(numbers[digit]);
             fractional &= FractionalBits;
+            
+            --decimalPlaces;
+            if(decimalPlaces == 0) {
+              break;
+            }
+          }
         }
       }
 
@@ -178,6 +201,23 @@ namespace Nuclex.Support {
     ///   is returned and the traditional double.ToString() method can be used.
     /// </remarks>
     public static bool Append(StringBuilder builder, double value) {
+      return Append(builder, value, int.MaxValue);
+    }
+
+    /// <summary>
+    ///   Appends a double precision floating point value to a string builder
+    ///   without generating garbage
+    /// </summary>
+    /// <param name="builder">String builder the value will be appended to</param>
+    /// <param name="value">Value that will be appended to the string builder</param>
+    /// <param name="decimalPlaces">Maximum number of decimal places to display</param>
+    /// <returns>Whether the value was inside the algorithm's supported range</returns>
+    /// <remarks>
+    ///   Uses an algorithm that covers the sane range of possible values but will
+    ///   fail to render extreme values, NaNs and infinity. In these cases, false
+    ///   is returned and the traditional double.ToString() method can be used.
+    /// </remarks>
+    public static bool Append(StringBuilder builder, double value, int decimalPlaces) {
       const long ExponentBits = 0x7FF; // Bit mask for the exponent bits
       const int FractionalBitCount = 52; // Number of bits for fractional part
       const int ExponentBias = 1023; // Bias subtraced from exponent
@@ -223,6 +263,7 @@ namespace Nuclex.Support {
         recursiveAppend(builder, integral);
       }
 
+      if(decimalPlaces > 0) {
         builder.Append('.');
 
         // Build the fractional part
@@ -234,6 +275,12 @@ namespace Nuclex.Support {
             long digit = (fractional >> FractionalBitCountPlusOne);
             builder.Append(numbers[digit]);
             fractional &= FractionalBits;
+
+            --decimalPlaces;
+            if(decimalPlaces == 0) {
+              break;
+            }
+          }
         }
       }