nuclex-shared-dotnet/Nuclex.Support
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Added double precision overloads for the garbage-free string builder appending methods; the string builder helper methods for floating point values now tell whether they successfully appended a value instead of using an assertion and appending a wrong(!) value; restored full test coverage for the whole assembly

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git-svn-id: file:///srv/devel/repo-conversion/nusu@189 d2e56fa2-650e-0410-a79f-9358c0239efd
This commit is contained in:
Markus Ewald 2010-02-11 21:50:41 +00:00
parent 237fb57fc8
commit 03eb31403d
2 changed files with 201 additions and 22 deletions
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108
Source/StringBuilderHelper.Test.cs
View File

@ -89,6 +89,39 @@ namespace Nuclex.Support {
Assert.AreEqual("-12345", builder.ToString());
}
/// <summary>
/// Verifies that a positive long integer is correctly appended to a string builder
/// </summary>
[Test]
public void TestAppendPositiveLong() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, 12345L);
Assert.AreEqual("12345", builder.ToString());
}
/// <summary>
/// Verifies that a long integer with value 0 is correctly appended to a string builder
/// </summary>
[Test]
public void TestAppendNullLong() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, 0L);
Assert.AreEqual("0", builder.ToString());
}
/// <summary>
/// Verifies that a negative long integer is correctly appended to a string builder
/// </summary>
[Test]
public void TestAppendNegativeLong() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, -12345L);
Assert.AreEqual("-12345", builder.ToString());
}
/// <summary>
/// Verifies that negative floating point values are correctly converted
/// </summary>
@ -133,6 +166,81 @@ namespace Nuclex.Support {
Assert.AreEqual("1000000000.0", builder.ToString());
}
/// <summary>
/// Verifies the behavior of the helper with unsupported floating point values
/// </summary>
[Test]
public void TestAppendOutOfRangeFloat() {
StringBuilder builder = new StringBuilder();
Assert.IsFalse(StringBuilderHelper.Append(builder, float.PositiveInfinity));
Assert.IsFalse(StringBuilderHelper.Append(builder, float.NegativeInfinity));
Assert.IsFalse(StringBuilderHelper.Append(builder, float.NaN));
Assert.IsFalse(StringBuilderHelper.Append(builder, 0.000000059604644775390625f));
}
/// <summary>
/// Verifies that negative double precision floating point values are
/// correctly converted
/// </summary>
[Test]
public void TestAppendNegativeDouble() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, -32.015625);
Assert.AreEqual("-32.015625", builder.ToString());
}
/// <summary>
/// Verifies that positive double precision floating point values are
/// correctly converted
/// </summary>
[Test]
public void TestAppendPositiveDouble() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, 10.0625);
Assert.AreEqual("10.0625", builder.ToString());
}
/// <summary>
/// Verifies that very small double precision floating point values are
/// correctly converted
/// </summary>
[Test]
public void TestAppendSmallDouble() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, 0.00390625);
Assert.AreEqual("0.00390625", builder.ToString());
}
/// <summary>
/// Verifies that very large double precision floating point values are
/// correctly converted
/// </summary>
[Test]
public void TestAppendHugeDouble() {
StringBuilder builder = new StringBuilder();
StringBuilderHelper.Append(builder, 1000000000000000000.0);
Assert.AreEqual("1000000000000000000.0", builder.ToString());
}
/// <summary>
/// Verifies the behavior of the helper with unsupported double precision
/// floating point values
/// </summary>
[Test]
public void TestAppendOutOfRangeDouble() {
StringBuilder builder = new StringBuilder();
Assert.IsFalse(StringBuilderHelper.Append(builder, double.PositiveInfinity));
Assert.IsFalse(StringBuilderHelper.Append(builder, double.NegativeInfinity));
Assert.IsFalse(StringBuilderHelper.Append(builder, double.NaN));
Assert.IsFalse(
StringBuilderHelper.Append(builder, 1.1102230246251565404236316680908e-16)
);
}
/// <summary>
/// Verifies that the contents of a string builder can be cleared
/// </summary>

115
Source/StringBuilderHelper.cs
View File

@ -96,19 +96,24 @@ namespace Nuclex.Support {
/// </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>
public static void Append(StringBuilder builder, float value) {
/// <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) {
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
const int NumericBitCount = 31; // Bits without sign
// You do not modify these as they're calculated based on the
// You don't need modify these as they're calculated based on the
const int FractionalBits = (2 << FractionalBitCount) - 1;
const int HighestFractionalBit = (1 << FractionalBitCount);
const int FractionalBitCountPlusOne = FractionalBitCount + 1;
int intValue = FloatHelper.ReinterpretAsInt(value);
int exponent = ((intValue >> FractionalBitCount) & ExponentBits) - ExponentBias;
int mantissa = (intValue & FractionalBits) | HighestFractionalBit;
@ -116,7 +121,9 @@ namespace Nuclex.Support {
int fractional;
if(exponent >= 0) {
if(exponent >= FractionalBitCount) {
Debug.Assert(exponent < NumericBitCount);
if(exponent >= NumericBitCount) {
return false;
}
integral = mantissa << (exponent - FractionalBitCount);
fractional = 0;
} else {
@ -124,26 +131,13 @@ namespace Nuclex.Support {
fractional = (mantissa << (exponent + 1)) & FractionalBits;
}
} else {
Debug.Assert(exponent >= -FractionalBitCount);
if(exponent < -FractionalBitCount) {
return false;
}
integral = 0;
fractional = (mantissa & FractionalBits) >> -(exponent + 1);
}
/*
if(exponent >= NumericBitCount) {
throw new ArgumentException("Value too large", "value");
} else if(exponent < -FractionalBitCount) {
throw new ArgumentException("Value too small", "value");
} else if(exponent >= FractionalBitCount) {
integral = mantissa << (exponent - FractionalBitCount);
fractional = 0;
} else if(exponent >= 0) {
integral = mantissa >> (FractionalBitCount - exponent);
fractional = (mantissa << (exponent + 1)) & FractionalBits;
} else { // exp2 < 0
integral = 0;
fractional = (mantissa & FractionalBits) >> -(exponent + 1);
}
*/
// Build the integral part
if(intValue < 0) {
builder.Append('-');
@ -167,6 +161,83 @@ namespace Nuclex.Support {
fractional &= FractionalBits;
}
}
return true;
}
/// <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>
/// <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) {
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
const int NumericBitCount = 63; // Bits without sign
// You don't need modify these as they're calculated based on the
const long FractionalBits = (2L << FractionalBitCount) - 1;
const long HighestFractionalBit = (1L << FractionalBitCount);
const int FractionalBitCountPlusOne = FractionalBitCount + 1;
long intValue = FloatHelper.ReinterpretAsLong(value);
long exponent = ((intValue >> FractionalBitCount) & ExponentBits) - ExponentBias;
long mantissa = (intValue & FractionalBits) | HighestFractionalBit;
long integral;
long fractional;
if(exponent >= 0) {
if(exponent >= FractionalBitCount) {
if(exponent >= NumericBitCount) {
return false;
}
integral = mantissa << (int)(exponent - FractionalBitCount);
fractional = 0;
} else {
integral = mantissa >> (int)(FractionalBitCount - exponent);
fractional = (mantissa << (int)(exponent + 1)) & FractionalBits;
}
} else {
if(exponent < -FractionalBitCount) {
return false;
}
integral = 0;
fractional = (mantissa & FractionalBits) >> -(int)(exponent + 1);
}
// Build the integral part
if(intValue < 0) {
builder.Append('-');
}
if(integral == 0) {
builder.Append('0');
} else {
recursiveAppend(builder, integral);
}
builder.Append('.');
// Build the fractional part
if(fractional == 0) {
builder.Append('0');
} else {
while(fractional != 0) {
fractional *= 10;
long digit = (fractional >> FractionalBitCountPlusOne);
builder.Append(numbers[digit]);
fractional &= FractionalBits;
}
}
return true;
}
/// <summary>Recursively appends a number's characters to a string builder</summary>