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Rewrite XslNumber.ConvertToDecimal #55868

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huoyaoyuan wants to merge 2 commits into from
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Rewrite XslNumber.ConvertToDecimal #55868

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e56c4dd
Rewrite ConvertToDecimal
huoyaoyuan Jun 12, 2021
bd9dca2
Merge branch 'main' into xslnumber-convertdecimal
huoyaoyuan Sep 23, 2021
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109 changes: 39 additions & 70 deletions src/libraries/System.Private.Xml/src/System/Xml/Xsl/Runtime/XslNumber.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Text;
using System.Xml.XPath;

Expand Down Expand Up @@ -306,89 +307,57 @@ private void FormatItem(StringBuilder sb, XPathItem item, char startChar, int le

private static string ConvertToDecimal(double val, int minLen, char zero, string groupSeparator, int groupSize)
{
Debug.Assert(val >= 0 && val == Math.Round(val), "ConvertToArabic operates on non-negative integer numbers only");
string str = XPathConvert.DoubleToString(val);
int shift = zero - '0';
Debug.Assert(val >= 0 && val == Math.Round(val), "ConvertToDecimal operates on non-negative integer numbers only");

// Figure out new string length without separators
int oldLen = str.Length;
int newLen = Math.Max(oldLen, minLen);

// Calculate length of string with separators
if (groupSize != 0)
// Costful for non-default numbers.
string[] nativeDigits = null;
if (zero != '0')
{
Debug.Assert(groupSeparator.Length == 1);
checked { newLen += (newLen - 1) / groupSize; }
nativeDigits = new string[10];
for (int i = 0; i < 10; i++)
nativeDigits[i] = ((char)(zero + i)).ToString();
}

// If the new number of characters equals the old one, no changes need to be made
if (newLen == oldLen && shift == 0)
if (groupSize == 0)
{
NumberFormatInfo info = nativeDigits == null
? NumberFormatInfo.InvariantInfo
: new NumberFormatInfo
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@jkotas jkotas Oct 25, 2021

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How does the performance of this rewrite compares to the existing implementation?

The existing implementation does not allocate NumberFormatInfo. Is allocating of NumberFormatInfo going to regress performance?

{
NativeDigits = nativeDigits
};
string str = val.ToString("F0", info);
if (str.Length < minLen)
{
str = str.PadLeft(minLen, zero);
}
return str;
}

// If grouping is not needed, add zero padding only
if (groupSize == 0 && shift == 0)
{
return str.PadLeft(newLen, zero);
}

// Add both grouping separators and zero padding to the string representation of a number
#if true
unsafe
else
{
char* result = stackalloc char[newLen];
char separator = (groupSeparator.Length > 0) ? groupSeparator[0] : ' ';

fixed (char* pin = str)
NumberFormatInfo info = NumberFormatInfo.InvariantInfo;
if (groupSeparator != "," || groupSize != 3 || nativeDigits != null)
{
char* pOldEnd = pin + oldLen - 1;
char* pNewEnd = result + newLen - 1;
int cnt = groupSize;

while (true)
info = new NumberFormatInfo
{
// Move digit to its new location (zero if we've run out of digits)
*pNewEnd-- = (pOldEnd >= pin) ? (char)(*pOldEnd-- + shift) : zero;
if (pNewEnd < result)
{
break;
}
if (/*groupSize > 0 && */--cnt == 0)
{
// Every groupSize digits insert the separator
*pNewEnd-- = separator;
cnt = groupSize;
Debug.Assert(pNewEnd >= result, "Separator cannot be the first character");
}
}
}
return new string(result, 0, newLen);
}
#else
// Safe version is about 20% slower after NGEN
char[] result = new char[newLen];
char separator = (groupSeparator.Length > 0) ? groupSeparator[0] : ' ';

int oldEnd = oldLen - 1;
int newEnd = newLen - 1;
int cnt = groupSize;

while (true) {
// Move digit to its new location (zero if we've run out of digits)
result[newEnd--] = (oldEnd >= 0) ? (char)(str[oldEnd--] + shift) : zero;
if (newEnd < 0) {
break;
NumberGroupSeparator = groupSeparator,
NumberGroupSizes = new[] { groupSize },
NativeDigits = nativeDigits ?? NumberFormatInfo.InvariantInfo.NativeDigits
};
}
if (/*groupSize > 0 && */--cnt == 0) {
// Every groupSize digits insert the separator
result[newEnd--] = separator;
cnt = groupSize;
Debug.Assert(newEnd >= 0, "Separator cannot be the first character");

string format = "N0";
if (minLen > 1 && val < Math.Pow(10, minLen - 1))
{
format = string.Create(minLen + 1, (object)null, (span, _) =>
{
span.Fill('0');
span[^2] = ',';
});
}

return val.ToString(format, info);
}
return new string(result, 0, newLen);
#endif
}
}
}