Remove a few char[] allocations from Xml (#82006)

dotnet · Feb 12, 2023 · b53c06b · b53c06b
1 parent 0a51a37
commit b53c06b
Show file tree

Hide file tree

Showing 4 changed files with 9 additions and 33 deletions.
diff --git a/src/libraries/System.Private.Xml/src/System/Xml/BinaryXml/SqlUtils.cs b/src/libraries/System.Private.Xml/src/System/Xml/BinaryXml/SqlUtils.cs
@@ -188,7 +188,7 @@ public override string ToString()
             // Make local copy of data to avoid modifying input.
             uint[] rgulNumeric = new uint[4] { m_data1, m_data2, m_data3, m_data4 };
             int culLen = m_bLen;
-            char[] pszTmp = new char[s_NUMERIC_MAX_PRECISION + 1];   //Local Character buffer to hold
+            Span<char> pszTmp = stackalloc char[s_NUMERIC_MAX_PRECISION + 1];   //Local Character buffer to hold
                                                                      //the decimal digits, from the
                                                                      //lowest significant to highest significant
 
@@ -222,7 +222,7 @@ public override string ToString()
             if (m_bScale > 0)
                 uiResultLen++;
 
-            char[] szResult = new char[uiResultLen];
+            Span<char> szResult = stackalloc char[uiResultLen];
             int iCurChar = 0;
 
             if (!fPositive)
@@ -385,15 +385,15 @@ private static void WriteTimeFullPrecision(StringBuilder sb, int hr, int min, in
                     fractionDigits--;
                     fraction /= 10;
                 }
-                char[] charArray = new char[fractionDigits];
+                Span<char> chars = stackalloc char[fractionDigits];
                 while (fractionDigits > 0)
                 {
                     fractionDigits--;
-                    charArray[fractionDigits] = (char)(fraction % 10 + '0');
+                    chars[fractionDigits] = (char)(fraction % 10 + '0');
                     fraction /= 10;
                 }
                 sb.Append('.');
-                sb.Append(charArray);
+                sb.Append(chars);
             }
         }
 

diff --git a/src/libraries/System.Private.Xml/src/System/Xml/Cache/XPathDocumentNavigator.cs b/src/libraries/System.Private.Xml/src/System/Xml/Cache/XPathDocumentNavigator.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Text;
@@ -894,7 +895,7 @@ internal override string UniqueId
             get
             {
                 // 32-bit integer is split into 5-bit groups, the maximum number of groups is 7
-                char[] buf = new char[1 + 7 + 1 + 7];
+                Span<char> buf = stackalloc char[1 + 7 + 1 + 7];
                 int idx = 0;
                 int loc;
 
@@ -921,7 +922,7 @@ internal override string UniqueId
                     loc >>= 5;
                 } while (loc != 0);
 
-                return new string(buf, 0, idx);
+                return buf.Slice(0, idx).ToString();
             }
         }
 

diff --git a/src/libraries/System.Private.Xml/src/System/Xml/Xsl/Runtime/XslNumber.cs b/src/libraries/System.Private.Xml/src/System/Xml/Xsl/Runtime/XslNumber.cs
@@ -333,7 +333,6 @@ private static string ConvertToDecimal(double val, int minLen, char zero, string
             }
 
             // Add both grouping separators and zero padding to the string representation of a number
-#if true
             unsafe
             {
                 char* result = stackalloc char[newLen];
@@ -364,30 +363,6 @@ private static string ConvertToDecimal(double val, int minLen, char zero, string
                 }
                 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;
-                }
-                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");
-                }
-            }
-            return new string(result, 0, newLen);
-#endif
         }
     }
 }
diff --git a/src/libraries/System.Private.Xml/src/System/Xml/Xsl/Xslt/XsltLoader.cs b/src/libraries/System.Private.Xml/src/System/Xml/Xsl/Xslt/XsltLoader.cs
@@ -953,7 +953,7 @@ private void LoadDecimalFormat(NsDecl? stylesheetNsList)
             }
 
             char[] DefaultValues = DecimalFormatDecl.Default.Characters;
-            char[] characters = new char[NumCharAttrs];
+            Span<char> characters = stackalloc char[NumCharAttrs];
             Debug.Assert(NumCharAttrs == DefaultValues.Length);
 
             for (int idx = 0; idx < NumCharAttrs; idx++)