PERFORMANCE: ICU4N.Impl.LocaleIDParser: Converted to ref struct using…

… ValueStringBuilder internally to reduce allocations
NightOwl888 · Nov 16, 2023 · d15cd2b · d15cd2b
1 parent 85d95d9
commit d15cd2b
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Showing 14 changed files with 1,534 additions and 553 deletions.
diff --git a/src/ICU4N/Impl/ICULocaleService.cs b/src/ICU4N/Impl/ICULocaleService.cs
@@ -194,7 +194,11 @@ private T[] GetCultures<T>(UCultureTypes types, Func<string, T> factory)
             else
             {
                 List<T> locales = new List<T>(visIDs.Count);
-                var parser = new LocaleIDParser(string.Empty);
+#if FEATURE_SPAN
+                using var parser = new LocaleIDParser(stackalloc char[16], ReadOnlySpan<char>.Empty);
+#else
+                using var parser = new LocaleIDParser(string.Empty);
+#endif
                 foreach (string id in visIDs)
                 {
                     // Filter the culture type before allocating the object

diff --git a/src/ICU4N/Impl/Locale/AsciiUtil.cs b/src/ICU4N/Impl/Locale/AsciiUtil.cs
@@ -1,10 +1,14 @@
-using J2N.Text;
+using ICU4N.Support.Text;
+using J2N.Text;
+using System;
 using System.Text;
 
 namespace ICU4N.Impl.Locale
 {
     public sealed class AsciiUtil
     {
+        private const int CharStackBufferSize = 128;
+
         public static bool CaseIgnoreMatch(string s1, string s2)
         {
             //if (Utility.SameObjects(s1, s2))
@@ -75,7 +79,12 @@ public static string ToLower(string s) // ICU4N specific - renamed from ToLowerS
             {
                 return s;
             }
+#if FEATURE_SPAN
+            ValueStringBuilder buf = s.Length <= CharStackBufferSize ? new ValueStringBuilder(stackalloc char[s.Length]) : new ValueStringBuilder(s.Length);
+            buf.Append(s.AsSpan(0, idx - 0)); // ICU4N: Checked 2nd parameter
+#else
             StringBuilder buf = new StringBuilder(s.Substring(0, idx - 0)); // ICU4N: Checked 2nd parameter
+#endif
             for (; idx < s.Length; idx++)
             {
                 buf.Append(ToLower(s[idx]));
@@ -98,7 +107,12 @@ public static string ToUpper(string s) // ICU4N specific - renamed from ToUpperS
             {
                 return s;
             }
+#if FEATURE_SPAN
+            ValueStringBuilder buf = s.Length <= CharStackBufferSize ? new ValueStringBuilder(stackalloc char[s.Length]) : new ValueStringBuilder(s.Length);
+            buf.Append(s.AsSpan(0, idx - 0)); // ICU4N: Checked 2nd parameter
+#else
             StringBuilder buf = new StringBuilder(s.Substring(0, idx - 0)); // ICU4N: Checked 2nd parameter
+#endif
             for (; idx < s.Length; idx++)
             {
                 buf.Append(ToUpper(s[idx]));
@@ -128,7 +142,12 @@ public static string ToTitle(string s) // ICU4N specific - renamed from ToTitleS
             {
                 return s;
             }
+#if FEATURE_SPAN
+            ValueStringBuilder buf = s.Length <= CharStackBufferSize ? new ValueStringBuilder(stackalloc char[s.Length]) : new ValueStringBuilder(s.Length);
+            buf.Append(s.AsSpan(0, idx - 0)); // ICU4N: Checked 2nd parameter
+#else
             StringBuilder buf = new StringBuilder(s.Substring(0, idx - 0)); // ICU4N: Checked 2nd parameter
+#endif
             if (idx == 0)
             {
                 buf.Append(ToUpper(s[idx]));