From bdfaa27eb6ada91380ac0622ca50bffe71d80d97 Mon Sep 17 00:00:00 2001
From: MihaZupan <mihazupan.zupan1@gmail.com>
Date: Sun, 5 Apr 2020 16:05:37 +0200
Subject: [PATCH] Cache string representations of numbers 0-26

---
 .../ListExtras/ListExtraItemParser.cs          | 10 +++++-----
 src/Markdig/Helpers/CharHelper.cs              | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/Markdig/Extensions/ListExtras/ListExtraItemParser.cs b/src/Markdig/Extensions/ListExtras/ListExtraItemParser.cs
index 4cd8171da..74d308878 100644
--- a/src/Markdig/Extensions/ListExtras/ListExtraItemParser.cs
+++ b/src/Markdig/Extensions/ListExtras/ListExtraItemParser.cs
@@ -45,16 +45,16 @@ public override bool TryParse(BlockProcessor state, char pendingBulletType, out
             if ((isRomanLow || isRomanUp) && (pendingBulletType == '\0' || pendingBulletType == 'i' || pendingBulletType == 'I'))
             {
                 int startChar = state.Start;
-                int endChar = 0;
                 // With a roman, we can have multiple characters
                 // Note that we don't validate roman numbers
-                while (isRomanLow ? CharHelper.IsRomanLetterLowerPartial(c) : CharHelper.IsRomanLetterUpperPartial(c))
+                do
                 {
-                    endChar = state.Start;
                     c = state.NextChar();
                 }
+                while (isRomanLow ? CharHelper.IsRomanLetterLowerPartial(c) : CharHelper.IsRomanLetterUpperPartial(c));
 
-                result.OrderedStart = CharHelper.RomanToArabic(state.Line.Text.AsSpan(startChar, endChar - startChar + 1)).ToString();
+                int orderValue = CharHelper.RomanToArabic(state.Line.Text.AsSpan(startChar, state.Start - startChar));
+                result.OrderedStart = CharHelper.SmallNumberToString(orderValue);
                 result.BulletType = isRomanLow ? 'i' : 'I';
                 result.DefaultOrderedStart = isRomanLow ? "i" : "I";
             }
@@ -62,7 +62,7 @@ public override bool TryParse(BlockProcessor state, char pendingBulletType, out
             {
                 // otherwise we expect a regular alpha lettered list with a single character.
                 var isUpper = c.IsAlphaUpper();
-                result.OrderedStart = (Char.ToUpperInvariant(c) - 64).ToString();
+                result.OrderedStart = CharHelper.SmallNumberToString((c | 0x20) - 'a' + 1);
                 result.BulletType = isUpper ? 'A' : 'a';
                 result.DefaultOrderedStart = isUpper ? "A" : "a";
                 state.NextChar();
diff --git a/src/Markdig/Helpers/CharHelper.cs b/src/Markdig/Helpers/CharHelper.cs
index b10fd21a8..7ea8972cd 100644
--- a/src/Markdig/Helpers/CharHelper.cs
+++ b/src/Markdig/Helpers/CharHelper.cs
@@ -745,6 +745,24 @@ public static bool IsLeftToRight(int c)
                    c == 0x002128 || c == 0x002395 ||
                    c == 0x01D4A2 || c == 0x01D4BB ||
                    c == 0x01D546;
+        }
+
+        // Used by ListExtraItemParser to format numbers from 1 - 26
+        private static readonly string[] smallNumberStringCache = {
+            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
+            "10", "11", "12", "13", "14", "15", "16", "17", "18", "19",
+            "20", "21", "22", "23", "24", "25", "26",
+        };
+
+        internal static string SmallNumberToString(int number)
+        {
+            string[] cache = smallNumberStringCache;
+            if ((uint)number < (uint)cache.Length)
+            {
+                return cache[number];
+            }
+
+            return number.ToString();
         }
     }
 }
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