Optimize ContainsEscapedWildcards to do the work in one pass

dotnet · Mar 9, 2021 · 5f4f7c2 · 5f4f7c2
1 parent 554de4b
commit 5f4f7c2
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Showing 2 changed files with 26 additions and 19 deletions.
diff --git a/src/Shared/EscapingUtilities.cs b/src/Shared/EscapingUtilities.cs
@@ -226,28 +226,30 @@ string unescapedString
         /// </summary>
         /// <param name="escapedString"></param>
         /// <returns></returns>
-        internal static bool ContainsEscapedWildcards
-            (
-            string escapedString
-            )
+        internal static bool ContainsEscapedWildcards(string escapedString)
         {
-            if (-1 != escapedString.IndexOf('%'))
+            if (escapedString.Length < 3)
             {
-                // It has a '%' sign.  We have promise.
-                if (
-                        (-1 != escapedString.IndexOf("%2", StringComparison.Ordinal)) ||
-                        (-1 != escapedString.IndexOf("%3", StringComparison.Ordinal))
-                    )
+                return false;
+            }
+            // Look for the first %. We know that it has to be followed by at least two more characters so we subtract 2
+            // from the length to search.
+            int index = escapedString.IndexOf('%', 0, escapedString.Length - 2);
+            while (index != -1)
+            {
+                if (escapedString[index + 1] == '2' && (escapedString[index + 2] == 'a' || escapedString[index + 2] == 'A'))
+                {
+                    // %2a or %2A
+                    return true;
+                }
+                if (escapedString[index + 1] == '3' && (escapedString[index + 2] == 'f' || escapedString[index + 2] == 'F'))
                 {
-                    // It has either a '%2' or a '%3'.  This is looking very promising.
-                    return
-
-                            (-1 != escapedString.IndexOf("%2a", StringComparison.Ordinal)) ||
-                            (-1 != escapedString.IndexOf("%2A", StringComparison.Ordinal)) ||
-                            (-1 != escapedString.IndexOf("%3f", StringComparison.Ordinal)) ||
-                            (-1 != escapedString.IndexOf("%3F", StringComparison.Ordinal))
-                        ;
+                    // %3f or %3F
+                    return true;
                 }
+                // Continue searching for % starting at (index + 1). We know that it has to be followed by at least two
+                // more characters so we subtract 2 from the length of the substring to search.
+                index = escapedString.IndexOf('%', index + 1, escapedString.Length - (index + 1) - 2);
             }
             return false;
         }

diff --git a/src/Shared/UnitTests/EscapingUtilities_Tests.cs b/src/Shared/UnitTests/EscapingUtilities_Tests.cs
@@ -75,13 +75,18 @@ public void EscapeUnescape()
         public void ContainsEscapedWildcards()
         {
             Assert.False(EscapingUtilities.ContainsEscapedWildcards("NoStarOrQMark"));
+            Assert.False(EscapingUtilities.ContainsEscapedWildcards("%"));
+            Assert.False(EscapingUtilities.ContainsEscapedWildcards("%%"));
+            Assert.False(EscapingUtilities.ContainsEscapedWildcards("%2"));
             Assert.False(EscapingUtilities.ContainsEscapedWildcards("%4"));
-            Assert.False(EscapingUtilities.ContainsEscapedWildcards("%3B"));
+            Assert.False(EscapingUtilities.ContainsEscapedWildcards("%3A"));
             Assert.False(EscapingUtilities.ContainsEscapedWildcards("%2B"));
             Assert.True(EscapingUtilities.ContainsEscapedWildcards("%2a"));
             Assert.True(EscapingUtilities.ContainsEscapedWildcards("%2A"));
             Assert.True(EscapingUtilities.ContainsEscapedWildcards("%3F"));
             Assert.True(EscapingUtilities.ContainsEscapedWildcards("%3f"));
+            Assert.True(EscapingUtilities.ContainsEscapedWildcards("%%3f"));
+            Assert.True(EscapingUtilities.ContainsEscapedWildcards("%3%3f"));
         }
     }
 }