Scan String before escaping

Author: robb

Sources/Swim/String+XML.swift

@@ -2,14 +2,29 @@ import Foundation
 
 extension String {
     func addingXMLEncoding() -> String {
+        guard unicodeScalars.contains(where: \.needsEscaping) else {
+            return self
+        }
+
         var result = ""
         result.reserveCapacity(count)
-        return unicodeScalars.reduce(into: result, { $0.append($1.named_escapingIfNeeded) })
+        return unicodeScalars.reduce(into: result, { $0.append($1.escapingIfNeeded) })
     }
 }
 
 extension UnicodeScalar {
-    fileprivate var named_escapingIfNeeded: String {
+    fileprivate var needsEscaping: Bool {
+        switch value {
+        case ("&" as Unicode.Scalar).value, ("<" as Unicode.Scalar).value,
+             (">" as Unicode.Scalar).value, ("\'" as Unicode.Scalar).value,
+             ("\"" as Unicode.Scalar).value:
+            return true
+        default:
+            return false
+        }
+    }
+
+    fileprivate var escapingIfNeeded: String {
         switch value {
         case ("&" as Unicode.Scalar).value:
             return "&amp;"