From 47067e41b921268ca8e257a0f7a45f45e0778f8e Mon Sep 17 00:00:00 2001
From: Enrico Zamagni <ezamagni@users.noreply.github.com>
Date: Sat, 18 Apr 2020 23:44:35 +0200
Subject: [PATCH] Performance fix for Guid initializers (#552)

* faster implementation of Guid._fromString

* also improved Guid._fromMacString

* faster non-hex char replacement method
---
 lib/src/guid.dart | 49 ++++++++++++++++++-----------------------------
 1 file changed, 19 insertions(+), 30 deletions(-)

diff --git a/lib/src/guid.dart b/lib/src/guid.dart
index 2a1b0457..10fbb350 100644
--- a/lib/src/guid.dart
+++ b/lib/src/guid.dart
@@ -18,55 +18,44 @@ class Guid {
 
   Guid.empty() : this._internal(new List.filled(16, 0));
 
-  static List<int> _fromMacString(input) {
-    var bytes = new List<int>.filled(16, 0);
-
+  static List<int> _fromMacString(String input) {
     if (input == null) {
       throw new ArgumentError("Input was null");
     }
-    input = input.toLowerCase();
 
-    final RegExp regex = new RegExp('[0-9a-f]{2}');
-    Iterable<Match> matches = regex.allMatches(input);
+    input = _removeNonHexCharacters(input);
+    final bytes = hex.decode(input);
 
-    if (matches.length != 6) {
+    if (bytes.length != 6) {
       throw new FormatException("The format is invalid: " + input);
     }
 
-    int i = 0;
-    for (Match match in matches) {
-      var hexString = input.substring(match.start, match.end);
-      bytes[i] = hex.decode(hexString)[0];
-      i++;
-    }
-
-    return bytes;
+    return bytes + List<int>.filled(10, 0);
   }
 
-  static List<int> _fromString(input) {
-    var bytes = new List<int>.filled(16, 0);
+  static List<int> _fromString(String input) {
     if (input == null) {
       throw new ArgumentError("Input was null");
     }
-    if (input.length < 32) {
-      throw new FormatException("The format is invalid");
-    }
-    input = input.toLowerCase();
 
-    final RegExp regex = new RegExp('[0-9a-f]{2}');
-    Iterable<Match> matches = regex.allMatches(input);
-    if (matches.length != 16) {
+    input = _removeNonHexCharacters(input);
+    final bytes = hex.decode(input);
+
+    if (bytes.length != 16) {
       throw new FormatException("The format is invalid");
     }
-    int i = 0;
-    for (Match match in matches) {
-      var hexString = input.substring(match.start, match.end);
-      bytes[i] = hex.decode(hexString)[0];
-      i++;
-    }
+
     return bytes;
   }
 
+  static String _removeNonHexCharacters(String sourceString) {
+    return String.fromCharCodes(sourceString.runes.where((r) =>
+      (r >= 48 && r <= 57) // characters 0 to 9
+      || (r >= 65 && r <= 70)  // characters A to F
+      || (r >= 97 && r <= 102) // characters a to f
+    ));
+  }
+
   static int _calcHashCode(List<int> bytes) {
     const equality = const ListEquality<int>();
     return equality.hash(bytes);