Add a Pub source for pub.dartlang.org.

utils/pub/utils.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Generic utility functions. Stuff that should possibly be in core.
  */
 #library('utils');
 
 /** Thrown by methods that parse text when the text isn't a valid. */
 class FormatException implements Exception {
   final String message;
 
   FormatException(this.message);
 
   String toString() => message;
 }
 
+/** A pair of values. */
+class Pair<E, F> {
+  E first;
+  F last;
+
+  Pair(this.first, this.last);
+
+  String toString() => '($first, $last)';
+}
+
 // TODO(rnystrom): Move into String?
 /** Pads [source] to [length] by adding spaces at the end. */
 String padRight(String source, int length) {
   final result = new StringBuffer();
   result.add(source);
 
   while (result.length < length) {
     result.add(' ');
   }
 
@@ skipping 34 matching lines @@
 /**
  * Asserts that [iter] contains only one element, and returns it.
  */
 only(Iterable iter) {
   var iterator = iter.iterator();
   assert(iterator.hasNext());
   var obj = iterator.next();
   assert(!iterator.hasNext());
   return obj;
 }
+
+/**
+ * Replace each instance of [matcher] in [source] with the return value of [fn].
+ */
+String replace(String source, Pattern matcher, String fn(Match)) {
+  var buffer = new StringBuffer();
+  var start = 0;
+  for (var match in matcher.allMatches(source)) {
+    buffer.add(source.substring(start, match.start()));
+    start = match.end();
+    buffer.add(fn(match));
+  }
+  buffer.add(source.substring(start));
+  return buffer.toString();
+}