Add measurements and send-metrics to dart2js's info.

lib/src/string_edit_buffer.dart

+// Copyright (c) 2015, 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.
+
+/// Defines [StringEditBuffer], a buffer that can be used to apply edits on a
+/// string.
+// TODO(sigmund): this should move to a separate package.
+library dart2js.src.string_edit_buffer;
+
+/// A buffer meant to apply edits on a string (rather than building a string
+/// from scratch). Each change is described using the location information on
+/// the original string. Internally this buffer keeps track of how a
+/// modification in one portion can offset a modification further down the
+/// string.
+class StringEditBuffer {
+  final String original;
+  final _edits = <_StringEdit>[];
+
+  StringEditBuffer(this.original);
+
+  bool get hasEdits => _edits.length > 0;
+
+  /// Edit the original text, replacing text on the range [begin] and
+  /// exclusive [end] with the [replacement] string.
+  void replace(int begin, int end, String replacement, [int sortId]) {
+    _edits.add(new _StringEdit(begin, end, replacement, sortId));
+  }
+
+  /// Insert [string] at [offset].
+  /// Equivalent to `replace(offset, offset, string)`.
+  void insert(int offset, String string, [sortId]) =>
+      replace(offset, offset, string, sortId);
+
+  /// Remove text from the range [begin] to exclusive [end].
+  /// Equivalent to `replace(begin, end, '')`.
+  void remove(int begin, int end) => replace(begin, end, '');
+
+  /// Applies all pending [edit]s and returns a new string.
+  ///
+  /// This method is non-destructive: it does not discard existing edits or
+  /// change the [original] string. Further edits can be added and this method
+  /// can be called again.
+  ///
+  /// Throws [UnsupportedError] if the edits were overlapping. If no edits were
+  /// made, the original string will be returned.
+  String toString() {
+    var sb = new StringBuffer();
+    if (_edits.length == 0) return original;
+
+    // Sort edits by start location.
+    _edits.sort();
+
+    int consumed = 0;
+    for (var edit in _edits) {
+      if (consumed > edit.begin) {
+        sb = new StringBuffer();
+        sb.write('overlapping edits. Insert at offset ');
+        sb.write(edit.begin);
+        sb.write(' but have consumed ');
+        sb.write(consumed);
+        sb.write(' input characters. List of edits:');
+        for (var e in _edits) {
+          sb.write('\n    ');
+          sb.write(e);
+        }
+        throw new UnsupportedError(sb.toString());
+      }
+
+      // Add characters from the original string between this edit and the last
+      // one, if any.
+      var betweenEdits = original.substring(consumed, edit.begin);
+      sb.write(betweenEdits);
+      sb.write(edit.string);
+      consumed = edit.end;
+    }
+
+    // Add any text from the end of the original string that was not replaced.
+    sb.write(original.substring(consumed));
+    return sb.toString();
+  }
+}
+
+/// A single edit in a [StringEditBuffer].
+class _StringEdit implements Comparable<_StringEdit> {
+  // Offset where edit begins
+  final int begin;
+
+  // Offset where edit ends
+  final int end;
+
+  // Sort index as a tie-breaker for edits that have the same location.
+  final int sortId;
+
+  // String to insert
+  final String string;
+
+  _StringEdit(int begin, this.end, this.string, [int sortId])
+      : begin = begin,
+        sortId = sortId == null ? begin : sortId;
+
+  int get length => end - begin;
+
+  String toString() => '(Edit @ $begin,$end: "$string")';
+
+  int compareTo(_StringEdit other) {
+    int diff = begin - other.begin;
+    if (diff != 0) return diff;
+    diff = end - other.end;
+    if (diff != 0) return diff;
+    // use edit order as a tie breaker
+    return sortId - other.sortId;
+  }
+}