Roll Observatory packages and add a roll script

utf/lib/src/utf_16_code_unit_decoder.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.
-
-library utf.utf_16_code_unit_decoder;
-
-import 'constants.dart';
-import 'list_range.dart';
-
-/**
- * An Iterator<int> of codepoints built on an Iterator of UTF-16 code units.
- * The parameters can override the default Unicode replacement character. Set
- * the replacementCharacter to null to throw an ArgumentError
- * rather than replace the bad value.
- */
-class Utf16CodeUnitDecoder implements Iterator<int> {
-  // TODO(kevmoo): should this field be private?
-  final ListRangeIterator utf16CodeUnitIterator;
-  final int replacementCodepoint;
-  int _current = null;
-
-  Utf16CodeUnitDecoder(List<int> utf16CodeUnits, [int offset = 0, int length,
-      int this.replacementCodepoint =
-      UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) :
-      utf16CodeUnitIterator =
-          (new ListRange(utf16CodeUnits, offset, length)).iterator;
-
-  Utf16CodeUnitDecoder.fromListRangeIterator(
-      ListRangeIterator this.utf16CodeUnitIterator,
-      int this.replacementCodepoint);
-
-  Iterator<int> get iterator => this;
-
-  int get current => _current;
-
-  bool moveNext() {
-    _current = null;
-    if (!utf16CodeUnitIterator.moveNext()) return false;
-
-    int value = utf16CodeUnitIterator.current;
-    if (value < 0) {
-      if (replacementCodepoint != null) {
-        _current = replacementCodepoint;
-      } else {
-        throw new ArgumentError(
-            "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
-      }
-    } else if (value < UNICODE_UTF16_RESERVED_LO ||
-        (value > UNICODE_UTF16_RESERVED_HI && value <= UNICODE_PLANE_ONE_MAX)) {
-      // transfer directly
-      _current = value;
-    } else if (value < UNICODE_UTF16_SURROGATE_UNIT_1_BASE &&
-        utf16CodeUnitIterator.moveNext()) {
-      // merge surrogate pair
-      int nextValue = utf16CodeUnitIterator.current;
-      if (nextValue >= UNICODE_UTF16_SURROGATE_UNIT_1_BASE &&
-          nextValue <= UNICODE_UTF16_RESERVED_HI) {
-        value = (value - UNICODE_UTF16_SURROGATE_UNIT_0_BASE) << 10;
-        value += UNICODE_UTF16_OFFSET +
-            (nextValue - UNICODE_UTF16_SURROGATE_UNIT_1_BASE);
-        _current = value;
-      } else {
-        if (nextValue >= UNICODE_UTF16_SURROGATE_UNIT_0_BASE &&
-           nextValue < UNICODE_UTF16_SURROGATE_UNIT_1_BASE) {
-          utf16CodeUnitIterator.backup();
-        }
-        if (replacementCodepoint != null) {
-          _current = replacementCodepoint;
-        } else {
-          throw new ArgumentError(
-              "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
-        }
-      }
-    } else if (replacementCodepoint != null) {
-      _current = replacementCodepoint;
-    } else {
-      throw new ArgumentError(
-          "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
-    }
-    return true;
-  }
-}
-