Unify most of our utf8 implementations. This takes the implementation

lib/utf/unicode_core.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("unicode_core");
-
-/*
- * Test for presence of bug related to the use of UTF-16 code units for
- * Dart compiled to JS.
- */
-bool _test16BitCodeUnit = null;
-// TODO is16BitCodeUnit() is used to work around a bug with frog/dartc
-// (http://code.google.com/p/dart/issues/detail?id=1357). Consider
-// removing after this issue is resolved.
-bool is16BitCodeUnit() {
-  if (_test16BitCodeUnit == null) {
-    _test16BitCodeUnit = (new String.fromCharCodes([0x1D11E])) ==
-        (new String.fromCharCodes([0xD11E]));
-  }
-  return _test16BitCodeUnit;
-}
-
-/**
- * Invalid codepoints or encodings may be substituted with the value U+fffd.
- */
-final int UNICODE_REPLACEMENT_CHARACTER_CODEPOINT = 0xfffd;
-final int UNICODE_BOM = 0xfeff;
-final int UNICODE_UTF_BOM_LO = 0xff;
-final int UNICODE_UTF_BOM_HI = 0xfe;
-
-final int UNICODE_BYTE_ZERO_MASK = 0xff;
-final int UNICODE_BYTE_ONE_MASK = 0xff00;
-final int UNICODE_VALID_RANGE_MAX = 0x10ffff;
-final int UNICODE_PLANE_ONE_MAX = 0xffff;
-final int UNICODE_UTF16_RESERVED_LO = 0xd800;
-final int UNICODE_UTF16_RESERVED_HI = 0xdfff;
-final int UNICODE_UTF16_OFFSET = 0x10000;
-final int UNICODE_UTF16_SURROGATE_UNIT_0_BASE = 0xd800;
-final int UNICODE_UTF16_SURROGATE_UNIT_1_BASE = 0xdc00;
-final int UNICODE_UTF16_HI_MASK = 0xffc00;
-final int UNICODE_UTF16_LO_MASK = 0x3ff;
-
-/**
- * Encode code points as UTF16 code units.
- */
-List<int> codepointsToUtf16CodeUnits(
-    List<int> codepoints, [int offset = 0, int length,
-    int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
-
-  ListRange<int> listRange = new ListRange<int>(codepoints, offset, length);
-  int encodedLength = 0;
-  for (int value in listRange) {
-    if ((value >= 0 && value < UNICODE_UTF16_RESERVED_LO) ||
-        (value > UNICODE_UTF16_RESERVED_HI && value <= UNICODE_PLANE_ONE_MAX)) {
-      encodedLength++;
-    } else if (value > UNICODE_PLANE_ONE_MAX &&
-        value <= UNICODE_VALID_RANGE_MAX) {
-      encodedLength += 2;
-    } else {
-      encodedLength++;
-    }
-  }
-
-  List<int> codeUnitsBuffer = new List<int>(encodedLength);
-  int j = 0;
-  for (int value in listRange) {
-    if ((value >= 0 && value < UNICODE_UTF16_RESERVED_LO) ||
-        (value > UNICODE_UTF16_RESERVED_HI && value <= UNICODE_PLANE_ONE_MAX)) {
-      codeUnitsBuffer[j++] = value;
-    } else if (value > UNICODE_PLANE_ONE_MAX &&
-        value <= UNICODE_VALID_RANGE_MAX) {
-      int base = value - UNICODE_UTF16_OFFSET;
-      codeUnitsBuffer[j++] = UNICODE_UTF16_SURROGATE_UNIT_0_BASE +
-          ((base & UNICODE_UTF16_HI_MASK) >> 10);
-      codeUnitsBuffer[j++] = UNICODE_UTF16_SURROGATE_UNIT_1_BASE +
-          (base & UNICODE_UTF16_LO_MASK);
-    } else if (replacementCodepoint != null) {
-      codeUnitsBuffer[j++] = replacementCodepoint;
-    } else {
-      throw new IllegalArgumentException("Invalid encoding");
-    }
-  }
-  return codeUnitsBuffer;
-}
-
-/**
- * Decodes the utf16 codeunits to codepoints.
- */
-List<int> utf16CodeUnitsToCodepoints(
-    List<int> utf16CodeUnits, [int offset = 0, int length,
-    int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
-  ListRangeIterator<int> source =
-      (new ListRange<int>(utf16CodeUnits, offset, length)).iterator();
-  Utf16CodeUnitDecoder decoder = new Utf16CodeUnitDecoder
-      .fromListRangeIterator(source, replacementCodepoint);
-  List<int> codepoints = new List<int>(source.remaining);
-  int i = 0;
-  while (decoder.hasNext()) {
-    codepoints[i++] = decoder.next();
-  }
-  if (i == codepoints.length) {
-    return codepoints;
-  } else {
-    List<int> codepointTrunc = new List<int>(i);
-    codepointTrunc.setRange(0, i, codepoints);
-    return codepointTrunc;
-  }
-}
-
-/**
- * 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 IllegalArgumentException
- * rather than replace the bad value.
- */
-class Utf16CodeUnitDecoder implements Iterator<int> {
-  final ListRangeIterator<int> utf16CodeUnitIterator;
-  final int replacementCodepoint;
-
-  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<int> this.utf16CodeUnitIterator,
-      int this.replacementCodepoint);
-
-  Iterator<int> iterator() => this;
-
-  bool hasNext() => utf16CodeUnitIterator.hasNext();
-
-  int next() {
-    int value = utf16CodeUnitIterator.next();
-    if (value < 0) {
-      if (replacementCodepoint != null) {
-        return replacementCodepoint;
-      } else {
-        throw new IllegalArgumentException(
-            "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
-      }
-    } else if (value < UNICODE_UTF16_RESERVED_LO ||
-        (value > UNICODE_UTF16_RESERVED_HI && value <= UNICODE_PLANE_ONE_MAX)) {
-      // transfer directly
-      return value;
-    } else if (value < UNICODE_UTF16_SURROGATE_UNIT_1_BASE &&
-        utf16CodeUnitIterator.hasNext()) {
-      // merge surrogate pair
-      int nextValue = utf16CodeUnitIterator.next();
-      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);
-        return value;
-      } else {
-        if (nextValue >= UNICODE_UTF16_SURROGATE_UNIT_0_BASE &&
-           nextValue < UNICODE_UTF16_SURROGATE_UNIT_1_BASE) {
-          utf16CodeUnitIterator.backup();
-        }
-        if (replacementCodepoint != null) {
-          return replacementCodepoint;
-        } else {
-          throw new IllegalArgumentException(
-              "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
-        }
-      }
-    } else if (replacementCodepoint != null) {
-      return replacementCodepoint;
-    } else {
-      throw new IllegalArgumentException(
-          "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
-    }
-  }
-}
-
-/**
- * ListRange in an internal type used to create a lightweight Interable on a
- * range within a source list. DO NOT MODIFY the underlying list while
- * iterating over it. The results of doing so are undefined.
- */
-class ListRange<T> implements Iterable<T> {
-  final List<T> _source;
-  final int _offset;
-  final int _length;
-
-  ListRange(List<T> source, [int offset = 0, int length]) :
-      this._source = source, this._offset = offset,
-      this._length = (length == null ? source.length - offset : length) {
-    if (_offset < 0 || _offset > _source.length) {
-      throw new IndexOutOfRangeException("offset out of range (< 0)");
-    }
-    if (_length != null && (_length < 0)) {
-      throw new IndexOutOfRangeException("length out of range (< 0)");
-    }
-    if (_length + _offset > _source.length) {
-      throw new IndexOutOfRangeException("offset + length > source.length");
-    }
-  }
-
-  ListRangeIterator<T> iterator() =>
-      new ListRangeIteratorImpl(_source, _offset, _offset + _length);
-
-  int get length() => _length;
-}
-
-/**
- * The ListRangeIterator provides more capabilities than a standard iterator,
- * including the ability to get the current position, count remaining items,
- * and move forward/backward within the iterator.
- */
-interface ListRangeIterator<T> extends Iterator<T> {
-  bool hasNext();
-  T next();
-  int get position();
-  void backup([int by]);
-  int get remaining();
-  void skip([int count]);
-}
-
-class ListRangeIteratorImpl<T> implements ListRangeIterator<T> {
-  final List<T> _source;
-  int _offset;
-  final int _end;
-
-  ListRangeIteratorImpl(List<T> source, int offset, int end) :
-      _source = source, _offset = offset, _end = end;
-
-  bool hasNext() => _offset < _end;
-  T next() => _source[_offset++];
-  int get position() => _offset;
-  void backup([int by = 1]) {
-    _offset -= by;
-  }
-  int get remaining() => _end - _offset;
-  void skip([int count = 1]) {
-    _offset += count;
-  }
-}