utf/lib/src/util.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.util;

import 'constants.dart';
import 'list_range.dart';
import 'utf_16_code_unit_decoder.dart';

/**
 * Decodes the utf16 codeunits to codepoints.
 */
List<int> utf16CodeUnitsToCodepoints(
    List<int> utf16CodeUnits, [int offset = 0, int length,
    int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
  ListRangeIterator source =
      (new ListRange(utf16CodeUnits, offset, length)).iterator;
  Utf16CodeUnitDecoder decoder = new Utf16CodeUnitDecoder
      .fromListRangeIterator(source, replacementCodepoint);
  List<int> codepoints = new List<int>(source.remaining);
  int i = 0;
  while (decoder.moveNext()) {
    codepoints[i++] = decoder.current;
  }
  if (i == codepoints.length) {
    return codepoints;
  } else {
    List<int> codepointTrunc = new List<int>(i);
    codepointTrunc.setRange(0, i, codepoints);
    return codepointTrunc;
  }
}

/**
 * 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 listRange = new ListRange(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 ArgumentError("Invalid encoding");
    }
  }
  return codeUnitsBuffer;
}