pkg/utf: fixed layout, added todos, updated docs and homepage pubspec links

pkg/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;
+}