convert: new LineSplitter, (io: Deprecate LineTransformer)

sdk/lib/convert/line_splitter.dart

+// Copyright (c) 2013, 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.
+
+part of dart.convert;
+
+/**
+ * This class splits [String] values into individual lines.
+ */
+class LineSplitter extends Converter<String, List<String>> {
+  List<String> convert(String data) {
+    var lines = new List<String>();
+
+    _LineSplitterSink._addSlice(data, 0, data.length, true, lines.add);
+
+    return lines;
+  }
+
+  ChunkedConversionSink startChunkedConversion(ChunkedConversionSink<String> sink) {
+    if (sink is! StringConversionSink) {
+      sink = new StringConversionSink.from(sink);
+    }
+    return new _LineSplitterSink(sink);
+  }
+}
+
+
+class _LineSplitterSink extends StringConversionSinkBase {
+  static const int _LF = 10;
+  static const int _CR = 13;
+
+  final StringConversionSink _sink;
+
+  String _carry;
+
+  _LineSplitterSink(this._sink);
+
+  void addSlice(String chunk, int start, int end, bool isLast) {
+    if(_carry != null) {
+      chunk = _carry + chunk.substring(start, end);
+      start = 0;
+      end = chunk.length;
+      _carry = null;
+    }
+    _carry = _addSlice(chunk, start, end, isLast, _sink.add);
+    if(isLast) _sink.close();
+  }
+
+  void close() {
+    addSlice('', 0, 0, true);
+  }
+
+  static String _addSlice(String chunk, int start, int end, bool isLast, void adder(String)) {
+    String carry = null;
+    int startPos = start;
+    int pos = start;
+    while (pos < end) {
+      int skip = 0;
+      int char = chunk.codeUnitAt(pos);
+      if (char == _LF) {
+        skip = 1;
+      } else if (char == _CR) {
+        skip = 1;
+        if (pos + 1 < end) {
+          if (chunk.codeUnitAt(pos + 1) == _LF) {
+            skip = 2;
+          }
+        } else if (!isLast) {
+          return chunk.substring(startPos, end);
+        }
+      }
+      if (skip > 0) {
+        adder(chunk.substring(startPos, pos));
+        startPos = pos = pos + skip;
+      } else {
+        pos++;
+      }
+    }
+    if (pos != startPos) {
+      // Add remaining
+      carry = chunk.substring(startPos, pos);
+    }
+    if(isLast && carry != null) {
+      adder(carry);
+      return null;
+    }
+    return carry;
+  }
+}