Move scanner out of generated and clean up imports

pkg/analyzer/lib/src/dart/scanner/reader.dart

+// Copyright (c) 2014, 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 analyzer.src.dart.scanner.reader;
+
+/**
+ * A [CharacterReader] that reads a range of characters from another character
+ * reader.
+ */
+class CharacterRangeReader extends CharacterReader {
+  /**
+   * The reader from which the characters are actually being read.
+   */
+  final CharacterReader baseReader;
+
+  /**
+   * The last character to be read.
+   */
+  final int endIndex;
+
+  /**
+   * Initialize a newly created reader to read the characters from the given
+   * [baseReader] between the [startIndex] inclusive to [endIndex] exclusive.
+   */
+  CharacterRangeReader(this.baseReader, int startIndex, this.endIndex) {
+    baseReader.offset = startIndex - 1;
+  }
+
+  @override
+  int get offset => baseReader.offset;
+
+  @override
+  void set offset(int offset) {
+    baseReader.offset = offset;
+  }
+
+  @override
+  int advance() {
+    if (baseReader.offset + 1 >= endIndex) {
+      return -1;
+    }
+    return baseReader.advance();
+  }
+
+  @override
+  String getString(int start, int endDelta) =>
+      baseReader.getString(start, endDelta);
+
+  @override
+  int peek() {
+    if (baseReader.offset + 1 >= endIndex) {
+      return -1;
+    }
+    return baseReader.peek();
+  }
+}
+
+/**
+ * An object used by the scanner to read the characters to be scanned.
+ */
+abstract class CharacterReader {
+  /**
+   * The current offset relative to the beginning of the source. Return the
+   * initial offset if the scanner has not yet scanned the source code, and one
+   * (1) past the end of the source code if the entire source code has been
+   * scanned.
+   */
+  int get offset;
+
+  /**
+   * Set the current offset relative to the beginning of the source to the given
+   * [offset]. The new offset must be between the initial offset and one (1)
+   * past the end of the source code.
+   */
+  void set offset(int offset);
+
+  /**
+   * Advance the current position and return the character at the new current
+   * position.
+   */
+  int advance();
+
+  /**
+   * Return the substring of the source code between the [start] offset and the
+   * modified current position. The current position is modified by adding the
+   * [endDelta], which is the number of characters after the current location to
+   * be included in the string, or the number of characters before the current
+   * location to be excluded if the offset is negative.
+   */
+  String getString(int start, int endDelta);
+
+  /**
+   * Return the character at the current position without changing the current
+   * position.
+   */
+  int peek();
+}
+
+/**
+ * A [CharacterReader] that reads characters from a character sequence.
+ */
+class CharSequenceReader implements CharacterReader {
+  /**
+   * The sequence from which characters will be read.
+   */
+  final String _sequence;
+
+  /**
+   * The number of characters in the string.
+   */
+  int _stringLength = 0;
+
+  /**
+   * The index, relative to the string, of the last character that was read.
+   */
+  int _charOffset = 0;
+
+  /**
+   * Initialize a newly created reader to read the characters in the given
+   * [_sequence].
+   */
+  CharSequenceReader(this._sequence) {
+    this._stringLength = _sequence.length;
+    this._charOffset = -1;
+  }
+
+  @override
+  int get offset => _charOffset;
+
+  @override
+  void set offset(int offset) {
+    _charOffset = offset;
+  }
+
+  @override
+  int advance() {
+    if (_charOffset + 1 >= _stringLength) {
+      return -1;
+    }
+    return _sequence.codeUnitAt(++_charOffset);
+  }
+
+  @override
+  String getString(int start, int endDelta) =>
+      _sequence.substring(start, _charOffset + 1 + endDelta).toString();
+
+  @override
+  int peek() {
+    if (_charOffset + 1 >= _stringLength) {
+      return -1;
+    }
+    return _sequence.codeUnitAt(_charOffset + 1);
+  }
+}
+
+/**
+ * A [CharacterReader] that reads characters from a character sequence, but adds
+ * a delta when reporting the current character offset so that the character
+ * sequence can be a subsequence from a larger sequence.
+ */
+class SubSequenceReader extends CharSequenceReader {
+  /**
+   * The offset from the beginning of the file to the beginning of the source
+   * being scanned.
+   */
+  final int _offsetDelta;
+
+  /**
+   * Initialize a newly created reader to read the characters in the given
+   * [sequence]. The [_offsetDelta] is the offset from the beginning of the file
+   * to the beginning of the source being scanned
+   */
+  SubSequenceReader(String sequence, this._offsetDelta) : super(sequence);
+
+  @override
+  int get offset => _offsetDelta + super.offset;
+
+  @override
+  void set offset(int offset) {
+    super.offset = offset - _offsetDelta;
+  }
+
+  @override
+  String getString(int start, int endDelta) =>
+      super.getString(start - _offsetDelta, endDelta);
+}