Move scanner into pkg/front_end/lib/src/scanner.

pkg/front_end/lib/src/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 front_end.src.scanner.reader;
+
+/**
+ * An object used by the scanner to read the characters to be scanned.
+ */
+abstract class CharacterReader {

[Brian Wilkerson, 2016/11/08 20:53:23]

Seems odd to not have a concrete implementation in the front-end.

[Paul Berry, 2016/11/08 21:47:06]

Acknowledged.  Concrete implementations will be moved in the next CL, when I
move scanner tests into the front end.

+  /**
+   * 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();
+}