| // Copyright (c) 2016, 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. |
| |
| /** |
| * 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 source to be scanned. |
| */ |
| String getContents(); |
| |
| /** |
| * 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; |
| |
| /** |
| * The index, relative to the string, of the next character to be read. |
| */ |
| int _charOffset; |
| |
| /** |
| * Initialize a newly created reader to read the characters in the given |
| * [_sequence]. |
| */ |
| CharSequenceReader(this._sequence) { |
| this._stringLength = _sequence.length; |
| this._charOffset = 0; |
| } |
| |
| @override |
| int get offset => _charOffset - 1; |
| |
| @override |
| void set offset(int offset) { |
| _charOffset = offset + 1; |
| } |
| |
| @override |
| int advance() { |
| if (_charOffset >= _stringLength) { |
| return -1; |
| } |
| return _sequence.codeUnitAt(_charOffset++); |
| } |
| |
| @override |
| String getContents() => _sequence; |
| |
| @override |
| String getString(int start, int endDelta) => |
| _sequence.substring(start, _charOffset + endDelta); |
| |
| @override |
| int peek() { |
| if (_charOffset >= _stringLength) { |
| return -1; |
| } |
| return _sequence.codeUnitAt(_charOffset); |
| } |
| } |
| |
| /** |
| * 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 getContents() => super.getContents(); |
| |
| @override |
| String getString(int start, int endDelta) => |
| super.getString(start - _offsetDelta, endDelta); |
| } |