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| 1 // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 import 'package:string_scanner/string_scanner.dart'; | |
| 6 | |
| 7 import '../../utils.dart'; | |
| 8 import 'token.dart'; | |
| 9 | |
| 10 /// A regular expression matching both whitespace and single-line comments. | |
| 11 /// | |
| 12 /// This will only match if consumes at least one character. | |
| 13 final _whitespaceAndSingleLineComments = | |
| 14 new RegExp(r"([ \t\n]+|//[^\n]*(\n|$))+"); | |
| 15 | |
| 16 /// A regular expression matching the body of a multi-line comment, after `/*` | |
| 17 /// but before `*/` or a nested `/*`. | |
| 18 /// | |
| 19 /// This will only match if it consumes at least one character. | |
| 20 final _multiLineCommentBody = new RegExp(r"([^/*]|/[^*]|\*[^/])+"); | |
| 21 | |
| 22 /// A scanner that converts a platform selector string into a stream of | |
| 23 /// tokens. | |
| 24 class Scanner { | |
| 25 /// The underlying string scanner. | |
| 26 final SpanScanner _scanner; | |
| 27 | |
| 28 /// The next token to emit. | |
| 29 Token _next; | |
| 30 | |
| 31 /// Whether the scanner has emitted a [TokenType.endOfFile] token. | |
| 32 bool _endOfFileEmitted = false; | |
| 33 | |
| 34 Scanner(String selector) | |
| 35 : _scanner = new SpanScanner(selector); | |
| 36 | |
| 37 /// Returns the next token that will be returned by [next]. | |
| 38 /// | |
| 39 /// Throws a [StateError] if a [TokenType.endOfFile] token has already been | |
| 40 /// consumed. | |
| 41 Token peek() { | |
| 42 if (_next == null) _next = _getNext(); | |
| 43 return _next; | |
| 44 } | |
| 45 | |
| 46 /// Consumes and returns the next token in the stream. | |
| 47 /// | |
| 48 /// Throws a [StateError] if a [TokenType.endOfFile] token has already been | |
| 49 /// consumed. | |
| 50 Token next() { | |
| 51 var token = _next == null ? _getNext() : _next; | |
| 52 _endOfFileEmitted = token.type == TokenType.endOfFile; | |
| 53 _next = null; | |
| 54 return token; | |
| 55 } | |
| 56 | |
| 57 /// If the next token matches [type], consumes it and returns `true`; | |
| 58 /// otherwise, returns `false`. | |
| 59 /// | |
| 60 /// Throws a [StateError] if a [TokenType.endOfFile] token has already been | |
| 61 /// consumed. | |
| 62 bool scan(TokenType type) { | |
| 63 if (peek().type != type) return false; | |
| 64 next(); | |
| 65 return true; | |
| 66 } | |
| 67 | |
| 68 /// Scan and return the next token in the stream. | |
| 69 Token _getNext() { | |
| 70 if (_endOfFileEmitted) throw new StateError("No more tokens."); | |
| 71 | |
| 72 _consumeWhitespace(); | |
| 73 if (_scanner.isDone) { | |
| 74 return new Token( | |
| 75 TokenType.endOfFile, _scanner.spanFrom(_scanner.state)); | |
| 76 } | |
| 77 | |
| 78 switch (_scanner.peekChar()) { | |
| 79 case 0x28 /* ( */: return _scanOperator(TokenType.leftParen); | |
| 80 case 0x29 /* ) */: return _scanOperator(TokenType.rightParen); | |
| 81 case 0x3F /* ? */: return _scanOperator(TokenType.questionMark); | |
| 82 case 0x3A /* : */: return _scanOperator(TokenType.colon); | |
| 83 case 0x21 /* ! */: return _scanOperator(TokenType.not); | |
| 84 case 0x7C /* | */: return _scanOr(); | |
| 85 case 0x26 /* & */: return _scanAnd(); | |
| 86 default: return _scanIdentifier(); | |
| 87 } | |
| 88 } | |
| 89 | |
| 90 /// Scans a single-character operator and returns a token of type [type]. | |
| 91 /// | |
| 92 /// This assumes that the caller has already verified that the next character | |
| 93 /// is correct for the given operator. | |
| 94 Token _scanOperator(TokenType type) { | |
| 95 var start = _scanner.state; | |
| 96 _scanner.readChar(); | |
| 97 return new Token(type, _scanner.spanFrom(start)); | |
| 98 } | |
| 99 | |
| 100 /// Scans a `||` operator and returns the appropriate token. | |
| 101 /// | |
| 102 /// This validates that the next two characters are `||`. | |
| 103 Token _scanOr() { | |
| 104 var start = _scanner.state; | |
| 105 _scanner.expect("||"); | |
| 106 return new Token(TokenType.or, _scanner.spanFrom(start)); | |
| 107 } | |
| 108 | |
| 109 /// Scans a `&&` operator and returns the appropriate token. | |
| 110 /// | |
| 111 /// This validates that the next two characters are `&&`. | |
| 112 Token _scanAnd() { | |
| 113 var start = _scanner.state; | |
| 114 _scanner.expect("&&"); | |
| 115 return new Token(TokenType.and, _scanner.spanFrom(start)); | |
| 116 } | |
| 117 | |
| 118 /// Scans and returns an identifier token. | |
| 119 Token _scanIdentifier() { | |
| 120 _scanner.expect(hyphenatedIdentifier, name: "expression"); | |
| 121 return new IdentifierToken(_scanner.lastMatch[0], _scanner.lastSpan); | |
| 122 } | |
| 123 | |
| 124 /// Consumes all whitespace and comments immediately following the cursor's | |
| 125 /// current position. | |
| 126 void _consumeWhitespace() { | |
| 127 while (_scanner.scan(_whitespaceAndSingleLineComments) || | |
| 128 _multiLineComment()) { | |
| 129 // Do nothing. | |
| 130 } | |
| 131 } | |
| 132 | |
| 133 /// Consumes a single multi-line comment. | |
| 134 /// | |
| 135 /// Returns whether or not a comment was consumed. | |
| 136 bool _multiLineComment() { | |
| 137 if (!_scanner.scan("/*")) return false; | |
| 138 | |
| 139 while (_scanner.scan(_multiLineCommentBody) || _multiLineComment()) { | |
| 140 // Do nothing. | |
| 141 } | |
| 142 _scanner.expect("*/"); | |
| 143 | |
| 144 return true; | |
| 145 } | |
| 146 } | |
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Chromium Code Reviews
Issue 1717483002:
Make PlatformSelector use boolean_selector. (Closed)
Base URL: git@github.com:dart-lang/test@master