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1 : // Copyright (c) 2014, 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:source_span/source_span.dart';
6 :
7 : import 'eager_span_scanner.dart';
8 : import 'exception.dart';
9 : import 'line_scanner.dart';
10 : import 'relative_span_scanner.dart';
11 : import 'string_scanner.dart';
12 : import 'utils.dart';
13 :
14 : /// A subclass of [LineScanner] that exposes matched ranges as source map
15 : /// [Span]s.
16 : class SpanScanner extends StringScanner implements LineScanner {
17 : /// The source of the scanner.
18 : ///
19 : /// This caches line break information and is used to generate [Span]s.
20 : final SourceFile _sourceFile;
21 :
22 0 : int get line => _sourceFile.getLine(position);
23 0 : int get column => _sourceFile.getColumn(position);
24 :
25 0 : LineScannerState get state => new _SpanScannerState(this, position);
26 :
27 : set state(LineScannerState state) {
28 0 : if (state is! _SpanScannerState ||
29 0 : !identical((state as _SpanScannerState)._scanner, this)) {
30 0 : throw new ArgumentError("The given LineScannerState was not returned by "
31 : "this LineScanner.");
32 : }
33 :
34 0 : this.position = state.position;
35 : }
36 :
37 : /// The [FileSpan] for [lastMatch].
38 : ///
39 : /// This is the span for the entire match. There's no way to get spans for
40 : /// subgroups since [Match] exposes no information about their positions.
41 : FileSpan get lastSpan {
42 0 : if (lastMatch == null) _lastSpan = null;
43 0 : return _lastSpan;
44 : }
45 : FileSpan _lastSpan;
46 :
47 : /// The current location of the scanner.
48 0 : FileLocation get location => _sourceFile.location(position);
49 :
50 : /// Returns an empty span at the current location.
51 0 : FileSpan get emptySpan => location.pointSpan();
52 :
53 : /// Creates a new [SpanScanner] that starts scanning from [position].
54 : ///
55 : /// [sourceUrl] is used as [SourceLocation.sourceUrl] for the returned
56 : /// [FileSpan]s as well as for error reporting. It can be a [String], a
57 : /// [Uri], or `null`.
58 : SpanScanner(String string, {sourceUrl, int position})
59 0 : : _sourceFile = new SourceFile.fromString(string, url: sourceUrl),
60 0 : super(string, sourceUrl: sourceUrl, position: position);
61 :
62 : /// Creates a new [SpanScanner] that eagerly computes line and column numbers.
63 : ///
64 : /// In general [new SpanScanner] will be more efficient, since it avoids extra
65 : /// computation on every scan. However, eager scanning can be useful for
66 : /// situations where the normal course of parsing frequently involves
67 : /// accessing the current line and column numbers.
68 : ///
69 : /// Note that *only* the `line` and `column` fields on the `SpanScanner`
70 : /// itself and its `LineScannerState` are eagerly computed. To limit their
71 : /// memory footprint, returned spans and locations will still lazily compute
72 : /// their line and column numbers.
73 : factory SpanScanner.eager(String string, {sourceUrl, int position}) =
74 : EagerSpanScanner;
75 :
76 : /// Creates a new [SpanScanner] that scans within [span].
77 : ///
78 : /// This scans through [span.text], but emits new spans from [span.file] in
79 : /// their appropriate relative positions. The [string] field contains only
80 : /// [span.text], and [position], [line], and [column] are all relative to the
81 : /// span.
82 : factory SpanScanner.within(FileSpan span) = RelativeSpanScanner;
83 :
84 : /// Creates a [FileSpan] representing the source range between [startState]
85 : /// and the current position.
86 : FileSpan spanFrom(LineScannerState startState, [LineScannerState endState]) {
87 0 : var endPosition = endState == null ? position : endState.position;
88 0 : return _sourceFile.span(startState.position, endPosition);
89 : }
90 :
91 : bool matches(Pattern pattern) {
92 0 : if (!super.matches(pattern)) {
93 0 : _lastSpan = null;
94 : return false;
95 : }
96 :
97 0 : _lastSpan = _sourceFile.span(position, lastMatch.end);
98 : return true;
99 : }
100 :
101 : void error(String message, {Match match, int position, int length}) {
102 0 : validateErrorArgs(string, match, position, length);
103 :
104 0 : if (match == null && position == null && length == null) match = lastMatch;
105 : if (position == null) {
106 0 : position = match == null ? this.position : match.start;
107 : }
108 0 : if (length == null) length = match == null ? 0 : match.end - match.start;
109 :
110 0 : var span = _sourceFile.span(position, position + length);
111 0 : throw new StringScannerException(message, span, string);
112 : }
113 : }
114 :
115 : /// A class representing the state of a [SpanScanner].
116 : class _SpanScannerState implements LineScannerState {
117 : /// The [SpanScanner] that created this.
118 : final SpanScanner _scanner;
119 :
120 : final int position;
121 0 : int get line => _scanner._sourceFile.getLine(position);
122 0 : int get column => _scanner._sourceFile.getColumn(position);
123 :
124 0 : _SpanScannerState(this._scanner, this.position);
125 : }
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