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string_scanner/lib/src/span_scanner.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 string_scanner.span_scanner;
-
-import 'package:source_span/source_span.dart';
-
-import 'eager_span_scanner.dart';
-import 'exception.dart';
-import 'line_scanner.dart';
-import 'string_scanner.dart';
-import 'utils.dart';
-
-/// A subclass of [LineScanner] that exposes matched ranges as source map
-/// [Span]s.
-class SpanScanner extends StringScanner implements LineScanner {
-  /// The source of the scanner.
-  ///
-  /// This caches line break information and is used to generate [Span]s.
-  final SourceFile _sourceFile;
-
-  int get line => _sourceFile.getLine(position);
-  int get column => _sourceFile.getColumn(position);
-
-  LineScannerState get state => new _SpanScannerState(this, position);
-
-  set state(LineScannerState state) {
-    if (state is! _SpanScannerState ||
-        !identical((state as _SpanScannerState)._scanner, this)) {
-      throw new ArgumentError("The given LineScannerState was not returned by "
-          "this LineScanner.");
-    }
-
-    this.position = state.position;
-  }
-
-  /// The [FileSpan] for [lastMatch].
-  ///
-  /// This is the span for the entire match. There's no way to get spans for
-  /// subgroups since [Match] exposes no information about their positions.
-  FileSpan get lastSpan => _lastSpan;
-  FileSpan _lastSpan;
-
-  /// The current location of the scanner.
-  FileLocation get location => _sourceFile.location(position);
-
-  /// Returns an empty span at the current location.
-  FileSpan get emptySpan => location.pointSpan();
-
-  /// Creates a new [SpanScanner] that starts scanning from [position].
-  ///
-  /// [sourceUrl] is used as [SourceLocation.sourceUrl] for the returned
-  /// [FileSpan]s as well as for error reporting. It can be a [String], a
-  /// [Uri], or `null`.
-  SpanScanner(String string, {sourceUrl, int position})
-      : _sourceFile = new SourceFile(string, url: sourceUrl),
-        super(string, sourceUrl: sourceUrl, position: position);
-
-  /// Creates a new [SpanScanner] that eagerly computes line and column numbers.
-  ///
-  /// In general [new SpanScanner] will be more efficient, since it avoids extra
-  /// computation on every scan. However, eager scanning can be useful for
-  /// situations where the normal course of parsing frequently involves
-  /// accessing the current line and column numbers.
-  ///
-  /// Note that *only* the `line` and `column` fields on the `SpanScanner`
-  /// itself and its `LineScannerState` are eagerly computed. To limit their
-  /// memory footprint, returned spans and locations will still lazily compute
-  /// their line and column numbers.
-  factory SpanScanner.eager(String string, {sourceUrl, int position}) =
-      EagerSpanScanner;
-
-  /// Creates a [FileSpan] representing the source range between [startState]
-  /// and the current position.
-  FileSpan spanFrom(LineScannerState startState, [LineScannerState endState]) {
-    var endPosition = endState == null ? position : endState.position;
-    return _sourceFile.span(startState.position, endPosition);
-  }
-
-  bool matches(Pattern pattern) {
-    if (!super.matches(pattern)) {
-      _lastSpan = null;
-      return false;
-    }
-
-    _lastSpan = _sourceFile.span(position, lastMatch.end);
-    return true;
-  }
-
-  void error(String message, {Match match, int position, int length}) {
-    validateErrorArgs(string, match, position, length);
-
-    if (match == null && position == null && length == null) match = lastMatch;
-    if (position == null) {
-      position = match == null ? this.position : match.start;
-    }
-    if (length == null) length = match == null ? 1 : match.end - match.start;
-
-    var span = _sourceFile.span(position, position + length);
-    throw new StringScannerException(message, span, string);
-  }
-}
-
-/// A class representing the state of a [SpanScanner].
-class _SpanScannerState implements LineScannerState {
-  /// The [SpanScanner] that created this.
-  final SpanScanner _scanner;
-
-  final int position;
-  int get line => _scanner._sourceFile.getLine(position);
-  int get column => _scanner._sourceFile.getColumn(position);
-
-  _SpanScannerState(this._scanner, this.position);
-}