Index: packages/string_scanner/lib/src/relative_span_scanner.dart |
diff --git a/packages/string_scanner/lib/src/relative_span_scanner.dart b/packages/string_scanner/lib/src/relative_span_scanner.dart |
new file mode 100644 |
index 0000000000000000000000000000000000000000..fdcd03fbaacdd6c74e473f3e31a38eb871d0f376 |
--- /dev/null |
+++ b/packages/string_scanner/lib/src/relative_span_scanner.dart |
@@ -0,0 +1,112 @@ |
+// 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. |
+ |
+import 'package:source_span/source_span.dart'; |
+ |
+import 'exception.dart'; |
+import 'line_scanner.dart'; |
+import 'span_scanner.dart'; |
+import 'string_scanner.dart'; |
+import 'utils.dart'; |
+ |
+/// A [SpanScanner] that scans within an existing [FileSpan]. |
+/// |
+/// This re-implements chunks of [SpanScanner] rather than using a dummy span or |
+/// inheritance because scanning is often a performance-critical operation, so |
+/// it's important to avoid adding extra overhead when relative scanning isn't |
+/// needed. |
+class RelativeSpanScanner extends StringScanner implements SpanScanner { |
+ /// The source of the scanner. |
+ /// |
+ /// This caches line break information and is used to generate [Span]s. |
+ final SourceFile _sourceFile; |
+ |
+ /// The start location of the span within which this scanner is scanning. |
+ /// |
+ /// This is used to convert between span-relative and file-relative fields. |
+ final FileLocation _startLocation; |
+ |
+ int get line => _sourceFile.getLine(_startLocation.offset + position) - |
+ _startLocation.line; |
+ |
+ int get column { |
+ var line = _sourceFile.getLine(_startLocation.offset + position); |
+ var column = _sourceFile.getColumn(_startLocation.offset + position, |
+ line: line); |
+ return line == _startLocation.line |
+ ? column - _startLocation.column |
+ : column; |
+ } |
+ |
+ 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; |
+ } |
+ |
+ FileSpan get lastSpan => _lastSpan; |
+ FileSpan _lastSpan; |
+ |
+ FileLocation get location => |
+ _sourceFile.location(_startLocation.offset + position); |
+ |
+ FileSpan get emptySpan => location.pointSpan(); |
+ |
+ RelativeSpanScanner(FileSpan span) |
+ : _sourceFile = span.file, |
+ _startLocation = span.start, |
+ super(span.text, sourceUrl: span.sourceUrl); |
+ |
+ FileSpan spanFrom(LineScannerState startState, [LineScannerState endState]) { |
+ var endPosition = endState == null ? position : endState.position; |
+ return _sourceFile.span( |
+ _startLocation.offset + startState.position, |
+ _startLocation.offset + endPosition); |
+ } |
+ |
+ bool matches(Pattern pattern) { |
+ if (!super.matches(pattern)) { |
+ _lastSpan = null; |
+ return false; |
+ } |
+ |
+ _lastSpan = _sourceFile.span( |
+ _startLocation.offset + position, |
+ _startLocation.offset + 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( |
+ _startLocation.offset + position, |
+ _startLocation.offset + 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 RelativeSpanScanner _scanner; |
+ |
+ final int position; |
+ int get line => _scanner._sourceFile.getLine(position); |
+ int get column => _scanner._sourceFile.getColumn(position); |
+ |
+ _SpanScannerState(this._scanner, this.position); |
+} |