Extract 'computeLineStarts' utility.

pkg/analyzer/lib/src/task/options.dart

 // Copyright (c) 2015, 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 analyzer.src.task.options;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/plugin/options.dart';
 import 'package:analyzer/source/analysis_options_provider.dart';
 import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/task/general.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:source_span/source_span.dart';
 import 'package:yaml/yaml.dart';
 
 /// The errors produced while parsing `.analysis_options` files.
 ///
 /// The list will be empty if there were no errors, but will not be `null`.
@@ skipping 67 matching lines @@
       new OptionsFileValidator(source).validate(options);
 
   /// Return a map from the names of the inputs of this kind of task to the
   /// task input descriptors describing those inputs for a task with the
   /// given [target].
   static Map<String, TaskInput> buildInputs(Source source) =>
       <String, TaskInput>{CONTENT_INPUT_NAME: CONTENT.of(source)};
 
   /// Compute [LineInfo] for the given [content].
   static LineInfo computeLineInfo(String content) {
-    List<int> lineStarts = <int>[0];
-    int length = content.length;
-    int unit;
-    for (int index = 0; index < length; index++) {
-      unit = content.codeUnitAt(index);
-      // Special-case \r\n.
-      if (unit == 0x0D /* \r */) {
-        // Peek ahead to detect a following \n.
-        if ((index + 1 < length) && content.codeUnitAt(index + 1) == 0x0A) {
-          // Line start will get registered at next index at the \n.
-        } else {
-          lineStarts.add(index + 1);
-        }
-      }
-
-      if (unit == 0x0A) {
-        lineStarts.add(index + 1);
-      }
-    }
+    List<int> lineStarts = StringUtilities.computeLineStarts(content);
     return new LineInfo(lineStarts);
   }
 
   /// Create a task based on the given [target] in the given [context].
   static GenerateOptionsErrorsTask createTask(
           AnalysisContext context, AnalysisTarget target) =>
       new GenerateOptionsErrorsTask(context, target);
 }
 
 /// Validates `linter` top-level options.
@@ skipping 42 matching lines @@
                 AnalysisOptionsWarningCode.UNSUPPORTED_OPTION,
                 k.span,
                 [pluginName, k.value]);
           }
         }
         //TODO(pq): consider an error if the node is not a Scalar.
       });
     }
   }
 }