| // 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 source_span.utils; |
| |
| /// Returns the minimum of [obj1] and [obj2] according to |
| /// [Comparable.compareTo]. |
| Comparable min(Comparable obj1, Comparable obj2) => |
| obj1.compareTo(obj2) > 0 ? obj2 : obj1; |
| |
| /// Returns the maximum of [obj1] and [obj2] according to |
| /// [Comparable.compareTo]. |
| Comparable max(Comparable obj1, Comparable obj2) => |
| obj1.compareTo(obj2) > 0 ? obj1 : obj2; |
| |
| /// Find the first entry in a sorted [list] that matches a monotonic predicate. |
| /// |
| /// Given a result `n`, that all items before `n` will not match, `n` matches, |
| /// and all items after `n` match too. The result is -1 when there are no |
| /// items, 0 when all items match, and list.length when none does. |
| int binarySearch(List list, bool matches(item)) { |
| if (list.length == 0) return -1; |
| if (matches(list.first)) return 0; |
| if (!matches(list.last)) return list.length; |
| |
| int min = 0; |
| int max = list.length - 1; |
| while (min < max) { |
| var half = min + ((max - min) ~/ 2); |
| if (matches(list[half])) { |
| max = half; |
| } else { |
| min = half + 1; |
| } |
| } |
| return max; |
| } |
| |
| /// Finds a line in [context] containing [text] at the specified [column]. |
| /// |
| /// Returns the index in [context] where that line begins, or null if none |
| /// exists. |
| int findLineStart(String context, String text, int column) { |
| var isEmpty = text == ''; |
| var index = context.indexOf(text); |
| while (index != -1) { |
| var lineStart = context.lastIndexOf('\n', index) + 1; |
| var textColumn = index - lineStart; |
| if (column == textColumn || (isEmpty && column == textColumn + 1)) { |
| return lineStart; |
| } |
| index = context.indexOf(text, index + 1); |
| } |
| return null; |
| } |