49 lines
1.7 KiB
Dart
49 lines
1.7 KiB
Dart
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// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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import 'characters.dart' as chars;
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/// Returns whether [char] is the code for an ASCII letter (uppercase or
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/// lowercase).
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bool isAlphabetic(int char) =>
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(char >= chars.upperA && char <= chars.upperZ) ||
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(char >= chars.lowerA && char <= chars.lowerZ);
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/// Returns whether [char] is the code for an ASCII digit.
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bool isNumeric(int char) => char >= chars.zero && char <= chars.nine;
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/// Returns whether [path] has a URL-formatted Windows drive letter beginning at
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/// [index].
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bool isDriveLetter(String path, int index) =>
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driveLetterEnd(path, index) != null;
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/// Returns the index of the first character after the drive letter or a
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/// URL-formatted path, or `null` if [index] is not the start of a drive letter.
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/// A valid drive letter must be followed by a colon and then either a `/` or
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/// the end of string.
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///
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/// ```
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/// d:/abc => 3
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/// d:/ => 3
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/// d: => 2
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/// d => null
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/// ```
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int? driveLetterEnd(String path, int index) {
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if (path.length < index + 2) return null;
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if (!isAlphabetic(path.codeUnitAt(index))) return null;
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if (path.codeUnitAt(index + 1) != chars.colon) {
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// If not a raw colon, check for escaped colon
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if (path.length < index + 4) return null;
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if (path.substring(index + 1, index + 4).toLowerCase() != '%3a') {
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return null;
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}
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// Offset the index to account for the extra 2 characters from the
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// colon encoding.
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index += 2;
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}
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if (path.length == index + 2) return index + 2;
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if (path.codeUnitAt(index + 2) != chars.slash) return null;
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return index + 3;
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}
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