Migrate dart2js stubs for dart:io

tool/input_sdk/lib/io/file_system_entity.dart

+// Copyright (c) 2013, 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.
+
+part of dart.io;
+
+/**
+ * The type of an entity on the file system, such as a file, directory, or link.
+ *
+ * These constants are used by the [FileSystemEntity] class
+ * to indicate the object's type.
+ *
+ */
+
+class FileSystemEntityType {
+  static const FILE = const FileSystemEntityType._internal(0);
+  static const DIRECTORY = const FileSystemEntityType._internal(1);
+  static const LINK = const FileSystemEntityType._internal(2);
+  static const NOT_FOUND = const FileSystemEntityType._internal(3);
+  static const _typeList = const [FileSystemEntityType.FILE,
+                                  FileSystemEntityType.DIRECTORY,
+                                  FileSystemEntityType.LINK,
+                                  FileSystemEntityType.NOT_FOUND];
+  final int _type;
+
+  const FileSystemEntityType._internal(this._type);
+
+  static FileSystemEntityType _lookup(int type) => _typeList[type];
+  String toString() => const ['FILE', 'DIRECTORY', 'LINK', 'NOT_FOUND'][_type];
+}
+
+/**
+ * A FileStat object represents the result of calling the POSIX stat() function
+ * on a file system object.  It is an immutable object, representing the
+ * snapshotted values returned by the stat() call.
+ */
+class FileStat {
+  // These must agree with enum FileStat in file.h.
+  static const _TYPE = 0;
+  static const _CHANGED_TIME = 1;
+  static const _MODIFIED_TIME = 2;
+  static const _ACCESSED_TIME = 3;
+  static const _MODE = 4;
+  static const _SIZE = 5;
+
+  static const _notFound = const FileStat._internalNotFound();
+
+  /**
+   * The time of the last change to the data or metadata of the file system
+   * object.  On Windows platforms, this is instead the file creation time.
+   */
+  final DateTime changed;
+  /**
+   * The time of the last change to the data of the file system
+   * object.
+   */
+  final DateTime modified;
+  /**
+   * The time of the last access to the data of the file system
+   * object.  On Windows platforms, this may have 1 day granularity, and be
+   * out of date by an hour.
+   */
+  final DateTime accessed;
+  /**
+   * The type of the object (file, directory, or link).  If the call to
+   * stat() fails, the type of the returned object is NOT_FOUND.
+   */
+  final FileSystemEntityType type;
+  /**
+   * The mode of the file system object.  Permissions are encoded in the lower
+   * 16 bits of this number, and can be decoded using the [modeString] getter.
+   */
+  final int mode;
+  /**
+   * The size of the file system object.
+   */
+  final int size;
+
+  FileStat._internal(this.changed,
+                     this.modified,
+                     this.accessed,
+                     this.type,
+                     this.mode,
+                     this.size);
+
+  const FileStat._internalNotFound() :
+      changed = null,  modified = null, accessed = null,
+      type = FileSystemEntityType.NOT_FOUND, mode = 0, size = -1;
+
+  external static _statSync(String path);
+
+
+  /**
+   * Calls the operating system's stat() function on [path].
+   * Returns a [FileStat] object containing the data returned by stat().
+   * If the call fails, returns a [FileStat] object with .type set to
+   * FileSystemEntityType.NOT_FOUND and the other fields invalid.
+   */
+  static FileStat statSync(String path) {
+    // Trailing path is not supported on Windows.
+    if (Platform.isWindows) {
+      path = FileSystemEntity._trimTrailingPathSeparators(path);
+    }
+    var data = _statSync(path);
+    if (data is OSError) return FileStat._notFound;
+    return new FileStat._internal(
+        new DateTime.fromMillisecondsSinceEpoch(data[_CHANGED_TIME]),
+        new DateTime.fromMillisecondsSinceEpoch(data[_MODIFIED_TIME]),
+        new DateTime.fromMillisecondsSinceEpoch(data[_ACCESSED_TIME]),
+        FileSystemEntityType._lookup(data[_TYPE]),
+        data[_MODE],
+        data[_SIZE]);
+  }
+
+  /**
+   * Asynchronously calls the operating system's stat() function on [path].
+   * Returns a Future which completes with a [FileStat] object containing
+   * the data returned by stat().
+   * If the call fails, completes the future with a [FileStat] object with
+   * .type set to FileSystemEntityType.NOT_FOUND and the other fields invalid.
+   */
+  static Future<FileStat> stat(String path) {
+    // Trailing path is not supported on Windows.
+    if (Platform.isWindows) {
+      path = FileSystemEntity._trimTrailingPathSeparators(path);
+    }
+    return _IOService._dispatch(_FILE_STAT, [path]).then((response) {
+      if (_isErrorResponse(response)) {
+        return FileStat._notFound;
+      }
+      // Unwrap the real list from the "I'm not an error" wrapper.
+      List data = response[1];
+      return new FileStat._internal(
+          new DateTime.fromMillisecondsSinceEpoch(data[_CHANGED_TIME]),
+          new DateTime.fromMillisecondsSinceEpoch(data[_MODIFIED_TIME]),
+          new DateTime.fromMillisecondsSinceEpoch(data[_ACCESSED_TIME]),
+          FileSystemEntityType._lookup(data[_TYPE]),
+          data[_MODE],
+          data[_SIZE]);
+    });
+  }
+
+  String toString() => """
+FileStat: type $type
+          changed $changed
+          modified $modified
+          accessed $accessed
+          mode ${modeString()}
+          size $size""";
+
+  /**
+   * Returns the mode value as a human-readable string, in the format
+   * "rwxrwxrwx", reflecting the user, group, and world permissions to
+   * read, write, and execute the file system object, with "-" replacing the
+   * letter for missing permissions.  Extra permission bits may be represented
+   * by prepending "(suid)", "(guid)", and/or "(sticky)" to the mode string.
+   */
+  String modeString() {
+    var permissions = mode & 0xFFF;
+    var codes = const ['---', '--x', '-w-', '-wx', 'r--', 'r-x', 'rw-', 'rwx'];
+    var result = [];
+    if ((permissions & 0x800) != 0) result.add("(suid) ");
+    if ((permissions & 0x400) != 0) result.add("(guid) ");
+    if ((permissions & 0x200) != 0) result.add("(sticky) ");
+    result
+        ..add(codes[(permissions >> 6) & 0x7])
+        ..add(codes[(permissions >> 3) & 0x7])
+        ..add(codes[permissions & 0x7]);
+    return result.join();
+  }
+}
+
+
+/**
+ * The common super class for [File], [Directory], and [Link] objects.
+ *
+ * [FileSystemEntity] objects are returned from directory listing
+ * operations. To determine if a FileSystemEntity is a [File], a
+ * [Directory], or a [Link] perform a type check:
+ *
+ *     if (entity is File) (entity as File).readAsStringSync();
+ *
+ * You can also use the [type] or [typeSync] methods to determine
+ * the type of a file system object.
+ *
+ * Most methods in this class occur in synchronous and asynchronous pairs,
+ * for example, [exists] and [existsSync].
+ * Unless you have a specific reason for using the synchronous version
+ * of a method, prefer the asynchronous version to avoid blocking your program.
+ *
+ * Here's the exists method in action:
+ *
+ *     entity.exists().then((isThere) {
+ *       isThere ? print('exists') : print('non-existent');
+ *     });
+ *
+ *
+ * ## Other resources
+ *
+ * * [Dart by
+ *   Example](https://www.dartlang.org/dart-by-example/#files-directories-and-symlinks)
+ *   provides additional task-oriented code samples that show how to use various
+ *   API from the [Directory] class and the [File] class, both subclasses of
+ *   FileSystemEntity.
+ *
+ * * [I/O for Command-Line
+ *   Apps](https://www.dartlang.org/docs/dart-up-and-running/ch03.html#dartio---io-for-command-line-apps),
+ *   a section from _A Tour of the Dart Libraries_ covers files and directories.
+ *
+ * * [Write Command-Line Apps](https://www.dartlang.org/docs/tutorials/cmdline/),
+ *   a tutorial about writing command-line apps, includes information about
+ *   files and directories.
+ */
+abstract class FileSystemEntity {
+  String get path;
+
+  /**
+   * Returns a [Uri] representing the file system entity's location.
+   *
+   * The returned URI's scheme is always "file" if the entity's [path] is
+   * absolute, otherwise the scheme will be empty.
+   */
+  Uri get uri => new Uri.file(path);
+
+  /**
+   * Checks whether the file system entity with this path exists. Returns
+   * a [:Future<bool>:] that completes with the result.
+   *
+   * Since FileSystemEntity is abstract, every FileSystemEntity object
+   * is actually an instance of one of the subclasses [File],
+   * [Directory], and [Link].  Calling [exists] on an instance of one
+   * of these subclasses checks whether the object exists in the file
+   * system object exists and is of the correct type (file, directory,
+   * or link).  To check whether a path points to an object on the
+   * file system, regardless of the object's type, use the [type]
+   * static method.
+   *
+   */
+  Future<bool> exists();
+
+  /**
+   * Synchronously checks whether the file system entity with this path
+   * exists.
+   *
+   * Since FileSystemEntity is abstract, every FileSystemEntity object
+   * is actually an instance of one of the subclasses [File],
+   * [Directory], and [Link].  Calling [existsSync] on an instance of
+   * one of these subclasses checks whether the object exists in the
+   * file system object exists and is of the correct type (file,
+   * directory, or link).  To check whether a path points to an object
+   * on the file system, regardless of the object's type, use the
+   * [typeSync] static method.
+   */
+  bool existsSync();
+
+  /**
+   * Renames this file system entity. Returns a `Future<FileSystemEntity>`
+   * that completes with a [FileSystemEntity] instance for the renamed
+   * file system entity.
+   *
+   * If [newPath] identifies an existing entity of the same type, that entity
+   * is replaced. If [newPath] identifies an existing entity of a different
+   * type, the operation fails and the future completes with an exception.
+   */
+  Future<FileSystemEntity> rename(String newPath);
+
+   /**
+   * Synchronously renames this file system entity. Returns a [FileSystemEntity]
+   * instance for the renamed entity.
+   *
+   * If [newPath] identifies an existing entity of the same type, that entity
+   * is replaced. If [newPath] identifies an existing entity of a different
+   * type, the operation fails and an exception is thrown.
+   */
+  FileSystemEntity renameSync(String newPath);
+
+  /**
+   * Resolves the path of a file system object relative to the
+   * current working directory, resolving all symbolic links on
+   * the path and resolving all `..` and `.` path segments.
+   *
+   * [resolveSymbolicLinks] uses the operating system's native
+   * file system API to resolve the path, using the `realpath` function
+   * on linux and OS X, and the `GetFinalPathNameByHandle` function on
+   * Windows. If the path does not point to an existing file system object,
+   * `resolveSymbolicLinks` throws a `FileSystemException`.
+   *
+   * On Windows the `..` segments are resolved _before_ resolving the symbolic
+   * link, and on other platforms the symbolic links are _resolved to their
+   * target_ before applying a `..` that follows.
+   *
+   * To ensure the same behavior on all platforms resolve `..` segments before
+   * calling `resolveSymbolicLinks`. One way of doing this is with the `Uri`
+   * class:
+   *
+   *     var path = Uri.parse('.').resolveUri(new Uri.file(input)).toFilePath();
+   *     if (path == '') path = '.';
+   *     new File(path).resolveSymbolicLinks().then((resolved) {
+   *       print(resolved);
+   *     });
+   *
+   * since `Uri.resolve` removes `..` segments. This will result in the Windows
+   * behavior.
+   */
+  Future<String> resolveSymbolicLinks() {
+    return _IOService._dispatch(_FILE_RESOLVE_SYMBOLIC_LINKS, [path])
+        .then((response) {
+          if (_isErrorResponse(response)) {
+            throw _exceptionFromResponse(response,
+                                         "Cannot resolve symbolic links",
+                                         path);
+          }
+          return response;
+        });
+  }
+
+  /**
+   * Resolves the path of a file system object relative to the
+   * current working directory, resolving all symbolic links on
+   * the path and resolving all `..` and `.` path segments.
+   *
+   * [resolveSymbolicLinksSync] uses the operating system's native
+   * file system API to resolve the path, using the `realpath` function
+   * on linux and OS X, and the `GetFinalPathNameByHandle` function on
+   * Windows. If the path does not point to an existing file system object,
+   * `resolveSymbolicLinksSync` throws a `FileSystemException`.
+   *
+   * On Windows the `..` segments are resolved _before_ resolving the symbolic
+   * link, and on other platforms the symbolic links are _resolved to their
+   * target_ before applying a `..` that follows.
+   *
+   * To ensure the same behavior on all platforms resolve `..` segments before
+   * calling `resolveSymbolicLinksSync`. One way of doing this is with the `Uri`
+   * class:
+   *
+   *     var path = Uri.parse('.').resolveUri(new Uri.file(input)).toFilePath();
+   *     if (path == '') path = '.';
+   *     var resolved = new File(path).resolveSymbolicLinksSync();
+   *     print(resolved);
+   *
+   * since `Uri.resolve` removes `..` segments. This will result in the Windows
+   * behavior.
+   */
+  String resolveSymbolicLinksSync() {
+    var result = _resolveSymbolicLinks(path);
+    _throwIfError(result, "Cannot resolve symbolic links", path);
+    return result;
+  }
+
+
+  /**
+   * Calls the operating system's stat() function on the [path] of this
+   * [FileSystemEntity].  Identical to [:FileStat.stat(this.path):].
+   *
+   * Returns a [:Future<FileStat>:] object containing the data returned by
+   * stat().
+   *
+   * If the call fails, completes the future with a [FileStat] object
+   * with .type set to
+   * FileSystemEntityType.NOT_FOUND and the other fields invalid.
+   */
+  Future<FileStat> stat();
+
+  /**
+   * Synchronously calls the operating system's stat() function on the
+   * [path] of this [FileSystemEntity].
+   * Identical to [:FileStat.statSync(this.path):].
+   *
+   * Returns a [FileStat] object containing the data returned by stat().
+   *
+   * If the call fails, returns a [FileStat] object with .type set to
+   * FileSystemEntityType.NOT_FOUND and the other fields invalid.
+   */
+  FileStat statSync();
+
+  /**
+   * Deletes this [FileSystemEntity].
+   *
+   * If the [FileSystemEntity] is a directory, and if [recursive] is false,
+   * the directory must be empty. Otherwise, if [recursive] is true, the
+   * directory and all sub-directories and files in the directories are
+   * deleted. Links are not followed when deleting recursively. Only the link
+   * is deleted, not its target.
+   *
+   * If [recursive] is true, the [FileSystemEntity] is deleted even if the type
+   * of the [FileSystemEntity] doesn't match the content of the file system.
+   * This behavior allows [delete] to be used to unconditionally delete any file
+   * system object.
+   *
+   * Returns a [:Future<FileSystemEntity>:] that completes with this
+   * [FileSystemEntity] when the deletion is done. If the [FileSystemEntity]
+   * cannot be deleted, the future completes with an exception.
+   */
+  Future<FileSystemEntity> delete({bool recursive: false})
+      => _delete(recursive: recursive);
+
+  /**
+   * Synchronously deletes this [FileSystemEntity].
+   *
+   * If the [FileSystemEntity] is a directory, and if [recursive] is false,
+   * the directory must be empty. Otherwise, if [recursive] is true, the
+   * directory and all sub-directories and files in the directories are
+   * deleted. Links are not followed when deleting recursively. Only the link
+   * is deleted, not its target.
+   *
+   * If [recursive] is true, the [FileSystemEntity] is deleted even if the type
+   * of the [FileSystemEntity] doesn't match the content of the file system.
+   * This behavior allows [deleteSync] to be used to unconditionally delete any
+   * file system object.
+   *
+   * Throws an exception if the [FileSystemEntity] cannot be deleted.
+   */
+  void deleteSync({bool recursive: false})
+      => _deleteSync(recursive: recursive);
+
+
+  /**
+   * Start watching the [FileSystemEntity] for changes.
+   *
+   * The implementation uses platform-dependent event-based APIs for receiving
+   * file-system notifications, thus behavior depends on the platform.
+   *
+   *   * `Windows`: Uses `ReadDirectoryChangesW`. The implementation only
+   *     supports watching directories. Recursive watching is supported.
+   *   * `Linux`: Uses `inotify`. The implementation supports watching both
+   *     files and directories. Recursive watching is not supported.
+   *     Note: When watching files directly, delete events might not happen
+   *     as expected.
+   *   * `OS X`: Uses `FSEvents`. The implementation supports watching both
+   *     files and directories. Recursive watching is supported.
+   *
+   * The system will start listening for events once the returned [Stream] is
+   * being listened to, not when the call to [watch] is issued.
+   *
+   * The returned value is an endless broadcast [Stream], that only stops when
+   * one of the following happends:
+   *
+   *   * The [Stream] is canceled, e.g. by calling `cancel` on the
+   *      [StreamSubscription].
+   *   * The [FileSystemEntity] being watches, is deleted.
+   *
+   * Use `events` to specify what events to listen for. The constants in
+   * [FileSystemEvent] can be or'ed together to mix events. Default is
+   * [FileSystemEvent.ALL].
+   *
+   * A move event may be reported as seperate delete and create events.
+   */
+  Stream<FileSystemEvent> watch({int events: FileSystemEvent.ALL,
+                                 bool recursive: false})
+     => _FileSystemWatcher._watch(_trimTrailingPathSeparators(path),
+                                 events,
+                                 recursive);
+
+  Future<FileSystemEntity> _delete({bool recursive: false});
+  void _deleteSync({bool recursive: false});
+
+  /**
+   * Checks whether two paths refer to the same object in the
+   * file system. Returns a [:Future<bool>:] that completes with the result.
+   *
+   * Comparing a link to its target returns false, as does comparing two links
+   * that point to the same target.  To check the target of a link, use
+   * Link.target explicitly to fetch it.  Directory links appearing
+   * inside a path are followed, though, to find the file system object.
+   *
+   * Completes the returned Future with an error if one of the paths points
+   * to an object that does not exist.
+   */
+  static Future<bool> identical(String path1, String path2) {
+    return _IOService._dispatch(_FILE_IDENTICAL, [path1, path2]).then((response) {
+      if (_isErrorResponse(response)) {
+        throw _exceptionFromResponse(response,
+            "Error in FileSystemEntity.identical($path1, $path2)", "");
+      }
+      return response;
+    });
+  }
+
+  static final RegExp _absoluteWindowsPathPattern =
+      new RegExp(r'^(\\\\|[a-zA-Z]:[/\\])');
+
+  /**
+   * Returns a [bool] indicating whether this object's path is absolute.
+   *
+   * On Windows, a path is absolute if it starts with \\ or a drive letter
+   * between a and z (upper or lower case) followed by :\ or :/.
+   * On non-Windows, a path is absolute if it starts with /.
+   */
+  bool get isAbsolute {
+    if (Platform.isWindows) {
+      return path.startsWith(_absoluteWindowsPathPattern);
+    } else {
+      return path.startsWith('/');
+    }
+  }
+
+  /**
+   * Returns a [FileSystemEntity] whose path is the absolute path to [this].
+   * The type of the returned instance is the type of [this].
+   *
+   * The absolute path is computed by prefixing
+   * a relative path with the current working directory, and returning
+   * an absolute path unchanged.
+   */
+  FileSystemEntity get absolute;
+
+  String get _absolutePath {
+    if (isAbsolute) return path;
+    String current = Directory.current.path;
+    if (current.endsWith('/') ||
+        (Platform.isWindows && current.endsWith('\\'))) {
+      return '$current$path';
+    } else {
+      return '$current${Platform.pathSeparator}$path';
+    }
+  }
+
+
+  /**
+   * Synchronously checks whether two paths refer to the same object in the
+   * file system.
+   *
+   * Comparing a link to its target returns false, as does comparing two links
+   * that point to the same target.  To check the target of a link, use
+   * Link.target explicitly to fetch it.  Directory links appearing
+   * inside a path are followed, though, to find the file system object.
+   *
+   * Throws an error if one of the paths points to an object that does not
+   * exist.
+   */
+  static bool identicalSync(String path1, String path2) {
+    var result = _identical(path1, path2);
+    _throwIfError(result, 'Error in FileSystemEntity.identicalSync');
+    return result;
+  }
+
+  /**
+   * Test if [watch] is supported on the current system.
+   *
+   * OS X 10.6 and below is not supported.
+   */
+  static bool get isWatchSupported => _FileSystemWatcher.isSupported;
+
+  /**
+   * Finds the type of file system object that a path points to. Returns
+   * a [:Future<FileSystemEntityType>:] that completes with the result.
+   *
+   * [FileSystemEntityType] has the constant instances FILE, DIRECTORY,
+   * LINK, and NOT_FOUND.  [type] will return LINK only if the optional
+   * named argument [followLinks] is false, and [path] points to a link.
+   * If the path does not point to a file system object, or any other error
+   * occurs in looking up the path, NOT_FOUND is returned.  The only
+   * error or exception that may be put on the returned future is ArgumentError,
+   * caused by passing the wrong type of arguments to the function.
+   */
+  static Future<FileSystemEntityType> type(String path,
+                                           {bool followLinks: true})
+      => _getTypeAsync(path, followLinks).then(FileSystemEntityType._lookup);
+
+  /**
+   * Synchronously finds the type of file system object that a path points to.
+   * Returns a [FileSystemEntityType].
+   *
+   * [FileSystemEntityType] has the constant instances FILE, DIRECTORY,
+   * LINK, and NOT_FOUND.  [type] will return LINK only if the optional
+   * named argument [followLinks] is false, and [path] points to a link.
+   * If the path does not point to a file system object, or any other error
+   * occurs in looking up the path, NOT_FOUND is returned.  The only
+   * error or exception that may be thrown is ArgumentError,
+   * caused by passing the wrong type of arguments to the function.
+   */
+  static FileSystemEntityType typeSync(String path, {bool followLinks: true})
+      => FileSystemEntityType._lookup(_getTypeSync(path, followLinks));
+
+  /**
+   * Checks if type(path, followLinks: false) returns
+   * FileSystemEntityType.LINK.
+   */
+  static Future<bool> isLink(String path) => _getTypeAsync(path, false)
+      .then((type) => (type == FileSystemEntityType.LINK._type));
+
+  /**
+   * Checks if type(path) returns FileSystemEntityType.FILE.
+   */
+  static Future<bool> isFile(String path) => _getTypeAsync(path, true)
+      .then((type) => (type == FileSystemEntityType.FILE._type));
+
+  /**
+   * Checks if type(path) returns FileSystemEntityType.DIRECTORY.
+   */
+  static Future<bool> isDirectory(String path) => _getTypeAsync(path, true)
+      .then((type) => (type == FileSystemEntityType.DIRECTORY._type));
+
+  /**
+   * Synchronously checks if typeSync(path, followLinks: false) returns
+   * FileSystemEntityType.LINK.
+   */
+  static bool isLinkSync(String path) =>
+      (_getTypeSync(path, false) == FileSystemEntityType.LINK._type);
+
+  /**
+   * Synchronously checks if typeSync(path) returns
+   * FileSystemEntityType.FILE.
+   */
+  static bool isFileSync(String path) =>
+      (_getTypeSync(path, true) == FileSystemEntityType.FILE._type);
+
+  /**
+   * Synchronously checks if typeSync(path) returns
+   * FileSystemEntityType.DIRECTORY.
+   */
+  static bool isDirectorySync(String path) =>
+      (_getTypeSync(path, true) == FileSystemEntityType.DIRECTORY._type);
+
+  external static _getType(String path, bool followLinks);
+  external static _identical(String path1, String path2);
+  external static _resolveSymbolicLinks(String path);
+
+  // Finds the next-to-last component when dividing at path separators.
+  static final RegExp _parentRegExp = Platform.isWindows ?
+     new RegExp(r'[^/\\][/\\]+[^/\\]') :
+     new RegExp(r'[^/]/+[^/]');
+
+  /**
+   * Removes the final path component of a path, using the platform's
+   * path separator to split the path.  Will not remove the root component
+   * of a Windows path, like "C:\" or "\\server_name\".
+   * Ignores trailing path separators, and leaves no trailing path separators.
+   */
+  static String parentOf(String path) {
+    int rootEnd = -1;
+    if (Platform.isWindows) {
+      if (path.startsWith(_absoluteWindowsPathPattern)) {
+        // Root ends at first / or \ after the first two characters.
+        rootEnd = path.indexOf(new RegExp(r'[/\\]'), 2);
+        if (rootEnd == -1) return path;
+      } else if (path.startsWith('\\') || path.startsWith('/')) {
+        rootEnd = 0;
+      }
+    } else if (path.startsWith('/')) {
+      rootEnd = 0;
+    }
+    // Ignore trailing slashes.
+    // All non-trivial cases have separators between two non-separators.
+    int pos = path.lastIndexOf(_parentRegExp);
+    if (pos > rootEnd) {
+      return path.substring(0, pos + 1);
+    } else if (rootEnd > -1) {
+      return path.substring(0, rootEnd + 1);
+    } else {
+      return '.';
+    }
+  }
+
+  /**
+   * The directory containing [this].  If [this] is a root
+   * directory, returns [this].
+   */
+  Directory get parent => new Directory(parentOf(path));
+
+  static int _getTypeSync(String path, bool followLinks) {
+    var result = _getType(path, followLinks);
+    _throwIfError(result, 'Error getting type of FileSystemEntity');
+    return result;
+  }
+
+  static Future<int> _getTypeAsync(String path, bool followLinks) {
+    return _IOService._dispatch(_FILE_TYPE, [path, followLinks])
+      .then((response) {
+        if (_isErrorResponse(response)) {
+          throw _exceptionFromResponse(response, "Error getting type", path);
+        }
+        return response;
+      });
+  }
+
+  static _throwIfError(Object result, String msg, [String path]) {
+    if (result is OSError) {
+      throw new FileSystemException(msg, path, result);
+    } else if (result is ArgumentError) {
+      throw result;
+    }
+  }
+
+  static String _trimTrailingPathSeparators(String path) {
+    // Don't handle argument errors here.
+    if (path is! String) return path;
+    if (Platform.isWindows) {
+      while (path.length > 1 &&
+             (path.endsWith(Platform.pathSeparator) ||
+              path.endsWith('/'))) {
+        path = path.substring(0, path.length - 1);
+      }
+    } else {
+      while (path.length > 1 && path.endsWith(Platform.pathSeparator)) {
+        path = path.substring(0, path.length - 1);
+      }
+    }
+    return path;
+  }
+
+  static String _ensureTrailingPathSeparators(String path) {
+    // Don't handle argument errors here.
+    if (path is! String) return path;
+    if (path.isEmpty) path = '.';
+    if (Platform.isWindows) {
+      while (!path.endsWith(Platform.pathSeparator) && !path.endsWith('/')) {
+        path = "$path${Platform.pathSeparator}";
+      }
+    } else {
+      while (!path.endsWith(Platform.pathSeparator)) {
+        path = "$path${Platform.pathSeparator}";
+      }
+    }
+    return path;
+  }
+}
+
+
+/**
+ * Base event class emitted by [FileSystemEntity.watch].
+ */
+class FileSystemEvent {
+  /**
+   * Bitfield for [FileSystemEntity.watch], to enable [FileSystemCreateEvent]s.
+   */
+  static const int CREATE = 1 << 0;
+
+  /**
+   * Bitfield for [FileSystemEntity.watch], to enable [FileSystemModifyEvent]s.
+   */
+  static const int MODIFY = 1 << 1;
+
+  /**
+   * Bitfield for [FileSystemEntity.watch], to enable [FileSystemDeleteEvent]s.
+   */
+  static const int DELETE = 1 << 2;
+
+  /**
+   * Bitfield for [FileSystemEntity.watch], to enable [FileSystemMoveEvent]s.
+   */
+  static const int MOVE = 1 << 3;
+
+  /**
+   * Bitfield for [FileSystemEntity.watch], for enabling all of [CREATE],
+   * [MODIFY], [DELETE] and [MOVE].
+   */
+  static const int ALL = CREATE | MODIFY | DELETE | MOVE;
+
+  static const int _MODIFY_ATTRIBUTES = 1 << 4;
+  static const int _DELETE_SELF = 1 << 5;
+  static const int _IS_DIR = 1 << 6;
+
+  /**
+   * The type of event. See [FileSystemEvent] for a list of events.
+   */
+  final int type;
+
+  /**
+   * The path that triggered the event. Depending on the platform and the
+   * FileSystemEntity, the path may be relative.
+   */
+  final String path;
+
+  /**
+   * Is `true` if the event target was a directory.
+   */
+  final bool isDirectory;
+
+  FileSystemEvent._(this.type, this.path, this.isDirectory);
+}
+
+
+/**
+ * File system event for newly created file system objects.
+ */
+class FileSystemCreateEvent extends FileSystemEvent {
+  FileSystemCreateEvent._(path, isDirectory)
+      : super._(FileSystemEvent.CREATE, path, isDirectory);
+
+  String toString() => "FileSystemCreateEvent('$path')";
+}
+
+
+/**
+ * File system event for modifications of file system objects.
+ */
+class FileSystemModifyEvent extends FileSystemEvent {
+  /**
+   * If the content was changed and not only the attributes, [contentChanged]
+   * is `true`.
+   */
+  final bool contentChanged;
+
+  FileSystemModifyEvent._(path, isDirectory, this.contentChanged)
+      : super._(FileSystemEvent.MODIFY, path, isDirectory);
+
+  String toString() =>
+      "FileSystemModifyEvent('$path', contentChanged=$contentChanged)";
+}
+
+
+/**
+ * File system event for deletion of file system objects.
+ */
+class FileSystemDeleteEvent extends FileSystemEvent {
+  FileSystemDeleteEvent._(path, isDirectory)
+      : super._(FileSystemEvent.DELETE, path, isDirectory);
+
+  String toString() => "FileSystemDeleteEvent('$path')";
+}
+
+
+/**
+ * File system event for moving of file system objects.
+ */
+class FileSystemMoveEvent extends FileSystemEvent {
+  /**
+   * If the underlaying implementation is able to identify the destination of
+   * the moved file, [destination] will be set. Otherwise, it will be `null`.
+   */
+  final String destination;
+
+  FileSystemMoveEvent._(path, isDirectory, this.destination)
+      : super._(FileSystemEvent.MOVE, path, isDirectory);
+
+  String toString() {
+    var buffer = new StringBuffer();
+    buffer.write("FileSystemMoveEvent('$path'");
+    if (destination != null) buffer.write(", '$destination'");
+    buffer.write(')');
+    return buffer.toString();
+  }
+}
+
+
+class _FileSystemWatcher {
+  external static Stream<FileSystemEvent> _watch(
+      String path, int events, bool recursive);
+  external static bool get isSupported;
+}