Repo created

TMessagesProj/jni/voip/webrtc/base/files/file_path_watcher.h

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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This module provides a way to monitor a file or directory for changes.
+
+#ifndef BASE_FILES_FILE_PATH_WATCHER_H_
+#define BASE_FILES_FILE_PATH_WATCHER_H_
+
+#include <memory>
+
+#include "base/base_export.h"
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/sequence_checker.h"
+#include "base/sequenced_task_runner.h"
+
+namespace base {
+
+// This class lets you register interest in changes on a FilePath.
+// The callback will get called whenever the file or directory referenced by the
+// FilePath is changed, including created or deleted. Due to limitations in the
+// underlying OS APIs, FilePathWatcher has slightly different semantics on OS X
+// than on Windows or Linux. FilePathWatcher on Linux and Windows will detect
+// modifications to files in a watched directory. FilePathWatcher on Mac will
+// detect the creation and deletion of files in a watched directory, but will
+// not detect modifications to those files. See file_path_watcher_kqueue.cc for
+// details.
+//
+// Must be destroyed on the sequence that invokes Watch().
+class BASE_EXPORT FilePathWatcher {
+ public:
+  // Callback type for Watch(). |path| points to the file that was updated,
+  // and |error| is true if the platform specific code detected an error. In
+  // that case, the callback won't be invoked again.
+  using Callback =
+      base::RepeatingCallback<void(const FilePath& path, bool error)>;
+
+  // Used internally to encapsulate different members on different platforms.
+  class PlatformDelegate {
+   public:
+    PlatformDelegate();
+    virtual ~PlatformDelegate();
+
+    // Start watching for the given |path| and notify |delegate| about changes.
+    virtual bool Watch(const FilePath& path,
+                       bool recursive,
+                       const Callback& callback) WARN_UNUSED_RESULT = 0;
+
+    // Stop watching. This is called from FilePathWatcher's dtor in order to
+    // allow to shut down properly while the object is still alive.
+    virtual void Cancel() = 0;
+
+   protected:
+    friend class FilePathWatcher;
+
+    scoped_refptr<SequencedTaskRunner> task_runner() const {
+      return task_runner_;
+    }
+
+    void set_task_runner(scoped_refptr<SequencedTaskRunner> runner) {
+      task_runner_ = std::move(runner);
+    }
+
+    // Must be called before the PlatformDelegate is deleted.
+    void set_cancelled() {
+      cancelled_ = true;
+    }
+
+    bool is_cancelled() const {
+      return cancelled_;
+    }
+
+   private:
+    scoped_refptr<SequencedTaskRunner> task_runner_;
+    bool cancelled_;
+
+    DISALLOW_COPY_AND_ASSIGN(PlatformDelegate);
+  };
+
+  FilePathWatcher();
+  ~FilePathWatcher();
+
+  // Returns true if the platform and OS version support recursive watches.
+  static bool RecursiveWatchAvailable();
+
+  // Invokes |callback| whenever updates to |path| are detected. This should be
+  // called at most once. Set |recursive| to true to watch |path| and its
+  // children. The callback will be invoked on the same sequence. Returns true
+  // on success.
+  //
+  // On POSIX, this must be called from a thread that supports
+  // FileDescriptorWatcher.
+  //
+  // Recursive watch is not supported on all platforms and file systems.
+  // Watch() will return false in the case of failure.
+  bool Watch(const FilePath& path, bool recursive, const Callback& callback);
+
+ private:
+  std::unique_ptr<PlatformDelegate> impl_;
+
+  SequenceChecker sequence_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilePathWatcher);
+};
+
+}  // namespace base
+
+#endif  // BASE_FILES_FILE_PATH_WATCHER_H_