Linux: Refactor udev device monitoring code into its own class so it can be reused more easily.

content/browser/udev_linux.h

+// 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.
+
+// UdevLinux listens for device change notifications from udev and runs
+// callbacks when notifications occur.
+//
+// UdevLinux must be created on a MessageLoop of TYPE_IO.
+// UdevLinux is not thread-safe.
+//
+// Example usage:
+//
+// class UdevLinux;
+//
+// class Foo {
+//  public:
+//   Foo() {
+//     std::vector<UdevLinux::UdevMonitorFilter> filters;
+//     filters.push_back(content::UdevLinux::UdevMonitorFilter("block", NULL));
+//     udev_.reset(new UdevLinux(filters,
+//                               base::Bind(&Foo::Notify, this)));
+//   }
+//
+//   // Called when a "block" device attaches/detaches.
+//   // To hold on to |device|, call udev_device_ref(device).
+//   void Notify(udev_device* device) {
+//     // Do something with |device|.
+//   }
+//
+//  private:
+//   scoped_ptr<UdevLinux> udev_;
+//
+//   DISALLOW_COPY_AND_ASSIGN(Foo);
+// };
+
+#ifndef CONTENT_BROWSER_UDEV_LINUX_H_
+#define CONTENT_BROWSER_UDEV_LINUX_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/compiler_specific.h"
+#include "base/message_pump_libevent.h"
+
+extern "C" {
+struct udev;
+struct udev_device;
+struct udev_monitor;
+}
+
+namespace content {
+
+class UdevLinux : public base::MessagePumpLibevent::Watcher {
+ public:
+  typedef base::Callback<void(udev_device*)> UdevNotificationCallback;
+
+  // subsystem and devtype parameter for
+  // udev_monitor_filter_add_match_subsystem_devtype().
+  struct UdevMonitorFilter {
+    UdevMonitorFilter(const char* subsystem_in, const char* devtype_in)
+        : subsystem(subsystem_in),
+          devtype(devtype_in) {
+    }
+    const char* subsystem;
+    const char* devtype;
+  };
+
+  // Filter incoming devices based on |filters|.
+  // Calls |callback| upon device change events.
+  UdevLinux(const std::vector<UdevMonitorFilter>& filters,
+            const UdevNotificationCallback& callback);
+  virtual ~UdevLinux();
+
+
+  // Returns the udev handle to be passed into other udev_*() functions.
+  udev* udev_handle();
+
+ private:
+  // base::MessagePump:Libevent::Watcher implementation.
+  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
+  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
+
+  // libudev-related items, the main context, and the monitoring context to be
+  // notified about changes to device states.
+  udev* udev_;
+  udev_monitor* monitor_;
+  int monitor_fd_;
+  base::MessagePumpLibevent::FileDescriptorWatcher monitor_watcher_;
+  UdevNotificationCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(UdevLinux);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_UDEV_LINUX_H_