Implement Linux media notifier.

content/browser/media_device_notifications_linux.cc

+// 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.
+
+#include "content/browser/media_device_notifications_linux.h"
+
+#include <mntent.h>
+#include <stdio.h>
+
+#include "base/file_util.h"
+#include "base/string_util.h"
+#include "base/system_monitor/system_monitor.h"
+#include "content/public/browser/browser_thread.h"
+
+using base::SystemMonitor;
+
+namespace {
+
+const char* const kDCIMDirName = "DCIM";
+
+// List of file systems we care about.
+const char* const kKnownFileSystems[] = {
+  "ext2",
+  "ext3",
+  "ext4",
+  "fat",
+  "hfsplus",
+  "iso9660",
+  "msdos",
+  "ntfs",
+  "udf",
+  "vfat",
+};
+
+}  // namespace
+
+namespace content {
+
+MediaDeviceNotificationsLinux::MediaDeviceNotificationsLinux(
+    const FilePath& path)
+    : initialized_(false),
+      mtab_path_(path),
+      current_device_id_(0U) {
+  CHECK(!path.empty());
+
+  // Put |kKnownFileSystems| in std::set to get O(log N) access time.
+  for (size_t i = 0; i < arraysize(kKnownFileSystems); ++i)
+    known_file_systems_.insert(kKnownFileSystems[i]);
+}
+
+MediaDeviceNotificationsLinux::~MediaDeviceNotificationsLinux() {
+}
+
+void MediaDeviceNotificationsLinux::InitOnFileThread() {
+  DCHECK(!initialized_);
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  initialized_ = true;
+
+  watcher_delegate_ = new WatcherDelegate(this);
+  if (!file_watcher_.Watch(mtab_path_, watcher_delegate_)) {
+    LOG(ERROR) << "Adding watch for " << mtab_path_.value() << " failed";
+    return;
+  }
+
+  UpdateMtab();
+}
+
+void MediaDeviceNotificationsLinux::OnFilePathChanged(const FilePath& path) {
+  if (path != mtab_path_) {
+    NOTREACHED();
+    return;
+  }
+
+  UpdateMtab();
+}
+
+void MediaDeviceNotificationsLinux::UpdateMtab() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+
+  MountMap new_mtab;
+  ReadMtab(&new_mtab);
+
+  // Check existing mtab entries for unaccounted mount points.
+  // These mount points must have been removed in the new mtab.
+  MountMap::iterator it = mtab_.begin();
+  while (it != mtab_.end()) {
+    const MountPoint& mount_point(it->first);
+    // |mount_point| not in |new_mtab|.
+    if (new_mtab.find(mount_point) == new_mtab.end()) {
+      const SystemMonitor::DeviceIdType& device_id(it->second.second);
+      RemoveOldDevice(device_id);
+      mtab_.erase(it++);
+      continue;
+    }
+    // Existing mount point. Ignore and deal in the next loop.
+    ++it;
+  }
+
+  // Check new mtab entries against existing ones.
+  for (MountMap::iterator newiter = new_mtab.begin();
+       newiter != new_mtab.end();
+       ++newiter) {
+    const MountPoint& mount_point(newiter->first);
+    const MountDeviceAndId& mount_device_and_id(newiter->second);
+    const MountDevice& mount_device(newiter->second.first);
+    SystemMonitor::DeviceIdType& id(newiter->second.second);
+    MountMap::iterator olditer = mtab_.find(mount_point);
+    // Check to see if it is a new mount point.
+    if (olditer == mtab_.end()) {
+      if (IsMediaDevice(mount_point)) {
+        AddNewDevice(mount_device, mount_point, &id);
+        mtab_[mount_point] = mount_device_and_id;
+      }
+      continue;
+    }
+
+    // Existing mount point. Check to see if a new device is mounted there.
+    MountDeviceAndId& old_mount_device_and_id(olditer->second);
+    if (mount_point == old_mount_device_and_id.first)
+      continue;
+
+    // New device mounted.
+    RemoveOldDevice(old_mount_device_and_id.second);
+    if (IsMediaDevice(mount_point)) {
+      AddNewDevice(mount_device, mount_point, &id);
+      olditer->second = mount_device_and_id;
+    }
+  }
+}
+
+void MediaDeviceNotificationsLinux::ReadMtab(MountMap* mtab) {
+  FILE* fp = setmntent(mtab_path_.value().c_str(), "r");
+  if (!fp)
+    return;
+
+  MountMap& new_mtab = *mtab;
+  struct mntent entry;
+  char buf[512];
+  SystemMonitor::DeviceIdType mount_position = 0;
+  typedef std::pair<MountPoint, SystemMonitor::DeviceIdType> MountPointAndId;
+  typedef std::map<MountDevice, MountPointAndId> DeviceMap;
+  DeviceMap device_map;
+  while (getmntent_r(fp, &entry, buf, sizeof(buf))) {
+    // We only care about real file systems.
+    if (known_file_systems_.find(entry.mnt_type) == known_file_systems_.end())
+      continue;
+    // Add entries, but overwrite entries for the same mount device. Keep track
+    // of the entry positions in the device id field and use that below to
+    // resolve multiple devices mounted at the same mount point.
+    device_map[entry.mnt_fsname] =
+        std::make_pair(entry.mnt_dir, mount_position++);
+  }
+  endmntent(fp);
+
+  for (DeviceMap::iterator device_it = device_map.begin();
+       device_it != device_map.end();
+       ++device_it) {
+    const MountDevice& device = device_it->first;
+    const MountPoint& mount_point = device_it->second.first;
+    const SystemMonitor::DeviceIdType& position = device_it->second.second;
+
+    // No device at |mount_point|, save |device| to it.
+    MountMap::iterator mount_it = new_mtab.find(mount_point);
+    if (mount_it == new_mtab.end()) {
+      new_mtab[mount_point] = std::make_pair(device, position);
+      continue;
+    }
+
+    // There is already a device mounted at |mount_point|. Check to see if
+    // the existing mount entry is newer than the current one.
+    MountDevice& existing_device = mount_it->second.first;
+    SystemMonitor::DeviceIdType& existing_position = mount_it->second.second;
+    if (existing_position > position)
+      continue;
+
+    // The current entry is newer, update the mount point entry.
+    existing_device = device;
+    existing_position = position;
+  }
+}
+
+bool MediaDeviceNotificationsLinux::IsMediaDevice(
+    const MountPoint& mount_point) {
+  FilePath dcim_path(mount_point);
+  FilePath::StringType dcim_dir(kDCIMDirName);
+  if (!file_util::DirectoryExists(dcim_path.Append(dcim_dir))) {
+    // Check for lowercase 'dcim' as well.
+    FilePath dcim_path_lower(dcim_path.Append(StringToLowerASCII(dcim_dir)));
+    if (!file_util::DirectoryExists(dcim_path_lower)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+void MediaDeviceNotificationsLinux::AddNewDevice(
+    const MountDevice& mount_device,
+    const MountPoint& mount_point,
+    base::SystemMonitor::DeviceIdType* device_id) {
+  *device_id = current_device_id_++;
+  base::SystemMonitor* system_monitor = base::SystemMonitor::Get();
+  system_monitor->ProcessMediaDeviceAttached(*device_id,
+                                             mount_device,
+                                             FilePath(mount_point));
+}
+
+void MediaDeviceNotificationsLinux::RemoveOldDevice(
+    const base::SystemMonitor::DeviceIdType& device_id) {
+  base::SystemMonitor* system_monitor = base::SystemMonitor::Get();
+  system_monitor->ProcessMediaDeviceDetached(device_id);
+}
+
+MediaDeviceNotificationsLinux::WatcherDelegate::WatcherDelegate(
+    MediaDeviceNotificationsLinux* notifier)
+    : notifier_(notifier) {
+}
+
+MediaDeviceNotificationsLinux::WatcherDelegate::~WatcherDelegate() {
+}
+
+void MediaDeviceNotificationsLinux::WatcherDelegate::OnFilePathChanged(
+    const FilePath& path) {
+  notifier_->OnFilePathChanged(path);
+}
+
+}  // namespace content