apps/saved_files_service.cc - chromium/src - Git at Google

 // Copyright 2013 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 "apps/saved_files_service.h"

 #include <stdint.h>

 #include <algorithm>
 #include <map>
 #include <memory>
 #include <unordered_map>
 #include <utility>

 #include "apps/saved_files_service_factory.h"
 #include "base/value_conversions.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/notification_service.h"
 #include "extensions/browser/api/file_system/saved_file_entry.h"
 #include "extensions/browser/extension_host.h"
 #include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/notification_types.h"
 #include "extensions/common/permissions/api_permission.h"
 #include "extensions/common/permissions/permission_set.h"
 #include "extensions/common/permissions/permissions_data.h"

 namespace apps {

 using extensions::APIPermission;
 using extensions::Extension;
 using extensions::ExtensionHost;
 using extensions::ExtensionPrefs;
 using extensions::SavedFileEntry;

 namespace {

 // Preference keys

 // The file entries that the app has permission to access.
 const char kFileEntries[] = "file_entries";

 // The path to a file entry that the app had permission to access.
 const char kFileEntryPath[] = "path";

 // Whether or not the the entry refers to a directory.
 const char kFileEntryIsDirectory[] = "is_directory";

 // The sequence number in the LRU of the file entry.
 const char kFileEntrySequenceNumber[] = "sequence_number";

 const size_t kMaxSavedFileEntries = 500;
 const int kMaxSequenceNumber = INT32_MAX;

 // These might be different to the constant values in tests.
 size_t g_max_saved_file_entries = kMaxSavedFileEntries;
 int g_max_sequence_number = kMaxSequenceNumber;

 // Persists a SavedFileEntry in ExtensionPrefs.
 void AddSavedFileEntry(ExtensionPrefs* prefs,
                        const std::string& extension_id,
                        const SavedFileEntry& file_entry) {
   ExtensionPrefs::ScopedDictionaryUpdate update(
       prefs, extension_id, kFileEntries);
   auto file_entries = update.Create();
   DCHECK(!file_entries->GetDictionaryWithoutPathExpansion(file_entry.id, NULL));

   std::unique_ptr<base::DictionaryValue> file_entry_dict =
       std::make_unique<base::DictionaryValue>();
   file_entry_dict->SetKey(kFileEntryPath, CreateFilePathValue(file_entry.path));
   file_entry_dict->SetBoolean(kFileEntryIsDirectory, file_entry.is_directory);
   file_entry_dict->SetInteger(kFileEntrySequenceNumber,
                               file_entry.sequence_number);
   file_entries->SetWithoutPathExpansion(file_entry.id,
                                         std::move(file_entry_dict));
 }

 // Updates the sequence_number of a SavedFileEntry persisted in ExtensionPrefs.
 void UpdateSavedFileEntry(ExtensionPrefs* prefs,
                           const std::string& extension_id,
                           const SavedFileEntry& file_entry) {
   ExtensionPrefs::ScopedDictionaryUpdate update(
       prefs, extension_id, kFileEntries);
   auto file_entries = update.Get();
   DCHECK(file_entries);
   std::unique_ptr<prefs::DictionaryValueUpdate> file_entry_dict;
   file_entries->GetDictionaryWithoutPathExpansion(file_entry.id,
                                                   &file_entry_dict);
   DCHECK(file_entry_dict);
   file_entry_dict->SetInteger(kFileEntrySequenceNumber,
                               file_entry.sequence_number);
 }

 // Removes a SavedFileEntry from ExtensionPrefs.
 void RemoveSavedFileEntry(ExtensionPrefs* prefs,
                           const std::string& extension_id,
                           const std::string& file_entry_id) {
   ExtensionPrefs::ScopedDictionaryUpdate update(
       prefs, extension_id, kFileEntries);
   auto file_entries = update.Create();
   file_entries->RemoveWithoutPathExpansion(file_entry_id, NULL);
 }

 // Clears all SavedFileEntry for the app from ExtensionPrefs.
 void ClearSavedFileEntries(ExtensionPrefs* prefs,
                            const std::string& extension_id) {
   prefs->UpdateExtensionPref(extension_id, kFileEntries, nullptr);
 }

 // Returns all SavedFileEntries for the app.
 std::vector<SavedFileEntry> GetSavedFileEntries(
     ExtensionPrefs* prefs,
     const std::string& extension_id) {
   std::vector<SavedFileEntry> result;
   const base::DictionaryValue* file_entries = NULL;
   if (!prefs->ReadPrefAsDictionary(extension_id, kFileEntries, &file_entries))
     return result;

   for (base::DictionaryValue::Iterator it(*file_entries); !it.IsAtEnd();
        it.Advance()) {
     const base::DictionaryValue* file_entry = NULL;
     if (!it.value().GetAsDictionary(&file_entry))
       continue;
     const base::Value* path_value;
     if (!file_entry->Get(kFileEntryPath, &path_value))
       continue;
     base::FilePath file_path;
     if (!GetValueAsFilePath(*path_value, &file_path))
       continue;
     bool is_directory = false;
     file_entry->GetBoolean(kFileEntryIsDirectory, &is_directory);
     int sequence_number = 0;
     if (!file_entry->GetInteger(kFileEntrySequenceNumber, &sequence_number))
       continue;
     if (!sequence_number)
       continue;
     result.push_back(
         SavedFileEntry(it.key(), file_path, is_directory, sequence_number));
   }
   return result;
 }

 }  // namespace

 class SavedFilesService::SavedFiles {
  public:
   SavedFiles(content::BrowserContext* context, const std::string& extension_id);
   ~SavedFiles();

   void RegisterFileEntry(const std::string& id,
                          const base::FilePath& file_path,
                          bool is_directory);
   void EnqueueFileEntry(const std::string& id);
   bool IsRegistered(const std::string& id) const;
   const SavedFileEntry* GetFileEntry(const std::string& id) const;
   std::vector<SavedFileEntry> GetAllFileEntries() const;

  private:
   // Compacts sequence numbers if the largest sequence number is
   // g_max_sequence_number. Outside of testing, it is set to kint32max, so this
   // will almost never do any real work.
   void MaybeCompactSequenceNumbers();

   void LoadSavedFileEntriesFromPreferences();

   content::BrowserContext* context_;
   const std::string extension_id_;

   // Contains all file entries that have been registered, keyed by ID.
   std::unordered_map<std::string, std::unique_ptr<SavedFileEntry>>
       registered_file_entries_;

   // The queue of file entries that have been retained, keyed by
   // sequence_number. Values are a subset of values in registered_file_entries_.
   // This should be kept in sync with file entries stored in extension prefs.
   std::map<int, SavedFileEntry*> saved_file_lru_;

   DISALLOW_COPY_AND_ASSIGN(SavedFiles);
 };

 // static
 SavedFilesService* SavedFilesService::Get(content::BrowserContext* context) {
   return SavedFilesServiceFactory::GetForBrowserContext(context);
 }

 SavedFilesService::SavedFilesService(content::BrowserContext* context)
     : context_(context) {
   registrar_.Add(this,
                  extensions::NOTIFICATION_EXTENSION_HOST_DESTROYED,
                  content::NotificationService::AllSources());
 }

 SavedFilesService::~SavedFilesService() = default;

 void SavedFilesService::Observe(int type,
                                 const content::NotificationSource& source,
                                 const content::NotificationDetails& details) {
   DCHECK_EQ(extensions::NOTIFICATION_EXTENSION_HOST_DESTROYED, type);
   ExtensionHost* host = content::Details<ExtensionHost>(details).ptr();
   const Extension* extension = host->extension();
   if (extension) {
     ClearQueueIfNoRetainPermission(extension);
     Clear(extension->id());
   }
 }

 void SavedFilesService::RegisterFileEntry(const std::string& extension_id,
                                           const std::string& id,
                                           const base::FilePath& file_path,
                                           bool is_directory) {
   GetOrInsert(extension_id)->RegisterFileEntry(id, file_path, is_directory);
 }

 void SavedFilesService::EnqueueFileEntry(const std::string& extension_id,
                                          const std::string& id) {
   GetOrInsert(extension_id)->EnqueueFileEntry(id);
 }

 std::vector<SavedFileEntry> SavedFilesService::GetAllFileEntries(
     const std::string& extension_id) {
   SavedFiles* saved_files = Get(extension_id);
   if (saved_files)
     return saved_files->GetAllFileEntries();
   return GetSavedFileEntries(ExtensionPrefs::Get(context_), extension_id);
 }

 bool SavedFilesService::IsRegistered(const std::string& extension_id,
                                      const std::string& id) {
   return GetOrInsert(extension_id)->IsRegistered(id);
 }

 const SavedFileEntry* SavedFilesService::GetFileEntry(
     const std::string& extension_id,
     const std::string& id) {
   return GetOrInsert(extension_id)->GetFileEntry(id);
 }

 void SavedFilesService::ClearQueueIfNoRetainPermission(
     const Extension* extension) {
   if (!extension->permissions_data()->active_permissions().HasAPIPermission(
           APIPermission::kFileSystemRetainEntries)) {
     ClearQueue(extension);
   }
 }

 void SavedFilesService::ClearQueue(const extensions::Extension* extension) {
   ClearSavedFileEntries(ExtensionPrefs::Get(context_), extension->id());
   Clear(extension->id());
 }

 void SavedFilesService::OnApplicationTerminating() {
   // Stop listening to NOTIFICATION_EXTENSION_HOST_DESTROYED in particular
   // as all extension hosts will be destroyed as a result of shutdown.
   registrar_.RemoveAll();
 }

 SavedFilesService::SavedFiles* SavedFilesService::Get(
     const std::string& extension_id) const {
   auto it = extension_id_to_saved_files_.find(extension_id);
   if (it != extension_id_to_saved_files_.end())
     return it->second.get();

   return NULL;
 }

 SavedFilesService::SavedFiles* SavedFilesService::GetOrInsert(
     const std::string& extension_id) {
   SavedFiles* saved_files = Get(extension_id);
   if (saved_files)
     return saved_files;

   std::unique_ptr<SavedFiles> scoped_saved_files(
       new SavedFiles(context_, extension_id));
   saved_files = scoped_saved_files.get();
   extension_id_to_saved_files_.insert(
       std::make_pair(extension_id, std::move(scoped_saved_files)));
   return saved_files;
 }

 void SavedFilesService::Clear(const std::string& extension_id) {
   extension_id_to_saved_files_.erase(extension_id);
 }

 SavedFilesService::SavedFiles::SavedFiles(content::BrowserContext* context,
                                           const std::string& extension_id)
     : context_(context), extension_id_(extension_id) {
   LoadSavedFileEntriesFromPreferences();
 }

 SavedFilesService::SavedFiles::~SavedFiles() = default;

 void SavedFilesService::SavedFiles::RegisterFileEntry(
     const std::string& id,
     const base::FilePath& file_path,
     bool is_directory) {
   auto it = registered_file_entries_.find(id);
   if (it != registered_file_entries_.end())
     return;

   registered_file_entries_[id] =
       std::make_unique<SavedFileEntry>(id, file_path, is_directory, 0);
 }

 void SavedFilesService::SavedFiles::EnqueueFileEntry(const std::string& id) {
   auto it = registered_file_entries_.find(id);
   DCHECK(it != registered_file_entries_.end());

   SavedFileEntry* file_entry = it->second.get();
   int old_sequence_number = file_entry->sequence_number;
   if (!saved_file_lru_.empty()) {
     // Get the sequence number after the last file entry in the LRU.
     std::map<int, SavedFileEntry*>::reverse_iterator it =
         saved_file_lru_.rbegin();
     if (it->second == file_entry)
       return;

     file_entry->sequence_number = it->first + 1;
   } else {
     // The first sequence number is 1, as 0 means the entry is not in the LRU.
     file_entry->sequence_number = 1;
   }
   saved_file_lru_.insert(
       std::make_pair(file_entry->sequence_number, file_entry));
   ExtensionPrefs* prefs = ExtensionPrefs::Get(context_);
   if (old_sequence_number) {
     saved_file_lru_.erase(old_sequence_number);
     UpdateSavedFileEntry(prefs, extension_id_, *file_entry);
   } else {
     AddSavedFileEntry(prefs, extension_id_, *file_entry);
     if (saved_file_lru_.size() > g_max_saved_file_entries) {
       std::map<int, SavedFileEntry*>::iterator it = saved_file_lru_.begin();
       it->second->sequence_number = 0;
       RemoveSavedFileEntry(prefs, extension_id_, it->second->id);
       saved_file_lru_.erase(it);
     }
   }
   MaybeCompactSequenceNumbers();
 }

 bool SavedFilesService::SavedFiles::IsRegistered(const std::string& id) const {
   auto it = registered_file_entries_.find(id);
   return it != registered_file_entries_.end();
 }

 const SavedFileEntry* SavedFilesService::SavedFiles::GetFileEntry(
     const std::string& id) const {
   auto it = registered_file_entries_.find(id);
   if (it == registered_file_entries_.end())
     return NULL;

   return it->second.get();
 }

 std::vector<SavedFileEntry> SavedFilesService::SavedFiles::GetAllFileEntries()
     const {
   std::vector<SavedFileEntry> result;
   for (auto it = registered_file_entries_.begin();
        it != registered_file_entries_.end(); ++it) {
     result.push_back(*it->second.get());
   }
   return result;
 }

 void SavedFilesService::SavedFiles::MaybeCompactSequenceNumbers() {
   DCHECK_GE(g_max_sequence_number, 0);
   DCHECK_GE(static_cast<size_t>(g_max_sequence_number),
             g_max_saved_file_entries);
   std::map<int, SavedFileEntry*>::reverse_iterator it =
       saved_file_lru_.rbegin();
   if (it == saved_file_lru_.rend())
     return;

   // Only compact sequence numbers if the last entry's sequence number is the
   // maximum value.  This should almost never be the case.
   if (it->first < g_max_sequence_number)
     return;

   int sequence_number = 0;
   ExtensionPrefs* prefs = ExtensionPrefs::Get(context_);
   for (std::map<int, SavedFileEntry*>::iterator it = saved_file_lru_.begin();
        it != saved_file_lru_.end();
        ++it) {
     sequence_number++;
     if (it->second->sequence_number == sequence_number)
       continue;

     SavedFileEntry* file_entry = it->second;
     file_entry->sequence_number = sequence_number;
     UpdateSavedFileEntry(prefs, extension_id_, *file_entry);
     saved_file_lru_.erase(it++);
     // Provide the following element as an insert hint. While optimized
     // insertion time with the following element as a hint is only supported by
     // the spec in C++11, the implementations do support this.
     it = saved_file_lru_.insert(
         it, std::make_pair(file_entry->sequence_number, file_entry));
   }
 }

 void SavedFilesService::SavedFiles::LoadSavedFileEntriesFromPreferences() {
   ExtensionPrefs* prefs = ExtensionPrefs::Get(context_);
   std::vector<SavedFileEntry> saved_entries =
       GetSavedFileEntries(prefs, extension_id_);
   for (std::vector<SavedFileEntry>::iterator it = saved_entries.begin();
        it != saved_entries.end();
        ++it) {
     std::unique_ptr<SavedFileEntry> file_entry(new SavedFileEntry(*it));
     const std::string& id = file_entry->id;
     saved_file_lru_.insert(
         std::make_pair(file_entry->sequence_number, file_entry.get()));
     registered_file_entries_[id] = std::move(file_entry);
   }
 }

 // static
 void SavedFilesService::SetMaxSequenceNumberForTest(int max_value) {
   g_max_sequence_number = max_value;
 }

 // static
 void SavedFilesService::ClearMaxSequenceNumberForTest() {
   g_max_sequence_number = kMaxSequenceNumber;
 }

 // static
 void SavedFilesService::SetLruSizeForTest(int size) {
   g_max_saved_file_entries = size;
 }

 // static
 void SavedFilesService::ClearLruSizeForTest() {
   g_max_saved_file_entries = kMaxSavedFileEntries;
 }

 }  // namespace apps
	// Copyright 2013 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 "apps/saved_files_service.h"

	#include <stdint.h>

	#include <algorithm>
	#include <map>
	#include <memory>
	#include <unordered_map>
	#include <utility>

	#include "apps/saved_files_service_factory.h"
	#include "base/value_conversions.h"
	#include "content/public/browser/browser_context.h"
	#include "content/public/browser/notification_service.h"
	#include "extensions/browser/api/file_system/saved_file_entry.h"
	#include "extensions/browser/extension_host.h"
	#include "extensions/browser/extension_prefs.h"
	#include "extensions/browser/extension_system.h"
	#include "extensions/browser/notification_types.h"
	#include "extensions/common/permissions/api_permission.h"
	#include "extensions/common/permissions/permission_set.h"
	#include "extensions/common/permissions/permissions_data.h"

	namespace apps {

	using extensions::APIPermission;
	using extensions::Extension;
	using extensions::ExtensionHost;
	using extensions::ExtensionPrefs;
	using extensions::SavedFileEntry;

	namespace {

	// Preference keys

	// The file entries that the app has permission to access.
	const char kFileEntries[] = "file_entries";

	// The path to a file entry that the app had permission to access.
	const char kFileEntryPath[] = "path";

	// Whether or not the the entry refers to a directory.
	const char kFileEntryIsDirectory[] = "is_directory";

	// The sequence number in the LRU of the file entry.
	const char kFileEntrySequenceNumber[] = "sequence_number";

	const size_t kMaxSavedFileEntries = 500;
	const int kMaxSequenceNumber = INT32_MAX;

	// These might be different to the constant values in tests.
	size_t g_max_saved_file_entries = kMaxSavedFileEntries;
	int g_max_sequence_number = kMaxSequenceNumber;

	// Persists a SavedFileEntry in ExtensionPrefs.
	void AddSavedFileEntry(ExtensionPrefs* prefs,
	const std::string& extension_id,
	const SavedFileEntry& file_entry) {
	ExtensionPrefs::ScopedDictionaryUpdate update(
	prefs, extension_id, kFileEntries);
	auto file_entries = update.Create();
	DCHECK(!file_entries->GetDictionaryWithoutPathExpansion(file_entry.id, NULL));

	std::unique_ptr<base::DictionaryValue> file_entry_dict =
	std::make_unique<base::DictionaryValue>();
	file_entry_dict->SetKey(kFileEntryPath, CreateFilePathValue(file_entry.path));
	file_entry_dict->SetBoolean(kFileEntryIsDirectory, file_entry.is_directory);
	file_entry_dict->SetInteger(kFileEntrySequenceNumber,
	file_entry.sequence_number);
	file_entries->SetWithoutPathExpansion(file_entry.id,
	std::move(file_entry_dict));
	}

	// Updates the sequence_number of a SavedFileEntry persisted in ExtensionPrefs.
	void UpdateSavedFileEntry(ExtensionPrefs* prefs,
	const std::string& extension_id,
	const SavedFileEntry& file_entry) {
	ExtensionPrefs::ScopedDictionaryUpdate update(
	prefs, extension_id, kFileEntries);
	auto file_entries = update.Get();
	DCHECK(file_entries);
	std::unique_ptr<prefs::DictionaryValueUpdate> file_entry_dict;
	file_entries->GetDictionaryWithoutPathExpansion(file_entry.id,
	&file_entry_dict);
	DCHECK(file_entry_dict);
	file_entry_dict->SetInteger(kFileEntrySequenceNumber,
	file_entry.sequence_number);
	}

	// Removes a SavedFileEntry from ExtensionPrefs.
	void RemoveSavedFileEntry(ExtensionPrefs* prefs,
	const std::string& extension_id,
	const std::string& file_entry_id) {
	ExtensionPrefs::ScopedDictionaryUpdate update(
	prefs, extension_id, kFileEntries);
	auto file_entries = update.Create();
	file_entries->RemoveWithoutPathExpansion(file_entry_id, NULL);
	}

	// Clears all SavedFileEntry for the app from ExtensionPrefs.
	void ClearSavedFileEntries(ExtensionPrefs* prefs,
	const std::string& extension_id) {
	prefs->UpdateExtensionPref(extension_id, kFileEntries, nullptr);
	}

	// Returns all SavedFileEntries for the app.
	std::vector<SavedFileEntry> GetSavedFileEntries(
	ExtensionPrefs* prefs,
	const std::string& extension_id) {
	std::vector<SavedFileEntry> result;
	const base::DictionaryValue* file_entries = NULL;
	if (!prefs->ReadPrefAsDictionary(extension_id, kFileEntries, &file_entries))
	return result;

	for (base::DictionaryValue::Iterator it(*file_entries); !it.IsAtEnd();
	it.Advance()) {
	const base::DictionaryValue* file_entry = NULL;
	if (!it.value().GetAsDictionary(&file_entry))
	continue;
	const base::Value* path_value;
	if (!file_entry->Get(kFileEntryPath, &path_value))
	continue;
	base::FilePath file_path;
	if (!GetValueAsFilePath(*path_value, &file_path))
	continue;
	bool is_directory = false;
	file_entry->GetBoolean(kFileEntryIsDirectory, &is_directory);
	int sequence_number = 0;
	if (!file_entry->GetInteger(kFileEntrySequenceNumber, &sequence_number))
	continue;
	if (!sequence_number)
	continue;
	result.push_back(
	SavedFileEntry(it.key(), file_path, is_directory, sequence_number));
	}
	return result;
	}

	} // namespace

	class SavedFilesService::SavedFiles {
	public:
	SavedFiles(content::BrowserContext* context, const std::string& extension_id);
	~SavedFiles();

	void RegisterFileEntry(const std::string& id,
	const base::FilePath& file_path,
	bool is_directory);
	void EnqueueFileEntry(const std::string& id);
	bool IsRegistered(const std::string& id) const;
	const SavedFileEntry* GetFileEntry(const std::string& id) const;
	std::vector<SavedFileEntry> GetAllFileEntries() const;

	private:
	// Compacts sequence numbers if the largest sequence number is
	// g_max_sequence_number. Outside of testing, it is set to kint32max, so this
	// will almost never do any real work.
	void MaybeCompactSequenceNumbers();

	void LoadSavedFileEntriesFromPreferences();

	content::BrowserContext* context_;
	const std::string extension_id_;

	// Contains all file entries that have been registered, keyed by ID.
	std::unordered_map<std::string, std::unique_ptr<SavedFileEntry>>
	registered_file_entries_;

	// The queue of file entries that have been retained, keyed by
	// sequence_number. Values are a subset of values in registered_file_entries_.
	// This should be kept in sync with file entries stored in extension prefs.
	std::map<int, SavedFileEntry*> saved_file_lru_;

	DISALLOW_COPY_AND_ASSIGN(SavedFiles);
	};

	// static
	SavedFilesService* SavedFilesService::Get(content::BrowserContext* context) {
	return SavedFilesServiceFactory::GetForBrowserContext(context);
	}

	SavedFilesService::SavedFilesService(content::BrowserContext* context)
	: context_(context) {
	registrar_.Add(this,
	extensions::NOTIFICATION_EXTENSION_HOST_DESTROYED,
	content::NotificationService::AllSources());
	}

	SavedFilesService::~SavedFilesService() = default;

	void SavedFilesService::Observe(int type,
	const content::NotificationSource& source,
	const content::NotificationDetails& details) {
	DCHECK_EQ(extensions::NOTIFICATION_EXTENSION_HOST_DESTROYED, type);
	ExtensionHost* host = content::Details<ExtensionHost>(details).ptr();
	const Extension* extension = host->extension();
	if (extension) {
	ClearQueueIfNoRetainPermission(extension);
	Clear(extension->id());
	}
	}

	void SavedFilesService::RegisterFileEntry(const std::string& extension_id,
	const std::string& id,
	const base::FilePath& file_path,
	bool is_directory) {
	GetOrInsert(extension_id)->RegisterFileEntry(id, file_path, is_directory);
	}

	void SavedFilesService::EnqueueFileEntry(const std::string& extension_id,
	const std::string& id) {
	GetOrInsert(extension_id)->EnqueueFileEntry(id);
	}

	std::vector<SavedFileEntry> SavedFilesService::GetAllFileEntries(
	const std::string& extension_id) {
	SavedFiles* saved_files = Get(extension_id);
	if (saved_files)
	return saved_files->GetAllFileEntries();
	return GetSavedFileEntries(ExtensionPrefs::Get(context_), extension_id);
	}

	bool SavedFilesService::IsRegistered(const std::string& extension_id,
	const std::string& id) {
	return GetOrInsert(extension_id)->IsRegistered(id);
	}

	const SavedFileEntry* SavedFilesService::GetFileEntry(
	const std::string& extension_id,
	const std::string& id) {
	return GetOrInsert(extension_id)->GetFileEntry(id);
	}

	void SavedFilesService::ClearQueueIfNoRetainPermission(
	const Extension* extension) {
	if (!extension->permissions_data()->active_permissions().HasAPIPermission(
	APIPermission::kFileSystemRetainEntries)) {
	ClearQueue(extension);
	}
	}

	void SavedFilesService::ClearQueue(const extensions::Extension* extension) {
	ClearSavedFileEntries(ExtensionPrefs::Get(context_), extension->id());
	Clear(extension->id());
	}

	void SavedFilesService::OnApplicationTerminating() {
	// Stop listening to NOTIFICATION_EXTENSION_HOST_DESTROYED in particular
	// as all extension hosts will be destroyed as a result of shutdown.
	registrar_.RemoveAll();
	}

	SavedFilesService::SavedFiles* SavedFilesService::Get(
	const std::string& extension_id) const {
	auto it = extension_id_to_saved_files_.find(extension_id);
	if (it != extension_id_to_saved_files_.end())
	return it->second.get();

	return NULL;
	}

	SavedFilesService::SavedFiles* SavedFilesService::GetOrInsert(
	const std::string& extension_id) {
	SavedFiles* saved_files = Get(extension_id);
	if (saved_files)
	return saved_files;

	std::unique_ptr<SavedFiles> scoped_saved_files(
	new SavedFiles(context_, extension_id));
	saved_files = scoped_saved_files.get();
	extension_id_to_saved_files_.insert(
	std::make_pair(extension_id, std::move(scoped_saved_files)));
	return saved_files;
	}

	void SavedFilesService::Clear(const std::string& extension_id) {
	extension_id_to_saved_files_.erase(extension_id);
	}

	SavedFilesService::SavedFiles::SavedFiles(content::BrowserContext* context,
	const std::string& extension_id)
	: context_(context), extension_id_(extension_id) {
	LoadSavedFileEntriesFromPreferences();
	}

	SavedFilesService::SavedFiles::~SavedFiles() = default;

	void SavedFilesService::SavedFiles::RegisterFileEntry(
	const std::string& id,
	const base::FilePath& file_path,
	bool is_directory) {
	auto it = registered_file_entries_.find(id);
	if (it != registered_file_entries_.end())
	return;

	registered_file_entries_[id] =
	std::make_unique<SavedFileEntry>(id, file_path, is_directory, 0);
	}

	void SavedFilesService::SavedFiles::EnqueueFileEntry(const std::string& id) {
	auto it = registered_file_entries_.find(id);
	DCHECK(it != registered_file_entries_.end());

	SavedFileEntry* file_entry = it->second.get();
	int old_sequence_number = file_entry->sequence_number;
	if (!saved_file_lru_.empty()) {
	// Get the sequence number after the last file entry in the LRU.
	std::map<int, SavedFileEntry*>::reverse_iterator it =
	saved_file_lru_.rbegin();
	if (it->second == file_entry)
	return;

	file_entry->sequence_number = it->first + 1;
	} else {
	// The first sequence number is 1, as 0 means the entry is not in the LRU.
	file_entry->sequence_number = 1;
	}
	saved_file_lru_.insert(
	std::make_pair(file_entry->sequence_number, file_entry));
	ExtensionPrefs* prefs = ExtensionPrefs::Get(context_);
	if (old_sequence_number) {
	saved_file_lru_.erase(old_sequence_number);
	UpdateSavedFileEntry(prefs, extension_id_, *file_entry);
	} else {
	AddSavedFileEntry(prefs, extension_id_, *file_entry);
	if (saved_file_lru_.size() > g_max_saved_file_entries) {
	std::map<int, SavedFileEntry*>::iterator it = saved_file_lru_.begin();
	it->second->sequence_number = 0;
	RemoveSavedFileEntry(prefs, extension_id_, it->second->id);
	saved_file_lru_.erase(it);
	}
	}
	MaybeCompactSequenceNumbers();
	}

	bool SavedFilesService::SavedFiles::IsRegistered(const std::string& id) const {
	auto it = registered_file_entries_.find(id);
	return it != registered_file_entries_.end();
	}

	const SavedFileEntry* SavedFilesService::SavedFiles::GetFileEntry(
	const std::string& id) const {
	auto it = registered_file_entries_.find(id);
	if (it == registered_file_entries_.end())
	return NULL;

	return it->second.get();
	}

	std::vector<SavedFileEntry> SavedFilesService::SavedFiles::GetAllFileEntries()
	const {
	std::vector<SavedFileEntry> result;
	for (auto it = registered_file_entries_.begin();
	it != registered_file_entries_.end(); ++it) {
	result.push_back(*it->second.get());
	}
	return result;
	}

	void SavedFilesService::SavedFiles::MaybeCompactSequenceNumbers() {
	DCHECK_GE(g_max_sequence_number, 0);
	DCHECK_GE(static_cast<size_t>(g_max_sequence_number),
	g_max_saved_file_entries);
	std::map<int, SavedFileEntry*>::reverse_iterator it =
	saved_file_lru_.rbegin();
	if (it == saved_file_lru_.rend())
	return;

	// Only compact sequence numbers if the last entry's sequence number is the
	// maximum value. This should almost never be the case.
	if (it->first < g_max_sequence_number)
	return;

	int sequence_number = 0;
	ExtensionPrefs* prefs = ExtensionPrefs::Get(context_);
	for (std::map<int, SavedFileEntry*>::iterator it = saved_file_lru_.begin();
	it != saved_file_lru_.end();
	++it) {
	sequence_number++;
	if (it->second->sequence_number == sequence_number)
	continue;

	SavedFileEntry* file_entry = it->second;
	file_entry->sequence_number = sequence_number;
	UpdateSavedFileEntry(prefs, extension_id_, *file_entry);
	saved_file_lru_.erase(it++);
	// Provide the following element as an insert hint. While optimized
	// insertion time with the following element as a hint is only supported by
	// the spec in C++11, the implementations do support this.
	it = saved_file_lru_.insert(
	it, std::make_pair(file_entry->sequence_number, file_entry));
	}
	}

	void SavedFilesService::SavedFiles::LoadSavedFileEntriesFromPreferences() {
	ExtensionPrefs* prefs = ExtensionPrefs::Get(context_);
	std::vector<SavedFileEntry> saved_entries =
	GetSavedFileEntries(prefs, extension_id_);
	for (std::vector<SavedFileEntry>::iterator it = saved_entries.begin();
	it != saved_entries.end();
	++it) {
	std::unique_ptr<SavedFileEntry> file_entry(new SavedFileEntry(*it));
	const std::string& id = file_entry->id;
	saved_file_lru_.insert(
	std::make_pair(file_entry->sequence_number, file_entry.get()));
	registered_file_entries_[id] = std::move(file_entry);
	}
	}

	// static
	void SavedFilesService::SetMaxSequenceNumberForTest(int max_value) {
	g_max_sequence_number = max_value;
	}

	// static
	void SavedFilesService::ClearMaxSequenceNumberForTest() {
	g_max_sequence_number = kMaxSequenceNumber;
	}

	// static
	void SavedFilesService::SetLruSizeForTest(int size) {
	g_max_saved_file_entries = size;
	}

	// static
	void SavedFilesService::ClearLruSizeForTest() {
	g_max_saved_file_entries = kMaxSavedFileEntries;
	}

	} // namespace apps