Add support for persistent file access in apps.

This replaces chrome.fileSystem.getEntry(By)Id with retainEntry,
restoreEntry and isRestorable, which enable restoring file access after
an app is closed for apps with the fileSystem.retainFiles permission.
Retained files are evicted by LRU, with a maximum of 500 retained files.

BUG=224684

Review URL: https://chromiumcodereview.appspot.com/14607023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202276 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 441 insertions, 0 deletions

diff --git a/apps/saved_files_service.cc b/apps/saved_files_service.cc
new file mode 100644
index 0000000..c509c08
--- /dev/null
+++ b/apps/saved_files_service.cc
@@ -0,0 +1,441 @@
+// 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 <algorithm>
+
+#include "apps/saved_files_service_factory.h"
+#include "base/basictypes.h"
+#include "base/hash_tables.h"
+#include "base/value_conversions.h"
+#include "chrome/browser/extensions/extension_host.h"
+#include "chrome/browser/extensions/extension_prefs.h"
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/extension_system.h"
+#include "chrome/common/extensions/permissions/api_permission.h"
+#include "chrome/common/extensions/permissions/permission_set.h"
+
+namespace apps {
+
+using extensions::APIPermission;
+using extensions::Extension;
+using extensions::ExtensionHost;
+using extensions::ExtensionPrefs;
+
+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 app had write access to a file entry.
+const char kFileEntryWritable[] = "writable";
+
+// The sequence number in the LRU of the file entry.
+const char kFileEntrySequenceNumber[] = "sequence_number";
+
+const size_t kMaxSavedFileEntries = 500;
+const int kMaxSequenceNumber = kint32max;
+
+// 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);
+  DictionaryValue* file_entries = update.Get();
+  if (!file_entries)
+    file_entries = update.Create();
+  DCHECK(!file_entries->GetDictionaryWithoutPathExpansion(file_entry.id, NULL));
+
+  DictionaryValue* file_entry_dict = new DictionaryValue();
+  file_entry_dict->Set(kFileEntryPath, CreateFilePathValue(file_entry.path));
+  file_entry_dict->SetBoolean(kFileEntryWritable, file_entry.writable);
+  file_entry_dict->SetInteger(kFileEntrySequenceNumber,
+                              file_entry.sequence_number);
+  file_entries->SetWithoutPathExpansion(file_entry.id, 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);
+  DictionaryValue* file_entries = update.Get();
+  DCHECK(file_entries);
+  DictionaryValue* file_entry_dict = NULL;
+  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);
+  DictionaryValue* file_entries = update.Get();
+  if (!file_entries)
+    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, NULL);
+}
+
+// Returns all SavedFileEntries for the app.
+std::vector<SavedFileEntry> GetSavedFileEntries(
+    ExtensionPrefs* prefs,
+    const std::string& extension_id) {
+  std::vector<SavedFileEntry> result;
+  const DictionaryValue* file_entries = NULL;
+  if (!prefs->ReadPrefAsDictionary(extension_id, kFileEntries, &file_entries))
+    return result;
+
+  for (DictionaryValue::Iterator it(*file_entries); !it.IsAtEnd();
+       it.Advance()) {
+    const 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 writable = false;
+    if (!file_entry->GetBoolean(kFileEntryWritable, &writable))
+      continue;
+    int sequence_number = 0;
+    if (!file_entry->GetInteger(kFileEntrySequenceNumber, &sequence_number))
+      continue;
+    if (!sequence_number)
+      continue;
+    result.push_back(
+        SavedFileEntry(it.key(), file_path, writable, sequence_number));
+  }
+  return result;
+}
+
+}  // namespace
+
+SavedFileEntry::SavedFileEntry() : writable(false), sequence_number(0) {}
+
+SavedFileEntry::SavedFileEntry(const std::string& id,
+                               const base::FilePath& path,
+                               bool writable,
+                               int sequence_number)
+    : id(id),
+      path(path),
+      writable(writable),
+      sequence_number(sequence_number) {}
+
+class SavedFilesService::SavedFiles {
+ public:
+  SavedFiles(Profile* profile, const std::string& extension_id);
+  ~SavedFiles();
+
+  void RegisterFileEntry(const std::string& id,
+                         const base::FilePath& file_path,
+                         bool writable);
+  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();
+
+  Profile* profile_;
+  const std::string extension_id_;
+
+  // Contains all file entries that have been registered, keyed by ID. Owns
+  // values.
+  base::hash_map<std::string, SavedFileEntry*> registered_file_entries_;
+  STLValueDeleter<base::hash_map<std::string, SavedFileEntry*> >
+      registered_file_entries_deleter_;
+
+  // 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(Profile* profile) {
+  return SavedFilesServiceFactory::GetForProfile(profile);
+}
+
+SavedFilesService::SavedFilesService(Profile* profile)
+    : extension_id_to_saved_files_deleter_(&extension_id_to_saved_files_),
+      profile_(profile) {
+  registrar_.Add(this,
+                 chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED,
+                 content::NotificationService::AllSources());
+  registrar_.Add(this,
+                 chrome::NOTIFICATION_APP_TERMINATING,
+                 content::NotificationService::AllSources());
+}
+
+SavedFilesService::~SavedFilesService() {}
+
+void SavedFilesService::Observe(int type,
+                                const content::NotificationSource& source,
+                                const content::NotificationDetails& details) {
+  switch (type) {
+    case chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED: {
+      ExtensionHost* host = content::Details<ExtensionHost>(details).ptr();
+      const Extension* extension = host->extension();
+      if (extension) {
+        ClearQueueIfNoRetainPermission(extension);
+        Clear(extension->id());
+      }
+      break;
+    }
+
+    case chrome::NOTIFICATION_APP_TERMINATING: {
+      // Stop listening to NOTIFICATION_EXTENSION_HOST_DESTROYED in particular
+      // as all extension hosts will be destroyed as a result of shutdown.
+      registrar_.RemoveAll();
+      break;
+    }
+  }
+}
+
+void SavedFilesService::RegisterFileEntry(const std::string& extension_id,
+                                          const std::string& id,
+                                          const base::FilePath& file_path,
+                                          bool writable) {
+  GetOrInsert(extension_id)->RegisterFileEntry(id, file_path, writable);
+}
+
+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) {
+  return GetOrInsert(extension_id)->GetAllFileEntries();
+}
+
+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->GetActivePermissions()->HasAPIPermission(
+          APIPermission::kFileSystemRetainFiles)) {
+    ClearSavedFileEntries(ExtensionPrefs::Get(profile_), extension->id());
+    Clear(extension->id());
+  }
+}
+
+SavedFilesService::SavedFiles* SavedFilesService::GetOrInsert(
+    const std::string& extension_id) {
+  std::map<std::string, SavedFiles*>::iterator it =
+      extension_id_to_saved_files_.find(extension_id);
+  if (it != extension_id_to_saved_files_.end())
+    return it->second;
+
+  SavedFiles* saved_files = new SavedFiles(profile_, extension_id);
+  extension_id_to_saved_files_.insert(
+      std::make_pair(extension_id, saved_files));
+  return saved_files;
+}
+
+void SavedFilesService::Clear(const std::string& extension_id) {
+  std::map<std::string, SavedFiles*>::iterator it =
+      extension_id_to_saved_files_.find(extension_id);
+  if (it != extension_id_to_saved_files_.end()) {
+    delete it->second;
+    extension_id_to_saved_files_.erase(it);
+  }
+}
+
+SavedFilesService::SavedFiles::SavedFiles(Profile* profile,
+                                          const std::string& extension_id)
+    : profile_(profile),
+      extension_id_(extension_id),
+      registered_file_entries_deleter_(&registered_file_entries_) {
+  LoadSavedFileEntriesFromPreferences();
+}
+
+SavedFilesService::SavedFiles::~SavedFiles() {}
+
+void SavedFilesService::SavedFiles::RegisterFileEntry(
+    const std::string& id,
+    const base::FilePath& file_path,
+    bool writable) {
+  if (ContainsKey(registered_file_entries_, id))
+    return;
+
+  registered_file_entries_.insert(
+      std::make_pair(id, new SavedFileEntry(id, file_path, writable, 0)));
+}
+
+void SavedFilesService::SavedFiles::EnqueueFileEntry(const std::string& id) {
+  base::hash_map<std::string, SavedFileEntry*>::iterator it =
+      registered_file_entries_.find(id);
+  DCHECK(it != registered_file_entries_.end());
+
+  SavedFileEntry* file_entry = it->second;
+  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(profile_);
+  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 {
+  return ContainsKey(registered_file_entries_, id);
+}
+
+const SavedFileEntry* SavedFilesService::SavedFiles::GetFileEntry(
+    const std::string& id) const {
+  base::hash_map<std::string, SavedFileEntry*>::const_iterator it =
+      registered_file_entries_.find(id);
+  if (it == registered_file_entries_.end())
+    return NULL;
+
+  return it->second;
+}
+
+std::vector<SavedFileEntry> SavedFilesService::SavedFiles::GetAllFileEntries()
+    const {
+  std::vector<SavedFileEntry> result;
+  for (base::hash_map<std::string, SavedFileEntry*>::const_iterator it =
+           registered_file_entries_.begin();
+       it != registered_file_entries_.end();
+       ++it) {
+    result.push_back(*it->second);
+  }
+  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(profile_);
+  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(profile_);
+  std::vector<SavedFileEntry> saved_entries =
+      GetSavedFileEntries(prefs, extension_id_);
+  for (std::vector<SavedFileEntry>::iterator it = saved_entries.begin();
+       it != saved_entries.end();
+       ++it) {
+    SavedFileEntry* file_entry = new SavedFileEntry(*it);
+    registered_file_entries_.insert(std::make_pair(file_entry->id, file_entry));
+    saved_file_lru_.insert(
+        std::make_pair(file_entry->sequence_number, 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