Add support for persistent file access in apps.

apps/saved_files_service.cc

Index: apps/saved_files_service.cc
diff --git a/apps/saved_files_service.cc b/apps/saved_files_service.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c021bb5538a0272bd63232ffd97cdbf14f4c7b97
--- /dev/null
+++ b/apps/saved_files_service.cc
@@ -0,0 +1,434 @@
+// 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();
+
+  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) {
+        MaybeClearQueue(extension);

[koz (OOO until 15th September), 2013/05/24 00:13:16]

ClearQueueIfNoRetainPermission()?

[Sam McNally, 2013/05/24 00:46:03]

Done.

+        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::MaybeClearQueue(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_) {

[koz (OOO until 15th September), 2013/05/23 07:32:22]

I think this would be clearer as a method, so the constructor body would just be
 ... {
  LoadSavedFileEntriesFromPreferences();
}

[Sam McNally, 2013/05/24 00:46:03]

Done.

+  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));
+  }
+}
+
+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());

[Matt Giuca, 2013/05/23 05:38:34]

Please make this a CHECK, since it's memory corruption ville if this condition
fails. (Actually I have no idea what end() is, maybe it's NULL, but still I
think it's worth checking in Release build.)

+
+  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(

[koz (OOO until 15th September), 2013/05/23 07:32:22]

I learned a new thing! Though I feel compelled to point out that as this will
almost never happen it's probably better to just not calculate the hint for the
extra code clarity. I leave it with you, though :-)

+        it, 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