Implement an initial extension settings API.

chrome/browser/extensions/extension_settings.cc

+// Copyright (c) 2011 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 "chrome/browser/extensions/extension_settings.h"
+
+#include "base/bind.h"
+#include "base/json/json_reader.h"
+#include "base/json/json_writer.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/browser/browser_thread.h"
+#include "chrome/browser/extensions/extension_settings_leveldb_storage.h"
+#include "chrome/browser/extensions/extension_settings_noop_storage.h"
+#include "chrome/browser/extensions/extension_settings_storage_cache.h"
+#include "third_party/leveldb/include/leveldb/iterator.h"
+#include "third_party/leveldb/include/leveldb/write_batch.h"
+
+// TODO(kalman): Policy for dots in the key names.  Make sure the behaviour of
+//               DictionaryValue and JSON classes is consistent with leveldb.
+// TODO(kalman): Integration tests.
+// TODO(kalman): More unit tests (see extension_settings_storage_unittest.cc).
+// TODO(kalman): Use structured cloning rather than JSON.
+// TODO(kalman): Quotas.
+
+ExtensionSettings::ExtensionSettings(const FilePath& base_path)
+    : base_path_(base_path) {
+}
+
+ExtensionSettings::~ExtensionSettings() {
+  std::map<std::string, ExtensionSettingsStorage*>::iterator it;
+  for (it = storage_objs_.begin(); it != storage_objs_.end(); ++it) {
+    it->second->DeleteSoon();
+  }
+}
+
+void ExtensionSettings::GetStorage(
+    const std::string& extension_id,
+    const ExtensionSettings::Callback& callback) {
+  if (!GetExistingStorage(extension_id, callback)) {
+    StartCreationOfStorage(
+        extension_id,
+        ExtensionSettingsStorage::LEVELDB,
+        ExtensionSettingsStorage::NOOP,
+        true,
+        callback);
+  }
+}
+
+void ExtensionSettings::GetStorageForTesting(
+    ExtensionSettingsStorage::Type type,
+    bool cached,
+    const std::string& extension_id,
+    const Callback& callback) {
+  if (!GetExistingStorage(extension_id, callback)) {
+    StartCreationOfStorage(extension_id, type, type, cached, callback);
+  }
+}
+
+bool ExtensionSettings::GetExistingStorage(
+    const std::string& extension_id, const Callback& callback) {
+  std::map<std::string, ExtensionSettingsStorage*>::iterator existing =
+      storage_objs_.find(extension_id);
+  if (existing == storage_objs_.end()) {
+    // No existing storage.
+    return false;
+  }
+  // Existing storage.  Reply with that.
+  ExtensionSettingsStorage* storage = existing->second;
+  DCHECK(storage != NULL);
+  MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &Callback::Run,
+          base::Unretained(new Callback(callback)),

[Matt Perry, 2011/06/29 18:08:11]

you're leaking the new Callback here. I don't believe Callback deletes itself
after running. you need a helper function to dispatch to Run and then delete.

[not at google - send to devlin, 2011/08/03 06:36:51]

Done.

+          storage));
+  return true;
+}
+
+void ExtensionSettings::StartCreationOfStorage(
+    const std::string& extension_id,
+    ExtensionSettingsStorage::Type type,
+    ExtensionSettingsStorage::Type fallback_type,
+    bool cached,
+    const Callback& callback) {
+  // Make sure we're not deleted mid-callback.
+  // Released in EndCreationOfStorage().
+  AddRef();

[Matt Perry, 2011/06/29 18:08:11]

base::Bind normally handles this for you - except your use of Unretained
prevents it. I guess you're doing this because you can't AddRef/Release on the
FILE thread? if so, please add a quick comment explaining that.

[not at google - send to devlin, 2011/08/03 06:36:51]

Actually it should be fine to just let Bind() refcount it.

[Matt Perry, 2011/08/03 19:33:52]

if Bind holds the last reference, then the Release on the FILE thread will cause
the object to be deleted on that thread.

[Matt Perry, 2011/08/03 19:33:52]

Bind will release its reference when the task is run, on the FILE thread. Since
this class doesn't use the thread-safe RefCountedThreadSafe, that won't work.
All refcounting must be on the same thread.

[not at google - send to devlin, 2011/08/03 22:06:55]

Changed to RefCountedThreadSafe.

The last reference should never be able to be let go from this method (and .:
not from the FILE thread), because at the end there is a Bind to this again, and
the reference is only Released after the method has run.

+  BrowserThread::PostTask(
+      BrowserThread::FILE,
+      FROM_HERE,
+      base::Bind(
+          &ExtensionSettings::CreateStorageOnFileThread,
+          base::Unretained(this),
+          extension_id,
+          type,
+          fallback_type,
+          cached,
+          callback));
+}
+
+void ExtensionSettings::CreateStorageOnFileThread(
+    const std::string& extension_id,
+    ExtensionSettingsStorage::Type type,
+    ExtensionSettingsStorage::Type fallback_type,
+    bool cached,
+    const Callback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  ExtensionSettingsStorage* storage = CreateStorage(extension_id, type, cached);
+  if (storage == NULL && fallback_type != type) {
+    storage = CreateStorage(extension_id, fallback_type, cached);
+  }
+  DCHECK(storage != NULL);
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(
+          &ExtensionSettings::EndCreationOfStorage,
+          base::Unretained(this),
+          extension_id,
+          storage,
+          callback));
+}
+
+ExtensionSettingsStorage* ExtensionSettings::CreateStorage(
+    const std::string& extension_id,
+    ExtensionSettingsStorage::Type type,
+    bool cached) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  ExtensionSettingsStorage* storage = NULL;
+  switch (type) {
+    case ExtensionSettingsStorage::NOOP:
+      storage = new ExtensionSettingsNoopStorage();
+      break;
+    case ExtensionSettingsStorage::LEVELDB:
+      storage = ExtensionSettingsLeveldbStorage::Create(
+          base_path_, extension_id);
+      break;
+    default:
+      NOTREACHED();
+  }
+  if (storage != NULL && cached) {
+    storage = new ExtensionSettingsStorageCache(storage);
+  }
+  return storage;
+}
+
+void ExtensionSettings::EndCreationOfStorage(
+    const std::string& extension_id,
+    ExtensionSettingsStorage* storage,
+    const Callback& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  // Cache the result now.  To avoid a race condition, check again to see
+  // whether a storage has been created already; if so, use that one.
+  std::map<std::string, ExtensionSettingsStorage*>::iterator existing =
+      storage_objs_.find(extension_id);
+  if (existing == storage_objs_.end()) {
+    storage_objs_[extension_id] = storage;
+  } else {
+    delete storage;
+    storage = existing->second;
+    DCHECK(storage != NULL);
+  }
+  callback.Run(storage);
+  // Release reference added by StartCreationOfStorage().
+  Release();
+}