Implement an initial extension settings API.

chrome/browser/extensions/extension_settings_storage_cache.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_storage_cache.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/message_loop.h"
+#include "base/task.h"
+#include "base/json/json_writer.h"
+
+namespace {
+
+void RemoveAll(DictionaryValue* from, const ListValue* keys_to_remove) {
+  std::string key;
+  for (ListValue::const_iterator it = keys_to_remove->begin();
+      it != keys_to_remove->end(); ++it) {
+    if ((*it)->GetAsString(&key)) {
+      from->Remove(key, NULL);
+    }
+  }
+}
+
+// Callback which delegates to a given callback but caches any result if
+// successful.  Takes an optional parameter of existing settings to merge with
+// before returning to the callback (may be NULL) and an optional parameter of
+// keys to remove from the cache post-success (may be NULL).
+class CacheModifyingCallback : public ExtensionSettingsStorage::Callback {
+ public:
+  // Takes ownership of callback, existing, and keys_to_remove.
+  CacheModifyingCallback(ExtensionSettingsStorage::Callback* delegate,
+      DictionaryValue* cache, DictionaryValue* existing,
+      ListValue* keys_to_remove)
+      : delegate_(delegate), cache_(cache), existing_(existing),
+        keys_to_remove_(keys_to_remove) {
+  }
+
+  ~CacheModifyingCallback() {}
+
+  static CacheModifyingCallback* Create(
+      ExtensionSettingsStorage::Callback* delegate, DictionaryValue* cache) {
+    return new CacheModifyingCallback(delegate, cache, NULL, NULL);
+  }
+
+  static CacheModifyingCallback* Create(
+      ExtensionSettingsStorage::Callback* delegate, DictionaryValue* cache,
+      DictionaryValue* existing) {
+    return new CacheModifyingCallback(delegate, cache, existing, NULL);
+  }
+
+  static CacheModifyingCallback* Create(
+      ExtensionSettingsStorage::Callback* delegate, DictionaryValue* cache,
+      ListValue* remove) {
+    return new CacheModifyingCallback(delegate, cache, NULL, remove);
+  }
+
+  void OnSuccess(DictionaryValue* settings) {
+    cache_->MergeDictionary(settings);
+    if (existing_ != NULL) {
+      settings->MergeDictionary(existing_.get());
+    }
+    if (keys_to_remove_ != NULL) {
+      RemoveAll(cache_, keys_to_remove_.get());
+    }
+    delegate_->OnSuccess(settings);
+  }
+
+  void OnFailure(const std::string& message) {
+    delegate_->OnFailure(message);
+  }
+
+ private:
+  scoped_ptr<ExtensionSettingsStorage::Callback> delegate_;
+  DictionaryValue* cache_;
+  scoped_ptr<DictionaryValue> existing_;
+  scoped_ptr<ListValue> keys_to_remove_;
+};
+
+// Runs OnSuccess() on the message loop of the calling thread.
+class SuccessClosure {
+ public:
+  SuccessClosure(ExtensionSettingsStorage::Callback* callback,
+      DictionaryValue* settings) : callback_(callback), settings_(settings) {
+  }
+
+  ~SuccessClosure() {
+    delete callback_;
+  }
+
+  void Run() {
+    MessageLoop::current()->PostTask(FROM_HERE,
+        base::Bind(&SuccessClosure::Run2, base::Unretained(this)));
+  }
+
+ private:
+  void Run2() {
+    callback_->OnSuccess(settings_);
+    delete this;
+  }
+
+  ExtensionSettingsStorage::Callback* callback_;
+  DictionaryValue* settings_;
+};
+
+}  // namespace
+
+ExtensionSettingsStorageCache::ExtensionSettingsStorageCache(
+    ExtensionSettingsStorage* delegate) : delegate_(delegate) {
+  DCHECK(delegate->type() == NOOP || delegate->type() == LEVELDB);
+}
+
+void ExtensionSettingsStorageCache::Get(const std::string& key,
+    ExtensionSettingsStorageCache::Callback* callback) {
+  Value *value;
+  if (GetFromCache(key, &value)) {
+    DictionaryValue* settings = new DictionaryValue();
+    settings->Set(key, value);
+    (new SuccessClosure(callback, settings))->Run();
+  } else {
+    delegate_->Get(key, CacheModifyingCallback::Create(callback, &cache_));
+  }
+}
+
+void ExtensionSettingsStorageCache::Get(const ListValue& keys,
+    ExtensionSettingsStorageCache::Callback* callback) {
+  std::string key;
+  DictionaryValue* settings = new DictionaryValue();
+  ListValue missing_keys;
+
+  for (ListValue::const_iterator it = keys.begin(); it != keys.end(); ++it) {
+    if ((*it)->GetAsString(&key)) {
+      Value *value;
+      if (GetFromCache(key, &value)) {
+        settings->Set(key, value);
+      } else {
+        missing_keys.Append(Value::CreateStringValue(key));
+      }
+    }
+  }
+
+  if (missing_keys.empty()) {
+    (new SuccessClosure(callback, settings))->Run();
+  } else {
+    delegate_->Get(missing_keys,
+        CacheModifyingCallback::Create(callback, &cache_, settings));
+  }
+}
+
+void ExtensionSettingsStorageCache::Get(
+    ExtensionSettingsStorageCache::Callback* callback) {
+  // Copy the cache when passing in, as a semi-hack so that caching a no-op
+  // storage object works (which always returns empty from Get()).
+  // TODO(kalman): Consider doing this conditionally on type == NOOP.
+  delegate_->Get(
+      CacheModifyingCallback::Create(callback, &cache_, cache_.DeepCopy()));
+}
+
+void ExtensionSettingsStorageCache::Set(const std::string& key,
+    const Value& value, ExtensionSettingsStorageCache::Callback* callback) {
+  // Invalidate the cached entry first, in case the set fails.
+  cache_.Remove(key, NULL);
+  delegate_->Set(key, value, CacheModifyingCallback::Create(callback, &cache_));
+}
+
+void ExtensionSettingsStorageCache::Set(const DictionaryValue& values,
+    ExtensionSettingsStorageCache::Callback* callback) {
+  // Invalidate the cached entries first, in case the set fails.
+  for (DictionaryValue::key_iterator it = values.begin_keys();
+      it != values.end_keys(); ++it) {
+    cache_.RemoveWithoutPathExpansion(*it, NULL);
+  }
+  delegate_->Set(values, CacheModifyingCallback::Create(callback, &cache_));
+}
+
+void ExtensionSettingsStorageCache::Remove(const std::string& key,
+    ExtensionSettingsStorageCache::Callback *callback) {
+  // Invalidate the cached entry first, in case the remove fails.
+  // We will also need to do if after the callback, to avoid race conditions
+  // whether other API calls fill the cache on the UI thread.
+  // This would be a good time to use structured cloning...
+  cache_.Remove(key, NULL);
+  ListValue* key_list = new ListValue();
+  key_list->Append(Value::CreateStringValue(key));
+  delegate_->Remove(key,
+      CacheModifyingCallback::Create(callback, &cache_, key_list));
+}
+
+void ExtensionSettingsStorageCache::Remove(const ListValue& keys,
+    ExtensionSettingsStorageCache::Callback *callback) {
+  std::string key;
+  // Invalidate each cached entry first, in case the remove fails.
+  // We will also need to do if after the callback, to avoid race conditions
+  // whether other API calls fill the cache on the UI thread.
+  RemoveAll(&cache_, &keys);
+  delegate_->Remove(keys,
+      CacheModifyingCallback::Create(callback, &cache_, keys.DeepCopy()));
+}
+
+void ExtensionSettingsStorageCache::Clear(
+    ExtensionSettingsStorageCache::Callback* callback) {
+  cache_.Clear();
+  delegate_->Clear(CacheModifyingCallback::Create(callback, &cache_));
+}
+
+bool ExtensionSettingsStorageCache::GetFromCache(const std::string& key,
+    Value** value) {
+  Value* cached_value;
+  if (!cache_.Get(key, &cached_value)) {
+    return false;
+  }
+  *value = cached_value->DeepCopy();
+  return true;
+}