Pref service: expose all read-only PrefStores through Mojo

services/preferences/public/cpp/pref_store_manager_impl.cc

+// Copyright 2017 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 "services/preferences/public/cpp/pref_store_manager_impl.h"
+
+#include "base/memory/ref_counted.h"
+#include "components/prefs/pref_value_store.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "services/service_manager/public/cpp/interface_registry.h"
+
+namespace prefs {
+
+using ConnectCallback = mojom::PrefStoreConnector::ConnectCallback;
+using PrefStorePtrs =
+    std::unordered_map<PrefValueStore::PrefStoreType, mojom::PrefStorePtr>;
+
+// Used to make sure all pref stores have been registered before replying to any
+// Connect calls.
+class ConnectionBarrier : public base::RefCounted<ConnectionBarrier> {
+ public:
+  static void Create(const PrefStorePtrs& pref_store_ptrs,
+                     const ConnectCallback& callback);
+
+  void Init(const PrefStorePtrs& pref_store_ptrs);
+
+ private:
+  friend class base::RefCounted<ConnectionBarrier>;
+  ConnectionBarrier(const PrefStorePtrs& pref_store_ptrs,
+                    const ConnectCallback& callback);
+  ~ConnectionBarrier() = default;
+
+  void OnConnect(PrefValueStore::PrefStoreType type,
+                 mojom::PrefStoreConnectionPtr connection_ptr);
+
+  ConnectCallback callback_;
+
+  std::unordered_map<PrefValueStore::PrefStoreType,
+                     mojom::PrefStoreConnectionPtr>
+      connections_;
+
+  const size_t expected_connections_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConnectionBarrier);
+};
+
+// static
+void ConnectionBarrier::Create(const PrefStorePtrs& pref_store_ptrs,
+                               const ConnectCallback& callback) {
+  make_scoped_refptr(new ConnectionBarrier(pref_store_ptrs, callback))
+      ->Init(pref_store_ptrs);
+}
+
+void ConnectionBarrier::Init(const PrefStorePtrs& pref_store_ptrs) {
+  for (const auto& ptr : pref_store_ptrs) {
+    ptr.second->AddObserver(
+        base::Bind(&ConnectionBarrier::OnConnect, this, ptr.first));
+  }
+}
+
+ConnectionBarrier::ConnectionBarrier(const PrefStorePtrs& pref_store_ptrs,
+                                     const ConnectCallback& callback)
+    : callback_(callback), expected_connections_(pref_store_ptrs.size()) {}
+
+void ConnectionBarrier::OnConnect(
+    PrefValueStore::PrefStoreType type,
+    mojom::PrefStoreConnectionPtr connection_ptr) {
+  connections_.insert(std::make_pair(type, std::move(connection_ptr)));
+  if (connections_.size() == expected_connections_) {
+    // After this method exits |this| will get destroyed so it's safe to move
+    // out the map.
+    callback_.Run(std::move(connections_));
+  }
+}
+
+PrefStoreManagerImpl::PrefStoreManagerImpl(PrefStoreTypes expected_pref_stores)
+    : expected_pref_stores_(std::move(expected_pref_stores)) {}
+
+PrefStoreManagerImpl::~PrefStoreManagerImpl() = default;
+
+void PrefStoreManagerImpl::Register(PrefValueStore::PrefStoreType type,
+                                    mojom::PrefStorePtr pref_store_ptr) {
+  if (expected_pref_stores_.count(type) == 0) {
+    LOG(WARNING) << "Not registering unexpected pref store: " << type;
+    return;
+  }
+  DVLOG(1) << "Registering pref store: " << type;
+  pref_store_ptr.set_connection_error_handler(
+      base::Bind(&PrefStoreManagerImpl::OnPrefStoreDisconnect,
+                 base::Unretained(this), type));
+  const bool success =
+      pref_store_ptrs_.insert(std::make_pair(type, std::move(pref_store_ptr)))
+          .second;
+  DCHECK(success) << "The same pref store registered twice: " << type;
+  if (AllConnected()) {
+    DVLOG(1) << "All pref stores registered.";
+    for (const auto& callback : pending_callbacks_)
+      ConnectionBarrier::Create(pref_store_ptrs_, callback);
+    pending_callbacks_.clear();
+  }
+}
+
+void PrefStoreManagerImpl::Connect(const ConnectCallback& callback) {
+  if (AllConnected())
+    ConnectionBarrier::Create(pref_store_ptrs_, callback);
+  else
+    pending_callbacks_.push_back(callback);
+}
+
+void PrefStoreManagerImpl::Create(
+    const service_manager::Identity& remote_identity,
+    prefs::mojom::PrefStoreConnectorRequest request) {
+  connector_bindings_.AddBinding(this, std::move(request));
+}
+
+void PrefStoreManagerImpl::Create(
+    const service_manager::Identity& remote_identity,
+    prefs::mojom::PrefStoreRegistryRequest request) {
+  registry_bindings_.AddBinding(this, std::move(request));
+}
+
+void PrefStoreManagerImpl::OnStart() {}
+
+bool PrefStoreManagerImpl::OnConnect(
+    const service_manager::ServiceInfo& remote_info,
+    service_manager::InterfaceRegistry* registry) {
+  registry->AddInterface<prefs::mojom::PrefStoreConnector>(this);
+  registry->AddInterface<prefs::mojom::PrefStoreRegistry>(this);
+  return true;
+}
+
+void PrefStoreManagerImpl::OnPrefStoreDisconnect(
+    PrefValueStore::PrefStoreType type) {
+  DVLOG(1) << "Deregistering pref store: " << type;
+  pref_store_ptrs_.erase(type);
+}
+
+bool PrefStoreManagerImpl::AllConnected() const {
+  return pref_store_ptrs_.size() == expected_pref_stores_.size();
+}
+
+}  // namespace prefs