[Sync] Refactor non-frontend DTC to handle new API properly.

chrome/browser/sync/glue/shared_change_processor.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/sync/glue/shared_change_processor.h"
+
+#include "base/location.h"
+#include "chrome/browser/sync/api/syncable_service.h"
+#include "chrome/browser/sync/api/sync_change.h"
+#include "chrome/browser/sync/api/sync_error.h"
+#include "content/browser/browser_thread.h"
+
+using base::AutoLock;
+
+namespace browser_sync {
+
+SharedChangeProcessor::SharedChangeProcessor(
+    UnrecoverableErrorHandler* error_handler)
+    : GenericChangeProcessor(error_handler),
+      disconnected_(false) {
+  // We're always created on the UI thread.
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DetachFromThread();
+}
+
+SharedChangeProcessor::~SharedChangeProcessor() {
+  // We should always be deleted on the UI thread.
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DetachFromThread();
+}
+
+// Connect to the syncer and SyncableService specified.
+void SharedChangeProcessor::Connect(SyncableService* local_service,
+                                    sync_api::UserShare* user_share) {
+  DCHECK(!BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(CalledOnValidThread());
+  AutoLock lock(monitor_lock_);
+  if (disconnected_)
+    return;
+  DCHECK(local_service);
+  set_local_service(local_service);
+  set_share_handle(user_share);
+}
+
+void SharedChangeProcessor::Disconnect() {
+  // May be called from any thread.
+  VLOG(1) << "Disconnecting change processor.";
+  AutoLock lock(monitor_lock_);
+  disconnected_ = true;
+}
+
+SyncError SharedChangeProcessor::GetSyncDataForType(
+    syncable::ModelType type,
+    SyncDataList* current_sync_data) {
+  DCHECK(CalledOnValidThread());
+  AutoLock lock(monitor_lock_);
+  if (disconnected_) {
+    SyncError error(FROM_HERE, "Change processor disconnected.", type);
+    return error;
+  }
+  return GenericChangeProcessor::GetSyncDataForType(type, current_sync_data);
+}
+
+SyncError SharedChangeProcessor::ProcessSyncChanges(
+    const tracked_objects::Location& from_here,
+    const SyncChangeList& list_of_changes) {
+  DCHECK(CalledOnValidThread());
+  AutoLock lock(monitor_lock_);
+  if (disconnected_) {
+    // The DTC that disconnects us must ensure it posts a StopSyncing task.
+    // If we reach this, it means it just hasn't executed yet.
+    syncable::ModelType type;
+    if (list_of_changes.size() > 0) {
+      type = list_of_changes[0].sync_data().GetDataType();
+    }
+    SyncError error(FROM_HERE, "Change processor disconnected.", type);
+    return error;
+  }
+  return GenericChangeProcessor::ProcessSyncChanges(from_here, list_of_changes);

[akalin, 2011/10/07 22:40:05]

it may suffice to store the result of the delegated fn, and then hold the lock
to decide whether to return it or the error.

That would mean that the data type thread may do extra work, but at least the UI
thread won't be blocked by it.

[Nicolas Zea, 2011/10/12 04:24:19]

Discussed offline, there's no risk of the UI thread being blocked here.

+}
+
+bool SharedChangeProcessor::SyncModelHasUserCreatedNodes(
+    syncable::ModelType type,
+    bool* has_nodes) {
+  DCHECK(CalledOnValidThread());
+  AutoLock lock(monitor_lock_);
+  if (disconnected_) {
+    LOG(ERROR) << "Change processor disconnected.";
+    return false;
+  }
+  return GenericChangeProcessor::SyncModelHasUserCreatedNodes(type, has_nodes);
+}
+
+bool SharedChangeProcessor::CryptoReadyIfNecessary(syncable::ModelType type) {
+  DCHECK(CalledOnValidThread());
+  AutoLock lock(monitor_lock_);
+  if (disconnected_) {
+    LOG(ERROR) << "Change processor disconnected.";
+    return true;  // Otherwise we get into infinite spin waiting.
+  }
+  return GenericChangeProcessor::CryptoReadyIfNecessary(type);
+}
+
+}  // namespace browser_sync