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/*
* Copyright (C) 2008 Apple Inc. All Rights Reserved.
* Copyright (C) 2011 Google, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include "modules/webdatabase/DatabaseContext.h"
#include "core/dom/Document.h"
#include "core/dom/ExecutionContext.h"
#include "modules/webdatabase/Database.h"
#include "modules/webdatabase/DatabaseManager.h"
#include "modules/webdatabase/DatabaseTask.h"
#include "modules/webdatabase/DatabaseThread.h"
#include "platform/weborigin/SchemeRegistry.h"
#include "platform/weborigin/SecurityOrigin.h"
#include "platform/wtf/Assertions.h"
namespace blink {
// How the DatabaseContext Life-Cycle works?
// ========================================
// ... in other words, who's keeping the DatabaseContext alive and how long does
// it need to stay alive?
//
// The DatabaseContext is referenced from:
// 1. DatabaseManager
// 2. Database
//
// At Birth:
// ========
// We create a DatabaseContext only when there is a need i.e. the script tries
// to open a Database via DatabaseManager::openDatabase().
//
// The DatabaseContext constructor will register itself to DatabaseManager. This
// lets DatabaseContext keep itself alive until it is unregisterd in
// contextDestroyed().
//
// Once a DatabaseContext is associated with a ExecutionContext, it will
// live until after the ExecutionContext destructs. This is true even if
// we don't succeed in opening any Databases for that context. When we do
// succeed in opening Databases for this ExecutionContext, the Database
// will re-use the same DatabaseContext.
//
// At Shutdown:
// ===========
// During shutdown, the DatabaseContext needs to:
// 1. "outlive" the ExecutionContext.
// - This is needed because the DatabaseContext needs to remove itself from
// the
// ExecutionContext's ContextLifecycleObserver list and
// ContextLifecycleObserver
// list. This removal needs to be executed on the script's thread. Hence,
// we
// rely on the ExecutionContext's shutdown process to call
// stop() and contextDestroyed() to give us a chance to clean these up from
// the script thread.
//
// 2. "outlive" the Databases.
// - This is because they may make use of the DatabaseContext to execute a
// close task and shutdown in an orderly manner. When the Databases are
// destructed, they will release the DatabaseContext reference from the
// DatabaseThread.
//
// During shutdown, the ExecutionContext is shutting down on the script thread
// while the Databases are shutting down on the DatabaseThread. Hence, there can
// be a race condition as to whether the ExecutionContext or the Databases
// destruct first.
//
// The Members in the Databases and DatabaseManager will ensure that the
// DatabaseContext will outlive Database and ExecutionContext regardless of
// which of the 2 destructs first.
DatabaseContext* DatabaseContext::Create(ExecutionContext* context) {
DatabaseContext* self = new DatabaseContext(context);
DatabaseManager::Manager().RegisterDatabaseContext(self);
return self;
}
DatabaseContext::DatabaseContext(ExecutionContext* context)
: ContextLifecycleObserver(context),
has_open_databases_(false),
has_requested_termination_(false) {
DCHECK(IsMainThread());
// For debug accounting only. We must do this before we register the
// instance. The assertions assume this.
DatabaseManager::Manager().DidConstructDatabaseContext();
}
DatabaseContext::~DatabaseContext() {
// For debug accounting only. We must call this last. The assertions assume
// this.
DatabaseManager::Manager().DidDestructDatabaseContext();
}
void DatabaseContext::Trace(blink::Visitor* visitor) {
visitor->Trace(database_thread_);
ContextLifecycleObserver::Trace(visitor);
}
// This is called if the associated ExecutionContext is destructing while
// we're still associated with it. That's our cue to disassociate and shutdown.
// To do this, we stop the database and let everything shutdown naturally
// because the database closing process may still make use of this context.
// It is not safe to just delete the context here.
void DatabaseContext::ContextDestroyed(ExecutionContext*) {
StopDatabases();
DatabaseManager::Manager().UnregisterDatabaseContext(this);
}
DatabaseContext* DatabaseContext::Backend() {
return this;
}
DatabaseThread* DatabaseContext::GetDatabaseThread() {
if (!database_thread_ && !has_open_databases_) {
// It's OK to ask for the m_databaseThread after we've requested
// termination because we're still using it to execute the closing
// of the database. However, it is NOT OK to create a new thread
// after we've requested termination.
DCHECK(!has_requested_termination_);
// Create the database thread on first request - but not if at least one
// database was already opened, because in that case we already had a
// database thread and terminated it and should not create another.
database_thread_ = DatabaseThread::Create();
database_thread_->Start();
}
return database_thread_.Get();
}
bool DatabaseContext::DatabaseThreadAvailable() {
return GetDatabaseThread() && !has_requested_termination_;
}
void DatabaseContext::StopDatabases() {
// Though we initiate termination of the DatabaseThread here in
// stopDatabases(), we can't clear the m_databaseThread ref till we get to
// the destructor. This is because the Databases that are managed by
// DatabaseThread still rely on this ref between the context and the thread
// to execute the task for closing the database. By the time we get to the
// destructor, we're guaranteed that the databases are destructed (which is
// why our ref count is 0 then and we're destructing). Then, the
// m_databaseThread RefPtr destructor will deref and delete the
// DatabaseThread.
if (DatabaseThreadAvailable()) {
has_requested_termination_ = true;
// This blocks until the database thread finishes the cleanup task.
database_thread_->Terminate();
}
}
bool DatabaseContext::AllowDatabaseAccess() const {
return ToDocument(GetExecutionContext())->IsActive();
}
const SecurityOrigin* DatabaseContext::GetSecurityOrigin() const {
return GetExecutionContext()->GetSecurityOrigin();
}
bool DatabaseContext::IsContextThread() const {
return GetExecutionContext()->IsContextThread();
}
} // namespace blink