text: /*
   * 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 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 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 "config.h"
  #include "DatabaseContext.h"
  
  #include "Chrome.h"
  #include "ChromeClient.h"
  #include "Database.h"
  #include "DatabaseManager.h"
  #include "DatabaseTask.h"
  #include "DatabaseThread.h"
  #include "Document.h"
  #include "Page.h"
  #include "SchemeRegistry.h"
  #include "ScriptExecutionContext.h"
  #include "SecurityOrigin.h"
  #include "SecurityOriginData.h"
  
  namespace WebCore {
  
  // 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 RefPtrs in:
  // 1. ScriptExecutionContext
  // 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 call setDatabaseContext() on the
  // the ScriptExecutionContext. This sets the RefPtr in the ScriptExecutionContext
  // for keeping the DatabaseContext alive. Since the DatabaseContext is only
  // created from the script thread, it is safe for the constructor to call
  // ScriptExecutionContext::setDatabaseContext().
  //
  // Once a DatabaseContext is associated with a ScriptExecutionContext, it will
  // live until after the ScriptExecutionContext 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 ScriptExecutionContext, the Database
  // will re-use the same DatabaseContext.
  //
  // At Shutdown:
  // ===========
  // During shutdown, the DatabaseContext needs to:
  // 1. "outlive" the ScriptExecutionContext.
  //    - This is needed because the DatabaseContext needs to remove itself from the
  //      ScriptExecutionContext's ActiveDOMObject list and ContextDestructionObserver
  //      list. This removal needs to be executed on the script's thread. Hence, we
  //      rely on the ScriptExecutionContext'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 deref the DatabaseContext from the DatabaseThread.
  //
  // During shutdown, the ScriptExecutionContext 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 ScriptExecutionContext or the Databases
  // destruct first.
  //
  // The RefPtrs in the Databases and ScriptExecutionContext will ensure that the
  // DatabaseContext will outlive both regardless of which of the 2 destructs first.
  
  
  DatabaseContext::DatabaseContext(ScriptExecutionContext& context)
      : ActiveDOMObject(&context)
  {
      // ActiveDOMObject expects this to be called to set internal flags.
      suspendIfNeeded();
  
      ASSERT(!context.databaseContext());
      context.setDatabaseContext(this);
  }
  
  DatabaseContext::~DatabaseContext()
  {
      stopDatabases();
      ASSERT(!m_databaseThread || m_databaseThread->terminationRequested());
      ASSERT(!scriptExecutionContext() || !scriptExecutionContext()->databaseContext());
  }
  
  // This is called if the associated ScriptExecutionContext is destroyed 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 shut down naturally
  // because the database closing process might still make use of this context.
  // It is not safe to just delete the context here.
  void DatabaseContext::contextDestroyed()
  {
      ActiveDOMObject::contextDestroyed();
      stopDatabases();
  }
  
  // stop() is from stopActiveDOMObjects() which indicates that the owner Frame
  // or WorkerThread is shutting down. Initiate the orderly shutdown by stopping
  // the associated databases.
  void DatabaseContext::stop()
  {
      stopDatabases();
  }
  
  bool DatabaseContext::canSuspendForDocumentSuspension() const
  {
      if (!hasOpenDatabases() || !m_databaseThread)
          return true;
  
      return !m_databaseThread->hasPendingDatabaseActivity();
  }
  
  DatabaseThread* DatabaseContext::databaseThread()
  {
      if (!m_databaseThread && !m_hasOpenDatabases) {
          // 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.
          ASSERT(!m_hasRequestedTermination);
  
          // 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.
          m_databaseThread = DatabaseThread::create();
          m_databaseThread->start();
      }
  
      return m_databaseThread.get();
  }
  
  bool DatabaseContext::stopDatabases(DatabaseTaskSynchronizer* synchronizer)
  {
      // FIXME: What guarantees this is never called after the script execution context is null?
      ASSERT(scriptExecutionContext());
  
      // 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.
      bool result = m_databaseThread && !m_hasRequestedTermination;
      if (result) {
          m_databaseThread->requestTermination(synchronizer);
          m_hasRequestedTermination = true;
      }
  
      auto& context = *scriptExecutionContext();
      if (context.databaseContext()) {
          ASSERT(context.databaseContext() == this);
          context.setDatabaseContext(nullptr);
      }
  
      return result;
  }
  
  bool DatabaseContext::allowDatabaseAccess() const
  {
      if (is<Document>(*m_scriptExecutionContext)) {
          Document& document = downcast<Document>(*m_scriptExecutionContext);
          if (!document.page() || (document.page()->usesEphemeralSession() && !SchemeRegistry::allowsDatabaseAccessInPrivateBrowsing(document.securityOrigin().protocol())))
              return false;
          return true;
      }
      ASSERT(m_scriptExecutionContext->isWorkerGlobalScope());
      // allowDatabaseAccess is not yet implemented for workers.
      return true;
  }
  
  void DatabaseContext::databaseExceededQuota(const String& name, DatabaseDetails details)
  {
      if (is<Document>(*m_scriptExecutionContext)) {
          Document& document = downcast<Document>(*m_scriptExecutionContext);
          if (Page* page = document.page())
              page->chrome().client().exceededDatabaseQuota(*document.frame(), name, details);
          return;
      }
      ASSERT(m_scriptExecutionContext->isWorkerGlobalScope());
  }
  
  SecurityOriginData DatabaseContext::securityOrigin() const
  {
      return SecurityOriginData::fromSecurityOrigin(*m_scriptExecutionContext->securityOrigin());
  }
  
  bool DatabaseContext::isContextThread() const
  {
      return m_scriptExecutionContext->isContextThread();
  }
  
  } // namespace WebCore
  