The Tor Browser: storage/src/SQLiteMutex.h@97036ab72558 (annotated)

storage/src/SQLiteMutex.h@97036ab72558 (annotated)

storage/src/SQLiteMutex.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
  * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #ifndef mozilla_storage_SQLiteMutex_h_
 #define mozilla_storage_SQLiteMutex_h_
 #include "mozilla/BlockingResourceBase.h"
 #include "sqlite3.h"
 namespace mozilla {
 namespace storage {
 /**
  * Wrapper class for sqlite3_mutexes.  To be used whenever we want to use a
  * sqlite3_mutex.
  *
  * @warning Never EVER wrap the same sqlite3_mutex with a different SQLiteMutex.
  *          If you do this, you void the deadlock detector's warranty!
  */
 class SQLiteMutex : private BlockingResourceBase
 {
 public:
   /**
    * Constructs a wrapper for a sqlite3_mutex that has deadlock detecting.
    *
    * @param aName
    *        A name which can be used to reference this mutex.
    */
   SQLiteMutex(const char *aName)
   : BlockingResourceBase(aName, eMutex)
   , mMutex(nullptr)
   {
   }
   /**
    * Sets the mutex that we are wrapping.  We generally do not have access to
    * our mutex at class construction, so we have to set it once we get access to
    * it.
    *
    * @param aMutex
    *        The sqlite3_mutex that we are going to wrap.
    */
   void initWithMutex(sqlite3_mutex *aMutex)
   {
     NS_ASSERTION(aMutex, "You must pass in a valid mutex!");
     NS_ASSERTION(!mMutex, "A mutex has already been set for this!");
     mMutex = aMutex;
   }
 #if !defined(DEBUG) || defined(MOZ_NATIVE_SQLITE)
   /**
    * Acquires the mutex.
    */
   void lock()
   {
     sqlite3_mutex_enter(mMutex);
   }
   /**
    * Releases the mutex.
    */
   void unlock()
   {
     sqlite3_mutex_leave(mMutex);
   }
   /**
    * Asserts that the current thread owns the mutex.
    */
   void assertCurrentThreadOwns()
   {
   }
   /**
    * Asserts that the current thread does not own the mutex.
    */
   void assertNotCurrentThreadOwns()
   {
   }
 #else
   void lock()
   {
     NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");
     // While SQLite Mutexes may be recursive, in our own code we do not want to
     // treat them as such.
     CallStack callContext = CallStack();
     CheckAcquire(callContext);
     sqlite3_mutex_enter(mMutex);
     Acquire(callContext); // Call is protected by us holding the mutex.
   }
   void unlock()
   {
     NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");
     // While SQLite Mutexes may be recursive, in our own code we do not want to
     // treat them as such.
     Release(); // Call is protected by us holding the mutex.
     sqlite3_mutex_leave(mMutex);
   }
   void assertCurrentThreadOwns()
   {
     NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");
     NS_ASSERTION(sqlite3_mutex_held(mMutex),
                  "Mutex is not held, but we expect it to be!");
   }
   void assertNotCurrentThreadOwns()
   {
     NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");
     NS_ASSERTION(sqlite3_mutex_notheld(mMutex),
                  "Mutex is held, but we expect it to not be!");
   }
 #endif // ifndef DEBUG
 private:
   sqlite3_mutex *mMutex;
 };
 /**
  * Automatically acquires the mutex when it enters scope, and releases it when
  * it leaves scope.
  */
 class MOZ_STACK_CLASS SQLiteMutexAutoLock
 {
 public:
   SQLiteMutexAutoLock(SQLiteMutex &aMutex)
   : mMutex(aMutex)
   {
     mMutex.lock();
   }
   ~SQLiteMutexAutoLock()
   {
     mMutex.unlock();
   }
 private:
   SQLiteMutex &mMutex;
 };
 /**
  * Automatically releases the mutex when it enters scope, and acquires it when
  * it leaves scope.
  */
 class MOZ_STACK_CLASS SQLiteMutexAutoUnlock
 {
 public:
   SQLiteMutexAutoUnlock(SQLiteMutex &aMutex)
   : mMutex(aMutex)
   {
     mMutex.unlock();
   }
   ~SQLiteMutexAutoUnlock()
   {
     mMutex.lock();
   }
 private:
   SQLiteMutex &mMutex;
 };
 } // namespace storage
 } // namespace mozilla
 #endif // mozilla_storage_SQLiteMutex_h_

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storage/src/SQLiteMutex.h@97036ab72558 (annotated)

storage/src/SQLiteMutex.h