The Tor Browser: media/webrtc/signaling/src/common/Wrapper.h@ac0c01689b40 (annotated)

media/webrtc/signaling/src/common/Wrapper.h@ac0c01689b40 (annotated)

media/webrtc/signaling/src/common/Wrapper.h

Thu, 15 Jan 2015 15:59:08 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:59:08 +0100
branch: TOR_BUG_9701
changeset 10: ac0c01689b40
permissions: -rw-r--r--

Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* 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/. */
 #pragma once
 /*
  * Wrapper - Helper class for wrapper objects.
  *
  * This helps to construct a shared_ptr object which wraps access to an underlying handle.
  * (The handle could be a pointer to some low-level type, a conventional C handle, an int ID, a GUID, etc.)
  *
  * Usage:
  *   To obtain a FooPtr from a foo_handle_t, call FooPtr Foo::wrap(foo_handle_t);
  *
  * To implement Foo using Wrapper, Foo needs to include this macro in its class definition:
  *   CSF_DECLARE_WRAP(Foo, foo_handle_t);
  * It also needs to include this in the cpp file, to provide the wrap() implementation and define the static Wrapper.
  *   CSF_IMPLEMENT_WRAP(Foo, foo_handle_t);
  * These are all declared in common/Wrapper.h - Foo.h needs to include this too.
  * The client needs to declare Foo(foo_handle_t) as private, and provide a suitable implementation, as well as
  *   implementing wrappers for any other functions to be exposed.
  * The client needs to implement ~Foo() to perform any cleanup as usual.
  *
  * wrap() will always return the same FooPtr for a given foo_handle_t, it will not construct additional objects
  *        if a suitable one already exists.
  * changeHandle() is used in rare cases where the underlying handle is changed, but the wrapper object is intended
  *                to remain.  This is the case for the "fake" CC_DPCall generated on CC_DPLine::CreateCall(), where
  *                the correct IDPCall* is provided later.
  * reset() is a cleanup step to wipe the handle map and allow memory to be reclaimed.
  *
  * Future enhancements:
  * - For now, objects remain in the map forever.  Better would be to add a releaseHandle() function which would
  *   allow the map to be emptied as underlying handles expired.  While we can't force the client to give up its
  *   shared_ptr<Foo> objects, we can remove our own copy, for instance on a call ended event.
  */
 #include <map>
 #include "prlock.h"
 #include "mozilla/Assertions.h"
 /*
  * Wrapper has its own autolock class because the instances are declared
  * statically and mozilla::Mutex will not work properly when instantiated
  * in a static constructor.
  */
 class LockNSPR {
 public:
   LockNSPR() : lock_(nullptr) {
     lock_ = PR_NewLock();
     MOZ_ASSERT(lock_);
   }
   ~LockNSPR() {
     PR_DestroyLock(lock_);
   }
   void Acquire() {
     PR_Lock(lock_);
   }
   void Release() {
     PR_Unlock(lock_);
   }
 private:
   PRLock *lock_;
 };
 class AutoLockNSPR {
 public:
   AutoLockNSPR(LockNSPR& lock) : lock_(lock) {
     lock_.Acquire();
   }
   ~AutoLockNSPR() {
     lock_.Release();
   }
 private:
   LockNSPR& lock_;
 };
 template <class T>
 class Wrapper
 {
 private:
     typedef std::map<typename T::Handle, typename T::Ptr>      	HandleMapType;
     HandleMapType handleMap;
     LockNSPR handleMapMutex;
 public:
 	Wrapper() {}
 	typename T::Ptr wrap(typename T::Handle handle)
 	{
 		AutoLockNSPR lock(handleMapMutex);
 		typename HandleMapType::iterator it = handleMap.find(handle);
 		if(it != handleMap.end())
 		{
 			return it->second;
 		}
 		else
 		{
 			typename T::Ptr p(new T(handle));
 			handleMap[handle] = p;
 			return p;
 		}
 	}
 	bool changeHandle(typename T::Handle oldHandle, typename T::Handle newHandle)
 	{
 		AutoLockNSPR lock(handleMapMutex);
 		typename HandleMapType::iterator it = handleMap.find(oldHandle);
 		if(it != handleMap.end())
 		{
 			typename T::Ptr p = it->second;
 			handleMap.erase(it);
 			handleMap[newHandle] = p;
 			return true;
 		}
 		else
 		{
 			return false;
 		}
 	}
 	bool release(typename T::Handle handle)
 	{
 		AutoLockNSPR lock(handleMapMutex);
 		typename HandleMapType::iterator it = handleMap.find(handle);
 		if(it != handleMap.end())
 		{
 			handleMap.erase(it);
 			return true;
 		}
 		else
 		{
 			return false;
 		}
 	}
 	void reset()
 	{
 		AutoLockNSPR lock(handleMapMutex);
 		handleMap.clear();
 	}
 };
 #define CSF_DECLARE_WRAP(classname, handletype) \
 	public: \
 		static classname ## Ptr wrap(handletype handle); \
 		static void reset(); \
                 static void release(handletype handle); \
 	private: \
 		friend class Wrapper<classname>; \
 		typedef classname ## Ptr Ptr; \
 		typedef handletype Handle; \
 		static Wrapper<classname>& getWrapper() { \
 			static Wrapper<classname> wrapper; \
 			return wrapper; \
 		}
 #define CSF_IMPLEMENT_WRAP(classname, handletype) \
 	classname ## Ptr classname::wrap(handletype handle) \
 	{ \
 		return getWrapper().wrap(handle); \
 	} \
 	void classname::reset() \
 	{ \
 		getWrapper().reset(); \
 	} \
         void classname::release(handletype handle) \
         { \
                 getWrapper().release(handle); \
         }

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media/webrtc/signaling/src/common/Wrapper.h@ac0c01689b40 (annotated)

media/webrtc/signaling/src/common/Wrapper.h