The Tor Browser: security/sandbox/chromium/base/memory/ref

security/sandbox/chromium/base/memory/ref_counted.h@97036ab72558 (annotated)

security/sandbox/chromium/base/memory/ref_counted.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.

 // Copyright (c) 2012 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.
 #ifndef BASE_MEMORY_REF_COUNTED_H_
 #define BASE_MEMORY_REF_COUNTED_H_
 #include <cassert>
 #include "base/atomic_ref_count.h"
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
 #include "base/threading/thread_collision_warner.h"
 namespace base {
 namespace subtle {
 class BASE_EXPORT RefCountedBase {
  public:
   bool HasOneRef() const { return ref_count_ == 1; }
  protected:
   RefCountedBase();
   ~RefCountedBase();
   void AddRef() const;
   // Returns true if the object should self-delete.
   bool Release() const;
  private:
   mutable int ref_count_;
 #ifndef NDEBUG
   mutable bool in_dtor_;
 #endif
   DFAKE_MUTEX(add_release_);
   DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
 };
 class BASE_EXPORT RefCountedThreadSafeBase {
  public:
   bool HasOneRef() const;
  protected:
   RefCountedThreadSafeBase();
   ~RefCountedThreadSafeBase();
   void AddRef() const;
   // Returns true if the object should self-delete.
   bool Release() const;
  private:
   mutable AtomicRefCount ref_count_;
 #ifndef NDEBUG
   mutable bool in_dtor_;
 #endif
   DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
 };
 }  // namespace subtle
 //
 // A base class for reference counted classes.  Otherwise, known as a cheap
 // knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your
 // class from it like so:
 //
 //   class MyFoo : public base::RefCounted<MyFoo> {
 //    ...
 //    private:
 //     friend class base::RefCounted<MyFoo>;
 //     ~MyFoo();
 //   };
 //
 // You should always make your destructor private, to avoid any code deleting
 // the object accidently while there are references to it.
 template <class T>
 class RefCounted : public subtle::RefCountedBase {
  public:
   RefCounted() {}
   void AddRef() const {
     subtle::RefCountedBase::AddRef();
   }
   void Release() const {
     if (subtle::RefCountedBase::Release()) {
       delete static_cast<const T*>(this);
     }
   }
  protected:
   ~RefCounted() {}
  private:
   DISALLOW_COPY_AND_ASSIGN(RefCounted<T>);
 };
 // Forward declaration.
 template <class T, typename Traits> class RefCountedThreadSafe;
 // Default traits for RefCountedThreadSafe<T>.  Deletes the object when its ref
 // count reaches 0.  Overload to delete it on a different thread etc.
 template<typename T>
 struct DefaultRefCountedThreadSafeTraits {
   static void Destruct(const T* x) {
     // Delete through RefCountedThreadSafe to make child classes only need to be
     // friend with RefCountedThreadSafe instead of this struct, which is an
     // implementation detail.
     RefCountedThreadSafe<T,
                          DefaultRefCountedThreadSafeTraits>::DeleteInternal(x);
   }
 };
 //
 // A thread-safe variant of RefCounted<T>
 //
 //   class MyFoo : public base::RefCountedThreadSafe<MyFoo> {
 //    ...
 //   };
 //
 // If you're using the default trait, then you should add compile time
 // asserts that no one else is deleting your object.  i.e.
 //    private:
 //     friend class base::RefCountedThreadSafe<MyFoo>;
 //     ~MyFoo();
 template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T> >
 class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
  public:
   RefCountedThreadSafe() {}
   void AddRef() const {
     subtle::RefCountedThreadSafeBase::AddRef();
   }
   void Release() const {
     if (subtle::RefCountedThreadSafeBase::Release()) {
       Traits::Destruct(static_cast<const T*>(this));
     }
   }
  protected:
   ~RefCountedThreadSafe() {}
  private:
   friend struct DefaultRefCountedThreadSafeTraits<T>;
   static void DeleteInternal(const T* x) { delete x; }
   DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe);
 };
 //
 // A thread-safe wrapper for some piece of data so we can place other
 // things in scoped_refptrs<>.
 //
 template<typename T>
 class RefCountedData
     : public base::RefCountedThreadSafe< base::RefCountedData<T> > {
  public:
   RefCountedData() : data() {}
   RefCountedData(const T& in_value) : data(in_value) {}
   T data;
  private:
   friend class base::RefCountedThreadSafe<base::RefCountedData<T> >;
   ~RefCountedData() {}
 };
 }  // namespace base
 //
 // A smart pointer class for reference counted objects.  Use this class instead
 // of calling AddRef and Release manually on a reference counted object to
 // avoid common memory leaks caused by forgetting to Release an object
 // reference.  Sample usage:
 //
 //   class MyFoo : public RefCounted<MyFoo> {
 //    ...
 //   };
 //
 //   void some_function() {
 //     scoped_refptr<MyFoo> foo = new MyFoo();
 //     foo->Method(param);
 //     // |foo| is released when this function returns
 //   }
 //
 //   void some_other_function() {
 //     scoped_refptr<MyFoo> foo = new MyFoo();
 //     ...
 //     foo = NULL;  // explicitly releases |foo|
 //     ...
 //     if (foo)
 //       foo->Method(param);
 //   }
 //
 // The above examples show how scoped_refptr<T> acts like a pointer to T.
 // Given two scoped_refptr<T> classes, it is also possible to exchange
 // references between the two objects, like so:
 //
 //   {
 //     scoped_refptr<MyFoo> a = new MyFoo();
 //     scoped_refptr<MyFoo> b;
 //
 //     b.swap(a);
 //     // now, |b| references the MyFoo object, and |a| references NULL.
 //   }
 //
 // To make both |a| and |b| in the above example reference the same MyFoo
 // object, simply use the assignment operator:
 //
 //   {
 //     scoped_refptr<MyFoo> a = new MyFoo();
 //     scoped_refptr<MyFoo> b;
 //
 //     b = a;
 //     // now, |a| and |b| each own a reference to the same MyFoo object.
 //   }
 //
 template <class T>
 class scoped_refptr {
  public:
   typedef T element_type;
   scoped_refptr() : ptr_(NULL) {
   }
   scoped_refptr(T* p) : ptr_(p) {
     if (ptr_)
       ptr_->AddRef();
   }
   scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
     if (ptr_)
       ptr_->AddRef();
   }
   template <typename U>
   scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
     if (ptr_)
       ptr_->AddRef();
   }
   ~scoped_refptr() {
     if (ptr_)
       ptr_->Release();
   }
   T* get() const { return ptr_; }
   operator T*() const { return ptr_; }
   T* operator->() const {
     assert(ptr_ != NULL);
     return ptr_;
   }
   scoped_refptr<T>& operator=(T* p) {
     // AddRef first so that self assignment should work
     if (p)
       p->AddRef();
     T* old_ptr = ptr_;
     ptr_ = p;
     if (old_ptr)
       old_ptr->Release();
     return *this;
   }
   scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
     return *this = r.ptr_;
   }
   template <typename U>
   scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
     return *this = r.get();
   }
   void swap(T** pp) {
     T* p = ptr_;
     ptr_ = *pp;
     *pp = p;
   }
   void swap(scoped_refptr<T>& r) {
     swap(&r.ptr_);
   }
  protected:
   T* ptr_;
 };
 // Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
 // having to retype all the template arguments
 template <typename T>
 scoped_refptr<T> make_scoped_refptr(T* t) {
   return scoped_refptr<T>(t);
 }
 #endif  // BASE_MEMORY_REF_COUNTED_H_

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security/sandbox/chromium/base/memory/ref_counted.h@97036ab72558 (annotated)

security/sandbox/chromium/base/memory/ref_counted.h