Add m-esr52 at 52.6.0

1 files changed, 345 insertions, 0 deletions

diff --git a/security/sandbox/chromium/base/memory/weak_ptr.h b/security/sandbox/chromium/base/memory/weak_ptr.h
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index 000000000..33d1e4736
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+++ b/security/sandbox/chromium/base/memory/weak_ptr.h
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+// 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.
+
+// Weak pointers are pointers to an object that do not affect its lifetime,
+// and which may be invalidated (i.e. reset to NULL) by the object, or its
+// owner, at any time, most commonly when the object is about to be deleted.
+
+// Weak pointers are useful when an object needs to be accessed safely by one
+// or more objects other than its owner, and those callers can cope with the
+// object vanishing and e.g. tasks posted to it being silently dropped.
+// Reference-counting such an object would complicate the ownership graph and
+// make it harder to reason about the object's lifetime.
+
+// EXAMPLE:
+//
+//  class Controller {
+//   public:
+//    Controller() : weak_factory_(this) {}
+//    void SpawnWorker() { Worker::StartNew(weak_factory_.GetWeakPtr()); }
+//    void WorkComplete(const Result& result) { ... }
+//   private:
+//    // Member variables should appear before the WeakPtrFactory, to ensure
+//    // that any WeakPtrs to Controller are invalidated before its members
+//    // variable's destructors are executed, rendering them invalid.
+//    WeakPtrFactory<Controller> weak_factory_;
+//  };
+//
+//  class Worker {
+//   public:
+//    static void StartNew(const WeakPtr<Controller>& controller) {
+//      Worker* worker = new Worker(controller);
+//      // Kick off asynchronous processing...
+//    }
+//   private:
+//    Worker(const WeakPtr<Controller>& controller)
+//        : controller_(controller) {}
+//    void DidCompleteAsynchronousProcessing(const Result& result) {
+//      if (controller_)
+//        controller_->WorkComplete(result);
+//    }
+//    WeakPtr<Controller> controller_;
+//  };
+//
+// With this implementation a caller may use SpawnWorker() to dispatch multiple
+// Workers and subsequently delete the Controller, without waiting for all
+// Workers to have completed.
+
+// ------------------------- IMPORTANT: Thread-safety -------------------------
+
+// Weak pointers may be passed safely between threads, but must always be
+// dereferenced and invalidated on the same SequencedTaskRunner otherwise
+// checking the pointer would be racey.
+//
+// To ensure correct use, the first time a WeakPtr issued by a WeakPtrFactory
+// is dereferenced, the factory and its WeakPtrs become bound to the calling
+// thread or current SequencedWorkerPool token, and cannot be dereferenced or
+// invalidated on any other task runner. Bound WeakPtrs can still be handed
+// off to other task runners, e.g. to use to post tasks back to object on the
+// bound sequence.
+//
+// If all WeakPtr objects are destroyed or invalidated then the factory is
+// unbound from the SequencedTaskRunner/Thread. The WeakPtrFactory may then be
+// destroyed, or new WeakPtr objects may be used, from a different sequence.
+//
+// Thus, at least one WeakPtr object must exist and have been dereferenced on
+// the correct thread to enforce that other WeakPtr objects will enforce they
+// are used on the desired thread.
+
+#ifndef BASE_MEMORY_WEAK_PTR_H_
+#define BASE_MEMORY_WEAK_PTR_H_
+
+#include "base/base_export.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/sequence_checker.h"
+#include "base/template_util.h"
+
+namespace base {
+
+template <typename T> class SupportsWeakPtr;
+template <typename T> class WeakPtr;
+
+namespace internal {
+// These classes are part of the WeakPtr implementation.
+// DO NOT USE THESE CLASSES DIRECTLY YOURSELF.
+
+class BASE_EXPORT WeakReference {
+ public:
+  // Although Flag is bound to a specific SequencedTaskRunner, it may be
+  // deleted from another via base::WeakPtr::~WeakPtr().
+  class BASE_EXPORT Flag : public RefCountedThreadSafe<Flag> {
+   public:
+    Flag();
+
+    void Invalidate();
+    bool IsValid() const;
+
+   private:
+    friend class base::RefCountedThreadSafe<Flag>;
+
+    ~Flag();
+
+    SequenceChecker sequence_checker_;
+    bool is_valid_;
+  };
+
+  WeakReference();
+  explicit WeakReference(const Flag* flag);
+  ~WeakReference();
+
+  bool is_valid() const;
+
+ private:
+  scoped_refptr<const Flag> flag_;
+};
+
+class BASE_EXPORT WeakReferenceOwner {
+ public:
+  WeakReferenceOwner();
+  ~WeakReferenceOwner();
+
+  WeakReference GetRef() const;
+
+  bool HasRefs() const {
+    return flag_.get() && !flag_->HasOneRef();
+  }
+
+  void Invalidate();
+
+ private:
+  mutable scoped_refptr<WeakReference::Flag> flag_;
+};
+
+// This class simplifies the implementation of WeakPtr's type conversion
+// constructor by avoiding the need for a public accessor for ref_.  A
+// WeakPtr<T> cannot access the private members of WeakPtr<U>, so this
+// base class gives us a way to access ref_ in a protected fashion.
+class BASE_EXPORT WeakPtrBase {
+ public:
+  WeakPtrBase();
+  ~WeakPtrBase();
+
+ protected:
+  explicit WeakPtrBase(const WeakReference& ref);
+
+  WeakReference ref_;
+};
+
+// This class provides a common implementation of common functions that would
+// otherwise get instantiated separately for each distinct instantiation of
+// SupportsWeakPtr<>.
+class SupportsWeakPtrBase {
+ public:
+  // A safe static downcast of a WeakPtr<Base> to WeakPtr<Derived>. This
+  // conversion will only compile if there is exists a Base which inherits
+  // from SupportsWeakPtr<Base>. See base::AsWeakPtr() below for a helper
+  // function that makes calling this easier.
+  template<typename Derived>
+  static WeakPtr<Derived> StaticAsWeakPtr(Derived* t) {
+    typedef
+        is_convertible<Derived, internal::SupportsWeakPtrBase&> convertible;
+    static_assert(convertible::value,
+                  "AsWeakPtr argument must inherit from SupportsWeakPtr");
+    return AsWeakPtrImpl<Derived>(t, *t);
+  }
+
+ private:
+  // This template function uses type inference to find a Base of Derived
+  // which is an instance of SupportsWeakPtr<Base>. We can then safely
+  // static_cast the Base* to a Derived*.
+  template <typename Derived, typename Base>
+  static WeakPtr<Derived> AsWeakPtrImpl(
+      Derived* t, const SupportsWeakPtr<Base>&) {
+    WeakPtr<Base> ptr = t->Base::AsWeakPtr();
+    return WeakPtr<Derived>(ptr.ref_, static_cast<Derived*>(ptr.ptr_));
+  }
+};
+
+}  // namespace internal
+
+template <typename T> class WeakPtrFactory;
+
+// The WeakPtr class holds a weak reference to |T*|.
+//
+// This class is designed to be used like a normal pointer.  You should always
+// null-test an object of this class before using it or invoking a method that
+// may result in the underlying object being destroyed.
+//
+// EXAMPLE:
+//
+//   class Foo { ... };
+//   WeakPtr<Foo> foo;
+//   if (foo)
+//     foo->method();
+//
+template <typename T>
+class WeakPtr : public internal::WeakPtrBase {
+ public:
+  WeakPtr() : ptr_(NULL) {
+  }
+
+  // Allow conversion from U to T provided U "is a" T. Note that this
+  // is separate from the (implicit) copy constructor.
+  template <typename U>
+  WeakPtr(const WeakPtr<U>& other) : WeakPtrBase(other), ptr_(other.ptr_) {
+  }
+
+  T* get() const { return ref_.is_valid() ? ptr_ : NULL; }
+
+  T& operator*() const {
+    DCHECK(get() != NULL);
+    return *get();
+  }
+  T* operator->() const {
+    DCHECK(get() != NULL);
+    return get();
+  }
+
+  // Allow WeakPtr<element_type> to be used in boolean expressions, but not
+  // implicitly convertible to a real bool (which is dangerous).
+  //
+  // Note that this trick is only safe when the == and != operators
+  // are declared explicitly, as otherwise "weak_ptr1 == weak_ptr2"
+  // will compile but do the wrong thing (i.e., convert to Testable
+  // and then do the comparison).
+ private:
+  typedef T* WeakPtr::*Testable;
+
+ public:
+  operator Testable() const { return get() ? &WeakPtr::ptr_ : NULL; }
+
+  void reset() {
+    ref_ = internal::WeakReference();
+    ptr_ = NULL;
+  }
+
+ private:
+  // Explicitly declare comparison operators as required by the bool
+  // trick, but keep them private.
+  template <class U> bool operator==(WeakPtr<U> const&) const;
+  template <class U> bool operator!=(WeakPtr<U> const&) const;
+
+  friend class internal::SupportsWeakPtrBase;
+  template <typename U> friend class WeakPtr;
+  friend class SupportsWeakPtr<T>;
+  friend class WeakPtrFactory<T>;
+
+  WeakPtr(const internal::WeakReference& ref, T* ptr)
+      : WeakPtrBase(ref),
+        ptr_(ptr) {
+  }
+
+  // This pointer is only valid when ref_.is_valid() is true.  Otherwise, its
+  // value is undefined (as opposed to NULL).
+  T* ptr_;
+};
+
+// A class may be composed of a WeakPtrFactory and thereby
+// control how it exposes weak pointers to itself.  This is helpful if you only
+// need weak pointers within the implementation of a class.  This class is also
+// useful when working with primitive types.  For example, you could have a
+// WeakPtrFactory<bool> that is used to pass around a weak reference to a bool.
+template <class T>
+class WeakPtrFactory {
+ public:
+  explicit WeakPtrFactory(T* ptr) : ptr_(ptr) {
+  }
+
+  ~WeakPtrFactory() {
+    ptr_ = NULL;
+  }
+
+  WeakPtr<T> GetWeakPtr() {
+    DCHECK(ptr_);
+    return WeakPtr<T>(weak_reference_owner_.GetRef(), ptr_);
+  }
+
+  // Call this method to invalidate all existing weak pointers.
+  void InvalidateWeakPtrs() {
+    DCHECK(ptr_);
+    weak_reference_owner_.Invalidate();
+  }
+
+  // Call this method to determine if any weak pointers exist.
+  bool HasWeakPtrs() const {
+    DCHECK(ptr_);
+    return weak_reference_owner_.HasRefs();
+  }
+
+ private:
+  internal::WeakReferenceOwner weak_reference_owner_;
+  T* ptr_;
+  DISALLOW_IMPLICIT_CONSTRUCTORS(WeakPtrFactory);
+};
+
+// A class may extend from SupportsWeakPtr to let others take weak pointers to
+// it. This avoids the class itself implementing boilerplate to dispense weak
+// pointers.  However, since SupportsWeakPtr's destructor won't invalidate
+// weak pointers to the class until after the derived class' members have been
+// destroyed, its use can lead to subtle use-after-destroy issues.
+template <class T>
+class SupportsWeakPtr : public internal::SupportsWeakPtrBase {
+ public:
+  SupportsWeakPtr() {}
+
+  WeakPtr<T> AsWeakPtr() {
+    return WeakPtr<T>(weak_reference_owner_.GetRef(), static_cast<T*>(this));
+  }
+
+ protected:
+  ~SupportsWeakPtr() {}
+
+ private:
+  internal::WeakReferenceOwner weak_reference_owner_;
+  DISALLOW_COPY_AND_ASSIGN(SupportsWeakPtr);
+};
+
+// Helper function that uses type deduction to safely return a WeakPtr<Derived>
+// when Derived doesn't directly extend SupportsWeakPtr<Derived>, instead it
+// extends a Base that extends SupportsWeakPtr<Base>.
+//
+// EXAMPLE:
+//   class Base : public base::SupportsWeakPtr<Producer> {};
+//   class Derived : public Base {};
+//
+//   Derived derived;
+//   base::WeakPtr<Derived> ptr = base::AsWeakPtr(&derived);
+//
+// Note that the following doesn't work (invalid type conversion) since
+// Derived::AsWeakPtr() is WeakPtr<Base> SupportsWeakPtr<Base>::AsWeakPtr(),
+// and there's no way to safely cast WeakPtr<Base> to WeakPtr<Derived> at
+// the caller.
+//
+//   base::WeakPtr<Derived> ptr = derived.AsWeakPtr();  // Fails.
+
+template <typename Derived>
+WeakPtr<Derived> AsWeakPtr(Derived* t) {
+  return internal::SupportsWeakPtrBase::StaticAsWeakPtr<Derived>(t);
+}
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_WEAK_PTR_H_