The Tor Browser: comparison security/sandbox/chromium/base/callback

--1:000000000000
+:7a097cc05a11
+// 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.
+// This file contains utility functions and classes that help the
+// implementation, and management of the Callback objects.
+#ifndef BASE_CALLBACK_INTERNAL_H_
+#define BASE_CALLBACK_INTERNAL_H_
+#include <stddef.h>
+#include "base/base_export.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+template <typename T>
+class ScopedVector;
+namespace base {
+namespace internal {
+// BindStateBase is used to provide an opaque handle that the Callback
+// class can use to represent a function object with bound arguments.  It
+// behaves as an existential type that is used by a corresponding
+// DoInvoke function to perform the function execution.  This allows
+// us to shield the Callback class from the types of the bound argument via
+// "type erasure."
+class BindStateBase : public RefCountedThreadSafe<BindStateBase> {
+protected:
+friend class RefCountedThreadSafe<BindStateBase>;
+virtual ~BindStateBase() {}
+};
+// Holds the Callback methods that don't require specialization to reduce
+// template bloat.
+class BASE_EXPORT CallbackBase {
+public:
+// Returns true if Callback is null (doesn't refer to anything).
+bool is_null() const;
+// Returns the Callback into an uninitialized state.
+void Reset();
+protected:
+// In C++, it is safe to cast function pointers to function pointers of
+// another type. It is not okay to use void*. We create a InvokeFuncStorage
+// that that can store our function pointer, and then cast it back to
+// the original type on usage.
+typedef void(*InvokeFuncStorage)(void);
+// Returns true if this callback equals |other|. |other| may be null.
+bool Equals(const CallbackBase& other) const;
+// Allow initializing of |bind_state_| via the constructor to avoid default
+// initialization of the scoped_refptr.  We do not also initialize
+// |polymorphic_invoke_| here because doing a normal assignment in the
+// derived Callback templates makes for much nicer compiler errors.
+explicit CallbackBase(BindStateBase* bind_state);
+// Force the destructor to be instantiated inside this translation unit so
+// that our subclasses will not get inlined versions.  Avoids more template
+// bloat.
+~CallbackBase();
+scoped_refptr<BindStateBase> bind_state_;
+InvokeFuncStorage polymorphic_invoke_;
+};
+// This is a typetraits object that's used to take an argument type, and
+// extract a suitable type for storing and forwarding arguments.
+//
+// In particular, it strips off references, and converts arrays to
+// pointers for storage; and it avoids accidentally trying to create a
+// "reference of a reference" if the argument is a reference type.
+//
+// This array type becomes an issue for storage because we are passing bound
+// parameters by const reference. In this case, we end up passing an actual
+// array type in the initializer list which C++ does not allow.  This will
+// break passing of C-string literals.
+template <typename T>
+struct CallbackParamTraits {
+typedef const T& ForwardType;
+typedef T StorageType;
+};
+// The Storage should almost be impossible to trigger unless someone manually
+// specifies type of the bind parameters.  However, in case they do,
+// this will guard against us accidentally storing a reference parameter.
+//
+// The ForwardType should only be used for unbound arguments.
+template <typename T>
+struct CallbackParamTraits<T&> {
+typedef T& ForwardType;
+typedef T StorageType;
+};
+// Note that for array types, we implicitly add a const in the conversion. This
+// means that it is not possible to bind array arguments to functions that take
+// a non-const pointer. Trying to specialize the template based on a "const
+// T[n]" does not seem to match correctly, so we are stuck with this
+// restriction.
+template <typename T, size_t n>
+struct CallbackParamTraits<T[n]> {
+typedef const T* ForwardType;
+typedef const T* StorageType;
+};
+// See comment for CallbackParamTraits<T[n]>.
+template <typename T>
+struct CallbackParamTraits<T[]> {
+typedef const T* ForwardType;
+typedef const T* StorageType;
+};
+// Parameter traits for movable-but-not-copyable scopers.
+//
+// Callback<>/Bind() understands movable-but-not-copyable semantics where
+// the type cannot be copied but can still have its state destructively
+// transferred (aka. moved) to another instance of the same type by calling a
+// helper function.  When used with Bind(), this signifies transferal of the
+// object's state to the target function.
+//
+// For these types, the ForwardType must not be a const reference, or a
+// reference.  A const reference is inappropriate, and would break const
+// correctness, because we are implementing a destructive move.  A non-const
+// reference cannot be used with temporaries which means the result of a
+// function or a cast would not be usable with Callback<> or Bind().
+//
+// TODO(ajwong): We might be able to use SFINAE to search for the existence of
+// a Pass() function in the type and avoid the whitelist in CallbackParamTraits
+// and CallbackForward.
+template <typename T, typename D>
+struct CallbackParamTraits<scoped_ptr<T, D> > {
+typedef scoped_ptr<T, D> ForwardType;
+typedef scoped_ptr<T, D> StorageType;
+};
+template <typename T, typename R>
+struct CallbackParamTraits<scoped_ptr_malloc<T, R> > {
+typedef scoped_ptr_malloc<T, R> ForwardType;
+typedef scoped_ptr_malloc<T, R> StorageType;
+};
+template <typename T>
+struct CallbackParamTraits<ScopedVector<T> > {
+typedef ScopedVector<T> ForwardType;
+typedef ScopedVector<T> StorageType;
+};
+// CallbackForward() is a very limited simulation of C++11's std::forward()
+// used by the Callback/Bind system for a set of movable-but-not-copyable
+// types.  It is needed because forwarding a movable-but-not-copyable
+// argument to another function requires us to invoke the proper move
+// operator to create a rvalue version of the type.  The supported types are
+// whitelisted below as overloads of the CallbackForward() function. The
+// default template compiles out to be a no-op.
+//
+// In C++11, std::forward would replace all uses of this function.  However, it
+// is impossible to implement a general std::forward with C++11 due to a lack
+// of rvalue references.
+//
+// In addition to Callback/Bind, this is used by PostTaskAndReplyWithResult to
+// simulate std::forward() and forward the result of one Callback as a
+// parameter to another callback. This is to support Callbacks that return
+// the movable-but-not-copyable types whitelisted above.
+template <typename T>
+T& CallbackForward(T& t) { return t; }
+template <typename T, typename D>
+scoped_ptr<T, D> CallbackForward(scoped_ptr<T, D>& p) { return p.Pass(); }
+template <typename T, typename R>
+scoped_ptr_malloc<T, R> CallbackForward(scoped_ptr_malloc<T, R>& p) {
+return p.Pass();
+}
+template <typename T>
+ScopedVector<T> CallbackForward(ScopedVector<T>& p) { return p.Pass(); }
+}  // namespace internal
+}  // namespace base
+#endif  // BASE_CALLBACK_INTERNAL_H_

The Tor Browser / file comparison

comparison: security/sandbox/chromium/base/callback_internal.h

security/sandbox/chromium/base/callback_internal.h