PolicyManager: Add a generic copy variable.
This patch includes a generic class of Variable that creates copies
of a referenced object using the copy constructor. A provider that
needs to return the value of fixed object like a private member can
simply use this generic CopyVariable class.
BUG=None
TEST=unittest
Change-Id: I4e7703c0d25990f42c9c83228ba177baffadc194
Reviewed-on: https://chromium-review.googlesource.com/181963
Reviewed-by: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
diff --git a/policy_manager/generic_variables.h b/policy_manager/generic_variables.h
new file mode 100644
index 0000000..321c89a
--- /dev/null
+++ b/policy_manager/generic_variables.h
@@ -0,0 +1,69 @@
+// Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Generic and provider independent Variable subclasses. These variables can be
+// used by any state provider to implement simple variables to avoid repeat the
+// same common code on different state providers.
+
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H
+
+#include "policy_manager/variable.h"
+
+namespace chromeos_policy_manager {
+
+// Variable class returning a copy of a given object using the copy constructor.
+// This template class can be used to define variables that expose as a variable
+// any fixed object, such as the a provider's private member. The variable will
+// create copies of the provided object using the copy constructor of that
+// class.
+//
+// For example, a state provider exposing a private method as a variable could
+// be implemented in this way:
+//
+// * On something_vars.h:
+// Variable<MyType>* var_something;
+//
+// * On something_provider:
+// class SomethingProvider {
+// public:
+// SomethingProvider(...) {
+// var_something = new CopyVariable<MyType>(priv_object_);
+// }
+// ~SomethingProvider() {
+// delete var_something;
+// var_something = NULL;
+// }
+// private:
+// MyType priv_object_;
+// };
+template<typename T>
+class CopyVariable : public Variable<T> {
+ public:
+ // Creates the variable returning copies of the passed |obj| reference. The
+ // reference to this object is kept and it should be available whenever the
+ // GetValue() method is called.
+ CopyVariable(const T& obj);
+
+ virtual ~CopyVariable() {}
+
+ protected:
+ friend class PMCopyVariableTest;
+ FRIEND_TEST(PMCopyVariableTest, SimpleTest);
+ FRIEND_TEST(PMCopyVariableTest, UseCopyConstructorTest);
+
+ // Variable override.
+ virtual const T* GetValue(base::TimeDelta timeout, std::string* errmsg);
+
+ private:
+ // Reference to the object to be copied by GetValue().
+ const T& ref_;
+};
+
+} // namespace chromeos_policy_manager
+
+// Include implementation on header files for templates.
+#include "policy_manager/generic_variables-inl.h"
+
+#endif // CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_GENERIC_VARIABLES_H