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// Copyright 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////////
#ifndef UTIL_VARSETTER_H_
#define UTIL_VARSETTER_H_
//
// Use a VarSetter object to temporarily set an object of some sort to
// a particular value. When the VarSetter object is destructed, the
// underlying object will revert to its former value.
//
// Sample code:
//
#if 0
{
bool b = true;
{
VarSetter<bool> bool_setter(&b, false);
// Now b == false.
}
// Now b == true again.
}
#endif
template <class C>
class VarSetter {
public:
// Constructor that just sets the object to a fixed value
VarSetter(C* object, const C& value) : object_(object), old_value_(*object) {
*object = value;
}
~VarSetter() { *object_ = old_value_; }
private:
C*const object_;
C old_value_;
// Disallow
VarSetter(const VarSetter&);
VarSetter& operator=(const VarSetter&);
// VarSetters always live on the stack
static void* operator new (size_t);
static void* operator new[](size_t); // Redundant, no default ctor
static void operator delete (void*);
static void operator delete[](void*);
};
#endif // UTIL_VARSETTER_H_
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