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// Copyright 2021 The Tint Authors.
//
// 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 SRC_TINT_UTILS_SCOPED_ASSIGNMENT_H_
#define SRC_TINT_UTILS_SCOPED_ASSIGNMENT_H_
#include <type_traits>
#include "src/tint/utils/concat.h"
namespace tint::utils {
/// Helper class that temporarily assigns a value to a variable for the lifetime
/// of the ScopedAssignment object. Once the ScopedAssignment is destructed, the
/// original value is restored.
template <typename T>
class ScopedAssignment {
public:
/// Constructor
/// @param var the variable to temporarily assign a new value to
/// @param val the value to assign to `ref` for the lifetime of this
/// ScopedAssignment.
ScopedAssignment(T& var, T val) : ref_(var) {
old_value_ = var;
var = val;
}
/// Destructor
/// Restores the original value of the variable.
~ScopedAssignment() { ref_ = old_value_; }
private:
ScopedAssignment(const ScopedAssignment&) = delete;
ScopedAssignment& operator=(const ScopedAssignment&) = delete;
T& ref_;
T old_value_;
};
} // namespace tint::utils
/// TINT_SCOPED_ASSIGNMENT(var, val) assigns `val` to `var`, and automatically
/// restores the original value of `var` when exiting the current lexical scope.
#define TINT_SCOPED_ASSIGNMENT(var, val) \
::tint::utils::ScopedAssignment<std::remove_reference_t<decltype(var)>> \
TINT_CONCAT(tint_scoped_assignment_, __COUNTER__) { \
var, val \
}
#endif // SRC_TINT_UTILS_SCOPED_ASSIGNMENT_H_