65 lines
2.1 KiB
C++
65 lines
2.1 KiB
C++
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// Copyright 2021 The Tint Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SRC_UTILS_SCOPED_ASSIGNMENT_H_
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#define SRC_UTILS_SCOPED_ASSIGNMENT_H_
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#include <type_traits>
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#include "src/utils/concat.h"
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namespace tint {
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namespace utils {
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/// Helper class that temporarily assigns a value to a variable for the lifetime
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/// of the ScopedAssignment object. Once the ScopedAssignment is destructed, the
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/// original value is restored.
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template <typename T>
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class ScopedAssignment {
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public:
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/// Constructor
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/// @param var the variable to temporarily assign a new value to
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/// @param val the value to assign to `ref` for the lifetime of this
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/// ScopedAssignment.
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ScopedAssignment(T& var, T val) : ref_(var) {
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old_value_ = var;
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var = val;
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}
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/// Destructor
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/// Restores the original value of the variable.
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~ScopedAssignment() { ref_ = old_value_; }
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private:
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ScopedAssignment(const ScopedAssignment&) = delete;
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ScopedAssignment& operator=(const ScopedAssignment&) = delete;
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T& ref_;
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T old_value_;
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};
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} // namespace utils
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} // namespace tint
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/// TINT_SCOPED_ASSIGNMENT(var, val) assigns `val` to `var`, and automatically
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/// restores the original value of `var` when exiting the current lexical scope.
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#define TINT_SCOPED_ASSIGNMENT(var, val) \
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::tint::utils::ScopedAssignment<std::remove_reference_t<decltype(var)>> \
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TINT_CONCAT(tint_scoped_assignment_, __COUNTER__) { \
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var, val \
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}
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#endif // SRC_UTILS_SCOPED_ASSIGNMENT_H_
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