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// Copyright 2020 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_SCOPE_STACK_H_
#define SRC_SCOPE_STACK_H_
#include <unordered_map>
#include <utility>
#include <vector>
#include "src/symbol.h"
namespace tint {
/// Used to store a stack of scope information.
/// The stack starts with a global scope which can not be popped.
template <class T>
class ScopeStack {
public:
/// Constructor
ScopeStack() {
// Push global bucket
stack_.push_back({});
}
/// Copy Constructor
ScopeStack(const ScopeStack&) = default;
~ScopeStack() = default;
/// Push a new scope on to the stack
void Push() { stack_.push_back({}); }
/// Pop the scope off the top of the stack
void Pop() {
if (stack_.size() > 1) {
stack_.pop_back();
}
}
/// Assigns the value into the top most scope of the stack.
/// @param symbol the symbol of the value
/// @param val the value
/// @returns the old value if there was an existing symbol at the top of the
/// stack, otherwise the zero initializer for type T.
T Set(const Symbol& symbol, T val) {
std::swap(val, stack_.back()[symbol]);
return val;
}
/// Retrieves a value from the stack
/// @param symbol the symbol to look for
/// @returns the value, or the zero initializer if the value was not found
T Get(const Symbol& symbol) const {
for (auto iter = stack_.rbegin(); iter != stack_.rend(); ++iter) {
auto& map = *iter;
auto val = map.find(symbol);
if (val != map.end()) {
return val->second;
}
}
return T{};
}
private:
std::vector<std::unordered_map<Symbol, T>> stack_;
};
} // namespace tint
#endif // SRC_SCOPE_STACK_H_