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