| // 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_TINT_SCOPE_STACK_H_ |
| #define SRC_TINT_SCOPE_STACK_H_ |
| |
| #include <unordered_map> |
| #include <utility> |
| #include <vector> |
| |
| #include "src/tint/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_TINT_SCOPE_STACK_H_ |