1 // Copyright 2017 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef V8_DETACHABLE_VECTOR_H_ 6 #define V8_DETACHABLE_VECTOR_H_ 7 8 #include <vector> 9 10 namespace v8 { 11 namespace internal { 12 13 // This class wraps a std::vector and provides a few of the common member 14 // functions for accessing the data. It acts as a lazy wrapper of the vector, 15 // not initiliazing the backing store until push_back() is first called. Two 16 // extra methods are also provided: free() and detach(), which allow for manual 17 // control of the backing store. This is currently required for use in the 18 // HandleScopeImplementer. Any other class should just use a std::vector 19 // directly. 20 template <typename T> 21 class DetachableVector { 22 public: 23 DetachableVector() : vector_(nullptr) {} 24 25 ~DetachableVector() { delete vector_; } 26 27 void push_back(const T& value) { 28 ensureAttached(); 29 vector_->push_back(value); 30 } 31 32 // Free the backing store and clear our reference to it. 33 void free() { 34 delete vector_; 35 vector_ = nullptr; 36 } 37 38 // Clear our reference to the backing store. Does not delete it! 39 void detach() { vector_ = nullptr; } 40 41 T& at(typename std::vector<T>::size_type i) const { return vector_->at(i); } 42 43 T& back() const { return vector_->back(); } 44 45 T& front() const { return vector_->front(); } 46 47 void pop_back() { vector_->pop_back(); } 48 49 typename std::vector<T>::size_type size() const { 50 if (vector_) return vector_->size(); 51 return 0; 52 } 53 54 bool empty() const { 55 if (vector_) return vector_->empty(); 56 return true; 57 } 58 59 private: 60 std::vector<T>* vector_; 61 62 // Attach a vector backing store if not present. 63 void ensureAttached() { 64 if (vector_ == nullptr) { 65 vector_ = new std::vector<T>(); 66 } 67 } 68 }; 69 70 } // namespace internal 71 } // namespace v8 72 73 #endif // V8_DETACHABLE_VECTOR_H_ 74
