106 lines
2.5 KiB
C++
106 lines
2.5 KiB
C++
/* Copyright (C) 2013 Interactive Brokers LLC. All rights reserved. This code is subject to the terms
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* and conditions of the IB API Non-Commercial License or the IB API Commercial License, as applicable. */
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#pragma once
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#ifndef shared_ptr_h_INCLUDED
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#define shared_ptr_h_INCLUDED
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//
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// Implements a subset of shared_prt found at www.boost.org.
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// Uses a singly linked circular list instead of a reference counter.
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// Avoids extra heap allocation needed to get a shared reference counter,
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// but sizeof(shared_ptr) == sizeof(void*) * 3 compared to sizeof(void*) * 2
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//
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// See "Handles and Exception Safety, Part 4: Tracking References without Counters"
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// by Andrew Koenig and Barbara E. Moo, Feb. 2003 C++ Users Journal
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//
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namespace ibapi {
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namespace shared_ptr_defs {
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class Use {
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public:
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Use() { forward_ = this; back_ = this; }
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~Use() { remove(); }
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Use(const Use& u) { insert(u); }
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Use& operator=(const Use& u)
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{
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if (this != &u) {
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remove();
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insert(u);
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}
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return *this;
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}
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bool only() const { return this == this->forward_; }
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private:
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mutable const Use *forward_;
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mutable const Use *back_;
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void insert(const Use& u) const {
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this->back_ = &u;
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this->forward_ = u.forward_;
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u.forward_->back_ = this;
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u.forward_ = this;
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}
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void remove() const {
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this->forward_->back_ = this->back_;
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this->back_->forward_ = this->forward_;
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}
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};
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} // end of namespace shared_ptr_defs
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template<typename X> class shared_ptr {
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public:
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typedef shared_ptr_defs::Use Use;
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template<typename Y> friend class shared_ptr;
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explicit shared_ptr(X* ptr = 0) : ptr_(ptr) {}
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~shared_ptr() { if (use_.only()) delete ptr_; }
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template<typename Y>
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shared_ptr(const shared_ptr<Y>& other)
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: ptr_(other.ptr_),
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use_(other.use_)
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{}
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shared_ptr& operator=(const shared_ptr& other) {
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if ( &use_ == &other.use_ ) { return *this; }
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if ( use_.only() ) { delete ptr_; }
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use_ = other.use_;
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ptr_ = other.ptr_;
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return *this;
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}
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X& operator*() const { return *ptr_; }
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X* operator->() const { return ptr_; }
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X* get() const { return ptr_; }
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bool only() const { return use_.only(); }
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void reset(X* ptr = 0) {
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if ( use_.only() ) { delete ptr_; }
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ptr_ = ptr;
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use_ = Use();
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}
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private:
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X *ptr_;
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Use use_;
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};
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} //end of namespace ibapi
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#else
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//#include <memory>
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//using std::shared_ptr;
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#endif /* shared_ptr_h_INCLUDED */ |