| // Copyright 2003 Google Inc. |
| // All rights reserved. |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived from |
| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| // |
| // Authors: Dan Egnor (egnor@google.com) |
| // |
| // A "smart" pointer type with reference tracking. Every pointer to a |
| // particular object is kept on a circular linked list. When the last pointer |
| // to an object is destroyed or reassigned, the object is deleted. |
| // |
| // Used properly, this deletes the object when the last reference goes away. |
| // There are several caveats: |
| // - Like all reference counting schemes, cycles lead to leaks. |
| // - Each smart pointer is actually two pointers (8 bytes instead of 4). |
| // - Every time a pointer is assigned, the entire list of pointers to that |
| // object is traversed. This class is therefore NOT SUITABLE when there |
| // will often be more than two or three pointers to a particular object. |
| // - References are only tracked as long as linked_ptr<> objects are copied. |
| // If a linked_ptr<> is converted to a raw pointer and back, BAD THINGS |
| // will happen (double deletion). |
| // |
| // A good use of this class is storing object references in STL containers. |
| // You can safely put linked_ptr<> in a vector<>. |
| // Other uses may not be as good. |
| // |
| // Note: If you use an incomplete type with linked_ptr<>, the class |
| // *containing* linked_ptr<> must have a constructor and destructor (even |
| // if they do nothing!). |
| // |
| // Bill Gibbons suggested we use something like this. |
| // |
| // Thread Safety: |
| // Unlike other linked_ptr implementations, in this implementation |
| // a linked_ptr object is thread-safe in the sense that: |
| // - it's safe to copy linked_ptr objects concurrently, |
| // - it's safe to copy *from* a linked_ptr and read its underlying |
| // raw pointer (e.g. via get()) concurrently, and |
| // - it's safe to write to two linked_ptrs that point to the same |
| // shared object concurrently. |
| // TODO(wan@google.com): rename this to safe_linked_ptr to avoid |
| // confusion with normal linked_ptr. |
| |
| #ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ |
| #define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ |
| |
| #include <stdlib.h> |
| #include <assert.h> |
| |
| #include "gtest/internal/gtest-port.h" |
| |
| namespace testing { |
| namespace internal { |
| |
| // Protects copying of all linked_ptr objects. |
| GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_linked_ptr_mutex); |
| |
| // This is used internally by all instances of linked_ptr<>. It needs to be |
| // a non-template class because different types of linked_ptr<> can refer to |
| // the same object (linked_ptr<Superclass>(obj) vs linked_ptr<Subclass>(obj)). |
| // So, it needs to be possible for different types of linked_ptr to participate |
| // in the same circular linked list, so we need a single class type here. |
| // |
| // DO NOT USE THIS CLASS DIRECTLY YOURSELF. Use linked_ptr<T>. |
| class linked_ptr_internal { |
| public: |
| // Create a new circle that includes only this instance. |
| void join_new() { |
| next_ = this; |
| } |
| |
| // Many linked_ptr operations may change p.link_ for some linked_ptr |
| // variable p in the same circle as this object. Therefore we need |
| // to prevent two such operations from occurring concurrently. |
| // |
| // Note that different types of linked_ptr objects can coexist in a |
| // circle (e.g. linked_ptr<Base>, linked_ptr<Derived1>, and |
| // linked_ptr<Derived2>). Therefore we must use a single mutex to |
| // protect all linked_ptr objects. This can create serious |
| // contention in production code, but is acceptable in a testing |
| // framework. |
| |
| // Join an existing circle. |
| void join(linked_ptr_internal const* ptr) |
| GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) { |
| MutexLock lock(&g_linked_ptr_mutex); |
| |
| linked_ptr_internal const* p = ptr; |
| while (p->next_ != ptr) p = p->next_; |
| p->next_ = this; |
| next_ = ptr; |
| } |
| |
| // Leave whatever circle we're part of. Returns true if we were the |
| // last member of the circle. Once this is done, you can join() another. |
| bool depart() |
| GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) { |
| MutexLock lock(&g_linked_ptr_mutex); |
| |
| if (next_ == this) return true; |
| linked_ptr_internal const* p = next_; |
| while (p->next_ != this) p = p->next_; |
| p->next_ = next_; |
| return false; |
| } |
| |
| private: |
| mutable linked_ptr_internal const* next_; |
| }; |
| |
| template <typename T> |
| class linked_ptr { |
| public: |
| typedef T element_type; |
| |
| // Take over ownership of a raw pointer. This should happen as soon as |
| // possible after the object is created. |
| explicit linked_ptr(T* ptr = NULL) { capture(ptr); } |
| ~linked_ptr() { depart(); } |
| |
| // Copy an existing linked_ptr<>, adding ourselves to the list of references. |
| template <typename U> linked_ptr(linked_ptr<U> const& ptr) { copy(&ptr); } |
| linked_ptr(linked_ptr const& ptr) { // NOLINT |
| assert(&ptr != this); |
| copy(&ptr); |
| } |
| |
| // Assignment releases the old value and acquires the new. |
| template <typename U> linked_ptr& operator=(linked_ptr<U> const& ptr) { |
| depart(); |
| copy(&ptr); |
| return *this; |
| } |
| |
| linked_ptr& operator=(linked_ptr const& ptr) { |
| if (&ptr != this) { |
| depart(); |
| copy(&ptr); |
| } |
| return *this; |
| } |
| |
| // Smart pointer members. |
| void reset(T* ptr = NULL) { |
| depart(); |
| capture(ptr); |
| } |
| T* get() const { return value_; } |
| T* operator->() const { return value_; } |
| T& operator*() const { return *value_; } |
| |
| bool operator==(T* p) const { return value_ == p; } |
| bool operator!=(T* p) const { return value_ != p; } |
| template <typename U> |
| bool operator==(linked_ptr<U> const& ptr) const { |
| return value_ == ptr.get(); |
| } |
| template <typename U> |
| bool operator!=(linked_ptr<U> const& ptr) const { |
| return value_ != ptr.get(); |
| } |
| |
| private: |
| template <typename U> |
| friend class linked_ptr; |
| |
| T* value_; |
| linked_ptr_internal link_; |
| |
| void depart() { |
| if (link_.depart()) delete value_; |
| } |
| |
| void capture(T* ptr) { |
| value_ = ptr; |
| link_.join_new(); |
| } |
| |
| template <typename U> void copy(linked_ptr<U> const* ptr) { |
| value_ = ptr->get(); |
| if (value_) |
| link_.join(&ptr->link_); |
| else |
| link_.join_new(); |
| } |
| }; |
| |
| template<typename T> inline |
| bool operator==(T* ptr, const linked_ptr<T>& x) { |
| return ptr == x.get(); |
| } |
| |
| template<typename T> inline |
| bool operator!=(T* ptr, const linked_ptr<T>& x) { |
| return ptr != x.get(); |
| } |
| |
| // A function to convert T* into linked_ptr<T> |
| // Doing e.g. make_linked_ptr(new FooBarBaz<type>(arg)) is a shorter notation |
| // for linked_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg)) |
| template <typename T> |
| linked_ptr<T> make_linked_ptr(T* ptr) { |
| return linked_ptr<T>(ptr); |
| } |
| |
| } // namespace internal |
| } // namespace testing |
| |
| #endif // GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ |