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-// 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.
-//
-// 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.
-// FIXME: rename this to safe_linked_ptr to avoid
-// confusion with normal linked_ptr.
-
-// GOOGLETEST_CM0001 DO NOT DELETE
-
-#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) {
- assert(p->next_ != this &&
- "Trying to join() a linked ring we are already in. "
- "Is GMock thread safety enabled?");
- 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) {
- assert(p->next_ != next_ &&
- "Trying to depart() a linked ring we are not in. "
- "Is GMock thread safety enabled?");
- 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_