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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_ |