[英]Does C++ offer a thread-safe reference counter?
标准 C++ 库中是否有线程安全的引用计数器 class(或作为 Visual Studio 中的扩展),或者我是否需要从头开始编写这种 object?
我希望 object 像shared_ptr
那样纯粹执行引用计数,除了它跨多个线程准确地执行此操作,并且不管理任何内容。 shared_ptr
和它的表亲结构很好,因为它们定义了你需要的所有复制构造函数和赋值运算符,它们......对我来说是 C++ 中最容易出错的部分; C++ 建设者之于 C++ 开球之于美式足球。
struct Fun {
// this member behaves in a way I appreciate, save for 2 short-comings:
// - needless allocation event (minor)
// - ref counting is only estimate if shared across threads (major)
std::shared_ptr<int> smartPtr {new int};
// this is the hypothetical object that I'm searching for
// + allocates only a control block for the ref count
// + refCount.unique() respects reality when refs exist across many threads
// I can always count on this being the last reference
std::object_of_desire refCount;
// no explicit copy constructors or assignment operators necessary
// + both members of this class provide this paperwork for me,
// so I can careless toss this Fun object around and it'll move
// as one would expect, making only shallow copies/moves and ref counting
Fun();
~Fun(){
if(refCount.unique()){
smart_assert("I swear refCount truly is unique, on pain of death");
}
}
}
关于线程安全的警告 w.r.t。 std::shared_ptr
是
use_count
为 1 之前。如果没有任何内容修改指向 object,则指向 object 上没有数据竞争。这是您想要的类型
class ref_count {
public:
bool unique() const { return ptr.use_count() == 1; }
private:
struct empty {};
std::shared_ptr<empty> ptr = std::make_shared<empty>();
};
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.