[英]C++ std::atomic union
How do I set a union to be atomic using std::atomic? 如何使用std :: atomic将并集设置为atomic? Or do I have to declare the members of the union to be atomic instead?
还是我必须声明工会的成员是原子的?
typedef union {
int integer;
float flt;
double dbl;
int *intArray;
float *floatArray;
unsigned char *byteArray;
} ValueUnion;
class FooClass {
public:
std::atomic<ValueUnion> value;
};
Access to the union gives an error: 访问联合会出现错误:
foo->value.floatArray = NULL;
error: no member named 'floatArray' in 'std::__1::atomic<ValueUnion>'
foo->value.floatArray = NULL;
Do I need to do something like: 我需要做类似的事情吗?
typedef union {
std::atomic<int> integer;
std::atomic<float> flt;
std::atomic<double> dbl;
std::atomic<int*> *intArray;
std::atomic<float*> *floatArray;
std::atomic<unsigned char*> *byteArray;
} ValueUnion;
and declare the member variable value to be as below? 并声明成员变量值如下?
class FooClass {
public:
ValueUnion value;
};
I suppose you'll have to use atomic memory access and writes: 我想您必须使用原子内存访问并编写:
typedef union {
int integer;
float flt;
double dbl;
int *intArray;
float *floatArray;
unsigned char *byteArray;
} ValueUnion;
class FooClass {
public:
std::atomic<ValueUnion> value;
};
int main()
{
FooClass obj;
ValueUnion temp = obj.value.load();
temp.floatArray = NULL;
obj.value.store(temp);
}
notice that this doesn't guarantee that the load/modify/store
sequence is atomic. 注意,这不能保证
load/modify/store
序列是原子的。 You'll have to deal with the safety of those instructions yourself (eg mutex ) 您必须自己处理这些说明的安全性(例如互斥体 )
It depends what you want to do with it. 这取决于您要如何处理。 For example, to store a value into an atomic union:
例如,要将值存储到原子联合中:
foo->value = []{ ValueUnion u; u.floatArray = NULL; return u; }();
or 要么
foo->value.store([]{ ValueUnion u; u.floatArray = NULL; return u; }());
If you want to be able to perform lock-free atomic arithmetic (eg atomic increment) on the contained values then you will need to go for your second design (a union of atomics). 如果您希望能够对所包含的值执行无锁原子算术(例如原子增量),那么您将需要进行第二个设计(原子的并集)。
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.