[英]copy Array to Member of Struct in C
I'm trying to transmit data wireless. 我正在尝试无线传输数据。 My payload-struct looks like this:
我的有效负载结构如下所示:
typedef struct
{
uint8_t data[3];
} data_t
I also have an array in my code: 我的代码中也有一个数组:
uint8_t data_to_be_copied[3];
if I try to simply assign each other I get the following error: 如果我尝试简单地互相分配,则会出现以下错误:
msg->data = data_to_be_copied;
incompatible types when assigning to type 'uint8_t[3]' from type 'uint8_t *' 从'uint8_t *'类型分配给'uint8_t [3]'类型时不兼容的类型
using a for-loop my microcontroller crashes: 使用for循环,我的微控制器崩溃:
for (int i = 0; i < 3; i++) {
msg->data[i] = data_to_be_copied[i];
}
Same happens, when I try to use memcpy: 当我尝试使用memcpy时,也会发生同样的情况:
memcpy(msg->data, data_to_be_copied, 3);
What am I missing here? 我在这里想念什么?
Thanks for your help. 谢谢你的帮助。
msg->data
is an array. msg->data
是一个数组。
As such, it does not have an l-value, and you cannot change it. 因此,它没有l值,因此无法更改。
That's why you're getting a compilation error for the first option mentioned above. 这就是为什么您遇到上述第一个选项的编译错误的原因。
For the second and third options mentioned above, you're getting a memory access violation during runtime, probably because your msg
variable is not initialized to point to a valid memory address. 对于上面提到的第二个和第三个选项,在运行时会遇到内存访问冲突,这可能是因为
msg
变量未初始化为指向有效的内存地址。
Assuming that you have data_t* msg
declared in the right place, you still need to initialize it: 假设您在正确的位置声明了
data_t* msg
,您仍然需要对其进行初始化:
data_t* msg = (data_t*)malloc(sizeof(data_t));
You should also make sure that you free(msg)
at a later point in the execution of your program. 您还应确保在以后执行程序时
free(msg)
。
BTW, you have not specified the entire structure of your program, but a simple data_t msg
instance might be sufficient for your needs (in which case, you don't need to use the malloc
and the free
). 顺便说一句,您尚未指定程序的整个结构,但是一个简单的
data_t msg
实例就可以满足您的需要(在这种情况下,您无需使用malloc
和free
)。
And as mentioned in a comment by @Shahbaz , if you do end up using malloc
and free
, then you need to make sure that your platform (OS or BSP) supports dynamic memory allocation (AKA heap ). 并且在由@Shahbaz的评论中提到,如果你最终使用
malloc
和free
,那么你需要确保你的平台(操作系统或BSP)支持动态内存分配(AKA 堆 )。
You have some possibilities: 您有一些可能:
memcpy (msg->data, data_to_be_copied, 3); memcpy(msg-> data,data_to_be_copied,3);
or change data_to_be_copied to 或将data_to_be_copied更改为
data_t data_to_be_copied;
and assign the whole thing: *msg = data_to_be_copied 并分配整个内容:* msg = data_to_be_copied
or if msg has actually more members, declare a struct that has an array of three chars as its only member. 或者,如果msg实际上有更多成员,则声明具有三个字符数组的结构作为其唯一成员。
If it crashes, then most likely msg is NULL or some uninitialised pointer. 如果崩溃,则很有可能味精为NULL或一些未初始化的指针。
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