[英]Copy multiple structs into a buffer using memcpy in c
I have several structs (of u8 fields) which I want to convert into a buffer, is this the best way? 我有几个要转换为缓冲区的(u8字段)结构,这是最好的方法吗?
struct struct_a a; struct struct_b b; u8 buffer[64]; u8 *next_pos; os_memcpy(buffer, &a, sizeof(struct_a)); next_pos = buffer + sizeof(struct_a)/sizeof(u8); os_memcpy(next_pos, &b, sizeof(struct_b));
Is this the best way to calculate the overall length of the buffer? 这是计算缓冲区总长度的最佳方法吗?
buffer_len = (sizeof(struct_a) + sizeof(struct_b) + ... )/sizeof(u8);
Thanks 谢谢
I assume that u8
means unsigned 8 bits. 我假设
u8
表示无符号的8位。 Hence, sizeof(u8)
equals 1. So you can simply write: 因此,
sizeof(u8)
等于1。因此,您可以简单地编写:
os_memcpy(&buffer[sizeof(struct_a)], &b, sizeof(struct_b));
For your second question, except that dividing by 1 is useless, it's a perfectly fine way to compute the len of the buffer. 对于您的第二个问题,除以1除无用外,这是计算缓冲区的len的绝佳方法。
I'm not a big fan of buffer + sizeof(struct_a)
but it's also good. 我不是
buffer + sizeof(struct_a)
但也很好。
Edit: Also, when doing that kind of stuff, if the size of the elements of buffer is not 1, I cast buffer into something with your equivalent of u8
. 编辑:此外,当做这种事情时,如果buffer的元素大小不为1,我会将buffer转换为与
u8
等效的东西。 This way, I don't have to divide by the size of the elements of buffer. 这样,我不必除以缓冲区元素的大小。
Define a buffer either this way, 通过这种方式定义一个缓冲区,
#define MAXBUF (999)
type struct
{
int size; //or short, or char, or long long, depending on size...
char buffer[MAXBUF];
} buffer_t;
Or, this way, and allocate enough space (enough defined to be how much you need), 或者,通过这种方式,分配足够的空间(足够定义为您需要的空间),
#define MAXBUF (999)
type struct
{
int size;
char buffer[MAXBUF];
} buffer_t;
Then a function to add stuff to the buffer, 然后是一个向缓冲区添加内容的函数,
int
buffer_add(buffer_t* buffer,void* thing,int len)
{
if(!thing) return 0;
if(len<1) return 0;
memcpy( &(buffer[buffer->size]),thing,len);
return(buffer->size+=len);
}
Now, using it is easy, 现在,使用起来很容易
typedef char u8;
struct struct_a { u8 x[100]; };
struct struct_b { int y[25]; };
int main()
{
u8 buffer[64];
u8 *next_pos;
buffer_t mybuffer;
buffer_add(&mybuffer,&a,sizeof(a));
buffer_add(&mybuffer,&b,sizeof(b));
buffer_add(&mybuffer,&buffer,sizeof(buffer));
buffer_add(&mybuffer,next_pos,sizeof(*next_pos));
//do stuff with mybuffer
}
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.