如何使用 memcpy 将一个数组复制到另一个数组？

Question

for (i = 0; i < n1; i++) 
   L[i] = arr[l + i]; 

Because I want to copy a large array,I heard that need to use memcpy.

Answer 1

memcpy as the name says, copy memory area. is a C standard function under string.h .

void *memcpy(void *dest, const void *src, size_t n); 

description:

The memcpy() function copies n bytes from memory area src to memory area dest . The memory areas must not overlap . Use memmove(3) if the memory areas do overlap. The memcpy() function returns a pointer to dest. for more details goto man7: memcpy

so in your case the call would be:

memcpy(L, &arr[l], n1*sizeof(arr[l]));

sizeof one array elementis:

sizeof(arr[l])

make sure that (l+n1) doesnot exceeds the array boundaries. its you responsibility.

Answer 2

memcopy(destination, source, length)

That would be in your case:

int len = sizeof(int) * n1;
memcopy(L, arr+l, len);

Note: You may have to fix the length calculation according to the type you are using. Moreover, you should also remember to add 1 to include the \0 character that terminates char arrays if you are dealing with strings.