如何将一个结构复制到另一个结构的元素数组？

Question

I have Two structure:1)ABC 2)CDE

typedef struct
{
  unsigned char b[8];
  unsigned char a[12];
  unsigned char c;
} ABC;

ABC sABC;

typedef struct
{
  unsigned char D;
  unsigned char E[22];           
} CDE;

I want to copy Structure ABC in E[22] which is member of CDE structure.

If anyone know this then how can i do this?

Answer 1

You could do it with memcpy . For instance something like this should work:

memcpy(&some_CDE_variable.E, &sABC, 22);

But take care that sizeof(ABC) may not be 22 and the elements inside may not be layed out the way you would expect if the compiler decides to add some padding when packing that struct in memory. If you're using gcc you may want to check for the packed attribute.

Answer 2

you can use memcpy in your case.

just use memcpy safely as memcpy replaces memory, it does not append. If you want to use memcpy, your code will need to be a little more complex.

void * memcpy ( void * destination, const void * source, size_t num );

also,take care of size here as num will vary on compiler basis because of padding.