函数 av_calloc 

pub unsafe extern "C" fn av_calloc(
    nmemb: usize,
    size: usize,
) -> *mut c_void

Allocate a memory block for an array with av_mallocz().

The allocated memory will have size size * nmemb bytes.

@param nmemb Number of elements @param size Size of the single element @return Pointer to the allocated block, or NULL if the block cannot be allocated

@see av_mallocz() @see av_malloc_array()