memcpy with startIndex?

Question

I wish to copy content of specific length from one buffer to another from a specific starting point. I checked memcpy() but it takes only the length of content

Answer 1

An index is not required because you can simply update the source pointer by the specified number of bytes. The following wrapper should do the trick

void* memcpy_index(void *s1, const void *s2, size_t index, size_t n) {
  s2 = ((char*)s2)+index;
  return memcpy(s1, s2,n);
}