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

Simply add the index to the address of the buffer, and pass it to memcpy() as the source parameter, e.g. copy from 3rd item of buffer b

char a[10], b[20];
::memcpy(a,b+2,10);

Also take into account the type of items in the buffer, length (3rd) parameter of memcpy() is in bytes, so to copy 4 ints you shall put 4*sizeof(int) - which will probably be 16 (on a 32 bit system. But the type does not matter for the start address, because of pointer arithmetics:

int a[10], b[10];
::memcpy( a+2, b, 2*sizeof(int) );
// a+2 will be address of 3rd item in buffer a
// not address of 1st item + 2 bytes