- ((nitems - f->head) < total_copy_bytes) ?
- (nitems - f->head) : total_copy_bytes;
- clib_memcpy (copy_here, &f->data[f->head], first_copy_bytes);
+ ((nitems - f->head + offset) < total_copy_bytes) ?
+ (nitems - f->head + offset) : total_copy_bytes;
+ clib_memcpy (copy_here, &f->data[f->head + offset], first_copy_bytes);