char_buf_ptr
memcpy(char_buf_ptr(tb, tb->used), chars, space);
*chars = char_buf_ptr(tb, tb->used);
p = char_buf_ptr(head, head->lookahead);
u8 *p = char_buf_ptr(head, head->read);
return char_buf_ptr(b, ofs) + b->size;
*char_buf_ptr(tb, tb->used++) = ch;