- macOS 10.4+
The mbuf to prepend data to. This may change if a new mbuf must be allocated or may be NULL if the operation fails.
The length, in bytes, to be prepended to the mbuf.
Blocking or non-blocking.
0 upon success otherwise the errno error.
Prepend len bytes to an mbuf. If there is space (mbuf_leadingspace >= len), the mbuf's data ptr is changed and the same mbuf is returned. If there is no space, a new mbuf may be allocated and prepended to the mbuf chain. If the operation fails, the mbuf may be freed (*mbuf will be NULL).