miscfs/fifofs/fifo.h Kernel.framework

Implements the lookup vnode operation (VNOP_LOOKUP) for FIFO vnodes. Trivial routine that always fails: sets *a_vpp to NULL and returns ENOTDIR, since a FIFO is not a directory and contains no entries.

Implements the open vnode operation (VNOP_OPEN) for FIFOs. Sets up a new instance of a fifo or finds an active one: on first open, creates a connected pair of AF_LOCAL stream sockets serving as the read and write endpoints, recorded in the vnode's fifoinfo. Increments the reader or writer count according to a_mode and wakes any openers blocked on the other end. A blocking open for reading sleeps until a writer appears; a blocking open for writing sleeps until a reader appears; a nonblocking (O_NONBLOCK) open for writing fails with ENXIO if no reader is present. An interrupted sleep undoes the open and returns the msleep error.

Implements the close vnode operation (VNOP_CLOSE) for FIFOs. Decrements the fifo's reader and/or writer count according to a_fflag; when the last reader closes, further sends are disallowed on the write socket (socantsendmore), and when the last writer closes, the read socket is marked so readers see EOF (socantrcvmore). When both counts drop to zero, both underlying sockets are closed via soclose and the fifo reverts to the uncreated state; the first soclose error, if any, is returned.

Implements the read vnode operation (VNOP_READ) for FIFOs. Receives data from the fifo's read socket via soreceive; IO_NDELAY in a_ioflag maps to a nonblocking (MSG_NBIO) receive. For POSIX conformance, if no writers are open and the receive buffer is empty the call returns 0 (EOF) rather than blocking. Posts a vnode knote event after a successful transfer and clears the socket's cannot-receive-more state when a read returns no data, so EOF is indicated only once.

Implements the write vnode operation (VNOP_WRITE) for FIFOs. Sends the uio data to the fifo's write socket via sosend, passing MSG_NBIO when IO_NDELAY is set in a_ioflag. Posts a vnode knote event on success, and also on a partial nonblocking write that stopped with EWOULDBLOCK because the fifo buffer filled. Returns the sosend error.

Implements the ioctl vnode operation (VNOP_IOCTL) for FIFOs. FIONBIO is accepted and ignored (returns 0). Other commands are forwarded through soo_ioctl to the fifo's underlying sockets using a temporary fileproc: to the read socket if FREAD is set in a_fflag and to the write socket if FWRITE is set, returning the first error.

Implements the select vnode operation (VNOP_SELECT) for FIFOs. Forwards the poll through soo_select to the fifo's read socket when FREAD is set in a_which and to the write socket when FWRITE is set, using a temporary fileproc. Returns nonzero as soon as either socket reports ready, 0 otherwise.

Implements the inactive vnode operation (VNOP_INACTIVE) for FIFOs. Nothing to do; returns 0.

Implements the pathconf vnode operation (VNOP_PATHCONF) for FIFOs. Returns POSIX pathconf information applicable to fifos: _PC_LINK_MAX LINK_MAX _PC_PIPE_BUF PIPE_BUF _PC_CHOWN_RESTRICTED 200112 (_POSIX_CHOWN_RESTRICTED) All other names return EINVAL.

Implements the advisory-lock vnode operation (VNOP_ADVLOCK) for FIFOs. Advisory byte-range locking is not supported on fifos; always returns ENOTSUP.