# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.

include <fset.h>


# NDOPEN -- Open a network device.  This is used by a client to connect to
# a server, or by a server to establish a port to which clients can connect.
# The open may or may not block until a client has connected, depending upon
# the type of connection.  The access mode should be NEW_FILE for a server
# connection, anything else is a client connection.  If the server is to
# support multiple client connections the server connection can be opened
# in nonblocking mode, then used to listen for client connections which are
# accepted each on a separate connection (see zfiond.c for details).  Most
# clients use mode READ_WRITE.  The connection is bidirectional and stream
# oriented.
#
# The syntax of the filename argument (network address) is determined by the
# host level ND driver.  The filename is passed on to the driver transparently
# to the portable IRAF code.  System independent IRAF code should treat these
# strings as data, like host filenames, and not attempt to parse or construct
# the strings.  Refer to the ND driver source for further information on the
# ND filename syntax.
#
# The host driver (os$zfiond.c) determines the types of network or
# interprocess connections supported.  For example, the initial ND driver for
# UNIX/IRAF systems supports Internet sockets, UNIX domain sockets, and FIFO
# pipes.
# 
# If the same file descriptor is used for both reading and writing some means
# is needed to synchronize data transfer.  When switching between reads and
# writes, the client code should execute a F_CANCEL on the stream before the
# first read or write of a sequence.  FLUSH should be called after the last
# write.  For example,
# 
# 	call fseti (fd, F_CANCEL, OK)
# 	call write (fd, buf, nchars)
# 	    <optional additional writes>
# 	call flush (fd)
# 
# 	call fseti (fd, F_CANCEL, OK)
# 	nchars = read (fd, buf, maxch)
# 	    <optional additional reads>
#
# A better approach however is to open two separate steams at the FIO level
# and use one for reading a one for writing.  After the first stream is 
# opened using NDOPEN, a second file descriptor can be opened using REOPEN.
# Both will share the same underlying network connection, but one stream
# can be used for reading and one for writing, with separate buffers for
# each stream and full streaming i/o capabilities.
#
# Any of the i/o routines may be used, e.g., getc/putc may be used to perform
# character i/o on the stream, with FIO doing the buffering.
#
# Once opened all ND connections are byte streams.  The protocol used for
# client-server communications is determined entirely by the server; an IRAF
# client may connect to a "foreign" server via an ND connection, so long
# as the correct client-server protocol is observed.  If the server supports
# multiple clients multiple ND connections may be made, either in the same
# process or in different processes.  An IRAF task using the ND interface
# may be a server, but currently the ND driver does not support multiple
# concurrent client connections, since the connection and i/o block.
# Multiple nonconcurrent (i.e. sequential) clients are possible.  Multiple
# conncurent connections are possible only if a scheme is used such as having
# inetd spawn a server process for each connection.

int procedure ndopen (fname, mode)

char	fname[ARB]		#I network address
int	mode			#I access mode

int	ip, fd
char	port[SZ_PATHNAME]
int	fopnbf(), strncmp(), ctoi(), fstati()
extern	zopnnd(), zardnd(), zawrnd(), zawtnd(), zsttnd(), zclsnd()

begin
	# If a server connection is being opened (mode NEW_FILE) then
	# check for the pseudo-domain "sock", which is defined by ZFIOND
	# and used to accept a client connection request made to a server
	# port.  The ND driver in the kernel requires a host channel number
	# so we must convert the FIO file descriptor passed in by the client.

	if (mode == NEW_FILE && strncmp(fname,"sock:",5) == 0) {
	    ip = 6
	    if (ctoi (fname, ip, fd) <= 0)
		return (ERR)
	    call sprintf (port, SZ_PATHNAME, "sock:%d")
		call pargi (fstati (fd, F_CHANNEL))
	} else
	    call strcpy (fname, port, SZ_PATHNAME)

	return (fopnbf (port, mode,
	    zopnnd, zardnd, zawrnd, zawtnd, zsttnd, zclsnd))
end