T_RCV(3NSL)T_RCV(3NSL)NAMEt_rcv - receive data or expedited data sent over a connection
SYNOPSIS
#include <xti.h>
int t_rcv(int fd, void *buf, unsigned int nbytes, int *flags);
DESCRIPTION
This function is part of the XTI interfaces which evolved from the TLI
interfaces. XTI represents the future evolution of these interfaces.
However, TLI interfaces are supported for compatibility. When using a
TLI function that has the same name as an XTI function, the tiuser.h
header file must be used. Refer to the TLI COMPATIBILITY section for
a description of differences between the two interfaces.
This function receives either normal or expedited data. The argument fd
identifies the local transport endpoint through which data will arrive,
buf points to a receive buffer where user data will be placed, and
nbytes specifies the size of the receive buffer. The argument flags may
be set on return from t_rcv() and specifies optional flags as described
below.
By default, t_rcv() operates in synchronous mode and will wait for data
to arrive if none is currently available. However, if O_NONBLOCK is set
by means of t_open(3NSL) or fcntl(2), t_rcv() will execute in asynchro‐
nous mode and will fail if no data is available. See TNODATA below.
On return from the call, if T_MORE is set in flags, this indicates
that there is more data, and the current transport service data unit
(TSDU) or expedited transport service data unit (ETSDU) must be
received in multiple t_rcv() calls. In the asynchronous mode, or under
unusual conditions (for example, the arrival of a signal or T_EXDATA
event), the T_MORE flag may be set on return from the t_rcv() call
even when the number of bytes received is less than the size of the
receive buffer specified. Each t_rcv() with the T_MORE flag set indi‐
cates that another t_rcv() must follow to get more data for the current
TSDU. The end of the TSDU is identified by the return of a t_rcv() call
with the T_MORE flag not set. If the transport provider does not sup‐
port the concept of a TSDU as indicated in the info argument on return
from t_open(3NSL) or t_getinfo(3NSL), the T_MORE flag is not meaning‐
ful and should be ignored. If nbytes is greater than zero on the call
to t_rcv(), t_rcv() will return 0 only if the end of a TSDU is being
returned to the user.
On return, the data is expedited if T_EXPEDITED is set in flags. If
T_MORE is also set, it indicates that the number of expedited bytes
exceeded nbytes, a signal has interrupted the call, or that an entire
ETSDU was not available (only for transport protocols that support
fragmentation of ETSDUs). The rest of the ETSDU will be returned by
subsequent calls to t_rcv() which will return with T_EXPEDITED set in
flags. The end of the ETSDU is identified by the return of a t_rcv()
call with T_EXPEDITED set and T_MORE cleared. If the entire ETSDU is
not available it is possible for normal data fragments to be returned
between the initial and final fragments of an ETSDU.
If a signal arrives, t_rcv() returns, giving the user any data cur‐
rently available. If no data is available, t_rcv() returns -1, sets
t_errno to TSYSERR and errno to EINTR. If some data is available,
t_rcv() returns the number of bytes received and T_MORE is set in
flags.
In synchronous mode, the only way for the user to be notified of the
arrival of normal or expedited data is to issue this function or check
for the T_DATA or T_EXDATA events using the t_look(3NSL) function.
Additionally, the process can arrange to be notified by means of the EM
interface.
RETURN VALUES
On successful completion, t_rcv() returns the number of bytes received.
Otherwise, it returns −1 on failure and t_errno is set to indicate the
error.
VALID STATES
T_DATAXFER, T_OUTREL.
ERRORS
On failure, t_errno is set to one of the following:
TBADF
The specified file descriptor does not refer to a trans‐
port endpoint.
TLOOK
An asynchronous event has occurred on this transport
endpoint and requires immediate attention.
TNODATA
O_NONBLOCK was set, but no data is currently available
from the transport provider.
TNOTSUPPORT
This function is not supported by the underlying trans‐
port provider.
TOUTSTATE
The communications endpoint referenced by fd is not in
one of the states in which a call to this function is
valid.
TPROTO
This error indicates that a communication problem has
been detected between XTI and the transport provider for
which there is no other suitable XTI error (t_errno).
TSYSERR
A system error has occurred during execution of this
function.
TLI COMPATIBILITY
The XTI and TLI interface definitions have common names but use differ‐
ent header files. This, and other semantic differences between the two
interfaces are described in the subsections below.
Interface Header
The XTI interfaces use the header file, xti.h. TLI interfaces should
not use this header. They should use the header:
#include <tiuser.h>
Error Description Values
The t_errno value that can be set by the XTI interface and cannot be
set by the TLI interface is:
TPROTO
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬───────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼───────────────────┤
│Interface Stability │ Committed │
├────────────────────┼───────────────────┤
│MT-Level │ Safe │
├────────────────────┼───────────────────┤
│Standard │ See standards(5). │
└────────────────────┴───────────────────┘
SEE ALSOfcntl(2), t_getinfo(3NSL), t_look(3NSL), t_open(3NSL), t_snd(3NSL),
attributes(5), standards(5)
Aug 24, 2007 T_RCV(3NSL)
