'\" te
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.TH T_RCV 3NSL "Aug 24, 2007"
.SH NAME
t_rcv \- receive data or expedited data sent over a connection
.SH SYNOPSIS
.LP
.nf
#include <xti.h>

\fBint\fR \fBt_rcv\fR(\fBint\fR \fIfd\fR, \fBvoid *\fR\fIbuf\fR, \fBunsigned int\fR \fInbytes\fR, \fBint *\fR\fIflags\fR);
.fi

.SH DESCRIPTION
.sp
.LP
This function is part of the \fBXTI\fR interfaces which evolved from the
\fBTLI\fR interfaces. \fBXTI\fR represents the future evolution of these
interfaces. However, \fBTLI\fR interfaces are supported for compatibility. When
using a \fBTLI\fR function that has the same name as an \fBXTI\fR function, the
\fBtiuser.h\fR header file must be used.  Refer to the  \fBTLI\fR
\fBCOMPATIBILITY\fR section for a description of differences between the two
interfaces.
.sp
.LP
This function receives either normal or expedited data. The argument \fIfd\fR
identifies the local transport endpoint through which data will arrive,
\fIbuf\fR points to a receive buffer where user data will be placed, and
\fInbytes\fR specifies the size of the receive buffer. The argument \fIflags\fR
may be set on return from \fBt_rcv()\fR and specifies optional flags as
described below.
.sp
.LP
By default, \fBt_rcv()\fR operates in synchronous mode and will wait for data
to arrive if none is currently available. However, if \fBO_NONBLOCK\fR is set
by means of \fBt_open\fR(3NSL) or \fBfcntl\fR(2), \fBt_rcv()\fR will execute in
asynchronous mode and will fail if no data is available. See \fBTNODATA\fR
below.
.sp
.LP
On return from the call, if  \fBT_MORE\fR is set in \fIflags\fR, 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
\fBt_rcv()\fR calls. In the asynchronous mode, or under unusual conditions (for
example, the arrival of a signal or  \fBT_EXDATA\fR event),  the  \fBT_MORE\fR
flag may be set on return from the \fBt_rcv()\fR call even when the number of
bytes received is less than the size of the receive buffer specified. Each
\fBt_rcv()\fR with the  \fBT_MORE\fR flag set indicates that another
\fBt_rcv()\fR must follow to get more data for the current TSDU. The end of the
TSDU is identified by the return of a \fBt_rcv()\fR call with the  \fBT_MORE\fR
flag not set. If the transport provider does not support the concept of a TSDU
as indicated in the \fIinfo\fR argument on return from \fBt_open\fR(3NSL) or
\fBt_getinfo\fR(3NSL), the  \fBT_MORE\fR flag is not meaningful and should be
ignored.  If \fInbytes\fR is greater than zero on the call to \fBt_rcv()\fR,
\fBt_rcv()\fR will return  \fB0\fR only if the end of a TSDU is being returned
to the user.
.sp
.LP
On return, the data is expedited if  \fBT_EXPEDITED\fR is set in flags.  If
\fBT_MORE\fR 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
\fBt_rcv()\fR which will return with  \fBT_EXPEDITED\fR set in flags. The end
of the ETSDU is identified by the return of a  \fBt_rcv()\fR call with
\fBT_EXPEDITED\fR set and  \fBT_MORE\fR 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.
.sp
.LP
If a signal arrives, \fBt_rcv()\fR returns, giving the user any data currently
available.  If no data is available,  \fBt_rcv()\fR returns  -1, sets
\fBt_errno\fR to \fBTSYSERR\fR and  \fBerrno\fR to \fBEINTR\fR. If some data is
available,  \fBt_rcv()\fR returns the number of bytes received and
\fBT_MORE\fR is set in flags.
.sp
.LP
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
\fBT_DATA\fR or  \fBT_EXDATA\fR events using the \fBt_look\fR(3NSL) function.
Additionally, the process can arrange to be notified by means of the EM
interface.
.SH RETURN VALUES
.sp
.LP
On successful completion, \fBt_rcv()\fR returns the number of bytes received.
Otherwise, it returns  \fB\(mi1\fR on failure and \fBt_errno\fR is set to
indicate the error.
.SH VALID STATES
.sp
.LP
\fBT_DATAXFER\fR, \fBT_OUTREL\fR.
.SH ERRORS
.sp
.LP
On failure, \fBt_errno\fR is set to one of the following:
.sp
.ne 2
.na
\fB\fBTBADF\fR\fR
.ad
.RS 15n
The specified file descriptor does not refer to a transport endpoint.
.RE

.sp
.ne 2
.na
\fB\fBTLOOK\fR\fR
.ad
.RS 15n
An asynchronous event has occurred on this transport endpoint and requires
immediate attention.
.RE

.sp
.ne 2
.na
\fB\fBTNODATA\fR\fR
.ad
.RS 15n
\fBO_NONBLOCK\fR was set, but no data is currently available from the transport
provider.
.RE

.sp
.ne 2
.na
\fB\fBTNOTSUPPORT\fR\fR
.ad
.RS 15n
This function is not supported by the underlying transport provider.
.RE

.sp
.ne 2
.na
\fB\fBTOUTSTATE\fR\fR
.ad
.RS 15n
The communications endpoint referenced by \fIfd\fR is not in one of the states
in which a call to this function is valid.
.RE

.sp
.ne 2
.na
\fB\fBTPROTO\fR\fR
.ad
.RS 15n
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
\fB(t_errno)\fR.
.RE

.sp
.ne 2
.na
\fB\fBTSYSERR\fR\fR
.ad
.RS 15n
A system error has occurred during execution of this function.
.RE

.SH TLI COMPATIBILITY
.sp
.LP
The \fBXTI\fR and \fBTLI\fR interface definitions have common names but use
different header files. This, and other semantic differences between the two
interfaces are described in the subsections below.
.SS "Interface Header"
.sp
.LP
The \fBXTI\fR interfaces use the header file, \fBxti.h\fR. \fBTLI\fR interfaces
should \fInot\fR use this header.  They should use the header:
.br
.in +2
#include <tiuser.h>
.in -2
.SS "Error Description Values"
.sp
.LP
The \fBt_errno\fR value that can be set by the \fBXTI\fR interface and cannot
be set by the \fBTLI\fR interface is:
.br
.in +2
\fBTPROTO\fR
.in -2
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5)  for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	Safe
_
Standard	See \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBfcntl\fR(2), \fBt_getinfo\fR(3NSL), \fBt_look\fR(3NSL), \fBt_open\fR(3NSL),
\fBt_snd\fR(3NSL), \fBattributes\fR(5), \fBstandards\fR(5)