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[unleashed/tickless.git] / usr / src / man / man3nsl / t_snd.3nsl

'\" te
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.TH T_SND 3NSL "May 7, 1998"
.SH NAME
t_snd \- send data or expedited data over a connection
.SH SYNOPSIS
.LP
.nf
#include <xti.h>



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

.SH DESCRIPTION
.sp
.LP
This routine 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 routine that has the same name as an \fBXTI\fR routine, 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 is used to send either normal or expedited data. The argument
\fIfd\fR identifies the local transport endpoint over which data should be
sent, \fIbuf\fR points to the user data, \fInbytes\fR specifies the number of
bytes of user data to be sent, and \fIflags\fR specifies any optional flags
described below:
.sp
.ne 2
.na
\fB\fBT_EXPEDITED\fR \fR
.ad
.RS 16n
If set in \fIflags\fR, the data will be sent as expedited data and will be
subject to the interpretations of the transport provider.
.RE

.sp
.ne 2
.na
\fB\fBT_MORE\fR \fR
.ad
.RS 16n
If set in \fIflags\fR, this indicates to the transport provider that the
transport service data unit (TSDU) (or expedited transport service data unit -
ETSDU) is being sent through multiple \fBt_snd()\fR calls.  Each \fBt_snd()\fR
with the  \fBT_MORE\fR flag set indicates that another \fBt_snd()\fR will
follow with more data for the current TSDU (or ETSDU).
.sp
The end of the TSDU (or ETSDU) is identified by a \fBt_snd()\fR call with the
\fBT_MORE\fR flag not set. Use of  \fBT_MORE\fR enables a user to break up
large logical data units without losing the boundaries of those units at the
other end of the connection. The flag implies nothing about how the data is
packaged for transfer below the transport interface. 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 will be ignored if set.
.sp
The sending of a zero-length fragment of a TSDU or ETSDU is only permitted
where this is used to indicate the end of a TSDU or ETSDU; that is, when the
\fBT_MORE\fR flag is not set. Some transport providers also forbid zero-length
TSDUs and ETSDUs.
.RE

.sp
.ne 2
.na
\fB\fBT_PUSH\fR \fR
.ad
.RS 16n
If set in \fIflags\fR, requests that the provider transmit all data that it has
accumulated but not sent.  The request is a local action on the provider and
does not affect any similarly named protocol flag (for example, the TCP PUSH
flag). This effect of setting this flag is protocol\(hydependent, and it may be
ignored entirely by transport providers which do not support the use of this
feature.
.RE

.sp
.LP
Note that the communications provider is free to collect data in a send buffer
until it accumulates a sufficient amount for transmission.
.sp
.LP
By default, \fBt_snd()\fR operates in synchronous mode and may wait if flow
control restrictions prevent the data from being accepted by the local
transport provider at the time the call is made.  However, if  \fBO_NONBLOCK\fR
is set by means of  \fBt_open\fR(3NSL) or \fBfcntl\fR(2), \fBt_snd()\fR will
execute in asynchronous mode, and will fail immediately if there are flow
control restrictions. The process can arrange to be informed when the flow
control restrictions are cleared by means of either \fBt_look\fR(3NSL) or the
EM interface.
.sp
.LP
On successful completion,  \fBt_snd()\fR returns the number of bytes (octets)
accepted by the communications provider.  Normally this will equal the number
of octets specified in nbytes.  However, if \fBO_NONBLOCK\fR is set or the
function is interrupted by a signal, it is possible that only part of the data
has actually been accepted by the communications provider.  In this case,
\fBt_snd()\fR returns a value that is less than the value of nbytes.  If
\fBt_snd()\fR is interrupted by a signal before it could transfer data to the
communications provider, it returns  -1 with  \fBt_errno\fR set to
\fBTSYSERR\fR and  \fBerrno\fR set to \fBEINTR\fR.
.sp
.LP
If nbytes is zero and sending of zero bytes is not supported by the underlying
communications service,  \fBt_snd()\fR returns \(mi1 with  \fBt_errno\fR set to
\fBTBADDATA\fR.
.sp
.LP
The size of each TSDU or ETSDU must not exceed the limits of the transport
provider as specified by the current values in the TSDU or ETSDU fields in the
\fIinfo\fR argument returned by \fBt_getinfo\fR(3NSL).
.sp
.LP
The error \fBTLOOK\fR is returned for asynchronous events. It is required only
for an incoming disconnect event but may be returned for other events.
.SH RETURN VALUES
.sp
.LP
On successful completion, \fBt_snd()\fR returns the number of bytes accepted by
the transport provider. Otherwise,  -1 is returned on failure and \fBt_errno\fR
is set to indicate the error.
.sp
.LP
Note that if the number of bytes accepted by the communications provider is
less than the number of bytes requested, this may either indicate that
\fBO_NONBLOCK\fR is set and the communications provider is blocked due to flow
control, or that  \fBO_NONBLOCK\fR is clear and the function was interrupted by
a signal.
.SH ERRORS
.sp
.LP
On failure, \fBt_errno\fR is set to one of the following:
.sp
.ne 2
.na
\fB\fBTBADDATA\fR\fR
.ad
.RS 15n
Illegal amount of data:
.RS +4
.TP
.ie t \(bu
.el o
A single send was attempted specifying a TSDU (ETSDU) or fragment TSDU (ETSDU)
greater than that specified by the current values of the TSDU or ETSDU fields
in the \fIinfo\fR argument.
.RE
.RS +4
.TP
.ie t \(bu
.el o
A send of a zero byte TSDU (ETSDU) or zero byte fragment of a TSDU (ETSDU) is
not supported by the provider.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Multiple sends were attempted resulting in a TSDU (ETSDU) larger than that
specified by the current value of the TSDU or ETSDU fields in the \fIinfo\fR
argument - the ability of an XTI implementation to detect such an error case is
implementation-dependent. See \fBWARNINGS\fR, below.
.RE
.RE

.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\fBTBADFLAG\fR\fR
.ad
.RS 15n
An invalid flag was specified.
.RE

.sp
.ne 2
.na
\fB\fBTFLOW\fR\fR
.ad
.RS 15n
\fBO_NONBLOCK\fR was set, but the flow control mechanism prevented the
transport provider from accepting any data at this time.
.RE

.sp
.ne 2
.na
\fB\fBTLOOK\fR\fR
.ad
.RS 15n
An asynchronous event has occurred on this transport endpoint.
.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 values that can be set by the \fBXTI\fR interface and cannot
be set by the \fBTLI\fR interface are:
.br
.in +2
\fBTPROTO\fR
.in -2
.br
.in +2
\fBTLOOK\fR
.in -2
.br
.in +2
\fBTBADFLAG\fR
.in -2
.br
.in +2
\fBTOUTSTATE\fR
.in -2
.sp
.LP
The \fBt_errno\fR values that this routine can return under different
circumstances than its \fBXTI\fR counterpart are:
.br
.in +2
\fBTBADDATA\fR
.in -2
.sp
.LP
In the \fBTBADDATA\fR error cases described above, \fBTBADDATA\fR is returned,
only for illegal zero byte \fBTSDU\fR ( \fBETSDU\fR) send attempts.
.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
_
MT Level        Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBfcntl\fR(2), \fBt_getinfo\fR(3NSL), \fBt_look\fR(3NSL), \fBt_open\fR(3NSL),
\fBt_rcv\fR(3NSL), \fBattributes\fR(5)
.SH WARNINGS
.sp
.LP
It is important to remember that the transport provider treats all users of a
transport endpoint as a single user. Therefore if several processes issue
concurrent \fBt_snd()\fR calls then the different data may be intermixed.
.sp
.LP
Multiple sends which exceed the maximum TSDU or ETSDU size may not be
discovered by XTI.  In this case an implementation-dependent error will result,
generated by the transport provider, perhaps on a subsequent XTI call.  This
error may take the form of a connection abort, a \fBTSYSERR\fR, a
\fBTBADDATA\fR or a \fBTPROTO\fR error.
.sp
.LP
If multiple sends which exceed the maximum TSDU or ETSDU size are detected by
XTI, \fBt_snd()\fR fails with \fBTBADDATA\fR.