t_snd.3xti

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3XTI 代码 · 共 169 行

.TH t_snd 3xti
.SH Name
t_snd \- send data or expedited data over a connection
.SH Syntax
.B #include <xti.h>
.br
.sp 1
.B int t_snd(\fIfd, buf, nbytes, flags\fB)
.br
.B int \fIfd\fB;
.br
.B char \fI*buf\fB;
.br
.B unsigned \fInbytes\fB;
.br
.B int \fIflags\fR;
.SH Arguments
.IP \fIfd\fR 10
Identifies the local transport endpoint over which data should be sent.
.IP \fIbuf\fR 10
Points to the user data.
.IP \fInbytes\fR 10
Specifies the number of bytes of user data to be sent.
.IP \fIflags\fR 10
Specifies any optional flags described below:
.RS 10
.IP T_EXPEDITED 14
If set in \fIflags\fP, the data is sent as expedited data and is 
subject to the interpretations of the transport provider.
.IP T_MORE 14
If set in \fIflags\fP, 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 
.PN t_snd()
calls. Each 
.PN t_snd() 
with the T_MORE flag set indicates that 
another 
.PN t_snd()
follows with more data for the current TSDU. 
The end of TSDU or ETSDU is identified by a 
.PN t_snd()
call with the T_MORE flag not set. Use of T_MORE enables a user to 
break up large logical data units without losing 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\fP argument on return 
from 
.PN t_open()
or 
.PN t_getinfo()\fR,\fR
the T_MORE flag is not meaningful and should be ignored.
.RE
.sp 3
.SH Description
This function is used to send either normal or expedited data.
.NXR "t_snd system call"
.NXR "sendind data" "normal"
.NXR "sending data" "expedited"
.PP
By default, 
.PN t_snd()
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
O_NONBLOCK is set by means of 
.PN t_open() 
or 
.PN fcntl()\fR,\fR
.PN t_snd()
executes in asynchronous mode, and fails immediately,
if there are flow control restrictions. The process can arrange to be informed when
the flow control restrictions are cleared by means of 
.PN t_look()\fR.\fR
.PP
On successful completion, 
.PN t_snd() 
returns the number of bytes accepted by the transport provider. Normally, this equals the number
of bytes specified in \fInbytes\fR. However, if O_NONBLOCK is set,
it is possible that only part of the data is accepted by the
transport provider. In this case, 
.PN t_snd() 
returns a value that is less than the value of \fInbytes\fR. If \fInbytes\fR is zero and
sending of zero octets is not supported by the underlying transport
service, the 
.PN t_snd() 
returns \-1 with \fBt_errno\fR set to [TBADDATA].
.PP
The size of each TSDU or ETSDU must not exceed the limits of the
transport provider as returned in the TSDU or ETSDU fields of the
\fIinfo\fR argument of 
.PN t_open() 
or 
.PN t_getinfo()\fR.\fR
Failure to comply results in protocol error (see [TSYSERR]
under the DIAGNOSTICS section).
.PP 
The error [TLOOK] may be returned to inform the process that
an event, such as a \fBdisconnect\fR, has occurred.
.PP
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 
.PN t_snd()
calls, then the different data may be
intermixed.
.PP
.TS
tab(@);
lfHB lfHB lfHB
lfR  lfR  lfR .
_
.sp 6p
Parameters@Before Call@After Call
.sp 6p
_
.sp 6p
fd@x@/
buf@x(x)@/
nbytes@x@/
flags@x@/
.sp 6p
_
.TE
.PP
.sp 12p
.SH Return Values
Upon successful completion, \fBt_errno\fR returns the number of bytes
accepted by the transport provider. On failure, a value of \-1 is returned, and 
\fBt_errno\fR is set to indicate the error.
.PP
In asynchronous mode, if the number of bytes accepted by the transport
provider is less than the number of bytes requested, this may indicate
that the transport provider is blocked due to flow control.
.SH Diagnostics
On failure, \fBt_errno\fR is set to one of the following:
.TP 20
[TBADF]
The specified file descriptor does not refer to a transport endpoint.
.TP 20 
[TOUTSTATE]
The function was issued in the wrong sequence on the transport endpoint
referenced by \fIfd\fR.
.TP 20
[TBADFLAG]
An invalid flag was specified.
.TP 20
[TFLOW]
O_NONBLOCK was set, but the flow control mechanism prevented the
transport provider from accepting any data at this time.
.TP
[TBADDATA]
Illegal amount of data: zero octets is not supported.
.TP 20
[TLOOK]
An asynchronous event has occurred on the transport endpoint.
.TP 20
[TNOTSUPPORT]
This function is not supported by the underlying transport provider. 
.TP 20
[TSYSERR]
A system error has occurred during execution of this function. A protocol error may
not cause \fBt_errno\fR to fail until a subsequent access of the transport endpoint.
.SH See Also
.MS t_getinfo 3xti , 
.MS t_open 3xti ,
.MS t_rcv 3xti