Networking Services Library Functions t_sndv(3NSL)
NAME
t_sndv - send data or expedited data, from one or more non-
contiguous buffers, on a connectionSYNOPSIS
#include
int t_sndv(int fd, const struct t_iovec *iov, unsigned int iovcount, int flags);
DESCRIPTION
This function is used to send either normal or expediteddata. The argument fd identifies the local transport end-
point over which data should be sent, iov points to anarray of buffer address/buffer length pairs. t_sndv()
sends data contained in buffers iov0 , iov1 , through iov[iovcount-1]. iovcount contains the number of non-contiguous
data buffers which is limited to T_IOV_MAX, an
implementation-defined value of at least 16. If the limit
is exceeded, the function fails with TBADDATA.iov(0).iov_len + . . + iov(iovcount-1).iov_len)
Note that the limit on the total number of bytes available in all buffers passed: may be constrained by implementation limits. If no otherconstraint applies, it will be limited by INT_MAX. In prac-
tice, the availability of memory to an application is likely to impose a lower limit on the amount of data that can be sent or received using scatter/gather functions. The argument flags specifies any optional flags described below:T_EXPEDITED If set in flags, the data will be sent as
expedited data and will be subject to the interpretations of the transport provider.T_MORE If set in flags, this indicates to the
transport provider that the transport ser-
vice data unit (TSDU) (or expedited tran-
sport service data unit - ETSDU) is being
sent through multiple t_sndv() calls. Each
t_sndv() with the T_MORE flag set indicates
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Networking Services Library Functions t_sndv(3NSL)
that another t_sndv() or t_snd(3NSL) will
follow with more data for the current TSDU (or ETSDU).The end of the TSDU (or ETSDU) is identified by a t_sndv()
call with the T_MORE flag not set. Use of T_MORE enables
a user to break up large logical data units without losingthe boundaries of those units at the other end of the con-
nection. 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 asindicated in the info argument on return from t_open(3NSL)
or t_getinfo(3NSL), the T_MORE flag is not meaningful and
will be ignored if set.The sending of a zero-length fragment of a TSDU or ETSDU is
only permitted where this is used to indicate the end of aTSDU or ETSDU, that is, when the T_MORE flag is not set.
Some transport providers also forbid zero-length TSDUs and
ETSDUs. If set in flags, requests that the provider transmit all data that it has accumulated but not sent. The request is alocal action on the provider and does not affect any simi-
larly named protocol flag (for example, the TCP PUSH flag).This effect of setting this flag is protocol-dependent, and
it may be ignored entirely by transport providers which do not support the use of this feature. The communications provider is free to collect data in a send buffer until it accumulates a sufficient amount for transmission.By default, t_sndv() operates in synchronous mode and may
wait if flow control restrictions prevent the data from being accepted by the local transport provider at the timethe call is made. However, if O_NONBLOCK is set by means
of t_open(3NSL) or fcntl(2), t_sndv() executes in asynchro-
nous mode, and will fail immediately if there are flow con-
trol restrictions. The process can arrange to be informed when the flow control restrictions are cleared via eithert_look(3NSL) or the EM interface.
On successful completion, t_sndv() returns the number of
bytes accepted by the transport provider. Normally thisSunOS 5.11 Last change: 23 Aug 2001 2
Networking Services Library Functions t_sndv(3NSL)
will equal the total number of bytes to be sent, that is,(iov0.iov_len + .. + iov[iovcount-1].iov_len)
However, the interface is constrained to send at mostINT_MAX bytes in a single send. When t_sndv() has submit-
ted INT_MAX (or lower constrained value, see the note
above) bytes to the provider for a single call, this valueis returned to the user. However, if O_NONBLOCK is set or
the function is interrupted by a signal, it is possible thatonly part of the data has actually been accepted by the com-
munications provider. In this case, t_sndv() returns a
value that is less than the value of nbytes. If t_sndv() is
interrupted by a signal before it could transfer data to thecommunications provider, it returns -1 with t_errno set to
TSYSERR and errno set to EINTR. If the number of bytes of data in the iov array is zero and sending of zero octets is not supported by the underlyingtransport service, t_sndv() returns -1 with t_errno set to
TBADDATA. 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 info argument returned byt_getinfo(3NSL).
The error TLOOK is returned for asynchronous events. It is required only for an incoming disconnect event but may be returned for other events.RETURN VALUES
On successful completion, t_sndv() returns the number of
bytes accepted by the transport provider. Otherwise, -1 is
returned on failure and t_errno is set to indicate the
error.Note that in synchronous mode, if more than INT_MAX bytes
of data are passed in the iov array, only the firstINT_MAX bytes will be passed to the provider.
If the number of bytes accepted by the communications pro-
vider is less than the number of bytes requested, this mayeither indicate that O_NONBLOCK is set and the communica-
tions provider is blocked due to flow control, or thatSunOS 5.11 Last change: 23 Aug 2001 3
Networking Services Library Functions t_sndv(3NSL)
O_NONBLOCK is clear and the function was interrupted by a
signal. VALID STATEST_DATAXFER, T_INREL.
ERRORS
On failure, t_errno is set to one of the following:
TBADDATA Illegal amount of data: TBADF The specified file descriptor does not refer to a transport endpoint.o A single send was attempted specify-
ing a TSDU (ETSDU) or fragment TSDU (ETSDU) greater than that specified by the current values of the TSDU or ETSDU fields in the info argument. o A send of a zero byte TSDU (ETSDU) or zero byte fragment of a TSDU(ETSDU) is not supported by the pro-
vider. o Multiple sends were attempted resulting in a TSDU (ETSDU) larger than that specified by the current value of the TSDU or ETSDU fields inthe info argument - the ability of
an XTI implementation to detect suchan error case is implementation-
dependent. See WARNINGS, below.o iovcount is greater than T_IOV_MAX.
TBADFLAG An invalid flag was specified.TFLOW O_NONBLOCK was set, but the flow control
mechanism prevented the transport provider from accepting any data at this time. TLOOK An asynchronous event has occurred on this transport endpoint.TNOTSUPPORT This function is not supported by the under-
lying transport provider.SunOS 5.11 Last change: 23 Aug 2001 4
Networking Services Library Functions t_sndv(3NSL)
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 noother suitable XTI error (t_errno).
TSYSERR A system error has occurred during execution of this function. TLI COMPATIBILITYIn the TLI interface definition, no counterpart of this rou-
tine was defined.ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT Level | Safe ||_____________________________|_____________________________|
SEE ALSO
t_getinfo(3NSL), t_open(3NSL), t_rcvv(3NSL) t_rcv(3NSL),
t_snd(3NSL), attributes(5)
WARNINGS 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 t_sndv() or
t_snd(3NSL) calls, then the different data may be inter-
mixed. Multiple sends which exceed the maximum TSDU or ETSDU size may not be discovered by XTI. In this case animplementation-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 TSYSERR, a TBADDATA or a TPROTO error.SunOS 5.11 Last change: 23 Aug 2001 5
Networking Services Library Functions t_sndv(3NSL)
If multiple sends which exceed the maximum TSDU or ETSDUsize are detected by XTI, t_sndv() fails with TBADDATA.
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