t_sndv(3) Library Functions Manual t_sndv(3)
NAME
t_sndv - Receives data or expedited data sent over a connection and puts the data into one or more non-contiguous buffers
LIBRARY
XTI Library (libxti.a)
SYNOPSIS
#include <xti.h>
int t_sndv(
int fd,
const struct t_iovec *iov,
unsigned int iovcount,
int *flags);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
t_sndv(): XNS5.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
The following table summarizes the relevance of input and output parameters before and after t_sndv() is called:
Parameters Before Call After Call
----------------------------------------------------
fd y n
iov y n
iovcount y n
iov[0].iov_base y(y) e(e)
iov[0].iov_len y e
...
iov[iovcount-1].iov_base y(y) e(e)
iov[iovcount-1].iov_len y e
flags y n
Notes to Table:
y This is a meaningful parameter.
(y)The content of the object pointed to by y is meaningful.
o This is a meaningful but optional parameter.
(o)The content of the object pointed to by o is meaningful.
e The parameter value after the call is the same as before the call.
(e)The content of the object pointed to by e after the call is
the same as before the call.
n This is not a meaningful parameter.
Identifies the local transport endpoint over which to send data. Points to an array of buffer address/buffer size pairs (iov_base,
iov_len). Specifies the number of buffers, which is limited to T_IOV_MAX (an implementation-defined value of at least 16). If the limit
is exceeded, the function will fail with [TBADDATA]. Specifies on of the following options flags: If set, the data will be sent as expe-
dited data and will be subject to the interpretations of the transport provider. If set, 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 t_sndv() calls.
VALID STATES
The t_sndv() function can be called in either the T_DATAXFER or T_INREL transport provider states.
DESCRIPTION
The t_sndv() function sends data either normal or expedited data. The data is contained in buffers iov[0], iov[1], through iov[iovcount-1].
The limit on the total number of bytes available in all buffers passed (that is, iov(0).iov_len + ... + iov(iovcount-1).iov_len) may be
constrained by implementation limits. If no other constraint applies, it will be limited by [INT_MAX]. In practice, 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 func-
tions.
Each t_sndv() with the T_MORE flag set indicates that another t_sndv() (or t_snd()) 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 the T_MORE flag 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 info argument on return from t_open() or t_getinfo(), 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 a TSDU 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 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 pro-
tocol-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 time the call is made. However, if O_NONBLOCK is set (via t_open() or fcntl()), t_sndv() executes in asyn-
chronous mode, and will fail immediately if there are flow control restrictions. The process can arrange to be informed when the flow con-
trol restrictions are cleared via either t_look() or the EM interface.
On successful completion, t_sndv() returns the number of bytes accepted by the transport provider. Normally this equals the total number
of bytes to be sent, according to the following formula: iov[0].iov_len + ... + iov[iovcount-1].iov_len
However, the interface is constrained to send at most INT_MAX bytes in a single send. When t_sndv() has submitted INT_MAX (or lower con-
strained value, see the previous note) bytes to the provider for a single call, this value is returned to the user. However, if O_NONBLOCK
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 communica-
tions 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 the communications 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 underlying transport 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 by t_getinfo().
The [TLOOK] error is returned for asynchronous events. It is required only for an incoming disconnect event, but may be returned for other
events.
NOTES
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() calls, the different data may be intermixed.
Multiple sends that 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
[TSYSERR], a [TBADDATA], or a [TPROTO] error.
If multiple sends that exceed the maximum TSDU or ETSDU size are detected by XTI, t_sndv() fails with [TBADDATA].
RETURN VALUE
Upon successful completion, t_sndv returns a value of 0 (zero). Otherwise, it returns a value of -1 and sets t_errno to indicate the
error.
In synchronous mode, if more than INT_MAX bytes of data are passed in the iov array, only the first INT_MAX bytes will be passed to the
provider.
If the number of bytes accepted by the communications provider is less than the number of bytes requested, this may either indicate that
O_NONBLOCK is set and the communications provider is blocked due to flow control, or that O_NONBLOCK is clear and the function was inter-
rupted by a signal.
ERRORS
If the t_sndv() function fails, t_errno may be set to one of the following values: Illegal amount of data. Possible reasons include: An
attempt to send once, specifying 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. An attempt to send zero-byte TSDU (ETSDU) or zero-byte fragment of a TSDU (ETSDU) is not supported by
the provider. An attempt to send multiple times, resulting in a TSDU (ETSDU) larger than that specified by the current value of the TSDU
or ETSDU fields in the info argument. The ability of an XTI implementation to detect such an error case is implementation-dependent (see
CAVEATS, below). The iovcount parameter is greater than T_IOV_MAX. File descriptor (fd) is not a valid transport endpoint. An invalid
flag was specified. O_NONBLOCK was set, but the flow control mechanism prevented the transport provider from accepting the function. An
asynchronous event occurred on this transport endpoint and requires immediate attention. This function is not supported by the underlying
transport provider. The communications endpoint referenced by fd is not in a valid state in which a call to this function. A communica-
tion problem has been detected between XTI and the transport provider for which there is no other suitable XTI error (t_errno). A system
error occurred during execution of this function.
RELATED INFORMATION
Functions: t_getinfo(3), t_open(3), t_rcv(3), t_rcvv(3), t_snd(3). delim off
t_sndv(3)