Tribblix: manual page: t

T_RCVVUDATA(3NSL) Networking Services Library Functions T_RCVVUDATA(3NSL)

NAME

t_rcvvudata - receive a data unit into one or more noncontiguous
buffers

SYNOPSIS

#include <xti.h>

int t_rcvvudata(int fd, struct t_unitdata *unitdata, struct t_iovec *iov,
unsigned int iovcount, int *flags);

DESCRIPTION

This function is used in connectionless mode to receive a data unit
from another transport user. The argument fd identifies the local
transport endpoint through which data will be received, unitdata
holds information associated with the received data unit, iovcount
contains the number of non-contiguous udata buffers which is limited
to T_IOV_MAX, which is an implementation-defined value of at least
16, and flags is set on return to indicate that the complete data
unit was not received. If the limit on iovcount is exceeded, the
function fails with TBADDATA. The argument unitdata points to a
t_unitdata structure containing the following members:

struct netbuf addr;
struct netbuf opt;
struct netbuf udata;

The maxlen field of addr and opt must be set before calling this
function to indicate the maximum size of the buffer for each. The
udata field of t_unitdata is not used. The iov_len and iov_base
fields of "iov0" through iov [iovcount-1] must be set before calling
t_rcvvudata() to define the buffer where the userdata will be placed.
If the maxlen field of addr or opt is set to zero then no
information is returned in the buf field for this parameter.

On return from this call, addr specifies the protocol address of the
sending user, opt identifies options that were associated with this
data unit, and iov[0].iov_base through iov [iovcount-1].iov_base
contains the user data that was received. The return value of
t_rcvvudata() is the number of bytes of user data given to the user.

Note that the limit on the total number of bytes available in all
buffers passed:

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
functions.

By default, t_rcvvudata() operates in synchronous mode and waits for
a data unit to arrive if none is currently available. However, if
O_NONBLOCK is set by means of t_open(3NSL) or fcntl(2), t_rcvvudata()
executes in asynchronous mode and fails if no data units are
available.

If the buffers defined in the iov[] array are not large enough to
hold the current data unit, the buffers will be filled and T_MORE
will be set in flags on return to indicate that another
t_rcvvudata() should be called to retrieve the rest of the data unit.
Subsequent calls to t_rcvvudata() will return zero for the length of
the address and options, until the full data unit has been received.

RETURN VALUES

On successful completion, t_rcvvudata() returns the number of bytes
received. Otherwise, it returns -1 on failure and t_errno is set to
indicate the error.

VALID STATES

T_IDLE.

ERRORS

On failure, t_errno is set to one of the following:

TBADDATA
iovcount is greater than T_IOV_MAX.

TBADF
The specified file descriptor does not refer to a
transport endpoint.

TBUFOVFLW
The number of bytes allocated for the incoming
protocol address or options (maxlen) is greater than
0 but not sufficient to store the information. The
unit data information to be returned in unitdata will
be discarded.

TLOOK
An asynchronous event has occurred on this transport
endpoint and requires immediate attention.

TNODATA
O_NONBLOCK was set, but no data units are currently
available from the transport provider.

TNOTSUPPORT
This function is not supported by the underlying
transport provider.

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 no other suitable XTI error
(t_errno).

TSYSERR
A system error has occurred during execution of this
function.

TLI COMPATIBILITY

In the TLI interface definition, no counterpart of this routine was
defined.

ATTRIBUTES