T_RCVVUDATA(3NSL)T_RCVVUDATA(3NSL)NAMEt_rcvvudata - receive a data unit into one or more noncontiguous buf‐
fers
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 struc‐
ture 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_rcvvu‐
data() 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 con‐
tains the user data that was received. The return value of t_rcvvu‐
data() 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 buf‐
fers 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 func‐
tions.
By default, t_rcvvudata() operates in synchronous mode and waits for a
data unit to arrive if none is currently available. However, if O_NON‐
BLOCK is set by means of t_open(3NSL) or fcntl(2), t_rcvvudata() exe‐
cutes 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 trans‐
port 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 dis‐
carded.
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 trans‐
port 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
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT Level │ Safe │
└───────────────┴─────────────────┘
SEE ALSOfcntl(2), t_alloc(3NSL), t_open(3NSL), t_rcvudata(3NSL), t_rcvud‐
err(3NSL), t_sndudata(3NSL), t_sndvudata(3NSL), attributes(5)
May 7, 1998 T_RCVVUDATA(3NSL)
