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t_rcvudata(3)
NAME
t_rcvudata - Receives a data unit
LIBRARY
XTI Library (libxti.a)
SYNOPSIS
#include <xti.h>
int t_rcvudata(
int fd,
struct t_unitdata *unitdata,
int *flags) ;
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
t_rcvudata: XPG4-UNIX
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 parameter
data before and after t_rcvudata() is called:
Parameters Before Call After Call
_________________________________________________
fd y n
unitdata->addr.maxlen y n
unitdata->addr.len n y
unitdata->addr.buf o (o)
unitdata->opt.maxlen y n
unitdata->opt.len n y
unitdata->opt.buf o (o)
unitdata->udata.maxlen y n
unitdata->udata.len n y
unitdata->udata.buf o (o)
flags n y
Notes to Table:
y This is a meaningful parameter.
n This is not a meaningful parameter.
(y) The content of the object pointed to by y is meaningful.
fd Specifies a file descriptor returned by the t_open() function that
identifies the transport endpoint.
unitdata
Points to a type t_unitdata structure used to specify information
required by the transport provider user to receive a data unit through
the transport endpoint specified by the fd parameter. The t_unitdata
structure has the following members:
struct netbuf addr
References a buffer for protocol address information required
from the transport endpoint specified by the fd parameter. The
type netbuf structure referenced by this member is defined in the
xti.h include file and has the following members:
unsigned int maxlen
Specifies the maximum byte length of the data buffer.
unsigned int len
Specifies the actual byte length of the data written to the
buffer.
char *buf
Points to the buffer location.
struct netbuf opt
Specifies a buffer for protocol-specific parameters associated
with the data unit.
struct netbuf udata
Specifies parameters for any user data unit that may be returned
to the caller.
Before the t_rcvudata() function is called the
unitdata->addr.maxlen, unitdata->opt.maxlen, and
unitdata->udata.maxlen parameters must be set to specify the
maximum byte length of the protocol address buffer, the protocol
options buffer, and the user data buffer, respectively.
flags
Points to a flag integer that indicates that the complete data
unit was not received. Corresponding values and symbolic names
for flags are defined in the xti.h include file (see the
t_optmgmt() and t_rcv() functions). The flag specified by this
function is:
T_MORE.
When the data buffer specified by the unitdata->udata.buf
parameter is not large enough to hold the current user data unit,
the buffer is filled and this bit is set to indicate that another
t_rcvudata() function should be called to retrieve the rest of
the data unit.
The set state of this bit notifies the local transport user that
the received data unit is a fragment and that another data unit
is available. When this bit is set on return of this function,
another data unit must also be fetched with another t_rcvudata()
call. Each time this flag is set on return, another t_rcvudata()
call must immediately be made to receive additional current data
units. When the final data unit is received, this flag bit has a
value of 0 (zero) on return.
Subsequent calls to the t_rcvudata() function return 0 (zero) as
the length of the address specified by the unitdata->addr.len and
unitdata->opt.len parameters until the full data unit has been
received.
VALID STATES
The t_rcvudata() function can only be called in the T_IDLE transport
provider state.
DESCRIPTION
The t_rcvudata() function is an XTI connectionless service function that is
used to receive a data unit from a remote transport provider user. By
default, t_rcvudata() executes in the synchronous operating mode. The
t_rcvudata() function waits for data to arrive at the transport endpoint
specified by fd before returning control to the transport user who called
this function.
However, when the transport endpoint, specified by the fd parameter, has
been previously opened with the O_NONBLOCK flag set in the t_open() or
fcntl() function, the t_rcvudata() function executes in asynchronous mode.
In asynchronous mode, when a data unit is unavailable, control is
immediately returned to the caller.
RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned. Otherwise, a
value of -1 is returned and t_errno is set to indicate the error.
ERRORS
If the t_rcvudata() function fails, t_errno may be set to one of the
following values:
[TBADF] The specified file descriptor does not refer to a transport
endpoint.
[TNODATA] Asynchronous mode is indicated because O_NONBLOCK was set, but no
data is currently available from the transport provider.
[TBUFOVFLW]
The number of bytes allocated for the incoming protocol address
or protocol options is not sufficient to store the information.
The unit data information normally returned to the unitdata
parameter is discarded.
[TLOOK] An asynchronous event that requires immediate attention has
occurred at the transport endpoint specified by the fd parameter.
[TOUTSTATE]
The t_rcvudata() function was issued in the wrong sequence at the
transport endpoint referenced by the fd parameter.
[TSYSERR] A system error occurred during execution of this function.
[TNOTSUPPORT]
This function is not supported by the underlying transport
provider.
[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(t_errno).
RELATED INFORMATION
Functions: fcntl(2), t_alloc(3), t_open(3), t_optmgmt(3), t_rcv(3),
t_rcvuderr(3), t_sndudata(3)