TGETINFO(3N-SVR4) RISC/os Reference Manual TGETINFO(3N-SVR4)
NAME
t_getinfo - get protocol-specific service information
SYNOPSIS
#include <tiuser.h>
int tgetinfo(fd, info)
int fd;
struct tinfo *info;
DESCRIPTION
This function returns the current characteristics of the
underlying transport protocol associated with file descrip-
tor fd. The info structure is used to return the same
information returned by t_open. This function enables a
transport user to access this information during any phase
of communication.
This argument points to a t_info structure, which contains
the following members:
long addr;/* max size of the transport protocol address */
long options;/* max number of bytes of protocol-specific options */
long tsdu;/* max size of a transport service data unit (TSDU) */
long etsdu;/* max size of an expedited transport service data unit (ETSDU) */
long connect;/* max amount of data allowed on connection establishment functions */
long discon;/* max amount of data allowed on t_snddis and t_rcvdis functions */
long servtype;/* service type supported by the transport provider */
The values of the fields have the following meanings:
addr A value greater than or equal to zero indi-
cates the maximum size of a transport protocol
address; a value of -1 specifies that there is
no limit on the address size; and a value of
-2 specifies that the transport provider does
not provide user access to transport protocol
addresses.
options A value greater than or equal to zero indi-
cates the maximum number of bytes of
protocol-specific options supported by the
provider; a value of -1 specifies that there
is no limit on the option size; and a value of
-2 specifies that the transport provider does
not support user-settable options.
tsdu A value greater than zero specifies the max-
imum size of a transport service data unit
(TSDU); a value of zero specifies that the
transport provider does not support the con-
cept of TSDU, although it does support the
sending of a data stream with no logical
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TGETINFO(3N-SVR4) RISC/os Reference Manual TGETINFO(3N-SVR4)
boundaries preserved across a connection; a
value of -1 specifies that there is no limit
on the size of a TSDU; and a value of -2
specifies that the transfer of normal data is
not supported by the transport provider.
etsdu A value greater than zero specifies the max-
imum size of an expedited transport service
data unit (ETSDU); a value of zero specifies
that the transport provider does not support
the concept of ETSDU, although it does support
the sending of an expedited data stream with
no logical boundaries preserved across a con-
nection; a value of -1 specifies that there is
no limit on the size of an ETSDU; and a value
of -2 specifies that the transfer of expedited
data is not supported by the transport pro-
vider.
connect A value greater than or equal to zero speci-
fies the maximum amount of data that may be
associated with connection establishment func-
tions; a value of -1 specifies that there is
no limit on the amount of data sent during
connection establishment; and a value of -2
specifies that the transport provider does not
allow data to be sent with connection estab-
lishment functions.
discon A value greater than or equal to zero speci-
fies the maximum amount of data that may be
associated with the t_snddis and t_rcvdis
functions; a value of -1 specifies that there
is no limit on the amount of data sent with
these abortive release functions; and a value
of -2 specifies that the transport provider
does not allow data to be sent with the abor-
tive release functions.
servtype This field specifies the service type sup-
ported by the transport provider, as described
below.
If a transport user is concerned with protocol independence,
the above sizes may be accessed to determine how large the
buffers must be to hold each piece of information. Alterna-
tively, the t_alloc function may be used to allocate these
buffers. An error will result if a transport user exceeds
the allowed data size on any function. The value of each
field may change as a result of option negotiation, and
tgetinfo enables a user to retrieve the current charac-
teristics.
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TGETINFO(3N-SVR4) RISC/os Reference Manual TGETINFO(3N-SVR4)
The servtype field of info may specify one of the following
values on return:
T_COTS The transport provider supports a
connection-mode service but does not support
the optional orderly release facility.
T_COTS_ORD The transport provider supports a
connection-mode service with the optional
orderly release facility.
T_CLTS The transport provider supports a
connectionless-mode service. For this ser-
vice type, t_open will return -2 for etsdu,
connect, and discon.
On failure, t_errno may be set to one of the following:
[TBADF] The specified file descriptor does not refer
to a transport endpoint.
[TSYSERR] A system error has occurred during execution
of this function.
SEE ALSO
t_open(3N).
DIAGNOSTICS
tgetinfo returns 0 on success and -1 on failure and t_errno
is set to indicate the error.
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