t_open.3xti

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3XTI 代码 · 共 178 行

.TH t_open 3xti
.SH Name
t_open \- establish a transport endpoint
.SH Syntax
.B #include <xti.h>
.br
.sp 1
.B #include <fcntl.h>
.br
.B int t_open(\fIname, oflag, info\fB)
.br
.B char \fI*name\fB;
.br
.B int \fIoflag\fB;
.br
.B struct t_info \fI*info\fB;
.SH Arguments
.IP \fIname\fR 10
Points to a transport provider identifier.
.IP \fIoflag\fR 10
Identifies any open flags as in 
.PN open(). 
The \fIoflag\fR argument
is constructed from O_RDWR optionally ORed with O_NONBLOCK.
These flags are defined by the header file \fB<fcntl.h>\fR. 
.IP \fIinfo\fR 10
Returns various default characteristics of the underlying transport
protocol by setting fields in the \fIinfo\fR structure. This argument
points to a 
.PN t_info()
structure that contains the following members:
.RS 10
.IP "long \fIaddr\fP" 15
/* max size of the transport protocol  address */
.IP "long \fIoptions\fP" 15
/* max number of bytes of protocol specific options */
.IP "long \fItsdu\fP" 15
/* max size of a transport service data  unit (TSDU) */
.IP "long \fIetsdu\fP" 15
/* max size of expedited transport  service data unit (ETSDU) */      
.IP "long \fIconnect\fP" 15
/* max amount of data allowed on connection establishment functions */
.IP "long \fIdiscon\fP" 15 
/* max amount of data allowed on  
.PN t_snddis()
and 
.PN t_rcvdis() 
functions */
.IP "long \fIservtype\fP" 15
/* service type supported by the transport provider */
.RE
.PP
The values of the fields have the following meanings:
.RS 15 
.IP  \fIaddr\fP 12
A value greater than or equal to zero indicates 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.
.IP \fIoptions\fP 12
A value greater than or equal to zero indicates 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.
.IP \fItsdu\fP 12
A value greater than zero specifies the maximum size of a transport service data unit (TSDU); a 
value of zero specifies that the transport provider does not support the concept of TSDU; although 
it does support the sending of a data stream with no logical boundaries preserved across a 
connection; 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 normal data is not supported by the transport provider.
.IP \fIetsdu\fP 12
A value greater than zero specifies the maximum size of an expedited transport service data unit 
(ETSDU); a value 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 connection; a value of \-1 specifies that there is no limit on the size of an 
ETSDU; and a value \-2 specifies that the transfer of expedited data is not supported by the 
transport provider.
.IP \fIconnect\fP 12
A value greater than or equal to zero specifies the maximum amount of data that may be associated 
with connection establishment functions; 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 establishment functions.
.IP \fIdiscon\fP 12
A value greater than or equal to zero specifies the maximum amount of data that may be associated 
with the 
.PN t_snddis()
and 
.PN 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 \-2 specifies that the
transport provider does not allow data to be sent with abortive release functions.
.IP \fIservtype\fP 12
This field specifies the service type supported by the transport provider, as described.
.RE
.PP 
If a transport user is concerned with protocol independence, the 
sizes can be accessed to determine how large the buffers must be to hold
each piece of information. Alternately, the 
.PN 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.
.PP
The \fIservtype\fR field of \fIinfo\fR specifies one of the following
values on return.
.RS 10
.IP T_COTS 15
The transport provider supports a connection-mode service but does not support the optional orderly
release facility.
.IP T_COTS_ORD 15
The transport provider supports a connection-mode service with the optional orderly release facility.
.IP T_CLTS 15
The transport provider supports a connectionless-mode service. For this service type, 
.PN t_open() 
returns \-2 for \fIetsdu\fP, \fIconnect\fP, and \fIdiscon\fP.
.RE
.PP
A single transport endpoint may support only one of the above services
at one time.
If \fIinfo\fR is set to NULL by the transport user, no protocol
information is returned by 
.PN t_open()\fR.\fR
.SH Description
The 
.PN t_open()
function must be called as the first step in the initialization of a transport endpoint. 
This function establishes a transport endpoint by supplying a transport provider identifier that
indicates a particular transport provider, that is a transport protocol,
and returns a file descriptor that identifies that endpoint.
.NXR "t_open system call"
.NXR "transport endpoint" "initializing"
.PP
The 
.PN t_open()
function returns a file descriptor that is used
by all subsequent functions to identify that particular local transport
endpoint.
.PP
.TS
tab(@);
lfHB lfHB lfHB
lfR  lfR  lfR .
_
.sp 6p
Parameters@Before Call@After Call
.sp 6p
_
.sp 6p
name@x@/
oflag@x@/
info->addr@/@x
info->options@/@x
info->tsdu@/@x
info->etsdu@/@x
info->connect@/@x
info->discon@/@x
info->servtype@/@x
.sp 6p
_
.TE
.PP
.sp 12p
.SH Return Values
Upon successful completion, 
.PN t_open() 
returns a file descriptor. On failure, \-1 is returned, and \fBt_errno\fR is set to indicate the
error.
.SH Diagnostics
On failure, \fBt_errno\fR is set to one of the following:
.TP 20
[TBADFLAG]
An invalid flag is specified.
.TP 20 
[TBADNAME]
Invalid transport provider name.
.TP 20
[TSYSERR]
A system error has occurred during execution of this function.
.SH See Also
open(2)