info |
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 subroutines */
long discon; /* max amount of data allowed on */
/* t_snddis and t_rcvdis subroutines */
long servtype; /* service type supported by the */
/* transport provider */
long flags; /* other info about the transport provider */
The values of the fields have the following meanings:
addr |
A value greater than zero indicates the maximum size of a transport protocol address and a value of -2 specifies that the transport provider does not provide user access to transport protocol addresses. |
options |
A value greater than zero indicates the maximum number of bytes of protocol-specific options supported by the provider, and a value of -2 specifies that the transport provider does not support user-settable options. |
tsdu |
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 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 maximum 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 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 expedited data is not supported by the transport provider. Note that the semantics of expedited data may be quite different for different transport providers. |
connect |
A value greater than zero specifies the maximum amount of data that may be associated with connection establishment subroutines and a value of -2 specifies that the transport provider does not allow data to be sent with connection establishment subroutines. |
discon |
A value greater than zero specifies the maximum amount of data that may be associated with the t_synddis and t_rcvdis subroutines and a value of -2 specifies that the transport provider does not allow data to be sent with the abortive release subroutines. |
servtype |
This field specifies the service type supported by the transport provider. The valid values on return are:
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 service type, t_open will return -2 for etsdu
, connect
and discon
. |
A single transport endpoint may support only one of the above services at one time. |
flags |
This is a bit field used to specify other information about the transport provider. If the T_SENDZERO bit is set in flags, this indicates the underlying transport provider supports the sending of zero-length TSDUs. |
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. Alternatively, the t_alloc subroutine may be used to allocate these buffers. An error will result if a transport user exceeds the allowed data size on any subroutine.
If the info parameter is set to a null pointer by the transport user, no protocol information is returned by the t_open subroutine. |