t_alloc - allocate a library structure
char *t_alloc(fd, struct_type, fields)
The t_alloc function dynamically allocates memory for the various
transport function argument structures as specified below. This function
will allocate memory for the specified structure, and will also allocate
memory for buffers referenced by the structure.
The structure to allocate is specified by struct_type, and can be one of
T_BIND struct t_bind
T_CALL struct t_call
T_OPTMGMT struct t_optmgmt
T_DIS struct t_discon
T_UNITDATA struct t_unitdata
T_UDERROR struct t_uderr
T_INFO struct t_info
where each of these structures may subsequently be used as an argument to
one or more transport functions.
Each of the above structures, except T_INFO, contains at least one field
of type struct netbuf. netbuf is described in intro(3N). For each field
of this type, the user may specify that the buffer for that field should
be allocated as well. The fields argument specifies this option, where
the argument is the bitwise-OR of any of the following:
T_ADDR The addr field of the t_bind, t_call, t_unitdata, or t_uderr
T_OPT The opt field of the t_optmgmt, t_call, t_unitdata, or t_uderr
T_UDATA The udata field of the t_call, t_discon, or t_unitdata
T_ALL All relevant fields of the given structure.
For each field specified in fields, t_alloc will allocate memory for the
buffer associated with the field, and initialize the buf pointer and
maxlen [see netbuf in intro(3N) for description of buf and maxlen] field
accordingly. The length of the buffer allocated will be based on the
same size information that is returned to the user on t_open and
t_getinfo. Thus, fd must refer to the transport endpoint through which
the newly allocated structure will be passed, so that the appropriate
size information can be accessed. If the size value associated with any
specified field is -1 or -2 (see t_open or t_getinfo), t_alloc will be
unable to determine the size of the buffer to allocate and will fail,
setting t_errno to TSYSERR and errno to EINVAL. For any field not
specified in fields, buf will be set to NULL and maxlen will be set to
Use of t_alloc to allocate structures will help ensure the compatibility
of user programs with future releases of the transport interface.
This function resides within both the X/Open compliant libxnet and the
SVR4 compliant libnsl Network Services libraries. Network Services
applications which require X/Open compliance must link-load with -lxnet.
Network Services applications which require SVR4 compliance must linkload
On failure, t_errno may be set to one of the following:
TBADF The specified file descriptor does not refer to a
TSYSERR A system error has occurred during execution of this
TNOSTRUCTYPE Unsupported struct_type requested. This can include a
request for a structure type which is inconsistent with
the transport provider type specified, that is,
connection-oriented or connectionless.
intro(3N), t_free(3N), t_getinfo(3N), t_open(3N)
On successful completion, t_alloc returns a pointer to the newly
allocated structure. On failure, NULL is returned.
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