t_alloc(3N)                    DG/UX R4.11MU05                   t_alloc(3N)


NAME
       t_alloc - allocate a library structure

SYNOPSIS
       #include <tiuser.h>

       char *t_alloc(fd, struct_type, fields)
       int fd;
       int struct_type;
       int fields;

DESCRIPTION
       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 the following:

       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(3).  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 structures.

       T_OPT     The opt field of the t_optmgmt, t_call, t_unitdata, or
                 t_uderr structures.

       T_UDATA   The udata field of the t_call, t_discon, or t_unitdata
                 structures.

       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(3) 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 zero.

       Use of t_alloc to allocate structures will help ensure the
       compatibility of user programs with future releases of the transport
       interface.

       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
       intro(3), t_free(3N), t_getinfo(3N), t_open(3N).
       UNIX System V Network Programmer's Guide.

DIAGNOSTICS
       On successful completion, t_alloc returns a pointer to the newly
       allocated structure.  On failure, NULL is returned.


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