t_alloc(3N) t_alloc(3N)
NAME
t_alloc - allocate a library data structure
SYNOPSIS
cc [options] file -lnsl
#include <xti.h>
char *t_alloc(int fd, int struct_type, int fields);
Parameters
fd the file descriptor for the transport endpoint.
struct_type identifies the type of structure for which memory
should be allocated.
fields indicates fields for which buffers should be
allocated.
DESCRIPTION
The t_alloc function is an TLI/XTI local management routine
used to allocate data structures associated with the endpoint
specified by fd. For struct_type T_INFO, fd is ignored, so
that T_INFO structures may be allocated for use in calls to
t_open.
t_alloc 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_OPTMGMT /* struct t_optmgmt */
T_CALL /* struct t_call */
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.
Copyright 1994 Novell, Inc. Page 1
t_alloc(3N) t_alloc(3N)
Structure Definitions
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 length of the buffer allocated will be equal to or greater
than the appropriate size as returned in the info argument of
t_open or t_getinfo. The relevant fields of the info argument
are described in the following list. The fields argument
specifies which buffers to allocate, 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. Fields
which are not supported by the transport provider
specified by fd will not be allocated.
For each field specified in fields, t_alloc will allocate
memory for the buffer associated with the field, initialize
the len field to 0 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, t_alloc will be unable to determine the size of the
buffer to allocate and will fail with t_errno set to TSYSERR,
unless when T_ALL is specified, in which case unsupported
fields are ignored silently.
For any field not specified in fields, buf will be set to NULL
and maxlen will be set to 0. If the fields argument is set to
T_ALL, fields that are not supported by the transport provider
specified by fd are not allocated.
Copyright 1994 Novell, Inc. Page 2
t_alloc(3N) t_alloc(3N)
Return Values
On successful completion, t_alloc returns a pointer to the
newly allocated structure. On failure, NULL is returned, and
t_errno is set to indicate the error.
Errors
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.
TNOSTRUCTYPE
The argument that specifies struct_type is invalid,
for example, because the type of structure requested
is inconsistent with the transport provider
(connection mode or connectionless) indicated by fd.
TPROTO A communication problem has been detected with the
transport provider and there is no other value of
t_errno to describe the error condition.
State Transitions
t_alloc has no effect on state. Valid states are T_UNBND,
T_IDLE, T_OUTCON, T_INCON, T_DATAXFER, T_OUTREL and T_INREL on
entry. On exit, they are unchanged.
Files
/usr/lib/libxti.so
X/Open Transport Interface Library (shared
object)
/usr/lib/libnsl.so
Network Services Library (shared object)
NOTICE
Use of t_alloc to allocate structures will help ensure the
compatibility of user programs with future releases of the
transport interface.
Buffers and memory that have been allocated with t_alloc may
be freed with t_free.
Copyright 1994 Novell, Inc. Page 3
t_alloc(3N) t_alloc(3N)
REFERENCES
intro(3), t_free(3N), t_getinfo(3N), t_open(3N)
Copyright 1994 Novell, Inc. Page 4