NAME [Toc] [Back]
t_alloc() - allocate a library structure
SYNOPSIS [Toc] [Back]
#include <xti.h> /* for X/OPEN Transport Interface - XTI */
/* or */
#include <tiuser.h> /* for Transport Layer Interface - TLI */
char *t_alloc (fd, struct_type, fields);
DESCRIPTION [Toc] [Back]
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 must 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. 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 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 buffer to
allocate, where the argument is the bitwise-OR of any of the
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
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T_ALL All relevant fields of the given structure.
Fields which are not supported by e transport
provider specified by fd will not be allocated
(info values are <= 0).
For each field specified in fields, t_alloc() will allocate memory for
the buffer associated with the field, and initialize the len field to
zero and the buf pointer and maxlen field accordingly. Since the
length of the buffer allocated will be based on the same size
information that is returned to the user on t_open() or t_getinfo(),
fd must refer to the transport endpoint through which the newly
allocated structure will be passed. In this way the appropriate size
information can be accessed. If the size value associated with any
specified field is -1 or -2 ( see t_open(3) or t_getinfo(3)),
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 a
null pointer 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
Thread-Safeness [Toc] [Back]
The t_alloc() function is safe to be called by multithreaded
applications, and it is thread-safe for both POSIX Threads and DCE
User Threads. It has a cancellation point. It is neither asynccancel
safe nor async-signal safe. Finally, it is not fork-safe.
Valid States [Toc] [Back]
All - apart from T_UNINIT
RETURN VALUE [Toc] [Back]
Upon successful completion, t_alloc() returns a pointer to the newly
allocated structure. On failure, a null pointer is returned.
ERRORS [Toc] [Back]
On failure, t_errno is set to one of the following:
[TBADF] fd The specified endpoint identifier does not
refer to a transport endpoint
[TSYSERR] A system error has occurred during execution of
[TPROTO] (XTI only) This error indicates that a
communication problem has been detected between
XTI and the transport provider for which there is
no suitable XTI (t_errno).
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[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
SEE ALSO [Toc] [Back]
t_free(3), t_getinfo(3), t_open(3).
STANDARDS CONFORMANCE [Toc] [Back]
t_alloc(): SVID2, XPG3, XPG4
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