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AIX Version 4.3 Communications Technical Reference, Volume 2
t_alloc Subroutine for X/Open Transport Interface
Purpose
Allocate a library structure.
Library
X/Open Transport Interface Library (libxti.a)
Syntax
#include <xti.h>
void *t_alloc (
int fd
int struct_type,
int fields)
Description
The t_alloc subroutine dynamically
allocates memory for the various transport function parameter structures. This
subroutine allocates memory for the specified structure, and also allocates
memory for buffers referenced by the structure.
Use of the t_alloc subroutine to
allocate structures helps ensure the compatibility of user programs with future
releases of the transport interface functions.
Parameters
fd |
Specifies the transport endpoint through which the newly allocated
structure will be passed. |
struc_type |
Specifies the structure to be allocated. The possible values are:
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 |
Each of these structures may subsequently be
used as a parameter to one or more transport functions. Each of the above
structures, except T_INFO, contains at least one field of the struct
netbuf type. 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 paramenter of the t_open or t_getinfo subroutines. |
fields |
Specfies whether the buffer should be allocated for each field type.
The fields parameter specifies which buffers to allocate, where the
parameter is the bitwise-OR of any of the following:
T_ADDR |
The addr field of the t_bind, t_call,
t_unitdata or t_underr structures. |
T_OPT |
The opt field of the t_optmgmt, t_call,
t_unitdata or t_underr 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 the fd parameter are not
allocated. |
For each relevant field specified in the
fields parameter, the t_alloc subroutine allocates memory for the
buffer associated with the field and initializes the len field to zero
and initializes the buf pointer and maxlen field accordingly.
Irrelevant or unknown values passed in fields are ignored. The length of the
buffer allocated is based on the same size information returned to the user on a
call to the t_open and t_getinfo subroutines. Thus, the fd
paramenter must refer to the transport endpoint through which the newly
allocated structure is passed so that the appropriate size information is
accessed. If the size value associated with any specified field is -1 or -2,
(see the t_open or t_getinfo subroutines), the t_alloc
subroutine is unable to determine the size of the buffer to allocate and fails,
setting t_errno to TSYSERR and errno to EINVAL. For
any field not specified in fields, buf will be set to the null pointer
and len and maxlen will be set to zero. |
Valid States
ALL - apart from T_UNINIT.
Return Values
On successful completion, the
t_alloc subroutinereturns a pointer to the newly allocated structure. On
failure, a null pointer is returned.
Error Codes
On failure, t_errno is 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 |
Unsupported structure type (struct_type) requested. This can
include a request for a structure type which is inconsistent with the transport
provider type specified, for example, connection-oriented or
connectionless. |
TPROTO |
This error indicates that a communication problem has been detected
between the X/Open Transport Interface and the transport provider for which there is no other
suitable X/Open Transport Interface (t_errno). |
Related Information
The t_free subroutine, t_getinfo subroutine, t_open subroutine.
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