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Name

t_alloc - allocate a library structure

Synopsis

cc [ flag ... ] file ... -lnsl [ library ... ]

#include <tiuser.h>

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

MT-Level

MT-Safe

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 t_connect(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 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 t_connect(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(3N) and t_getinfo(3N) . Thus, fildes 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, the underlying service provider can support a buffer of unlimited size. If this is the case, t_alloc() will allocate a buffer with the default size 1024 bytes. See the NOTES section for information regarding memory allocation for buffers other than 1024 bytes. If the size value is -2, t_alloc() will set the buffer pointer to NULL and the buffer maximum size to 0, and then will return success (see t_open(3N) or t_getinfo(3N) ).
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.

Return Values

On successful completion, t_alloc() returns a pointer to the newly allocated structure. On failure, NULL is returned, t_errno is set to indicate the error, and possibly errno is set.

Errors

On failure, t_errno will 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, errno will be set to the specific error.

See Also

t_connect(3N) , t_free(3N) , t_getinfo(3N) , t_open(3N)

Notes

If the underlying service provider supports a buffer of unlimited size in the netbuf structure (see t_connect(3N) ), t_alloc() will return a buffer of size 1024 bytes. If a larger size buffer is required, it will need to be allocated separately using a memory allocation routine such as malloc(3C) . The buf and maxlen fields of the netbuf data structure can then be updated with the address of the new buffer and the 1024 byte buffer originally allocated by t_alloc() can be freed using free(3C) .

This interface is safe in multithreaded applications.

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