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This routine is part of the XTI interfaces which evolved from the TLI interfaces. XTI represents
the future evolution of these interfaces. However, TLI interfaces are supported for compatibility. When using a TLI routine that has the same name as an XTI routine, a different header file, tiuser.h, must be used. Refer to the section, TLI COMPATIBILITY, for a description of differences between the two interfaces.
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:
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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
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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 as returned in the info argument of t_open(3NSL) or t_getinfo(3NSL). 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:
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T_ADDR
- The addr field of the t_bind, t_call, t_unitdata or t_uderr structures.
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T_OPT
- The opt field of the t_optmgmt, t_call, t_unitdata or t_uderr structures.
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T_UDATA
- The udata field of the t_call, t_discon or t_unitdata structures.
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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 relevant 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. Irrelevant or unknown values passed in fields are ignored. Since the length of the buffer allocated will be based on the same size information that is returned to the user on a call to t_open(3NSL) and t_getinfo(3NSL), fd must refer to the transport endpoint through which the newly allocated structure will
be passed. In the case where a T_INFO structure is to be allocated, fd may be set to any value. In this way the appropriate size information can be accessed. If the size value associated with any specified field is T_INVALID, 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. See t_open(3NSL) or t_getinfo(3NSL). If the size value associated with any specified field is T_INFINITE, then the behavior of t_alloc() is implementation-defined. For any field not specified in fields, buf will be set to the null pointer and len and maxlen
will be set to zero. See t_open(3NSL) or t_getinfo(3NSL).
The pointer returned if the allocation succeeds is suitably aligned so that it can be assigned to a pointer to any type of object and then used to access such an object or array of such objects in the space allocated.
Use of t_alloc() to allocate structures will help ensure the compatibility of user programs with future releases of the transport interface functions.
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