Manual Pages for UNIX Operating System command usage for man xdr_union

Networking Services Library Functions           xdr_complex(3NSL)



NAME
     xdr_complex, xdr_array, xdr_bytes, xdr_opaque,  xdr_pointer,
     xdr_reference,     xdr_string,     xdr_union,    xdr_vector,
     xdr_wrapstring  -  library  routines   for   external   data
     representation

DESCRIPTION
     XDR library routines allow C programmers to describe complex
     data  structures in a machine-independent fashion. Protocols
     such as remote procedure calls (RPC) use these  routines  to
     describe  the format of the data. These routines are the XDR
     library routines for complex data structures.  They  require
     the creation of XDR streams. See xdr_create(3NSL).

  Routines
     See rpc(3NSL) for the definition of the XDR data  structure.
     Note  that  any  buffers  passed to the XDR routines must be
     properly aligned. It is suggested either  that  malloc()  be
     used  to  allocate  these  buffers,  or  that the programmer
     insure  that the buffer address is divisible evenly by four.


     #include 

     bool_t xdr_array(XDR *xdrs, caddr_t *arrp, uint_t *sizep,
     const uint_t maxsize, const uint_t elsize, const xdrproc_t
     elproc);

         xdr_array() translates  between  variable-length  arrays
         and  their  corresponding  external representations. The
         parameter arrp is the address  of  the  pointer  to  the
         array,  while  sizep is the address of the element count
         of the array; this element count cannot exceed  maxsize.
         The  parameter elsize is the size of each of the array's
         elements, and elproc is an XDR routine  that  translates
         between  the  array  elements' C form and their external
         representation.  If  *aarp  is   NULL   when   decoding,
         xdr_array()  allocates  memory  and  *aarp points to it.
         This routine returns TRUE if it succeeds,  FALSE  other-
         wise.


     bool_t xdr_bytes(XDR *xdrs, char **sp, uint_t *sizep, const
     uint_t maxsize);

         xdr_bytes() translates between counted byte strings  and
         their  external representations. The parameter sp is the
         address of the string pointer. The length of the  string
         is  located  at  address sizep; strings cannot be longer
         than maxsize. If *sp is  NULL when decoding, xdr_bytes()
         allocates  memory  and  *sp  points  to it. This routine
         returns TRUE if it succeeds, FALSE otherwise.



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Networking Services Library Functions           xdr_complex(3NSL)



     bool_t xdr_opaque(XDR *xdrs, caddr_t cp, const uint_t cnt);

         xdr_opaque() translates between fixed size  opaque  data
         and its external representation. The parameter cp is the
         address of the opaque object, and cnt  is  its  size  in
         bytes.  This  routine returns TRUE if it succeeds, FALSE
         otherwise.


     bool_t xdr_pointer(XDR *xdrs, char **objpp, uint_t objsize,
     const xdrproc_t xdrobj);

         Like xdr_reference()  except  that  it  serializes  null
         pointers,   whereas  xdr_reference()  does  not.   Thus,
         xdr_pointer() can represent recursive  data  structures,
         such as binary trees or linked lists. If *objpp is  NULL
         when decoding, xdr_pointer() allocates memory and *objpp
         points to it.


     bool_t xdr_reference(XDR *xdrs, caddr_t *pp, uint_t size,
     const xdrproc_t proc);

         xdr_reference() provides pointer chasing  within  struc-
         tures.   The parameter pp is the address of the pointer;
         size is the sizeof the structure that *pp points to; and
         proc  is  an XDR procedure that translates the structure
         between its C form and its external  representation.  If
         *pp  is   NULL  when decoding, xdr_reference() allocates
         memory and *pp points to it.  This routine returns 1  if
         it succeeds, 0 otherwise.

         Warning: this routine does not understand null pointers.
         Use xdr_pointer() instead.


     bool_t xdr_string(XDR *xdrs, char **sp, const uint_t max-
     size);

         xdr_string() translates  between  C  strings  and  their
         corresponding  external  representations. Strings cannot
         be longer than maxsize. Note: sp is the address  of  the
         string's   pointer.  If  *sp  is   NULL  when  decoding,
         xdr_string() allocates memory and *sp points to it. This
         routine  returns  TRUE  if it succeeds, FALSE otherwise.
         Note: xdr_string() can be used to send an  empty  string
         (""), but not a null string.


     bool_t xdr_union(XDR *xdrs, enum_t *dscmp, char *unp, const
     struct xdr_discrim *choices, const xdrproc_t (*defaultarm));




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Networking Services Library Functions           xdr_complex(3NSL)



         xdr_union() translates between a discriminated  C  union
         and  its corresponding external representation. It first
         translates the discriminant  of  the  union  located  at
         dscmp.  This  discriminant is always an enum_t. Next the
         union located  at  unp  is  translated.   The  parameter
         choices  is  a pointer to an array of xdr_discrim struc-
         tures.  Each  structure  contains  an  ordered  pair  of
         [value,  proc].  If the union's discriminant is equal to
         the  associated  value,  then  the  proc  is  called  to
         translate  the  union. The end of the xdr_discrim struc-
         ture array is denoted by a routine of value NULL. If the
         discriminant is not found in the choices array, then the
         defaultarm procedure is called (if it is not  NULL).  It
         returns TRUE if it succeeds, FALSE otherwise.


     bool_t xdr_vector(XDR *xdrs, char *arrp, const uint_t size,
     const uint_t elsize, const xdrproc_t elproc);

         xdr_vector() translates between fixed-length arrays  and
         their corresponding external representations. The param-
         eter arrp is the address of the pointer  to  the  array,
         while size is the element count of the array. The param-
         eter elsize is the sizeof each of the array's  elements,
         and elproc is an XDR routine that translates between the
         array elements' C form and  their  external  representa-
         tion.  This  routine  returns TRUE if it succeeds, FALSE
         otherwise.


     bool_t xdr_wrapstring(XDR *xdrs, char **sp);

         A routine  that  calls  xdr_string(xdrs,  sp,  maxuint);
         where  maxuint  is  the  maximum  value  of  an unsigned
         integer.

         Many routines, such as xdr_array(),  xdr_pointer(),  and
         xdr_vector()   take   a   function   pointer   of   type
         xdrproc_t(), which takes  two  arguments.  xdr_string(),
         one of the most frequently used routines, requires three
         arguments, while xdr_wrapstring() only requires two. For
         these routines, xdr_wrapstring() is desirable. This rou-
         tine returns TRUE if it succeeds, FALSE otherwise.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:







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Networking Services Library Functions           xdr_complex(3NSL)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | Safe                        |
    |_____________________________|_____________________________|


SEE ALSO
     malloc(3C),  rpc(3NSL),  xdr_admin(3NSL),  xdr_create(3NSL),
     xdr_simple(3NSL), attributes(5)













































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