xdr_string


SYNOPSIS AND DESCRIPTION
       These  routines  allow  C programmers to describe arbitrary data struc-
       tures in a machine-independent  fashion.   Data  for  remote  procedure
       calls are transmitted using these routines.

       The  prototypes  below  are declared in <rpc/xdr.h> and make use of the
       following types:

           typedef int bool_t;

           typedef bool_t (*xdrproc_t) (XDR *, void *,...);

       For the declaration of the XDR type, see <rpc/xdr.h>.

       bool_t xdr_array(XDR *xdrs, char **arrp, unsigned int *sizep,
                        unsigned int maxsize, unsigned int elsize,
                        xdrproc_t elproc);

              A  filter  primitive  that  translates  between  variable-length
              arrays  and  their  corresponding external representations.  The
              argument 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 argument elsize is the
              sizeof each of the array's elements, and elproc is an XDR filter
              that translates between the array elements' C  form,  and  their
              external  representation.   This  routine returns one if it suc-
              ceeds, zero otherwise.

       bool_t xdr_bool(XDR *xdrs, bool_t *bp);

              A filter primitive that translates between booleans (C integers)
              and  their  external  representations.  When encoding data, this
              filter produces values of either  one  or  zero.   This  routine
              returns one if it succeeds, zero otherwise.

       bool_t xdr_bytes(XDR *xdrs, char **sp, unsigned int *sizep,
                        unsigned int maxsize);

              A  filter primitive that translates between counted byte strings
              and their external representations.   The  argument  sp  is  the
              address  of  the  string  pointer.   The length of the string is
              located at address sizep; strings cannot be longer than maxsize.
              This routine returns one if it succeeds, zero otherwise.

       bool_t xdr_char(XDR *xdrs, char *cp);

              A  filter  primitive  that  translates  between C characters and
              their external representations.  This routine returns one if  it
              succeeds,  zero  otherwise.   Note:  encoded  characters are not
              packed, and occupy 4 bytes each.  For arrays of  characters,  it
              is   worthwhile   to   consider   xdr_bytes(),  xdr_opaque()  or
              xdr_string().


       bool_t xdr_enum(XDR *xdrs, enum_t *ep);

              A  filter  primitive  that  translates between C enums (actually
              integers) and  their  external  representations.   This  routine
              returns one if it succeeds, zero otherwise.

       bool_t xdr_float(XDR *xdrs, float *fp);

              A  filter  primitive  that translates between C floats and their
              external representations.  This routine returns one if  it  suc-
              ceeds, zero otherwise.

       void xdr_free(xdrproc_t proc, char *objp);

              Generic  freeing routine.  The first argument is the XDR routine
              for the object being freed.  The second argument is a pointer to
              the  object itself.  Note: the pointer passed to this routine is
              not freed, but what it points to is freed (recursively).

       unsigned int xdr_getpos(XDR *xdrs);

              A macro that invokes the get-position  routine  associated  with
              the  XDR stream, xdrs.  The routine returns an unsigned integer,
              which indicates the position of the XDR byte stream.   A  desir-
              able feature of XDR streams is that simple arithmetic works with
              this number, although the XDR stream instances need not  guaran-
              tee this.

       long *xdr_inline(XDR *xdrs, int len);

              A  macro that invokes the inline routine associated with the XDR
              stream, xdrs.  The routine returns a  pointer  to  a  contiguous
              piece  of  the  stream's  buffer;  len is the byte length of the
              desired buffer.  Note: pointer is cast to long *.

              Warning: xdr_inline() may return NULL (0) if it cannot  allocate
              a contiguous piece of a buffer.  Therefore the behavior may vary
              among stream instances; it exists for the sake of efficiency.

       bool_t xdr_int(XDR *xdrs, int *ip);

              A filter primitive that translates between C integers and  their
              external  representations.   This routine returns one if it suc-
              ceeds, zero otherwise.

       bool_t xdr_long(XDR *xdrs, long *lp);

              A filter primitive that translates between C long  integers  and
              their  external representations.  This routine returns one if it
              succeeds, zero otherwise.

       void xdrmem_create(XDR *xdrs, char *addr, unsigned int size,
                          enum xdr_op op);

              This routine returns one if it succeeds, zero otherwise.

       bool_t xdr_pointer(XDR *xdrs, char **objpp,
                          unsigned int objsize, xdrproc_t xdrobj);

              Like  xdr_reference()  except  that it serializes NULL pointers,
              whereas xdr_reference() does not.  Thus, xdr_pointer() can  rep-
              resent recursive data structures, such as binary trees or linked
              lists.

       void xdrrec_create(XDR *xdrs, unsigned int sendsize,
                          unsigned int recvsize, char *handle,
                          int (*readit) (char *, char *, int),
                          int (*writeit) (char *, char *, int));

              This routine initializes the XDR stream  object  pointed  to  by
              xdrs.   The  stream's  data is written to a buffer of size send-
              size; a value of zero indicates the system should use a suitable
              default.   The stream's data is read from a buffer of size recv-
              size; it too can be set to a suitable default by passing a  zero
              value.   When  a  stream's  output  buffer  is  full, writeit is
              called.  Similarly, when a stream's input buffer is empty,  rea-
              dit is called.  The behavior of these two routines is similar to
              the system calls read(2) and write(2),  except  that  handle  is
              passed  to the former routines as the first argument.  Note: the
              XDR stream's op field must be set by the caller.

              Warning: this  XDR  stream  implements  an  intermediate  record
              stream.   Therefore  there are additional bytes in the stream to
              provide record boundary information.

       bool_t xdrrec_endofrecord(XDR *xdrs, int sendnow);

              This routine can be invoked only  on  streams  created  by  xdr-
              rec_create().  The data in the output buffer is marked as a com-
              pleted record, and the output buffer is optionally  written  out
              if sendnow is nonzero.  This routine returns one if it succeeds,
              zero otherwise.

       bool_t xdrrec_eof(XDR *xdrs);

              This routine can be invoked only  on  streams  created  by  xdr-
              rec_create().  After consuming the rest of the current record in
              the stream, this routine returns one if the stream has  no  more
              input, zero otherwise.

       bool_t xdrrec_skiprecord(XDR *xdrs);

              This  routine  can  be  invoked  only on streams created by xdr-
              rec_create().  It tells the XDR implementation that the rest  of
              the  current  record in the stream's input buffer should be dis-
              carded.  This routine returns one if it  succeeds,  zero  other-
              wise.


       xdr_setpos(XDR *xdrs, unsigned int pos);

              A  macro  that  invokes the set position routine associated with
              the XDR stream xdrs.  The  argument  pos  is  a  position  value
              obtained from xdr_getpos().  This routine returns one if the XDR
              stream could be repositioned, and zero otherwise.

              Warning: it  is  difficult  to  reposition  some  types  of  XDR
              streams,  so  this  routine may fail with one type of stream and
              succeed with another.

       bool_t xdr_short(XDR *xdrs, short *sp);

              A filter primitive that translates between C short integers  and
              their  external representations.  This routine returns one if it
              succeeds, zero otherwise.

       void xdrstdio_create(XDR *xdrs, FILE *file, enum xdr_op op);

              This routine initializes the XDR stream  object  pointed  to  by
              xdrs.   The  XDR  stream  data  is written to, or read from, the
              stdio stream file.  The argument op determines the direction  of
              the XDR stream (either XDR_ENCODE, XDR_DECODE, or XDR_FREE).

              Warning:  the  destroy  routine associated with such XDR streams
              calls fflush(3) on the file stream, but never fclose(3).

       bool_t xdr_string(XDR *xdrs, char **sp, unsigned int maxsize);

              A filter primitive that 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.   This  routine returns one if it succeeds, zero other-
              wise.

       bool_t xdr_u_char(XDR *xdrs, unsigned char *ucp);

              A filter primitive that translates between unsigned C characters
              and their external representations.  This routine returns one if
              it succeeds, zero otherwise.

       bool_t xdr_u_int(XDR *xdrs, unsigned *up);

              A filter primitive that translates between C  unsigned  integers
              and their external representations.  This routine returns one if
              it succeeds, zero otherwise.

       bool_t xdr_u_long(XDR *xdrs, unsigned long *ulp);

              A filter primitive that translates between C unsigned long inte-
              gers  and  their external representations.  This routine returns
              one if it succeeds, zero otherwise.

              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 argument choices is a pointer to an array of
              xdr_discrim()  structures.   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() structure 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).  Returns one if it succeeds, zero otherwise.

       bool_t xdr_vector(XDR *xdrs, char *arrp, unsigned int size,
                         unsigned int elsize, xdrproc_t elproc);

              A  filter  primitive that translates between fixed-length arrays
              and their corresponding external representations.  The  argument
              arrp  is  the address of the pointer to the array, while size is
              the element count of the array.   The  argument  elsize  is  the
              sizeof each of the array's elements, and elproc is an XDR filter
              that translates between the array elements' C  form,  and  their
              external  representation.   This  routine returns one if it suc-
              ceeds, zero otherwise.

       bool_t xdr_void(void);

              This routine always returns one.  It may be passed to  RPC  rou-
              tines  that  require a function argument, where nothing is to be
              done.

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

              A primitive that  calls  xdr_string(xdrs,  sp,MAXUN.UNSIGNED  );
              where  MAXUN.UNSIGNED  is the maximum value of an unsigned inte-
              ger.  xdr_wrapstring() is handy because the RPC package passes a
              maximum  of two XDR routines as arguments, and xdr_string(), one
              of the most frequently used primitives, requires three.  Returns
              one if it succeeds, zero otherwise.

SEE ALSO
       rpc(3)

       The following manuals:
              eXternal Data Representation Standard: Protocol Specification
              eXternal Data Representation: Sun Technical Notes
              XDR:   External  Data  Representation  Standard,  RFC 1014,  Sun
              Microsystems, Inc., USC-ISI.

COLOPHON
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