# xdr

## NAME



           xdr - library routines for external data representation
    


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS AND DESCRIPTION



           These routines allow C programmers to describe arbitrary data
           structures 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 typeof(bool_t (XDR *, void *, ...))  ***_xdrproc_t_**;**
    
           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 succeeds, 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**().
    
           **void xdr_destroy(XDR ***_xdrs_**);**
    
                  A macro that invokes the destroy routine associated with
                  the XDR stream, _xdrs_.  Destruction usually involves freeing
                  private data structures associated with the stream.  Using
                  _xdrs_ after invoking **xdr_destroy**() is undefined.
    
           **bool_t xdr_double(XDR ***_xdrs_**, double ***_dp_**);**
    
                  A filter primitive that translates between C _double_
                  precision numbers and their external representations.  This
                  routine returns one if it succeeds, zero otherwise.
    
           **bool_t xdr_enum(XDR ***_xdrs_**, enum_t ***_ep_**);**
    
                  A filter primitive that translates between C _enum_ s
                  (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 _float_ s and
                  their external representations.  This routine returns one
                  if it succeeds, 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 desirable feature of XDR streams is that simple
                  arithmetic works with this number, although the XDR stream
                  instances need not guarantee 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 succeeds, 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 initializes the XDR stream object pointed to
                  by _xdrs_.  The stream's data is written to, or read from, a
                  chunk of memory at location _addr_ whose length is no more
                  than _size_ bytes long.  The _op_ determines the direction of
                  the XDR stream (either **XDR_ENCODE** , **XDR_DECODE** , or
                  **XDR_FREE**).
    
           **bool_t xdr_opaque(XDR ***_xdrs_**, char ***_cp_**, unsigned int** _cnt_**);**
    
                  A filter primitive that translates between fixed size
                  opaque data and its external representation.  The argument
                  _cp_ is the address of the opaque object, and _cnt_ is its size
                  in bytes.  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 represent recursive data structures, such
                  as binary trees or linked lists.
    
           **void xdrrec_create(XDR ***_xdrs_**, unsigned int** _sendsize_**,**
                              **unsigned int** _recvsize_**, char ***_handle_**,**
                              **typeof(int (char *, char *, int)) ***_readit_**,**
                              **typeof(int (char *, char *, int)) ***_writeit_**);**
    
                  This routine initializes the XDR stream object pointed to
                  by _xdrs_.  The stream's data is written to a buffer of size
                  _sendsize_ ; a value of zero indicates the system should use a
                  suitable default.  The stream's data is read from a buffer
                  of size _recvsize_ ; 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, _readit_ 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: to read from an XDR stream created by this API,
                  you'll need to call **xdrrec_skiprecord**() first before
                  calling any other XDR APIs.  This inserts additional bytes
                  in the stream to provide record boundary information.
                  Also, XDR streams created with different **xdr*_create** APIs
                  are not compatible for the same reason.
    
           **bool_t xdrrec_endofrecord(XDR ***_xdrs_**, int** _sendnow_**);**
    
                  This routine can be invoked only on streams created by
                  **xdrrec_create**().  The data in the output buffer is marked
                  as a completed 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
                  **xdrrec_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
                  **xdrrec_create**().  It tells the XDR implementation that the
                  rest of the current record in the stream's input buffer
                  should be discarded.  This routine returns one if it
                  succeeds, zero otherwise.
    
           **bool_t xdr_reference(XDR ***_xdrs_**, char ****_pp_**, unsigned int** _size_**,**
                                **xdrproc_t** _proc_**);**
    
                  A primitive that provides pointer chasing within
                  structures.  The argument _pp_ is the address of the pointer;
                  _size_ is the _sizeof_ the structure that _*pp_ points to; and
                  _proc_ is an XDR procedure that filters the structure between
                  its C form and its external representation.  This routine
                  returns one if it succeeds, zero otherwise.
    
                  Warning: this routine does not understand null pointers.
                  Use **xdr_pointer**() instead.
    
           **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 otherwise.
    
           **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 int ***_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_
                  integers and their external representations.  This routine
                  returns one if it succeeds, zero otherwise.
    
           **bool_t xdr_u_short(XDR ***_xdrs_**, unsigned short ***_usp_**);**
    
                  A filter primitive that translates between C _unsigned short_
                  integers and their external representations.  This routine
                  returns one if it succeeds, zero otherwise.
    
           **bool_t xdr_union(XDR ***_xdrs_**, enum_t ***_dscmp_**, char ***_unp_**,**
                            **const struct xdr_discrim ***_choices_**,**
                            **xdrproc_t** _defaultarm_**);     /* may equal NULL */**
    
                  A filter primitive that 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 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 succeeds, zero otherwise.
    
           **bool_t xdr_void(void);**
    
                  This routine always returns one.  It may be passed to RPC
                  routines 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
                  integer.  **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.
    


## ATTRIBUTES



           For an explanation of the terms used in this section, see
           attributes(7).
           ┌──────────────────────────────────────┬───────────────┬─────────┐
           │ **Interface** │ **Attribute** │ **Value** │
           ├──────────────────────────────────────┼───────────────┼─────────┤
           │ **xdr_array**(), **xdr_bool**(),             │ Thread safety │ MT-Safe │
           │ **xdr_bytes**(), **xdr_char**(),             │               │         │
           │ **xdr_destroy**(), **xdr_double**(),         │               │         │
           │ **xdr_enum**(), **xdr_float**(), **xdr_free**(), │               │         │
           │ **xdr_getpos**(), **xdr_inline**(),          │               │         │
           │ **xdr_int**(), **xdr_long**(),               │               │         │
           │ **xdrmem_create**(), **xdr_opaque**(),       │               │         │
           │ **xdr_pointer**(), **xdrrec_create**(),      │               │         │
           │ **xdrrec_eof**(), **xdrrec_endofrecord**(),  │               │         │
           │ **xdrrec_skiprecord**(),                 │               │         │
           │ **xdr_reference**(), **xdr_setpos**(),       │               │         │
           │ **xdr_short**(), **xdrstdio_create**(),      │               │         │
           │ **xdr_string**(), **xdr_u_char**(),          │               │         │
           │ **xdr_u_int**(), **xdr_u_long**(),           │               │         │
           │ **xdr_u_short**(), **xdr_union**(),          │               │         │
           │ **xdr_vector**(), **xdr_void**(),            │               │         │
           │ **xdr_wrapstring**()                     │               │         │
           └──────────────────────────────────────┴───────────────┴─────────┘
    


* * *