xdr(3) - Linux manual page (original) (raw)
xdr(3) Library Functions Manual xdr(3)
NAME top
xdr - library routines for external data representationLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS AND DESCRIPTION top
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** _boolt_**;**
**typedef typeof(bool_t (XDR *, void *, ...)) ***_xdrproct_**;**
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)](../man2/read.2.html) and
[write(2)](../man2/write.2.html), 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)](../man3/fflush.3.html) on the _file_ stream, but never
[fclose(3)](../man3/fclose.3.html).
**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 _enumt_. 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 top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **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**() │ │ │
└──────────────────────────────────────┴───────────────┴─────────┘SEE ALSO top
[rpc(3)](../man3/rpc.3.html)
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 top
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