xdr(3)xdr(3)NAME
xdr, xdr_array, xdr_bool, xdr_bytes, xdr_char, xdr_destroy, xdr_double,
xdr_enum, xdr_float, xdr_free, xdr_functions, xdr_getpos, xdr_hyper,
xdr_inline, xdr_int, xdr_long, xdr_longlong_t, xdr_opaque, xdr_pmap,
xdr_pmaplist, xdr_pointer, xdr_reference, xdr_setpos, xdr_short,
xdr_string, xdr_u_char, xdr_u_hyper, xdr_u_int, xdr_u_long, xdr_u_long‐
long_t, xdr_u_short, xdr_union, xdr_vector, xdr_void, xdr_wrapstring,
xdrmem_create, xdrrec_create, xdrrec_endofrecord, xdrrec_eof, xdr‐
rec_skiprecord, xdrstdio_create - library routines for external data
representation
SYNOPSIS
#include <rpc/xdr.h>
xdr_array(
XDR *xdrs,
char **arrp,
u_int *sizep,
u_int *maxsize,
u_int *elsize,
xdrproc_t elproc ); xdr_bool(
XDR *xdrs,
bool_t bp ); xdr_bytes(
XDR *xdrs,
char **sp,
u_int *sizep,
u_int maxsize ); xdr_char(
XDR *xdrs,
char*cp ); void xdr_destroy(
XDR *xdrs ); xdr_double(
XDR *xdrs,
double *dp ); xdr_enum(
XDR *xdrs,
enum_t *ep ); xdr_float(
XDR *xdrs,
float *fp ); void xdr_free(
xdrproc_t proc,
char *objp ); u_int xdr_getpos(
XDR *xdrs ); xdr_hyper(
XDR *xdrs,
longlong_t *hp ); long *xdr_inline(
XDR *xdrs,
int len ); xdr_int(
XDR *xdrs,
int *ip ); xdr_long(
XDR *xdrs,
long *lp ); xdr_longlong_t(
XDR *xdrs,
longlong_t *hp ); xdr_opaque(
XDR *xdrs,
char *cp,
u_int cnt ); xdr_pmap(
XDR *xdrs,
struct pmap *regs ); xdr_pmaplist(
XDR *xdrs,
struct pmaplist **rp ); xdr_pointer(
XDR *xdrs,
char **objpp,
u_int objsize,
xdrproc_t xdrobj ); xdr_reference(
XDR *xdrs,
char **pp,
u_int size,
xdrproc_t proc ); xdr_setpos(
XDR *xdrs,
u_int pos ); xdr_short(
XDR *xdrs,
short *sp ); xdr_string(
XDR *xdrs,
char **sp,
u_int maxsize ); xdr_u_char(
XDR *xdrs,
unsigned char *ucp ); xdr_u_hyper(
XDR *xdrs,
u_longlong_t *uhp ); xdr_u_int(
XDR *xdrs,
unsigned *up ); xdr_u_long(
XDR *xdrs,
unsigned long *ulp ); xdr_u_longlong_t(
XDR *xdrs,
u_longlong_t *uhp ); xdr_u_short(
XDR *xdrs,
unsigned short *usp ); xdr_union(
XDR *xdrs,
int *dscmp,
char *unp,
struct xdr_discrim *choices,
bool_t (*defaultarm) (void) ); xdr_vector(
XDR *xdrs,
char *arrp,
u_int size,
u_int elsize,
xdrproc_t elproc ); xdr_void(
void ); xdr_wrapstring(
XDR *xdrs,
char **sp ); void xdrmem_create(
XDR *xdrs,
char *addr,
u_int size,
enum xdr_op op ); void xdrrec_create(
XDR *xdrs,
u_int sendsize,
u_int recvsize,
char *handle,
int (*readit) (void),
int (*writeit) (void) ); xdrrec_endofrecord(
XDR *xdrs,
int sendnow ); xdrrec_eof(
XDR *xdrs,
int empty ); xdrrec_skiprecord(
XDR *xdrs ); void xdrstdio_create(
XDR *xdrs,
FILE *file,
enum xdr_op op );
DESCRIPTION
These routines allow C programmers to describe arbitrary data struc‐
tures in a machine-independent fashion. Data for ONC remote procedure
calls are transmitted using the following routines:
A filter primitive that translates between variable-length arrays and
their corresponding external representations. The arrp parameter 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 elsize parameter is the sizeof of 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 (1) if
it succeeds, zero (0) otherwise. A filter primitive that translates
between Booleans (C integers) and their external representations. When
encoding data, this filter produces values of either one (1) or zero
(0). This routine returns one (1) if it succeeds, zero (0) otherwise.
A filter primitive that translates between counted byte strings and
their external representations. The sp parameter 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 (1) if
it succeeds, zero (0) otherwise. A filter primitive that translates
between C characters and their external representations. This routine
returns one (1) if it succeeds, zero (0) otherwise. Note: Encoded char‐
acters are not packed and occupy 4 bytes each. For arrays of charac‐
ters, it is worthwhile to consider xdr_bytes(), xdr_opaque(), or
xdr_string(). 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. A filter primitive that translates between
C double-precision numbers and their external representations. This
routine returns one (1) if it succeeds, zero (0) otherwise. A filter
primitive that translates between C enums (actually integers) and their
external representations. This routine returns one (1) if it succeeds,
zero (0) otherwise. A filter primitive that translates between C
floats and their external representations. This routine returns one (1)
if it succeeds, zero (0) otherwise. A generic freeing routine. The
first argument is the XDR routine for the object being freed. The sec‐
ond 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). A macro that invokes the get-position routine associ‐
ated with the XDR stream, xdrs. The routine returns an unsigned inte‐
ger, which indicates the position of the XDR byte stream. A desirable
feature of XDR streams is that simple arithmetic works with this num‐
ber, although the XDR stream instances need not guarantee this. A fil‐
ter primitive that translates between C long integers and their exter‐
nal representations. (The typedef longlong_t is defined as long in the
<rpc/types.h> file, which is included from the <rpc/xdr.h> file.) This
routine will translate all 8 bytes of data to the XDR stream. Note that
this differentiates this routine from xdr_long() in that they both take
a pointer to a long as an argument, while xdr_long() only translates 4
bytes of data to the XDR stream. This routine returns one (1) if it
succeeds, zero (0) otherwise.
The xdr_hyper() routine is functionally equivalent to the
xdr_longlong_t() routine.
See the next section for an explanation of the differences
betweenxdr_long() and xdr_hyper(). A macro that invokes the in-
line 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 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. A
filter primitive that translates between C integers and their
external representations. This routine returns one (1) if it
succeeds, zero (0) otherwise. A filter primitive that trans‐
lates between C long integers and their external representa‐
tions. This routine returns one (1) if it succeeds, zero (0)
otherwise.
Note that the lp argument must be the C type long. The amount of
data encoded to the XDR stream is only 4 bytes (not the full 8
bytes of data represented by the C long type). This is because
a long type is considered to be 4 bytes in the context of XDR
streams. When data is encoded from the XDR stream, 4 bytes will
be received from the XDR stream; the xdr_long() interface then
sign extends the high-order 4 bytes of the C long type.
Prior to serializing the data on the ENCODE side, xdr_long()
performs a validity check to ensure that the value represents a
valid 32-bit signed number. This involves determining that the
signed value is no less than the most negative 32-bit signed
quantity (which is the hexadecimal value 0x80000000) and no
greater than the most positive 32-bit signed quantity (which is
the hexadecimal value 0x7fffffff). If the value pointed to by
the lp argument is not within this range, the xdr_long() inter‐
face returns an error.
To translate the full 8 bytes of a C long, use the xdr_hyper()
interface.
See the next section for an explanation of the differences
between xdr_long() and xdr_hyper(). A filter primitive that
translates between C long integers and their external represen‐
tations. (The typedef longlong_t is defined as long in the
<rpc/types.h> file, which is included from the <rpc/xdr.h>
file.) This routine will translate all 8 bytes of data to the
XDR stream. Note that this differentiates this routine from
xdr_long() in that they both take a pointer to a long as an
argument, while xdr_long() only translates 4 bytes of data to
the XDR stream. This routine returns one (1) if it succeeds,
zero (0) otherwise.
The xdr_longlong_t() routine is functionally equivalent to the
xdr_hyper() routine.
See the next section for an explanation of the differences
between xdr_long() and xdr_hyper(). A filter primitive that
translates between fixed size opaque data and its external rep‐
resentation. The cp parameter is the address of the opaque
object, and cnt is its size in bytes. This routine returns one
(1) if it succeeds, zero (0) otherwise. Used for describing
parameters to various portmap procedures, externally. This rou‐
tine is useful for users who wish to generate these parameters
without using the pmap interface. Used for describing a list of
port mappings, externally. This routine is useful for users who
wish to generate these parameters without using the pmap inter‐
face. 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. A primitive that provides pointer chasing within
structures. The pp parameter is the address of the pointer; size
is the sizeof of 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 (1) if
it succeeds, zero (0) otherwise.
Warning: This routine does not understand NULL pointers. Use
xdr_pointer() instead. A macro that invokes the set position
routine associated with the XDR stream, xdrs. The pos parameter
is a position value obtained from xdr_getpos(). This routine
returns one (1) if the XDR stream could be repositioned, and
zero (0) 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. A filter primitive that translates
between C short integers and their external representations.
This routine returns one (1) if it succeeds, zero (0) otherwise.
A filter primitive that translates between C strings and their
corresponding external representations. Strings cannot be
longer than maxsize. The sp parameter is the address of the
string's pointer. While encoding, if sp is NULL, an error is
returned. While decoding, if *sp is NULL, the necessary storage
is allocated to hold this null-terminated string and *sp is set
to point to this. This storage can be freed by using xdr_free().
This routine returns one (1) if it succeeds, zero (0) otherwise.
A filter primitive that translates between unsigned C characters
and their external representations. This routine returns one
(1) if it succeeds, zero (0) otherwise. A filter primitive that
translates between C unsigned long integers and their external
representations. (The typedef u_longlong_t is defined as
unsigned long in the <rpc/types.h> file, which is included from
the <rpc/xdr.h> file.) This routine will translate all 8 bytes
of data to the XDR stream. Note that this differentiates this
routine from xdr_u_long() in that they both take a pointer to an
unsigned long as an argument, while xdr_u_long() only translates
4 bytes of data to the XDR stream. This routine returns one (1)
if it succeeds, zero (0) otherwise.
The xdr_u_hyper() routine is functionally equivalent to the
xdr_u_longlong_t() routine.
See the next section for an explanation of the differences
between xdr_long() and xdr_hyper(). A filter primitive that
translates between C unsigned integers and their external repre‐
sentations. This routine returns one (1) if it succeeds, zero
(0) otherwise. A filter primitive that translates between C
unsigned long integers and their external representations. This
routine returns one (1) if it succeeds, zero (0) otherwise.
Prior to serializing the data on the ENCODE side, xdr_u_long()
performs a validity check to insure that the value represents a
valid 32-bit unsigned number. This involves determining that the
unsigned value is no greater than the largest 32-bit unsigned
quantity (which is the hexadecimal value 0xffffffff). If the
value pointed to by the ulp argument is not within this range,
the xdr_u_long() interface returns an error.
For DECODE operations, the 32-bit unsigned value is sign
extended into the 64-bit unsigned long referred to by the ulp
argument.
Note that this routine actually translates 4 bytes of the data
to or from the XDR stream. Refer to the description of
xdr_long() for a more detailed explanation. A filter primitive
that translates between C unsigned long integers and their
external representations. (The typedef u_longlong_t is defined
as unsigned long in the <rpc/types.h> file, which is included
from the <rpc/xdr.h> file.) This routine will translate all 8
bytes of data to the XDR stream. Note that this differentiates
this routine from xdr_u_long() in that they both take a pointer
to an unsigned long as an argument, while xdr_u_long() only
translates 4 bytes of data to the XDR stream. This routine
returns one (1) if it succeeds, zero (0) otherwise.
The xdr_u_longlong routine is functionally equivalent to the
xdr_u_hyper() routine.
See the next section for an explanation of the differences
between xdr_long() and xdr_hyper(). A filter primitive that
translates between C unsigned short integers and their external
representations. This routine returns one (1) if it succeeds,
zero (0) otherwise. A filter primitive that translates between
a discriminated C union and its corresponding external represen‐
tation. 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 choices parameter is
a pointer to an array of xdr_discrim structures. Each structure
contains an ordered pair of [value,proc]. If the union's dis‐
criminant is equal to any of the values, the associated proc is
called to translate the union. The end of the xdr_discrim struc‐
ture array is denoted by a NULL pointer. If the discriminant is
not found in the choices array, then the defaultarm procedure is
called (if it is not NULL). Returns one (1) if it succeeds, zero
(0) otherwise. A filter primitive that translates between
fixed-length arrays and their corresponding external representa‐
tions. The arrp parameter is the address of the array, while
size is the element count of the array. The elsize parameter is
the sizeof of 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 (1) if
it succeeds, zero (0) otherwise. This routine always returns
one (1). It may be passed to RPC routines that require a func‐
tion parameter, but where nothing is to be done. A primitive
that calls xdr_string(xdrs,sp,MAXUNSIGNED); where MAXUNSIGNED is
the maximum value of an unsigned integer. The xdr_wrapstring()
primitive is handy because the RPC package passes a maximum of
two XDR routines as parameters, and xdr_string(), one of the
most frequently used primitives, requires three. The sp parame‐
ter is the address of the pointer to the string. While decoding,
if sp is NULL, the necessary storage is allocated to hold the
null-terminated string and sp is set to point to this. This
storage can be freed by using xdr_free(). Returns one (1) if it
succeeds, zero (0) otherwise. 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). 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 (0) 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 (0) 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() and write(), except that han‐
dle is passed to the former routines as the first parameter.
The XDR stream's op field must be set by the caller. The send‐
size and recvsize parameters should be multiples of 4.
Warning: This XDR stream implements an intermediate record
stream. Therefore there are additional bytes in the stream to
provide record boundary information. 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 out‐
put buffer is optionally written out if sendnow is nonzero. This
routine returns one (1) if it succeeds, zero (0) otherwise.
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 (1) if the stream has no
more input, zero (0) otherwise. 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 (1) if it succeeds, zero (0) otherwise. This routine ini‐
tializes the XDR stream object pointed to by xdrs. The XDR
stream data is written to, or read from, the Standard I/O stream
file. The op parameter 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() on the file stream, but never fclose().
Differences Between xdr_long and xdr_hyper Routines
On Tru64 UNIX platforms, the C programming language and the XDR rou‐
tines apply different conventions to the definitions of the long data
type.
On Tru64 UNIX platforms, the C programming language applies the follow‐
ing conventions for int and long data types:
───────────────────────────
Data Type bits bytes
───────────────────────────
int 32 4 bytes
long 64 8 bytes
───────────────────────────
The XDR routines apply the following conventions:
───────────────────────────
Data Type bits bytes
───────────────────────────
int 32 4 bytes
long 32 4 bytes
hyper 64 8 bytes
───────────────────────────
The xdr_long() and xdr_u_long() interfaces serialize 4 bytes of data.
The xdr_hyper() and xdr_u_hyper() interfaces serialize 8 bytes of data.
On Tru64 UNIX systems, the second argument to both xdr_long() and
xdr_hyper() must be either a pointer or of the C language type long (8
bytes). When xdr_hyper() is called with a parameter that points to a
long, all 8 bytes are serialized. In contrast, when xdr_long() is
called with a parameter that points to a long, only the low-order 4
bytes are serialized.
When calling xdr_long() on the DECODE operation, the upper 4 bytes of
the long are sign extended in accordance with the high-order bit of the
lower 4-byte quantity. This is necessary to maintain the XDR conven‐
tion of xdr_long() serializing 4 bytes.
If you want all 8 bytes to be serialized, use the xdr_hyper() inter‐
face.
The xdr_longlong_t() and xdr_u_longlong_t() interfaces perform the same
function as the xdr_hyper() and the xdr_u_hyper() interfaces, respec‐
tively.
SEE ALSO
Routines: rpc(3), rpc_clnt(3), rpc_misc(3), rpc_svc(3), rpc_xdr(3)xdr(3)
