xdr(3) Library Functions Manual 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_longlong_t, xdr_u_short, xdr_union, xdr_vector, xdr_void,
xdr_wrapstring, xdrmem_create, xdrrec_create, xdrrec_endofrecord, xdrrec_eof, xdrrec_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(xdrs, sp, sizep, maxsize) 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) ());
xdr_vector( XDR *xdrs, char *arrp, u_int size, u_int elsize, xdrproc_t elproc);
xdr_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) (), int (*writeit)
());
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 structures in a machine-independent fashion. Data for ONC remote procedure
calls are transmitted using these 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 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 fil-
ter primitive that translates between C characters and their external representations. This routine returns one (1) if it succeeds, zero
(0) 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(). 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 fil-
ter 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. 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). 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. A filter primitive that trans-
lates between C long integers and their external 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 differen-
tiates 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 following section that explains the differences between xdr_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 translates between C
long integers and their external representations. This routine returns one (1) if it succeeds, zero (0) otherwise.
Note that the lp argument must be the C language 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 in the context of XDR streams a long type is considered to be
4 bytes. 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 the 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 interface returns an error.
To translate the full 8 bytes of a C long, use the xdr_hyper interface.
See the following section that explains the differences between xdr_long and xdr_hyper. A filter primitive that translates between
C long integers and their external 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 differenti-
ates 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 following section that explains the differences between xdr_long and xdr_hyper. A filter primitive that translates between
fixed size opaque data and its external representation. 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 pro-
cedures, externally. This routine 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 interface. 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 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 rep-
resentations. 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 rou-
tine 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 following section that explains the differences between xdr_long and xdr_hyper. A filter primitive that translates between
C unsigned integers 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. This routine returns one (1) if it
succeeds, zero (0) otherwise.
Prior to serializing the data on the ENCODE side the 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 representa-
tions. (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 following section that explains 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 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 trans-
lated. 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 discriminant is equal to any of the values, the associated proc is called to translate the union. The
end of the xdr_discrim() structure 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 representations. The arrp parameter is the address of
the array, while size is the element count of the array. The elsize parameter 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 (1) if it succeeds, zero (0) otherwise. This routine always returns one (1). It may be passed to RPC routines that require a
function parameter, 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 parameter 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 handle is passed to the former routines as the first parame-
ter. The XDR stream's op field must be set by the caller. The sendsize 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 output buffer is optionally written out if sendnow is non-zero. This routine returns one
(1) if it succeeds, zero (0) otherwise. 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 (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 cur-
rent record in the stream's input buffer should be discarded. This routine returns one (1) if it succeeds, zero (0) otherwise.
This routine initializes 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 routines apply different conventions to the definitions of the long data
type.
On Tru64 UNIX platforms, the C programming language applies the following 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() 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 convention of xdr_long serializing 4-bytes.
If you want all 8-bytes to be serialized, use the xdr_hyper interface.
The xdr_longlong_t and the xdr_u_longlong_t perform the same function as the xdr_hyper and the xdr_u_hyper interfaces respectively.
RELATED INFORMATION
Routines: rpc(3), rpc_clnt(3), rpc_misc(3), rpc_svc(3), rpc_xdr(3) delim off
xdr(3)