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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(
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 structures in
a machine-independent fashion. Data for ONC remote procedure calls are
transmitted using the following routines:
xdr_array
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.
xdr_bool
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.
xdr_bytes
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.
xdr_char
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 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
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.
xdr_double
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.
xdr_enum
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.
xdr_float
A filter primitive that translates between C floats and their external
representations. This routine returns one (1) if it succeeds, zero (0)
otherwise.
void xdr_free
A 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).
u_int xdr_getpos
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.
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 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().
xdr_inline
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.
xdr_int
A filter primitive that translates between C integers and their
external representations. This routine returns one (1) if it succeeds,
zero (0) otherwise.
xdr_long
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 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() interface 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().
xdr_longlong_t
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 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().
xdr_opaque
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.
xdr_pmap
Used for describing parameters to various portmap procedures,
externally. This routine is useful for users who wish to generate these
parameters without using the pmap interface.
xdr_pmaplist
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.
xdr_pointer
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.
xdr_reference
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.
xdr_setpos
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.
xdr_short
A filter primitive that translates between C short integers and their
external representations. This routine returns one (1) if it succeeds,
zero (0) otherwise.
xdr_string
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.
xdr_u_char
A filter primitive that translates between unsigned C characters and
their external representations. This routine returns one (1) if it
succeeds, zero (0) otherwise.
xdr_u_hyper
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().
xdr_u_int
A filter primitive that translates between C unsigned integers and
their external representations. This routine returns one (1) if it
succeeds, zero (0) otherwise.
xdr_u_long
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.
xdr_u_longlong_t
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().
xdr_u_short
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.
xdr_union
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 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.
xdr_vector
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 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.
xdr_void
This routine always returns one (1). It may be passed to RPC routines
that require a function parameter, but where nothing is to be done.
xdr_wrapstring
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.
void xdrmem_create
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).
void xdrrec_create
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 parameter. 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.
xdrrec_endofrecord
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 (1) if it succeeds, zero (0) otherwise.
xdrrec_eof
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.
xdrrec_skiprecord
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.
void xdrstdio_create
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() 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 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 xdr_u_longlong_t() interfaces perform the same
function as the xdr_hyper() and the xdr_u_hyper() interfaces, respectively.
SEE ALSO
Routines: rpc(3), rpc_clnt(3), rpc_misc(3), rpc_svc(3), rpc_xdr(3)
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