XDR(3)

📦

version 15.1 · 2 versions

15.1 · freebsd 15.1 (latest)
14.5 · freebsd 14.5

💅 XDR(3) 💅

okay bestie, welcome to the XDR(3) page from the Library Functions Manual — part 1, and it's all about library routines for external data representation. basically C programmers describing arbitrary data structures in a machine-independent fashion, and remote procedure call data hitching a ride on these routines. 🫶

🌸 NAME 🌸

okay so the whole squad on this page is: xdr, xdr_array, xdr_bool, xdr_bytes, xdr_char, xdr_destroy, xdr_double, xdr_enum, xdr_float, xdr_free, xdr_getpos, xdr_hyper, xdr_inline, xdr_int, xdr_long, xdr_longlong_t, xdrmem_create, xdr_opaque, xdr_pointer, xdrrec_create, xdrrec_endofrecord, xdrrec_eof, xdrrec_skiprecord, xdr_reference, xdr_setpos, xdr_short, xdr_sizeof, xdrstdio_create, 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 — library routines for external data representation.

🧚 LIBRARY 🧚

Standard C Library (libc, -lc) — that's the home base, no cap. ✨

✨ SYNOPSIS ✨

#include <rpc/types.h>
#include <rpc/xdr.h>

See “DESCRIPTION” for function declarations. the actual declarations are all down there, iykyk.

💖 DESCRIPTION 💖

okay so these routines let C programmers describe arbitrary data structures in a machine-independent fashion. Data for remote procedure calls are transmitted using these routines — that's the vibe, bestie. 💫

🎀 `xdr_array`

int
xdr_array(XDR *xdrs, char **arrp, u_int *sizep, u_int maxsize,
        u_int elsize, xdrproc_t elproc)

A filter primitive that translates between variable-length arrays and their corresponding external representations. 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. 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. 🫶

🎀 `xdr_bool`

int
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. 🔥

🎀 `xdr_bytes`

int
xdr_bytes(XDR *xdrs, char **sp, u_int *sizep, u_int maxsize)

A filter primitive that translates between counted byte strings and their external representations. 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. ✨

🎀 `xdr_char`

int
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(). literally don't sleep on that, bestie. 😭

🎀 `xdr_destroy`

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. fr fr, undefined is not a vibe. 💀

🎀 `xdr_double`

int
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. 💅

🎀 `xdr_enum`

int
xdr_enum(XDR *xdrs, enum_t *ep)

A filter primitive that translates between C enums (actually integers) and their external representations. This routine returns one if it succeeds, zero otherwise. 👑

🎀 `xdr_float`

int
xdr_float(XDR *xdrs, float *fp)

A filter primitive that translates between C floats and their external representations. This routine returns one if it succeeds, zero otherwise. 🌸

🎀 `xdr_free`

void
xdr_free(xdrproc_t proc, void *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). read that twice, bestie. 🙈

🎀 `xdr_getpos`

u_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. lowkey iconic. ⭐

🎀 `xdr_hyper`

int
xdr_hyper(XDR *xdrs, quad_t *llp)

A filter primitive that translates between ANSI C long long integers and their external representations. This routine returns one if it succeeds, zero otherwise. 🦋

🎀 `xdr_inline`

long *
xdr_inline(XDR *xdrs, int len)

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 (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. efficiency ate, but NULL still said hi. 😭

🎀 `xdr_int`

int
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. 💜

🎀 `xdr_long`

int
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. 🌈

🎀 `xdr_longlong_t`

int
xdr_longlong_t(XDR *xdrs, quad_t *llp)

A filter primitive that translates between ANSI C long long integers and their external representations. This routine returns one if it succeeds, zero otherwise. 🍓

🎀 `xdrmem_create`

void
xdrmem_create(XDR *xdrs, char *addr, u_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 argument determines the direction of the XDR stream (either XDR_ENCODE, XDR_DECODE, or XDR_FREE). main character energy for memory streams. 👑

🎀 `xdr_opaque`

int
xdr_opaque(XDR *xdrs, char *cp, u_int cnt)

A filter primitive that translates between fixed size opaque data and its external representation. The cp argument is the address of the opaque object, and cnt is its size in bytes. This routine returns one if it succeeds, zero otherwise. 🎀

🎀 `xdr_pointer`

int
xdr_pointer(XDR *xdrs, char **objpp, u_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. it's giving pointer-chasing but with NULL representation, slay. 🌳

🎀 `xdrrec_create`

void
xdrrec_create(XDR *xdrs, u_int sendsize, u_int recvsize, void *handle,
        int (*readit)(), 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: this XDR stream implements an intermediate record stream. Therefore there are additional bytes in the stream to provide record boundary information. not extra bytes for no reason, bestie. 💀

🎀 `xdrrec_endofrecord`

int
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 non-zero. This routine returns one if it succeeds, zero otherwise. 🔥

🎀 `xdrrec_eof`

int
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. 🫶

🎀 `xdrrec_skiprecord`

int
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. bye leftover record, periodt. 💅

🎀 `xdr_reference`

int
xdr_reference(XDR *xdrs, char **pp, u_int size, xdrproc_t proc)

A primitive that provides pointer chasing within structures. The pp argument 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. okay so don't make it confront NULL, bestie. 🙈

🎀 `xdr_setpos`

int
xdr_setpos(XDR *xdrs, u_int pos)

A macro that invokes the set position routine associated with the XDR stream xdrs. The pos argument 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. vibe check varies by stream, ngl. 😭

🎀 `xdr_short`

int
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. 🌸

🎀 `xdr_sizeof`

unsigned long
xdr_sizeof(xdrproc_t func, void *data)

This routine returns the amount of memory required to encode data using filter func. it's giving "how much room do we need" realness. ✨

🎀 `xdrstdio_create`

#ifdef _STDIO_H_
/* XDR using stdio library */
void
xdrstdio_create(XDR *xdrs, FILE *file, enum xdr_op op)
#endif

Okay so 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 argument determines the direction of the XDR stream — either XDR_ENCODE, XDR_DECODE, or XDR_FREE. iconic little trio, no notes 💅

Warning: the destroy routine associated with such XDR streams calls fflush(3) on the file stream, but never fclose(3). bestie, please remember that — it's giving "cleanup but not that cleanup" 💀

💅 `xdr_string`

int
xdr_string(XDR *xdrs, char **sp, u_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. 🫶

🦋 `xdr_u_char`

int
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. tiny but fierce ✨

🎀 `xdr_u_hyper`

int
xdr_u_hyper(XDR *xdrs, u_quad_t *ullp)

A filter primitive that translates between unsigned ANSI C long long integers and their external representations. This routine returns one if it succeeds, zero otherwise. big number energy 🔥

🌸 `xdr_u_int`

int
xdr_u_int(XDR *xdrs, unsigned *up)

A filter primitive that translates between C unsigned integers and their external representations. This routine returns one if it succeeds, zero otherwise. classic, reliable, lowkey MVP 💖

🌈 `xdr_u_long`

int
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. long but make it unsigned 💚

⭐ `xdr_u_longlong_t`

int
xdr_u_longlong_t(XDR *xdrs, u_quad_t *ullp)

A filter primitive that translates between unsigned ANSI C long long integers and their external representations. This routine returns one if it succeeds, zero otherwise. the long long of it all 🌀

🍓 `xdr_u_short`

int
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. short king behavior 🍑

👑 `xdr_union`

int
xdr_union(XDR *xdrs, enum_t *dscmp, char *unp,
          const struct xdr_discrim *choices, xdrproc_t defaultarm)

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 argument 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. this one has main character energy fr fr 👑

🧚 `xdr_vector`

int
xdr_vector(XDR *xdrs, char *arrp, u_int size, u_int elsize,
           xdrproc_t elproc)

A filter primitive that translates between fixed-length arrays and their corresponding external representations. The arrp argument is the address of the pointer to the array, while size is the element count of the array. The elsize argument 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. fixed-length, fixed vibe, slay ✨

💜 `xdr_void`

int
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. does literally nothing and still ate 💅

🎀 `xdr_wrapstring`

int
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. The xdr_wrapstring() function 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. the little wrapper that could 🫶

🔍 SEE ALSO 🔍

rpc(3)
eXternal Data Representation Standard: Protocol Specification.
eXternal Data Representation: Sun Technical Notes.
XDR: External Data Representation Standard, Sun Microsystems, Inc., USC-ISI, RFC1014.

🌸 HISTORY 🌸

The xdr_sizeof function first appeared in FreeBSD 9.0. that's the whole history entry, bestie — short and iconic 💅

and that's the page! it's from Debian, dated February 16, 1988, and it lives under XDR(3) — periodt. 🎀

📦 where this page comes from

freebsd 15.1: base 15.1
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms

XDR(3)

💅 XDR(3) 💅

🌸 NAME 🌸

🧚 LIBRARY 🧚

✨ SYNOPSIS ✨

💖 DESCRIPTION 💖

🎀 xdr_array

🎀 xdr_bool

🎀 xdr_bytes

🎀 xdr_char

🎀 xdr_destroy

🎀 xdr_double

🎀 xdr_enum

🎀 xdr_float

🎀 xdr_free

🎀 xdr_getpos

🎀 xdr_hyper

🎀 xdr_inline

🎀 xdr_int

🎀 xdr_long

🎀 xdr_longlong_t

🎀 xdrmem_create

🎀 xdr_opaque

🎀 xdr_pointer

🎀 xdrrec_create

🎀 xdrrec_endofrecord

🎀 xdrrec_eof

🎀 xdrrec_skiprecord

🎀 xdr_reference

🎀 xdr_setpos

🎀 xdr_short

🎀 xdr_sizeof

🎀 xdrstdio_create

💅 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