XDR_ARRAY(3) | Library Functions Manual | XDR_ARRAY(3)

# NAME

`xdr_array`, `xdr_bool`, `xdr_bytes`, `xdr_char`, `xdr_destroy`, `xdr_double`, `xdr_enum`, `xdr_float`, `xdr_free`, `xdr_getpos`, `xdr_inline`, `xdr_int`, `xdr_long`, `xdr_int64_t`, `xdrmem_create`, `xdr_opaque`, `xdr_pointer`, `xdrrec_create`, `xdrrec_endofrecord`, `xdrrec_eof`, `xdrrec_skiprecord`, `xdr_reference`, `xdr_setpos`, `xdr_short`, `xdrstdio_create`, `xdr_string`, `xdr_u_char`, `xdr_u_int`, `xdr_u_long`, `xdr_u_int64_t`, `xdr_u_short`, `xdr_union`, `xdr_vector`, `xdr_void`, `xdr_wrapstring` — library routines for external data representation

# SYNOPSIS

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

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

int
`xdr_bool`(XDR *xdrs, bool_t *bp);

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

int
`xdr_char`(XDR *xdrs, char *cp);

void
`xdr_destroy`(XDR *xdrs);

int
`xdr_double`(XDR *xdrs, double *dp);

int
`xdr_enum`(XDR *xdrs, enum_t *ep);

int
`xdr_float`(XDR *xdrs, float *fp);

void
`xdr_free`(xdrproc_t proc, char *objp);

u_int
`xdr_getpos`(XDR *xdrs);

long *
`xdr_inline`(XDR *xdrs, int len);

int
`xdr_int`(XDR *xdrs, int *ip);

int
`xdr_long`(XDR *xdrs, long *lp);

int
`xdr_int64_t`(XDR *xdrs, int64_t *lp);

void
`xdrmem_create`(XDR *xdrs, char *addr, u_int size, enum xdr_op op);

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

int
`xdr_pointer`(XDR *xdrs, char **objpp, u_int objsize, xdrproc_t xdrobj);

void
`xdrrec_create`(XDR *xdrs, u_int sendsize, u_int recvsize, char *handle, int (*readit)(), int (*writeit)());

int
`xdrrec_endofrecord`(XDR *xdrs, int sendnow);

int
`xdrrec_eof`(XDR *xdrs);

int
`xdrrec_skiprecord`(XDR *xdrs);

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

int
`xdr_setpos`(XDR *xdrs, u_int pos);

int
`xdr_short`(XDR *xdrs, short *sp);

void
`xdrstdio_create`(XDR *xdrs, FILE *file, enum xdr_op op);

int
`xdr_string`(XDR *xdrs, char **sp, u_int maxsize);

int
`xdr_u_char`(XDR *xdrs, unsigned char *ucp);

int
`xdr_u_int`(XDR *xdrs, unsigned int *up);

int
`xdr_u_long`(XDR *xdrs, unsigned long *ulp);

int
`xdr_u_int64_t`(XDR *xdrs, u_int64_t *ullp);

int
`xdr_u_short`(XDR *xdrs, unsigned short *usp);

int
`xdr_union`(XDR *xdrs, int *dscmp, char *unp, struct xdr_discrim *choices, bool_t (*defaultarm)());

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

int
`xdr_void`(void);

int
`xdr_wrapstring`(XDR *xdrs, char **sp);

# DESCRIPTION

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.

`xdr_array`() is a filter primitive that translates between variable-length arrays and their corresponding external representations. The parameter 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 parameter elsize is the size 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 if it succeeds, zero otherwise.

`xdr_bool`() is 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`() is a filter primitive that translates between counted byte strings and their external representations. The parameter 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`() is 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`().

`xdr_destroy`() is 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`() is 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`() is a filter primitive that translates between the C enum type (actually an integer) and its external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_float`() is a filter primitive that translates between the C float type and its external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_free`() is 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).

`xdr_getpos`() is 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_inline`() is 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`() is a filter primitive that translates between C integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_long`() is a filter primitive that translates between C long integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_int64_t`() is a filter primitive that translates between C int64_t integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdrmem_create`() is a routine which 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`).

`xdr_opaque`() is a filter primitive that translates between fixed size opaque data and its external representation. The parameter cp 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`() is 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.

`xdrrec_create`() is a routine which 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`() and `write`(), except that handle is passed to the former routines as the first parameter. 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.

`xdrrec_endofrecord`() is a routine which 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`() is a routine which 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`() is a routine which 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.

`xdr_reference`() is a primitive that provides pointer chasing within structures. The parameter pp is the address of the pointer; size is the size 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 if it succeeds, zero otherwise. Warning: this routine does not understand `NULL` pointers. Use `xdr_pointer`() instead.

`xdr_setpos`() is a macro that invokes the set position routine associated with the XDR stream xdrs. The parameter 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.

`xdr_short`() is a filter primitive that translates between C short integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdrstdio_create`() is a routine which 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 parameter 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`() on the file stream, but never `fclose`().

`xdr_string`() is 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`() is a filter primitive that translates between unsigned C characters and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_u_int`() is a filter primitive that translates between C unsigned integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_u_long`() is a filter primitive that translates between C unsigned long integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_u_int64_t`() is a filter primitive that translates between C u_int64_t integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_u_short`() is a filter primitive that translates between C unsigned short integers and their external representations. This routine returns one if it succeeds, zero otherwise.

`xdr_union`() is 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 parameter choices is a pointer to an array of struct xdr_discrim structures, containing the two members value and 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 struct 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.

`xdr_vector`() is a filter primitive that translates between fixed-length arrays and their corresponding external representations. The parameter arrp is the address of the pointer to the array, while size is the element count of the array. The parameter elsize is the size 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 if it succeeds, zero otherwise.

`xdr_void`() is a routine which always returns one. It may be passed to RPC routines that require a function parameter, but where nothing is to be done.

`xdr_wrapstring`() is 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 parameters, and `xdr_string`(), one of the most frequently used primitives, requires three. Returns one if it succeeds, zero otherwise.

# SEE ALSO

rpc(3)

eXternal Data Representation Standard: Protocol Specification.

eXternal Data Representation: Sun Technical Notes.

# STANDARDS

XDR: External Data Representation Standard, RFC 1014, Sun Microsystems, Inc., June 1987.

September 11, 2022 | Debian