.\" $OpenBSD: xdr.3,v 1.7 1998/03/11 18:54:17 deraadt Exp $ .\" Mostly converted to mandoc by Theo de Raadt, Tue Feb 24 04:04:46 MST 1998 .\" .Dd February 16, 1988 .Dt XDR 3 .Os .Sh NAME .Nm xdr_array , .Nm xdr_bool , .Nm xdr_bytes , .Nm xdr_char , .Nm xdr_destroy , .Nm xdr_double , .Nm xdr_enum , .Nm xdr_float , .Nm xdr_free , .Nm xdr_getpos , .Nm xdr_inline , .Nm xdr_int , .Nm xdr_long , .Nm xdrmem_create , .Nm xdr_opaque , .Nm xdr_pointer , .Nm xdrrec_create , .Nm xdrrec_endofrecord , .Nm xdrrec_eof , .Nm xdrrec_skiprecord , .Nm xdr_reference , .Nm xdr_setpos , .Nm xdr_short , .Nm xdrstdio_create , .Nm xdr_string , .Nm xdr_u_char , .Nm xdr_u_int , .Nm xdr_u_long , .Nm xdr_u_short , .Nm xdr_union , .Nm xdr_vector , .Nm xdr_void , .Nm xdr_wrapstring .Nd library routines for external data representation .Sh SYNOPSIS .Fd #include .Fd #include .Ft int .Fn xdr_array "XDR *xdrs" "char **arrp" "u_int *sizep" "u_int maxsize" "u_int elsize" "xdrproc_t elproc" .Ft int .Fn xdr_bool "XDR *xdrs" "bool_t *bp" .Ft int .Fn xdr_bytes "XDR *xdrs" "char **sp" "u_int *sizep" "u_int maxsize" .Ft int .Fn xdr_char "XDR *xdrs" "char *cp" .Ft void .Fn xdr_destroy "XDR *xdrs" .Ft int .Fn xdr_double "XDR *xdrs" "double *dp" .Ft int .Fn xdr_enum "XDR *xdrs" "enum_t *ep" .Ft int .Fn xdr_float "XDR *xdrs" "float *fp" .Ft void .Fn xdr_free "xdrproc_t proc" "char *objp" .Ft u_int .Fn xdr_getpos "XDR *xdrs" .Ft long * .Fn xdr_inline "XDR *xdrs" "int len" .Ft int .Fn xdr_int "XDR *xdrs" "int *ip" .Ft int .Fn xdr_long "XDR *xdrs" "long *lp" .Ft void .Fn xdrmem_create "XDR *xdrs" "char *addr" "u_int size" "enum xdr_op op" .Ft int .Fn xdr_opaque "XDR *xdrs" "char *cp" "u_int cnt" .Ft int .Fn xdr_pointer "XDR *xdrs" "char **objpp" "u_int objsize" "xdrproc_t xdrobj" .Ft void .Fn xdrrec_create "XDR *xdrs" "u_int sendsize" "u_int recvsize" "char *handle" "int (*readit)()" "int (*writeit)()" .Ft int .Fn xdrrec_endofrecord "XDR *xdrs" "int sendnow" .Ft int .Fn xdrrec_eof "XDR *xdrs" "int empty" .Ft int .Fn xdrrec_skiprecord "XDR *xdrs" .Ft int .Fn xdr_reference "XDR *xdrs" "char **pp" "u_int size" "xdrproc_t proc" .Ft int .Fn xdr_setpos "XDR *xdrs" "u_int pos" .Ft int .Fn xdr_short "XDR *xdrs" "short *sp" .Ft void .Fn xdrstdio_create "XDR *xdrs" "FILE *file" "enum xdr_op op" .Ft int .Fn xdr_string "XDR *xdrs" "char **sp" "u_int maxsize" .Ft int .Fn xdr_u_char "XDR *xdrs" "unsigned char *ucp" .Ft int .Fn xdr_u_int "XDR *xdrs" "unsigned int *up" .Ft int .Fn xdr_u_long "XDR *xdrs" "unsigned long *ulp" .Ft int .Fn xdr_u_short "XDR *xdrs" "unsigned short *usp" .Ft int .Fn xdr_union "XDR *xdrs" "int *dscmp" "char *unp" "struct xdr_discrim *choices" "bool_t (*defaultarm)()" .Ft int .Fn xdr_vector "XDR *xdrs" "char *arrp" "u_int size" "u_int elsize" "xdrproc_t elproc" .Ft int .Fn xdr_void "void" .Ft int .Fn xdr_wrapstring "XDR *xdrs" "char **sp" .Sh 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. .Pp .Fn xdr_array is a filter primitive that translates between variable-length arrays and their corresponding external representations. The parameter .Fa arrp is the address of the pointer to the array, while .Fa sizep is the address of the element count of the array; this element count cannot exceed .Fa maxsize . The parameter .Fa elsize is the size of each of the array's elements, and .Fa elproc is an .Tn XDR filter that translates between the array elements' C form, and their external representation. This routine returns one if it succeeds, zero otherwise. .Pp .Fn 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. .Pp .Fn xdr_bytes is a filter primitive that translates between counted byte strings and their external representations. The parameter .Fa sp is the address of the string pointer. The length of the string is located at address .Fa sizep ; strings cannot be longer than .Fa maxsize . This routine returns one if it succeeds, zero otherwise. .Pp .Fn 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 .Fn xdr_bytes , .Fn xdr_opaque , or .Fn xdr_string . .Pp .Fn xdr_destroy is a macro that invokes the destroy routine associated with the .Tn XDR stream .Fa xdrs . Destruction usually involves freeing private data structures associated with the stream. Using .Fa xdrs after invoking .Fn xdr_destroy is undefined. .Pp .Fn xdr_double is a filter primitive that translates between C .Ft double precision numbers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_enum is a filter primitive that translates between the C .Ft enum type (actually an integer) and its external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_float is a filter primitive that translates between the C .Ft float type and its external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_free is a generic freeing routine. The first argument is the .Tn 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 .Fa not freed, but what it points to is freed (recursively). .Pp .Fn xdr_getpos is a macro that invokes the get-position routine associated with the .Tn XDR stream .Fa xdrs . The routine returns an unsigned integer, which indicates the position of the .Tn XDR byte stream. A desirable feature of .Tn XDR streams is that simple arithmetic works with this number, although the .Tn XDR stream instances need not guarantee this. .Pp .Fn xdr_inline is a macro that invokes the in-line routine associated with the .Tn XDR stream .Fa xdrs . The routine returns a pointer to a contiguous piece of the stream's buffer; .Fa len is the byte length of the desired buffer. Note: pointer is cast to .Ft "long *" . Warning: .Fn xdr_inline may return .Tn 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. .Pp .Fn xdr_int is a filter primitive that translates between C integers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_long is a filter primitive that translates between C .Ft long integers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdrmem_create is a routine which initializes the .Tn XDR stream object pointed to by .Fa xdrs . The stream's data is written to, or read from, a chunk of memory at location .Fa addr whose length is no more than .Fa size bytes long. The .Fa op determines the direction of the .Tn XDR stream (either .Tn XDR_ENCODE , .Tn XDR_DECODE , or .Tn XDR_FREE Ns ). .Pp .Fn xdr_opaque is a filter primitive that translates between fixed size opaque data and its external representation. The parameter .Fa cp is the address of the opaque object, and .Fa cnt is its size in bytes. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_pointer is like .Fn xdr_reference execpt that it serializes .Tn NULL pointers, whereas .Fn xdr_reference does not. Thus, .Fn xdr_pointer can represent recursive data structures, such as binary trees or linked lists. .Pp .Fn xdrrec_create is a routine which initializes the .Tn XDR stream object pointed to by .Fa xdrs . The stream's data is written to a buffer of size .Fa sendsize ; a value of zero indicates the system should use a suitable default. The stream's data is read from a buffer of size .Fa recvsize ; it too can be set to a suitable default by passing a zero value. When a stream's output buffer is full, .Fn (*writeit) is called. Similarly, when a stream's input buffer is empty, .Fn (*readit) is called. The behavior of these two routines is similar to the system calls .Fn read and .Fn write , except that .Fa handle is passed to the former routines as the first parameter. Note: the .Tn XDR stream's .Fa op field must be set by the caller. Warning: this .Tn XDR stream implements an intermediate record stream. Therefore there are additional bytes in the stream to provide record boundary information. .Pp .Fn xdrrec_endofrecord is a routine which can be invoked only on streams created by .Fn xdrrec_create . The data in the output buffer is marked as a completed record, and the output buffer is optionally written out if .Fa sendnow is non-zero. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdrrec_eof is a routine which can be invoked only on streams created by .Fn 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. .Pp .Fn xdrrec_skiprecord is a routine which can be invoked only on streams created by .Fn xdrrec_create . It tells the .Tn 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. .Pp .Fn xdr_reference is a primitive that provides pointer chasing within structures. The parameter .Fa pp is the address of the pointer; .Fa size is the size of the structure that .Fa *pp points to; and .Fa proc is an .Tn 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 .Tn NULL pointers. Use .Fn xdr_pointer instead. .Pp .Fn xdr_setpos is a macro that invokes the set position routine associated with the .Tn XDR stream .Fa xdrs . The parameter .Fa pos is a position value obtained from .Fn xdr_getpos . This routine returns one if the .Tn XDR stream could be repositioned, and zero otherwise. Warning: it is difficult to reposition some types of .Tn XDR streams, so this routine may fail with one type of stream and succeed with another. .Pp .Fn xdr_short is a filter primitive that translates between C .Ft short integers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdrstdio_create is a routine which initializes the .Tn XDR stream object pointed to by .Fa xdrs . The .Tn XDR stream data is written to, or read from, the Standard I/O stream .Fa file . The parameter .Fa op determines the direction of the .Tn XDR stream (either .Tn XDR_ENCODE , .Tn XDR_DECODE , or .Tn XDR_FREE Ns ). Warning: the destroy routine associated with such .Tn XDR streams calls .Fn fflush on the .Fa file stream, but never .Fn fclose . .Pp .Fn xdr_string is a filter primitive that translates between C strings and their corresponding external representations. Strings cannot be longer than .Fa maxsize . Note: .Fa sp is the address of the string's pointer. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_u_char is a filter primitive that translates between .Ft unsigned C characters and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_u_int is a filter primitive that translates between C .Ft unsigned integers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_u_long is a filter primitive that translates between C .Ft "unsigned long" integers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_u_short is a filter primitive that translates between C .Ft "unsigned short" integers and their external representations. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_union is a filter primitive that translates between a discriminated C .Ft union and its corresponding external representation. It first translates the discriminant of the union located at .Fa dscmp . This discriminant is always an .Ft enum_t . Next the union located at .Fa unp is translated. The parameter .Fa choices is a pointer to an array of .Ft struct xdr_discrim structures. Each structure contains an ordered pair of .Ft [ value , proc ]. If the union's discriminant is equal to the associated .Fa value , then the .Fa proc is called to translate the union. The end of the .Fa struct xdr_discrim structure array is denoted by a routine of value .Tn NULL. If the discriminant is not found in the .Fa choices array, then the .Fn (*defaultarm) procedure is called (if it is not .Tn NULL Ns ). Returns one if it succeeds, zero otherwise. .Pp .Fn xdr_vector is a filter primitive that translates between fixed-length arrays and their corresponding external representations. The parameter .Fa arrp is the address of the pointer to the array, while .Fa size is is the element count of the array. The parameter .Fa elsize is the size of each of the array's elements, and .Fa elproc is an .Tn XDR filter that translates between the array elements' C form, and their external representation. This routine returns one if it succeeds, zero otherwise. .Pp .Fn xdr_void is a routine which always returns one. It may be passed to .Tn RPC routines that require a function parameter, but where nothing is to be done. .Pp .Fn xdr_wrapstring is a primitive that calls .Pa "xdr_string(xdrs, sp, MAXUN.UNSIGNED );" where .Tn MAXUN.UNSIGNED is the maximum value of an unsigned integer. .Fn xdr_wrapstring is handy because the .Tn RPC package passes a maximum of two .Tn XDR routines as parameters, and .Fn xdr_string , one of the most frequently used primitives, requires three. Returns one if it succeeds, zero otherwise. .Sh SEE ALSO .Xr rpc 3 . .Pp The following manuals: .RS .ft I eXternal Data Representation Standard: Protocol Specification .br eXternal Data Representation: Sun Technical Notes .ft R .br .Tn "XDR: External Data Representation Standard" , .Tn RFC1014, Sun Microsystems, Inc., .Tn USC-ISI.