1XDR(3) Linux Programmer's Manual XDR(3)
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6 xdr - library routines for external data representation
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9 These routines allow C programmers to describe arbitrary data struc‐
10 tures in a machine-independent fashion. Data for remote procedure
11 calls are transmitted using these routines.
12 The prototypes below are declared in <rpc/xdr.h> and make use of the
14 following types:
15 typedef int bool_t;
17 typedef bool_t (*xdrproc_t) (XDR *, void *,...);
19 For the declaration of the XDR type, see <rpc/xdr.h>.
21 bool_t xdr_array(XDR *xdrs, char **arrp, unsigned int *sizep,
23 unsigned int maxsize, unsigned int elsize,
24 xdrproc_t elproc);
25 A filter primitive that translates between variable-length
27 arrays and their corresponding external representations. The
28 argument arrp is the address of the pointer to the array, while
29 sizep is the address of the element count of the array; this
30 element count cannot exceed maxsize. The argument elsize is the
31 sizeof each of the array's elements, and elproc is an XDR filter
32 that translates between the array elements' C form, and their
33 external representation. This routine returns one if it suc‐
34 ceeds, zero otherwise.
35 bool_t xdr_bool(XDR *xdrs, bool_t *bp);
37 A filter primitive that translates between booleans (C integers)
39 and their external representations. When encoding data, this
40 filter produces values of either one or zero. This routine
41 returns one if it succeeds, zero otherwise.
42 bool_t xdr_bytes(XDR *xdrs, char **sp, unsigned int *sizep,
44 unsigned int maxsize);
45 A filter primitive that translates between counted byte strings
47 and their external representations. The argument sp is the
48 address of the string pointer. The length of the string is
49 located at address sizep; strings cannot be longer than maxsize.
50 This routine returns one if it succeeds, zero otherwise.
51 bool_t xdr_char(XDR *xdrs, char *cp);
53 A filter primitive that translates between C characters and
55 their external representations. This routine returns one if it
56 succeeds, zero otherwise. Note: encoded characters are not
57 packed, and occupy 4 bytes each. For arrays of characters, it
58 is worthwhile to consider xdr_bytes(), xdr_opaque() or
59 xdr_string().
60 void xdr_destroy(XDR *xdrs);
62 A macro that invokes the destroy routine associated with the XDR
64 stream, xdrs. Destruction usually involves freeing private data
65 structures associated with the stream. Using xdrs after invok‐
66 ing xdr_destroy() is undefined.
67 bool_t xdr_double(XDR *xdrs, double *dp);
69 A filter primitive that translates between C double precision
71 numbers and their external representations. This routine
72 returns one if it succeeds, zero otherwise.
73 bool_t xdr_enum(XDR *xdrs, enum_t *ep);
75 A filter primitive that translates between C enums (actually
77 integers) and their external representations. This routine
78 returns one if it succeeds, zero otherwise.
79 bool_t xdr_float(XDR *xdrs, float *fp);
81 A filter primitive that translates between C floats and their
83 external representations. This routine returns one if it suc‐
84 ceeds, zero otherwise.
85 void xdr_free(xdrproc_t proc, char *objp);
87 Generic freeing routine. The first argument is the XDR routine
89 for the object being freed. The second argument is a pointer to
90 the object itself. Note: the pointer passed to this routine is
91 not freed, but what it points to is freed (recursively).
92 unsigned int xdr_getpos(XDR *xdrs);
94 A macro that invokes the get-position routine associated with
96 the XDR stream, xdrs. The routine returns an unsigned integer,
97 which indicates the position of the XDR byte stream. A desir‐
98 able feature of XDR streams is that simple arithmetic works with
99 this number, although the XDR stream instances need not guaran‐
100 tee this.
101 long *xdr_inline(XDR *xdrs, int len);
103 A macro that invokes the inline routine associated with the XDR
105 stream, xdrs. The routine returns a pointer to a contiguous
106 piece of the stream's buffer; len is the byte length of the
107 desired buffer. Note: pointer is cast to long *.
108 Warning: xdr_inline() may return NULL (0) if it cannot allocate
110 a contiguous piece of a buffer. Therefore the behavior may vary
111 among stream instances; it exists for the sake of efficiency.
112 bool_t xdr_int(XDR *xdrs, int *ip);
114 A filter primitive that translates between C integers and their
116 external representations. This routine returns one if it suc‐
117 ceeds, zero otherwise.
118 bool_t xdr_long(XDR *xdrs, long *lp);