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Annotation of 43BSD/contrib/sunrpc/pmap_prot.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
                      3:  * unrestricted use provided that this legend is included on all tape
                      4:  * media and as a part of the software program in whole or part.  Users
                      5:  * may copy or modify Sun RPC without charge, but are not authorized
                      6:  * to license or distribute it to anyone else except as part of a product or
                      7:  * program developed by the user.
                      8:  * 
                      9:  * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
                     10:  * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
                     11:  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
                     12:  * 
                     13:  * Sun RPC is provided with no support and without any obligation on the
                     14:  * part of Sun Microsystems, Inc. to assist in its use, correction,
                     15:  * modification or enhancement.
                     16:  * 
                     17:  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
                     18:  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
                     19:  * OR ANY PART THEREOF.
                     20:  * 
                     21:  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
                     22:  * or profits or other special, indirect and consequential damages, even if
                     23:  * Sun has been advised of the possibility of such damages.
                     24:  * 
                     25:  * Sun Microsystems, Inc.
                     26:  * 2550 Garcia Avenue
                     27:  * Mountain View, California  94043
                     28:  */
                     29: #ifndef lint
                     30: static char sccsid[] = "@(#)pmap_prot.c 1.2 85/02/08 Copyr 1984 Sun Micro";
                     31: #endif
                     32: 
                     33: /*
                     34:  * pmap_prot.c
                     35:  * Protocol for the local binder service, or pmap.
                     36:  *
                     37:  * Copyright (C) 1984, Sun Microsystems, Inc.
                     38:  */
                     39: 
                     40: #include "types.h"
                     41: #include "xdr.h"
                     42: #include "pmap_prot.h"
                     43: 
                     44: #define NULL ((struct pmaplist *)0)
                     45: 
                     46: bool_t
                     47: xdr_pmap(xdrs, regs)
                     48:        XDR *xdrs;
                     49:        struct pmap *regs;
                     50: {
                     51: 
                     52:        if (xdr_u_long(xdrs, &regs->pm_prog) && 
                     53:                xdr_u_long(xdrs, &regs->pm_vers) && 
                     54:                xdr_u_long(xdrs, &regs->pm_prot))
                     55:                return (xdr_u_long(xdrs, &regs->pm_port));
                     56:        return (FALSE);
                     57: }
                     58: 
                     59: /* 
                     60:  * What is going on with linked lists? (!)
                     61:  * First recall the link list declaration from pmap_prot.h:
                     62:  *
                     63:  * struct pmaplist {
                     64:  *     struct pmap pml_map;
                     65:  *     struct pmaplist *pml_map;
                     66:  * };
                     67:  *
                     68:  * Compare that declaration with a corresponding xdr declaration that 
                     69:  * is (a) pointer-less, and (b) recursive:
                     70:  *
                     71:  * typedef union switch (bool_t) {
                     72:  * 
                     73:  *     case TRUE: struct {
                     74:  *             struct pmap;
                     75:  *             pmaplist_t foo;
                     76:  *     };
                     77:  *
                     78:  *     case FALSE: struct {};
                     79:  * } pmaplist_t;
                     80:  *
                     81:  * Notice that the xdr declaration has no nxt pointer while
                     82:  * the C declaration has no bool_t variable.  The bool_t can be
                     83:  * interpreted as ``more data follows me''; if FALSE then nothing
                     84:  * follows this bool_t; if TRUE then the bool_t is followed by
                     85:  * an actual struct pmap, and then (recursively) by the 
                     86:  * xdr union, pamplist_t.  
                     87:  *
                     88:  * This could be implemented via the xdr_union primitive, though this
                     89:  * would cause a one recursive call per element in the list.  Rather than do
                     90:  * that we can ``unwind'' the recursion
                     91:  * into a while loop and do the union arms in-place.
                     92:  *
                     93:  * The head of the list is what the C programmer wishes to past around
                     94:  * the net, yet is the data that the pointer points to which is interesting;
                     95:  * this sounds like a job for xdr_reference!
                     96:  */
                     97: bool_t
                     98: xdr_pmaplist(xdrs, rp)
                     99:        register XDR *xdrs;
                    100:        register struct pmaplist **rp;
                    101: {
                    102:        /*
                    103:         * more_elements is pre-computed in case the direction is
                    104:         * XDR_ENCODE or XDR_FREE.  more_elements is overwritten by
                    105:         * xdr_bool when the direction is XDR_DECODE.
                    106:         */
                    107:        bool_t more_elements;
                    108:        register int freeing = (xdrs->x_op == XDR_FREE);
                    109:        register struct pmaplist **next;
                    110: 
                    111:        while (TRUE) {
                    112:                more_elements = (bool_t)(*rp != NULL);
                    113:                if (! xdr_bool(xdrs, &more_elements))
                    114:                        return (FALSE);
                    115:                if (! more_elements)
                    116:                        return (TRUE);  /* we are done */
                    117:                /*
                    118:                 * the unfortunate side effect of non-recursion is that in
                    119:                 * the case of freeing we must remember the next object
                    120:                 * before we free the current object ...
                    121:                 */
                    122:                if (freeing)
                    123:                        next = &((*rp)->pml_next); 
                    124:                if (! xdr_reference(xdrs, (caddr_t *)rp,
                    125:                    (u_int)sizeof(struct pmaplist), xdr_pmap))
                    126:                        return (FALSE);
                    127:                rp = (freeing) ? next : &((*rp)->pml_next);
                    128:        }
                    129: }

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