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Annotation of 43BSDReno/lib/librpc/pmap_prot.c, revision 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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