pmap_prot2.c 3.7 KB

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  1. /* @(#)pmap_prot2.c 2.1 88/07/29 4.0 RPCSRC */
  2. /*
  3. * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
  4. * unrestricted use provided that this legend is included on all tape
  5. * media and as a part of the software program in whole or part. Users
  6. * may copy or modify Sun RPC without charge, but are not authorized
  7. * to license or distribute it to anyone else except as part of a product or
  8. * program developed by the user.
  9. *
  10. * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
  11. * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  12. * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  13. *
  14. * Sun RPC is provided with no support and without any obligation on the
  15. * part of Sun Microsystems, Inc. to assist in its use, correction,
  16. * modification or enhancement.
  17. *
  18. * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  19. * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
  20. * OR ANY PART THEREOF.
  21. *
  22. * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  23. * or profits or other special, indirect and consequential damages, even if
  24. * Sun has been advised of the possibility of such damages.
  25. *
  26. * Sun Microsystems, Inc.
  27. * 2550 Garcia Avenue
  28. * Mountain View, California 94043
  29. */
  30. #if !defined(lint) && defined(SCCSIDS)
  31. static char sccsid[] = "@(#)pmap_prot2.c 1.3 87/08/11 Copyr 1984 Sun Micro";
  32. #endif
  33. /*
  34. * pmap_prot2.c
  35. * Protocol for the local binder service, or pmap.
  36. *
  37. * Copyright (C) 1984, Sun Microsystems, Inc.
  38. */
  39. #include <rpc/types.h>
  40. #include <rpc/xdr.h>
  41. #include <rpc/pmap_prot.h>
  42. /*
  43. * What is going on with linked lists? (!)
  44. * First recall the link list declaration from pmap_prot.h:
  45. *
  46. * struct pmaplist {
  47. * struct pmap pml_map;
  48. * struct pmaplist *pml_map;
  49. * };
  50. *
  51. * Compare that declaration with a corresponding xdr declaration that
  52. * is (a) pointer-less, and (b) recursive:
  53. *
  54. * typedef union switch (bool_t) {
  55. *
  56. * case TRUE: struct {
  57. * struct pmap;
  58. * pmaplist_t foo;
  59. * };
  60. *
  61. * case FALSE: struct {};
  62. * } pmaplist_t;
  63. *
  64. * Notice that the xdr declaration has no nxt pointer while
  65. * the C declaration has no bool_t variable. The bool_t can be
  66. * interpreted as ``more data follows me''; if FALSE then nothing
  67. * follows this bool_t; if TRUE then the bool_t is followed by
  68. * an actual struct pmap, and then (recursively) by the
  69. * xdr union, pamplist_t.
  70. *
  71. * This could be implemented via the xdr_union primitive, though this
  72. * would cause a one recursive call per element in the list. Rather than do
  73. * that we can ``unwind'' the recursion
  74. * into a while loop and do the union arms in-place.
  75. *
  76. * The head of the list is what the C programmer wishes to past around
  77. * the net, yet is the data that the pointer points to which is interesting;
  78. * this sounds like a job for xdr_reference!
  79. */
  80. bool_t
  81. xdr_pmaplist(xdrs, rp)
  82. register XDR *xdrs;
  83. register struct pmaplist **rp;
  84. {
  85. /*
  86. * more_elements is pre-computed in case the direction is
  87. * XDR_ENCODE or XDR_FREE. more_elements is overwritten by
  88. * xdr_bool when the direction is XDR_DECODE.
  89. */
  90. bool_t more_elements;
  91. register int freeing = (xdrs->x_op == XDR_FREE);
  92. register struct pmaplist **next;
  93. while (TRUE) {
  94. more_elements = (bool_t)(*rp != NULL);
  95. if (! xdr_bool(xdrs, &more_elements))
  96. return (FALSE);
  97. if (! more_elements)
  98. return (TRUE); /* we are done */
  99. /*
  100. * the unfortunate side effect of non-recursion is that in
  101. * the case of freeing we must remember the next object
  102. * before we free the current object ...
  103. */
  104. if (freeing)
  105. next = &((*rp)->pml_next);
  106. if (! xdr_reference(xdrs, (caddr_t *)rp,
  107. (u_int)sizeof(struct pmaplist), xdr_pmap))
  108. return (FALSE);
  109. rp = (freeing) ? next : &((*rp)->pml_next);
  110. }
  111. }