servers/inet/queryparam.c

   1 /*      queryparam() - allow program parameters to be queried
   2  *                                                      Author: Kees J. Bot
   3  *                                                              21 Apr 1994
   4  */
   5 #define nil 0
   6 #include <stddef.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include "queryparam.h"
  10
  11 #if EXAMPLE
  12 struct stat st[2];
  13
  14 struct export_param_list ex_st_list[]= {
  15         QP_VARIABLE(st),
  16         QP_ARRAY(st),
  17         QP_FIELD(st_dev, struct stat),
  18         QP_FIELD(st_ino, struct stat),
  19         ...
  20         QP_END()
  21 };
  22
  23 struct buf { block_t b_blocknr; ... } *buf;
  24 size_t nr_bufs;
  25
  26 struct export_param_list ex_buf_list[]=
  27         QP_VECTOR(buf, buf, nr_bufs),
  28         QP_FIELD(b_blocknr),
  29         ...
  30         QP_END()
  31 };
  32
  33 struct export_params ex_st= { ex_st_list, 0 };
  34 struct export_params ex_buf= { ex_buf_list, 0 };
  35 #endif
  36
  37 #define between(a, c, z)    ((unsigned) ((c) - (a)) <= (unsigned) ((z) - (a)))
  38
  39 static int isvar(int c)
  40 {
  41         return between('a', c, 'z') || between('A', c, 'Z')
  42                                 || between('0', c, '9') || c == '_';
  43 }
  44
  45 static struct export_params *params;
  46
  47 void qp_export(struct export_params *ex_params)
  48 {
  49         /* Add a set of exported parameters. */
  50
  51         if (ex_params->next == nil) {
  52                 ex_params->next= params;
  53                 params= ex_params;
  54         }
  55 }
  56
  57 int queryparam(int qgetc(void), void **poffset, size_t *psize)
  58 {
  59         char *prefix;
  60         struct export_params *ep;
  61         struct export_param_list *epl;
  62         size_t offset= 0;
  63         size_t size= -1;
  64         size_t n;
  65         static size_t retval;
  66         int c, firstc;
  67
  68         firstc= c= (*qgetc)();
  69         if (c == '&' || c == '$') c= (*qgetc)();
  70         if (!isvar(c)) goto fail;
  71
  72         if ((ep= params) == nil) goto fail;
  73         epl= ep->list;
  74
  75         while (c != 0 && c != ',') {
  76                 prefix= "x";
  77                 n= 0;
  78
  79                 for (;;) {
  80                         while (epl->name == nil) {
  81                                 if ((ep= ep->next) == nil) goto fail;
  82                                 epl= ep->list;
  83                         }
  84                         if (strncmp(prefix, epl->name, n) == 0) {
  85                                 prefix= epl->name;
  86                                 while (prefix[n] != 0 && c == prefix[n]) {
  87                                         n++;
  88                                         c= (*qgetc)();
  89                                 }
  90                         }
  91                         if (prefix[n] == 0 && (!isvar(c) || prefix[0] == '[')) {
  92                                 /* Got a match. */
  93                                 break;
  94                         }
  95                         epl++;
  96                 }
  97
  98                 if (prefix[0] == '[') {
  99                         /* Array reference. */
 100                         size_t idx= 0, cnt= 1, max= size / epl->size;
 101
 102                         while (between('0', c, '9')) {
 103                                 idx= idx * 10 + (c - '0');
 104                                 if (idx > max) goto fail;
 105                                 c= (*qgetc)();
 106                         }
 107                         if (c == ':') {
 108                                 cnt= 0;
 109                                 while (between('0', (c= (*qgetc)()), '9')) {
 110                                         cnt= cnt * 10 + (c - '0');
 111                                 }
 112                         }
 113                         if (c != ']') goto fail;
 114                         if (idx + cnt > max) cnt= max - idx;
 115                         offset+= idx * epl->size;
 116                         size= cnt * epl->size;
 117                         c= (*qgetc)();
 118                 } else
 119                 if (epl->size == -1) {
 120                         /* Vector. */
 121                         offset= (size_t) * (void **) epl->offset;
 122                         size= (* (size_t *) epl[1].offset) * epl[1].size;
 123                 } else {
 124                         /* Variable or struct field. */
 125                         offset+= (size_t) epl->offset;
 126                         if ((size_t) epl->offset > size) goto fail;
 127                         size-= (size_t) epl->offset;
 128                         if (size < epl->size) goto fail;
 129                         size= epl->size;
 130                 }
 131         }
 132         if (firstc == '&' || firstc == '$') {
 133                 retval= firstc == '&' ? offset : size;
 134                 offset= (size_t) &retval;
 135                 size= sizeof(retval);
 136         }
 137         if (c != 0 && c != ',') goto fail;
 138         *poffset= (void *) offset;
 139         *psize= size;
 140         return c != 0;
 141 fail:
 142         while (c != 0 && c != ',') c= (*qgetc)();
 143         *poffset= nil;
 144         *psize= 0;
 145         return c != 0;
 146 }
 147
 148 /*
 149  * $PchId: queryparam.c,v 1.1 2005/06/28 14:30:56 philip Exp $
 150  */