4.3BSD - /usr/src/etc/talkd/table.c

   1: /*
   2:  * Copyright (c) 1983 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  */
   6: 
   7: #ifndef lint
   8: static char sccsid[] = "@(#)table.c	5.2 (Berkeley) 3/13/86";
   9: #endif not lint
  10: 
  11: /*
  12:  * Routines to handle insertion, deletion, etc on the table
  13:  * of requests kept by the daemon. Nothing fancy here, linear
  14:  * search on a double-linked list. A time is kept with each
  15:  * entry so that overly old invitations can be eliminated.
  16:  *
  17:  * Consider this a mis-guided attempt at modularity
  18:  */
  19: #include <stdio.h>
  20: #include <sys/time.h>
  21: #include <syslog.h>
  22: 
  23: #include <protocols/talkd.h>
  24: 
  25: #define MAX_ID 16000    /* << 2^15 so I don't have sign troubles */
  26: 
  27: #define NIL ((TABLE_ENTRY *)0)
  28: 
  29: extern  int debug;
  30: struct  timeval tp;
  31: struct  timezone *txp;
  32: 
  33: typedef struct table_entry TABLE_ENTRY;
  34: 
  35: struct table_entry {
  36:     CTL_MSG request;
  37:     long    time;
  38:     TABLE_ENTRY *next;
  39:     TABLE_ENTRY *last;
  40: };
  41: 
  42: TABLE_ENTRY *table = NIL;
  43: CTL_MSG *find_request();
  44: CTL_MSG *find_match();
  45: char    *malloc();
  46: 
  47: /*
  48:  * Look in the table for an invitation that matches the current
  49:  * request looking for an invitation
  50:  */
  51: CTL_MSG *
  52: find_match(request)
  53:     register CTL_MSG *request;
  54: {
  55:     register TABLE_ENTRY *ptr;
  56:     long current_time;
  57: 
  58:     gettimeofday(&tp, &txp);
  59:     current_time = tp.tv_sec;
  60:     if (debug)
  61:         print_request("find_match", request);
  62:     for (ptr = table; ptr != NIL; ptr = ptr->next) {
  63:         if ((ptr->time - current_time) > MAX_LIFE) {
  64:             /* the entry is too old */
  65:             if (debug)
  66:                 print_request("deleting expired entry",
  67:                     &ptr->request);
  68:             delete(ptr);
  69:             continue;
  70:         }
  71:         if (debug)
  72:             print_request("", &ptr->request);
  73:         if (strcmp(request->l_name, ptr->request.r_name) == 0 &&
  74:             strcmp(request->r_name, ptr->request.l_name) == 0 &&
  75:              ptr->request.type == LEAVE_INVITE)
  76:             return (&ptr->request);
  77:     }
  78:     return ((CTL_MSG *)0);
  79: }
  80: 
  81: /*
  82:  * Look for an identical request, as opposed to a complimentary
  83:  * one as find_match does
  84:  */
  85: CTL_MSG *
  86: find_request(request)
  87:     register CTL_MSG *request;
  88: {
  89:     register TABLE_ENTRY *ptr;
  90:     long current_time;
  91: 
  92:     gettimeofday(&tp, &txp);
  93:     current_time = tp.tv_sec;
  94:     /*
  95: 	 * See if this is a repeated message, and check for
  96: 	 * out of date entries in the table while we are it.
  97: 	 */
  98:     if (debug)
  99:         print_request("find_request", request);
 100:     for (ptr = table; ptr != NIL; ptr = ptr->next) {
 101:         if ((ptr->time - current_time) > MAX_LIFE) {
 102:             /* the entry is too old */
 103:             if (debug)
 104:                 print_request("deleting expired entry",
 105:                     &ptr->request);
 106:             delete(ptr);
 107:             continue;
 108:         }
 109:         if (debug)
 110:             print_request("", &ptr->request);
 111:         if (strcmp(request->r_name, ptr->request.r_name) == 0 &&
 112:             strcmp(request->l_name, ptr->request.l_name) == 0 &&
 113:             request->type == ptr->request.type &&
 114:             request->pid == ptr->request.pid) {
 115:             /* update the time if we 'touch' it */
 116:             ptr->time = current_time;
 117:             return (&ptr->request);
 118:         }
 119:     }
 120:     return ((CTL_MSG *)0);
 121: }
 122: 
 123: insert_table(request, response)
 124:     CTL_MSG *request;
 125:     CTL_RESPONSE *response;
 126: {
 127:     register TABLE_ENTRY *ptr;
 128:     long current_time;
 129: 
 130:     gettimeofday(&tp, &txp);
 131:     current_time = tp.tv_sec;
 132:     request->id_num = new_id();
 133:     response->id_num = htonl(request->id_num);
 134:     /* insert a new entry into the top of the list */
 135:     ptr = (TABLE_ENTRY *)malloc(sizeof(TABLE_ENTRY));
 136:     if (ptr == NIL) {
 137:         syslog(LOG_ERR, "insert_table: Out of memory");
 138:         _exit(1);
 139:     }
 140:     ptr->time = current_time;
 141:     ptr->request = *request;
 142:     ptr->next = table;
 143:     if (ptr->next != NIL)
 144:         ptr->next->last = ptr;
 145:     ptr->last = NIL;
 146:     table = ptr;
 147: }
 148: 
 149: /*
 150:  * Generate a unique non-zero sequence number
 151:  */
 152: new_id()
 153: {
 154:     static int current_id = 0;
 155: 
 156:     current_id = (current_id + 1) % MAX_ID;
 157:     /* 0 is reserved, helps to pick up bugs */
 158:     if (current_id == 0)
 159:         current_id = 1;
 160:     return (current_id);
 161: }
 162: 
 163: /*
 164:  * Delete the invitation with id 'id_num'
 165:  */
 166: delete_invite(id_num)
 167:     int id_num;
 168: {
 169:     register TABLE_ENTRY *ptr;
 170: 
 171:     ptr = table;
 172:     if (debug)
 173:         syslog(LOG_DEBUG, "delete_invite(%d)", id_num);
 174:     for (ptr = table; ptr != NIL; ptr = ptr->next) {
 175:         if (ptr->request.id_num == id_num)
 176:             break;
 177:         if (debug)
 178:             print_request("", &ptr->request);
 179:     }
 180:     if (ptr != NIL) {
 181:         delete(ptr);
 182:         return (SUCCESS);
 183:     }
 184:     return (NOT_HERE);
 185: }
 186: 
 187: /*
 188:  * Classic delete from a double-linked list
 189:  */
 190: delete(ptr)
 191:     register TABLE_ENTRY *ptr;
 192: {
 193: 
 194:     if (debug)
 195:         print_request("delete", &ptr->request);
 196:     if (table == ptr)
 197:         table = ptr->next;
 198:     else if (ptr->last != NIL)
 199:         ptr->last->next = ptr->next;
 200:     if (ptr->next != NIL)
 201:         ptr->next->last = ptr->last;
 202:     free((char *)ptr);
 203: }

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