BSD 4_3_Net_1 release

[unix-history] / talkd / table.c

/*
* Copyright (c) 1983 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Berkeley.  The name of the
* University may not be used to endorse or promote products derived
* from this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#ifndef lint
static char sccsid[] = "@(#)table.c     5.5 (Berkeley) 6/18/88";
#endif /* not lint */

/*
* Routines to handle insertion, deletion, etc on the table
* of requests kept by the daemon. Nothing fancy here, linear
* search on a double-linked list. A time is kept with each 
* entry so that overly old invitations can be eliminated.
*
* Consider this a mis-guided attempt at modularity
*/
#include <stdio.h>
#include <sys/time.h>
#include <syslog.h>
#include <sys/param.h>

#include <protocols/talkd.h>

#define MAX_ID 16000    /* << 2^15 so I don't have sign troubles */

#define NIL ((TABLE_ENTRY *)0)

extern  int debug;
struct  timeval tp;
struct  timezone *txp;

typedef struct table_entry TABLE_ENTRY;

struct table_entry {
       CTL_MSG request;
       long    time;
       TABLE_ENTRY *next;
       TABLE_ENTRY *last;
};

TABLE_ENTRY *table = NIL;
CTL_MSG *find_request();
CTL_MSG *find_match();
char    *malloc();

/*
* Look in the table for an invitation that matches the current
* request looking for an invitation
*/
CTL_MSG *
find_match(request)
       register CTL_MSG *request;
{
       register TABLE_ENTRY *ptr;
       long current_time;

       gettimeofday(&tp, &txp);
       current_time = tp.tv_sec;
       if (debug)
               print_request("find_match", request);
       for (ptr = table; ptr != NIL; ptr = ptr->next) {
               if ((ptr->time - current_time) > MAX_LIFE) {
                       /* the entry is too old */
                       if (debug)
                               print_request("deleting expired entry",
                                   &ptr->request);
                       delete(ptr);
                       continue;
               }
               if (debug)
                       print_request("", &ptr->request);
               if (strcmp(request->l_name, ptr->request.r_name) == 0 &&
                   strcmp(request->r_name, ptr->request.l_name) == 0 &&
                    ptr->request.type == LEAVE_INVITE)
                       return (&ptr->request);
       }
       return ((CTL_MSG *)0);
}

/*
* Look for an identical request, as opposed to a complimentary
* one as find_match does 
*/
CTL_MSG *
find_request(request)
       register CTL_MSG *request;
{
       register TABLE_ENTRY *ptr;
       long current_time;

       gettimeofday(&tp, &txp);
       current_time = tp.tv_sec;
       /*
        * See if this is a repeated message, and check for
        * out of date entries in the table while we are it.
        */
       if (debug)
               print_request("find_request", request);
       for (ptr = table; ptr != NIL; ptr = ptr->next) {
               if ((ptr->time - current_time) > MAX_LIFE) {
                       /* the entry is too old */
                       if (debug)
                               print_request("deleting expired entry",
                                   &ptr->request);
                       delete(ptr);
                       continue;
               }
               if (debug)
                       print_request("", &ptr->request);
               if (strcmp(request->r_name, ptr->request.r_name) == 0 &&
                   strcmp(request->l_name, ptr->request.l_name) == 0 &&
                   request->type == ptr->request.type &&
                   request->pid == ptr->request.pid) {
                       /* update the time if we 'touch' it */
                       ptr->time = current_time;
                       return (&ptr->request);
               }
       }
       return ((CTL_MSG *)0);
}

insert_table(request, response)
       CTL_MSG *request;
       CTL_RESPONSE *response;
{
       register TABLE_ENTRY *ptr;
       long current_time;

       gettimeofday(&tp, &txp);
       current_time = tp.tv_sec;
       request->id_num = new_id();
       response->id_num = htonl(request->id_num);
       /* insert a new entry into the top of the list */
       ptr = (TABLE_ENTRY *)malloc(sizeof(TABLE_ENTRY));
       if (ptr == NIL) {
               syslog(LOG_ERR, "insert_table: Out of memory");
               _exit(1);
       }
       ptr->time = current_time;
       ptr->request = *request;
       ptr->next = table;
       if (ptr->next != NIL)
               ptr->next->last = ptr;
       ptr->last = NIL;
       table = ptr;
}

/*
* Generate a unique non-zero sequence number
*/
new_id()
{
       static int current_id = 0;

       current_id = (current_id + 1) % MAX_ID;
       /* 0 is reserved, helps to pick up bugs */
       if (current_id == 0)
               current_id = 1;
       return (current_id);
}

/*
* Delete the invitation with id 'id_num'
*/
delete_invite(id_num)
       int id_num;
{
       register TABLE_ENTRY *ptr;

       ptr = table;
       if (debug)
               syslog(LOG_DEBUG, "delete_invite(%d)", id_num);
       for (ptr = table; ptr != NIL; ptr = ptr->next) {
               if (ptr->request.id_num == id_num)
                       break;
               if (debug)
                       print_request("", &ptr->request);
       }
       if (ptr != NIL) {
               delete(ptr);
               return (SUCCESS);
       }
       return (NOT_HERE);
}

/*
* Classic delete from a double-linked list
*/
delete(ptr)
       register TABLE_ENTRY *ptr;
{

       if (debug)
               print_request("delete", &ptr->request);
       if (table == ptr)
               table = ptr->next;
       else if (ptr->last != NIL)
               ptr->last->next = ptr->next;
       if (ptr->next != NIL)
               ptr->next->last = ptr->last;
       free((char *)ptr);
}