inetutils/talkd/table.c

/*
  Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
  2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

#include <intalkd.h>

typedef struct request_table table_t;

struct request_table
{
  table_t *next, *prev;
  CTL_MSG request;
  time_t time;
};

static table_t *table;

static void
table_delete (table_t * ptr)
{
  table_t *t;

  if ((t = ptr->prev) != NULL)
    t->next = ptr->next;
  else
    table = ptr->next;
  if ((t = ptr->next) != NULL)
    t->prev = ptr->prev;
  free (ptr);
}

/* Look in the table for an invitation that matches given criteria.
   Linear search: premature optimisation is the root of all
   Evil) */

static CTL_MSG *
lookup_request (CTL_MSG * request,
		int (*comp) (table_t *, CTL_MSG *, time_t *))
{
  table_t *ptr;
  time_t now;

  time (&now);

  if (debug)
    print_request ("lookup_request", request);

  for (ptr = table; ptr; ptr = ptr->next)
    {
      if (debug)
	print_request ("comparing against: ", &ptr->request);

      if ((ptr->time - now) > max_request_ttl)
	{
	  /* the entry is too old */
	  if (debug)
	    print_request ("deleting expired entry", &ptr->request);
	  table_delete (ptr);
	}
      else
	{
	  if (comp (ptr, request, &now) == 0)
	    {
	      if (debug)
		print_request ("found", &ptr->request);
	      return &ptr->request;
	    }
	}
    }
  if (debug)
    syslog (LOG_DEBUG, "not found");
  return NULL;
}

static int
fuzzy_comp (table_t * ptr, CTL_MSG * request, time_t * unused ARG_UNUSED)
{
  if (ptr->request.type == LEAVE_INVITE
      && strcmp (request->l_name, ptr->request.r_name) == 0
      && strcmp (request->r_name, ptr->request.l_name) == 0)
    return 0;
  return 1;
}

/* Look in the table for an invitation that matches the current
   request looking for an invitation */
CTL_MSG *
find_match (CTL_MSG * request)
{
  return lookup_request (request, fuzzy_comp);
}

static int
exact_comp (table_t * ptr, CTL_MSG * request, time_t * now)
{
  if (request->type == ptr->request.type
      && request->pid == ptr->request.pid
      && strcmp (request->r_name, ptr->request.r_name) == 0
      && strcmp (request->l_name, ptr->request.l_name) == 0)
    {
      ptr->time = *now;
      return 0;
    }
  return 1;
}

/* Look for an identical request, as opposed to a complementary
   one as find_match does */

CTL_MSG *
find_request (CTL_MSG * request)
{
  return lookup_request (request, exact_comp);
}

#define MAX_ID 16000

/* Generate a unique non-zero sequence number */
int
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;
}

int
insert_table (CTL_MSG * request, CTL_RESPONSE * response)
{
  table_t *ptr;

  ptr = malloc (sizeof *ptr);
  if (!ptr)
    {
      syslog (LOG_CRIT, "out of memory");
      exit (1);
    }

  request->id_num = new_id ();

  if (debug)
    print_request ("insert_table", request);

  response->id_num = htonl (request->id_num);

  time (&ptr->time);
  ptr->request = *request;
  ptr->prev = NULL;
  ptr->next = table;
  table = ptr;
  return 0;
}

/* Delete the invitation with id 'id_num' */
int
delete_invite (unsigned long id_num)
{
  table_t *ptr;

  for (ptr = table; ptr; ptr = ptr->next)
    if (ptr->request.id_num == id_num)
      {
	table_delete (ptr);
	return SUCCESS;
      }
  return NOT_HERE;
}