table.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifndef lint
static	char	*sccsid = "@(#)table.c	4.1	(ULTRIX)	7/2/90";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1984,1988 by			*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/
/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */
/*
#ifndef lint
static char sccsid[] = "table.c	5.3 (Berkeley) 9/4/87";
#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);
}