simple-cache.c 44.6 KB
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/*
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 * $Id: simple-cache.c,v 0.41 1993/11/22 19:09:46 ceder Exp $
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 * Copyright (C) 1991  Lysator Academic Computer Association.
 *
 * This file is part of the LysKOM server.
 * 
 * LysKOM 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 1, or (at your option) 
 * any later version.
 * 
 * LysKOM 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 LysKOM; see the file COPYING.  If not, write to
 * Lysator, c/o ISY, Linkoping University, S-581 83 Linkoping, SWEDEN,
 * or the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, 
 * MA 02139, USA.
 *
 * Please mail bug reports to bug-lyskom@lysator.liu.se. 
 */
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/*
 * This module contains some simple simulations of the routines in
 * cache.c.
 *
 * Extracted from ram-cache.c and rewritten by ceder.
 *
 * New database format with texts in their own file by Inge Wallin.
 *
 * New save algorithm by ceder.
 */

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static char *rcsid = "$Id: simple-cache.c,v 0.41 1993/11/22 19:09:46 ceder Exp $";
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#include "rcs.h"
USE(rcsid);
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#include <errno.h>
#include <stdio.h>
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#include <sys/types.h>
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#ifndef SEEK_END
#  include <fcntl.h>
#endif
#ifndef SEEK_END
#  include <unistd.h>
#endif
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#ifndef SEEK_END
#  define SEEK_SET 0
#  define SEEK_END 2
#endif
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#include <time.h>
#ifndef HAVE_DIFFTIME
#  include "tmp-difftime.h"
#endif
#include <setjmp.h>
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#ifdef HAVE_STDARG_H
#  include <stdarg.h>
#endif
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#include "exp.h"
#include "misc-types.h"
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#include "s-string.h"
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#include "kom-types.h"
#include "tmp-limits.h"
#include "cache-node.h"
#include "cache.h"
#include "parser.h"
#include "ram-parse.h"
#include "ram-output.h"
#include "server/smalloc.h"
#include "kom-memory.h"
#include "lyskomd.h"
#include "debug.h"
#include "kom-errno.h"
#include "log.h"
#include "com.h"
#include "connections.h"
#include "send-async.h"
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/*
 * Possible improvements: +++
 *  When there are consecutive items in file A that shall be copied
 *  to file B, copy them in one transfer (up to a certain limit).
 *
 *  In pre_sync: compute size of, and allocate disk space for file B.
 */

/*
 * All functions that can fail sets kom_errno to a suitable value
 * if they fail.
 */

static Small_conf	* small_conf_arr[ MAX_CONF ];
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static Cache_node_mcb	* pers_mcb;
static Cache_node_mcb 	* conf_mcb;
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static int		  next_free_num = 1;

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static Cache_node_mcb 	* text_mcb;
static int		  next_text_num = 1;
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/* Defined in ramkomd.c */
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extern char datafilename[BUFSIZ];
extern char backupfilename[BUFSIZ];
extern char textfilename[BUFSIZ];
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/*
 * The elements in the following lists with same index refers to the same
 * conference.
 */
static int    no_of_match_info;
EXPORT Matching_info *match_table = NULL;
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EXPORT Conf_no       *conf_table  = NULL; /* Used in conference.c. */
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static FILE	*text_file= NULL;
static FILE	*file_a = NULL;	/* Current file. */
static FILE	*file_b = NULL;	/* File under construction. */

/*
 * Four state variables for the background save.
 */
static enum {
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    sync_idle,
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    sync_save_conf,
    sync_save_pers,
    sync_save_text,
    sync_error,
    sync_wait,
    sync_ready
} sync_state;

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/* The state machine sync_state works like this:
 *
 *  Old state              action           new state
 *  none               sync_part called     sync_idle
 *                     for the first time
 *  sync_idle	       SYNC_INTERVAL        sync_save_conf
 *  sync_save_conf     all confs saved      sync_save_pers
 *  sync_save_pers     all persons saved    sync_save_text
 *  sync_save_text     all texts saved      sync_ready
 *  sync_ready         sync_part called     sync_idle
 *  any                error occurs         sync_error
 *  sync_error         sync_part called     sync_wait
 *  sync_wait          SYNC_RETRY_INTERVAL  sync_save_conf
 */

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static long sync_next;

static Conf_no highest_conf_no;
static Text_no highest_text_no;

BUGDECL;

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/* Define LOGACCESSES if you want to be able to log all accesses to
   the data base. */

#ifdef LOGACCESSES
extern char *logaccess_file;	/* From ramkomd.c */

typedef enum {
    lt_restart,
    lt_text_stat,
    lt_text_mass,
    lt_conf_stat,
    lt_pers_stat,
    
    lt_text_def,
    lt_conf_def,
    lt_pers_def,

    lt_create_text,
    lt_garb_text,
    lt_delete_text,
    lt_create_conf,
    lt_delete_conf,
    lt_create_pers,
    lt_delete_pers,

    lt_lock_conf,
    lt_unlock_conf,
    lt_lock_pers,
    lt_unlock_pers,

    lt_get_highest,		/* Get highest Local_text_no for a conf. */
    lt_get_conf_type
    /* Note: mark_*_as_changed is not logged. */
} Log_type;

static FILE *logfile = NULL;
static int syncing_or_saving = 0;
static int garb_running = 0;

static void log_access(Log_type t,
		       int id)
{
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    extern int putw(int, FILE *);

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    if (garb_running + syncing_or_saving == 0)
    {
	putc(t, logfile);
	putw(id, logfile);
    }
}
#define LOGACC(a,b) {if (logfile) log_access(a, b);}
#else
#define LOGACC(a,b)
#endif

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/* Macros */

#define TRACE2(format, arg) if ( buglevel > 2 ) printf(format, arg)
#define TRACE1(format) if ( buglevel > 2 ) printf(format)
#define TRACESTR(str)  if ( buglevel > 2 ) s_puts(str)


static Person *
read_person(FILE *fp,
	    long pos,
	    long size)
{
    Person *p;

    p = alloc_person();
    fseek(fp, pos+1, SEEK_SET);	/* Skip '+' */
    if ( fparse_person(fp, p) != OK )
    {
	free_person(p);
	return NULL;
    }
    else
	return p;
}



static Conference *
read_conference(FILE *fp,
		long pos,
		long size)
{
    Conference *c;

    c = alloc_conference();
    fseek(fp, pos+1, SEEK_SET);	/* Skip '+' */
    if ( fparse_conference(fp, c) != OK )
    {
	free_conference(c);
	return NULL;
    }
    else
	return c;
}
	

static Text_stat *
read_text_stat(FILE *fp,
	       long pos,
	       long size)
{
    Text_stat *t;

    t = alloc_text_stat();
    fseek(fp, pos+1, SEEK_SET);	/* Skip '+' */
    if ( fparse_text_stat(fp, t) != OK )
    {
	free_text_stat(t);
	return NULL;
    }
    else
	return t;
}

static void
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pers_set_mru(Pers_no pers_no)
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{
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    set_mru(pers_mcb, pers_no);
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}

static void
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text_set_mru(Text_no text_no)
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{
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    set_mru(text_mcb, text_no);
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}

static void
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conf_set_mru(Conf_no conf_no)
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{
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    set_mru(conf_mcb, conf_no);
}
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static Cache_node *
get_pers_node(Pers_no pers_no)
{
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    if ( pers_no >= next_free_num )
	return NULL;

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    return get_cache_node(pers_mcb, pers_no);
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}

static void
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unlink_text_lru (Cache_node *node)
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{
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    unlink_lru (node, &text_mcb->lru, &text_mcb->mru);
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}

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static void
unlink_conf_lru (Cache_node *node)
{
    unlink_lru (node, &conf_mcb->lru, &conf_mcb->mru);
}
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static void
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unlink_pers_lru (Cache_node *node)
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{
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    unlink_lru (node, &pers_mcb->lru, &pers_mcb->mru);
}
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static Cache_node *
get_conf_node(Conf_no conf_no)
{
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    if ( conf_no >= next_free_num )
	return NULL;

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    return get_cache_node(conf_mcb, conf_no);
}
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static Cache_node *
get_text_node(Text_no text_no)
{
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    if ( text_no >= next_text_num )
	return NULL;

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    return get_cache_node(text_mcb, text_no);
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}

	
/*
 * Name caching routines
 */

/*
 * change_name changes the cached conference name. It is only called when
 * a conference name is changed or a conference is deleted.
 */
void
cached_change_name( Conf_no name_num,
		    String new_name )
{
    if ( name_num < 1 || name_num >= next_free_num )
	restart_kom("cached_change_name(%d, ----): next_free_num==%d",
		    name_num, next_free_num);

    s_clear( &small_conf_arr[name_num]->name );
    s_strcpy( &small_conf_arr[name_num]->name, new_name);
    build_matching_info();
}


extern Conf_type
cached_get_conf_type (Conf_no conf_no)
{
    if ( conf_no < 1 || conf_no >= next_free_num )
	restart_kom("cached_get_conf_type(%d): next_free_num==%d",
		    conf_no, next_free_num);
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    if ( small_conf_arr [ conf_no ] == NULL )
	restart_kom("cached_get_conf_type(%d): conference does not exist.\n",
		    conf_no);

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    LOGACC(lt_get_conf_type, conf_no);

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    return small_conf_arr [ conf_no ]->type;
}

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/*
 * Return number of conferences present.  (Actually, return a number
 * at least as large as the number of conferences present).
 */
extern Conf_no
cached_no_of_existing_conferences(void)
{
    return next_free_num;	/* This is too large, but who cares? */
}
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/*
 * Various function calls to tell the cache that something is changed.
 */

void
mark_person_as_changed(Pers_no	pers_no)
{
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    Cache_node *node;

    node = get_pers_node(pers_no);
    
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    TRACE2("Person %d is changed\n", pers_no);
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    if ( node == NULL || node->s.exists == 0)
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	restart_kom("mark_person_as_changed(%d): nonexistent.\n", pers_no);

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    node->s.dirty = 1;
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    pers_set_mru( pers_no );
}

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/*
 * Mark the conference as dirty, so that it will be written to
 * the disk.
 *
 * Also update all fields in the Small_conf except then name, so that
 * they are always current.
 *
 * NOTE: You must call cached_change_name when the name changes.
 *       It is not necessary to call cached_change_name after
 *       cached_create_conf.
 */
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void
mark_conference_as_changed(Conf_no	conf_no)
{
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    Cache_node *node;
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    Conference *conf_c;
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    node = get_conf_node (conf_no);

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    TRACE2("Conf.  %d is changed\n", conf_no);
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    if ( node == NULL || node->s.exists == 0)
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	restart_kom("mark_conference_as_changed(%d): nonexistent.\n", conf_no);

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    node->s.dirty = 1;
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    conf_set_mru( conf_no );
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    conf_c = (Conference *) node->ptr;

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    small_conf_arr[ conf_no ]->highest_local_no
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	= (conf_c->texts.first_local_no - 1 + conf_c->texts.no_of_texts );

    small_conf_arr[ conf_no ]->nice = conf_c->nice;
    small_conf_arr[ conf_no ]->type = conf_c->type;
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}

void
mark_text_as_changed( Text_no text_no )
{
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    Cache_node *node;

    node = get_text_node (text_no);

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    TRACE2("Text %u is changed.\n", text_no);
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    if ( text_no < 1 || text_no >= next_text_num
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	|| node == NULL || node->s.exists == 0)
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    {
	restart_kom("mark_text_as_changed(%d): nonexistent.\n", text_no);
    }

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    node->s.dirty = 1;
    text_set_mru (text_no);
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}    



/*
 * Person-related calls
 */


extern Success
cached_create_person( Pers_no person )
{
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    Cache_node *node;

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    TRACE2("Person %d is being created.\n", person);

    if ( person < 1 || person >= next_free_num )
    {
	restart_kom("cached_create_person(%d): next_free_num == %d.\n",
		    person, next_free_num);
    }

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    if ( get_pers_node(person) != NULL )
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    {
	restart_kom("cached_create_person(%d): Person existed.\n",
		    person);
    }

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    create_cache_node (pers_mcb, person);
    node = get_pers_node (person);

    if ( node == NULL )
	restart_kom("cached_create_person(): couldn't get cache_node.\n");
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    node->ptr = alloc_person();
    node->s.dirty = 1;
    node->s.exists = 1;
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    pers_set_mru( person );
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    LOGACC(lt_create_pers, person);

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    return OK;
}


extern Person *
cached_get_person_stat( Pers_no	person )
{
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    Cache_node *node;

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    TRACE2("cached_get_person_stat %d\n", person);

    if ( person == 0 )
    {
	kom_errno = KOM_CONF_ZERO;
	return NULL;
    }
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    if ( person >= next_free_num )
    {
	kom_errno = KOM_UNDEF_PERS;
	return NULL;
    }

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    node = get_pers_node (person);

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    if ( node == NULL || node->s.exists == 0 )
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    {
	kom_errno = KOM_UNDEF_PERS;
	return NULL;
    }

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    LOGACC(lt_pers_stat, person);

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    if ( node->ptr != NULL )
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    {
	pers_set_mru( person );
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	++pers_mcb->hits;
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	return node->ptr;
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    }

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    if ( node->snap_shot != NULL )
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    {
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	node->ptr = copy_person (node->snap_shot);
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	pers_set_mru (person);
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	++pers_mcb->hits;
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	return node->ptr;
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    }

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    node->ptr = read_person(file_a, node->pos, node->size);
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    ++pers_mcb->misses;
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    pers_set_mru (person);
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    return node->ptr;
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}


/*
 * Conference-related calls
 */
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static int no_of_allocated_small_confs = 0;

static void
free_small_conf (Small_conf *sc)
{
    if ( sc != NULL )
    {
	--no_of_allocated_small_confs;
	s_clear ( &sc->name );
	sfree (sc);
    }
}


static Small_conf *
alloc_small_conf(void)
{
    Small_conf *s;
    s = smalloc(sizeof(Small_conf));
    *s = EMPTY_SMALL_CONF;
    ++no_of_allocated_small_confs;

    return s;
}


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/*
 * Create a conference.
 *
 * Set up a Conference and cache the name in the small_conf_array.
 */
extern Conf_no
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cached_create_conf (String  name)
{
    Conference * conf_c;
    Conf_no	 conf_no;
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    Cache_node  *node;
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    TRACE1("cached_create_conf( ");
    TRACESTR(name);
    TRACE1(" )\n");

    if ( next_free_num >= MAX_CONF )
    {
	kom_errno = KOM_INDEX_OUT_OF_RANGE;
	return 0;
    }
    
    conf_no = next_free_num++;

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    create_cache_node (conf_mcb, conf_no);
    node = get_conf_node (conf_no);

    if ( node == NULL )
	restart_kom("cached_create_conf(): failed to allocate cache_node.\n");
    
    node->s.exists = 1;
    node->s.dirty = 1;
    node->ptr = conf_c = alloc_conference();
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    conf_set_mru(conf_no);    

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    zero_init_cache_node (pers_mcb, conf_no);
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    small_conf_arr[ conf_no ] = alloc_small_conf();

    conf_c->name = EMPTY_STRING;
    s_strcpy(&conf_c->name, name);
    cached_change_name( conf_no, name);

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    TRACE2("Created conference number %d\n", conf_no);
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    LOGACC(lt_create_conf, conf_no);

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    return conf_no;
}


extern Success
cached_delete_conf( Conf_no	conf )
{
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    Cache_node *node;

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    if ( conf == 0 )
    {
	kom_errno = KOM_CONF_ZERO;
	return FAILURE;
    }
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    if ( conf >= next_free_num )
    {
	kom_errno = KOM_UNDEF_CONF;
	return FAILURE;
    }

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    node = get_conf_node (conf);

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    if ( node == NULL || node->s.exists == 0 )
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    {
	kom_errno = KOM_UNDEF_CONF;
	return FAILURE;
    }

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    if ( node->lock_cnt > 0 )
	log("WNG: cached_delete_conf(%d): lock_cnt === %d\n",
	    conf, node->lock_cnt);
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    free_conference(node->ptr);
    node->ptr = NULL;
    node->s.exists = 0;
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    LOGACC(lt_delete_conf, conf);

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    return OK;
}

Success
cached_delete_person(Pers_no pers)
{
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    Cache_node *node;

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    if ( pers == 0 )
    {
	kom_errno = KOM_CONF_ZERO;
	return FAILURE;
    }
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    if ( pers >= next_free_num )
    {
	log("cached_delete_person(%lu): next_free_num == %lu\n",
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	    (unsigned long)pers, (unsigned long)next_free_num);
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	kom_errno = KOM_UNDEF_PERS;
	return FAILURE;
    }

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    node = get_pers_node (pers);

    if ( pers >= next_free_num || node == NULL || node->s.exists == 0 )
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    {
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	log("cached_delete_person(): attempt to delete void person.\n");
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	kom_errno = KOM_UNDEF_PERS;
	return FAILURE;
    }

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    if ( node->lock_cnt > 0 )
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	log("cached_delete_pers(%lu): lock_cnt === %lu\n",
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	    (unsigned long)pers, (unsigned long)node->lock_cnt);
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    LOGACC(lt_delete_pers, pers);

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    free_person (node->ptr);
    node->ptr = NULL;
    node->s.exists = 0;
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    return OK;
}

Success
cached_delete_text(Text_no text)
{
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    Cache_node *node;

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    if ( text == 0 )
    {
	kom_errno = KOM_TEXT_ZERO;
	return FAILURE;
    }
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    node = get_text_node (text);

    if ( text >= next_text_num || node == NULL
	|| node->s.exists == 0 )
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    {
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	log("cached_delete_text(): attempt to delete void text %d.\n", text);
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	kom_errno = KOM_NO_SUCH_TEXT;
	return FAILURE;
    }

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    if ( node->lock_cnt > 0 )
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	log("cached_delete_text(%d): lock_cnt === %d\n",
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	    text, node->lock_cnt);
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    free_text_stat(node->ptr);
    node->ptr = NULL;
    node->s.exists = 0;
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#ifdef LOGACCESSES
    if (garb_running)
    {
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	LOGACC(lt_garb_text, text);
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    }
    else
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	LOGACC(lt_delete_text, text);
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#endif
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    return OK;
}


extern Conference *
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cached_get_conf_stat (Conf_no   conf_no)
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{
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    Cache_node *node;

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    TRACE2("cached_get_conf_stat %d\n", conf_no);

    if ( conf_no == 0 )
    {
	kom_errno = KOM_CONF_ZERO;
	return NULL;
    }
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    node = get_conf_node (conf_no);

    if ( conf_no >= next_free_num || node == NULL || node->s.exists == 0 )
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    {
	kom_errno = KOM_UNDEF_CONF;
	return NULL;
    }

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    LOGACC(lt_conf_stat, conf_no);

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    if ( node->ptr != NULL )
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    {
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	conf_set_mru (conf_no);
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	++conf_mcb->hits;
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	return node->ptr;
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    }

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    if ( node->snap_shot != NULL )
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    {
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	node->ptr = copy_conf (node->snap_shot);
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	conf_set_mru (conf_no);
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	++conf_mcb->hits;
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	return node->ptr;
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    }

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    node->ptr = read_conference(file_a, node->pos, node->size);
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    ++conf_mcb->misses;
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    conf_set_mru (conf_no);
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    return node->ptr;
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}

/*
 * Return TRUE if conf_no exists.
 */
Bool
cached_conf_exists(Conf_no conf_no)
{
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    Cache_node *node;

    if (conf_no == 0 || conf_no >= next_free_num )
	return FALSE;

    node = get_conf_node (conf_no);

    return node != NULL && node->s.exists != 0;
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}

    
/*
 * Calls to handle texts
 */

/*
 * +++ Should return Success.
 */
extern String
cached_get_text( Text_no text )
{
    String  the_string;
    Text_stat *t_stat;

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    TRACE2("cached_get_text %u\n", text);
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    if ( (t_stat = cached_get_text_stat (text)) == NULL )
	return EMPTY_STRING;
    else
    {
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	LOGACC(lt_text_mass, text);
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	the_string.string = tmp_alloc( t_stat->no_of_chars );
	the_string.len = t_stat->no_of_chars;
	fseek(text_file, t_stat->file_pos, SEEK_SET);

	if ( fread(the_string.string, sizeof(char), the_string.len, text_file)
	    != the_string.len )
	{
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	    log("WARNING: cached_get_text: premature end on text %d\n",
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		text);
	    return EMPTY_STRING;
	}
		    
	return the_string;
    }
}


extern Text_stat *	/* NULL on error */
cached_get_text_stat(	Text_no		text )
{
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    Cache_node *node;

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    TRACE2("cached_get_text_stat(%u);  next_text_num == ", text);
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    TRACE2("%d\n", next_text_num);

    if ( text == 0 )
    {
	kom_errno = KOM_TEXT_ZERO;
	return NULL;
    }
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    node = get_text_node (text);

    if ( text >= next_text_num || node == NULL || node->s.exists == 0 )
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    {
	TRACE1("cached_get_text_stat: no such text.\n");
	kom_errno = KOM_NO_SUCH_TEXT;
	return NULL;
    }

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    LOGACC(lt_text_stat, text);

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    if ( node->ptr != NULL )
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    {
	TRACE1("Found in ptr.\n");
	text_set_mru( text );
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	++text_mcb->hits;
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	return node->ptr;
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    }

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    if ( node->snap_shot != NULL )
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    {
	TRACE1("Found in snap_shot\n");
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	node->ptr = copy_text_stat(node->snap_shot);
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	text_set_mru (text);
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	++text_mcb->hits;
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	return node->ptr;
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    }

    TRACE1("Found in file A.\n");
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    node->ptr = read_text_stat(file_a, node->pos, node->size);
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    text_set_mru (text);
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    ++text_mcb->misses;
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    return node->ptr;
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}



/*
 * The text is set up with an empty misc-field. The misc field is
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 * then initialized by create_text.
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 */

extern Text_no
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cached_create_text(const String message)
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{
    Text_no tno;
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    Cache_node *node;
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    tno = next_text_num++;

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    TRACE2("cached_create_text (len=%u)\n", message.len);
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    if ( tno >= MAX_TEXT )
    {
	kom_errno = KOM_INDEX_OUT_OF_RANGE;
	next_text_num = MAX_TEXT;
	
	return 0;
    }

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    create_cache_node(text_mcb, tno);
    node = get_text_node (tno);
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    if ( node == NULL )
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	restart_kom("cached_create_text(): couldn't create cache-node.\n");
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    node->s.exists = 1;
    node->s.dirty = 1;
    node->ptr = alloc_text_stat();
    ((Text_stat *)node->ptr)->no_of_misc = 0;
    ((Text_stat *)node->ptr)->misc_items = NULL;
    ((Text_stat *)node->ptr)->no_of_marks = 0;
    ((Text_stat *)node->ptr)->no_of_lines = 0;
    ((Text_stat *)node->ptr)->no_of_chars = 0;
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    fseek(text_file, 0, SEEK_END);
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    ((Text_stat *)node->ptr)->file_pos = ftell(text_file);
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    text_set_mru( tno );

    if ( fwrite(message.string, sizeof(char), message.len, text_file)
	!= message.len ) {
	log("WARNING: cached_create_text: Couldn't write the text %d\n",
	    tno);
    }

    fflush(text_file);
    
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    LOGACC(lt_create_text, tno);
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    TRACE2("cached_create_text -> %u\n", tno);
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    return tno;
}


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EXPORT Text_no
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traverse_text(Text_no seed)
{
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    Cache_node *node;

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    seed++;
    
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    while ( seed < next_text_num )
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    {
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	node = get_text_node (seed);
	if ( node != NULL && node->s.exists != 0 )
	    break;

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	seed++;
    }
    
    return (seed >= next_text_num) ? 0 : seed ;
}

Pers_no
traverse_person(Pers_no seed)
{
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    Cache_node *node;

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    seed++;

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    while ( seed < next_free_num )
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    {
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	node = get_pers_node (seed);
	if (node != NULL && node->s.exists != 0 )
	    break;

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	seed++;
    }

    return (seed >= next_free_num) ? 0 : seed ;
}

Conf_no
traverse_conference(Conf_no seed)
{
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    Cache_node *node;

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    seed++;
    
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    while ( seed < next_free_num )
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    {
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	node = get_conf_node (seed);
	if (node != NULL && node->s.exists != 0 )
	    break;

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	seed++;
    }

    return (seed >= next_free_num) ? 0 : seed ;
}

extern Garb_nice
cached_get_garb_nice (Conf_no conf_no)
{
    return small_conf_arr [ conf_no ]->nice;
}

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extern String
cached_get_name (Conf_no conf_no)
{
    return small_conf_arr [ conf_no ]->name;
}
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extern Local_text_no
cached_get_highest_local_no (Conf_no conf_no)
{
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    LOGACC(lt_get_highest, conf_no);

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    return small_conf_arr[ conf_no ]->highest_local_no;
}

/* Lock a person struct in memory. Increase a referenc count. */
void
cached_lock_person(Pers_no pers_no)
{
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    Cache_node *node;

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    LOGACC(lt_lock_pers, pers_no);

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    node = get_pers_node(pers_no);
    
    if ( node == NULL || node->s.exists == 0 )
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	restart_kom("cached_lock_person(%d): nonexistent.\n", pers_no);

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    if ( node->ptr == NULL )
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    {
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	Person *pers_stat_ptr;
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	pers_stat_ptr = cached_get_person_stat( pers_no );
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	if ( pers_stat_ptr == NULL )
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	    restart_kom("cached_lock_person(%d): couldn't read in person.\n",
			pers_no);

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	if ( pers_stat_ptr != node->ptr )
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	    restart_kom("%s(%d): pers_stat_ptr == %d, node->ptr == %d.\n", 
			"cached_lock_person", pers_no, pers_stat_ptr,
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			node->ptr);
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    }

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    node->lock_cnt++;
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}

/* Decrease reference count. If zero, unlock person. */
void
cached_unlock_person(Pers_no pers_no)
{
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    Cache_node *node;

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    LOGACC(lt_unlock_pers, pers_no);

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    node = get_pers_node (pers_no);

    if ( node == NULL )
	restart_kom("cached_unlock_person(): couldn't get cache-node.\n");

    if ( node->lock_cnt <= 0 )
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    {
	log("cached_unlock_person(%d): lock_cnt == %d.\n",
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	    pers_no, node->lock_cnt);
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	node->lock_cnt = 0;
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    }
    else
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	node->lock_cnt--;
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}


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/* Lock a conf struct in memory. Increase a reference count. */
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void
cached_lock_conf(Conf_no conf_no)
{
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    Cache_node *node;

    node = get_conf_node(conf_no);

    if ( node == NULL)
	restart_kom("cached_lock_conf(): can't get cache-node.\n");

    if ( node->s.exists == 0 )
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	restart_kom("cached_lock_conf(%d): nonexistent.\n", conf_no);

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    LOGACC(lt_lock_conf, conf_no);

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    if ( node->ptr == NULL )
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    {
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	Conference *conference_ptr;
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	conference_ptr = cached_get_conf_stat( conf_no );
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