lib/libnisdb/db_table.cc

	db_table.cc revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 *  db_table.cc
 *
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <stdio.h>
#include <malloc.h>
#include <string.h>
#include <stdlib.h>     /* srand48() */
#include <lber.h>
#include <ldap.h>
#include "db_headers.h"
#include "db_table.h"
#include "db_pickle.h"    /* for dump and load */
#include "db_entry.h"
#include "nisdb_mt.h"

#include "ldap_parse.h"
#include "ldap_util.h"
#include "ldap_map.h"
#include "ldap_xdr.h"
#include "nis_hashitem.h"
#include "nisdb_ldap.h"
#include "nis_parse_ldap_conf.h"

static time_t   maxTimeT;

/*
 * Find the largest (positive) value of time_t.
 *
 * If time_t is unsigned, the largest possible value is just ~0.
 * However, if it's signed, then ~0 is negative. Since lint (for
 * sure), and perhaps the compiler too, dislike comparing an
 * unsigned quantity to see if it's less than zero, we compare
 * to one instead. If negative, the largest possible value is
 * th inverse of 2**(N-1), where N is the number of bits in a
 * time_t.
 */
extern "C" {
static void
__setMaxTimeT(void)
{
    unsigned char   b[sizeof (time_t)];
    int     i;

    /* Compute ~0 for an unknown length integer */
    for (i = 0; i < sizeof (time_t); i++) {
        b[i] = 0xff;
    }
    /* Set maxTimeT to ~0 of appropriate length */
    (void) memcpy(&maxTimeT, b, sizeof (time_t));

    if (maxTimeT < 1)
        maxTimeT = ~(1<<((8*sizeof (maxTimeT))-1));
}
#pragma init(__setMaxTimeT)
}

/* How much to grow table by */
#define DB_TABLE_GROWTH_INCREMENT 1024

/* 0'th not used; might be confusing. */
#define DB_TABLE_START 1

/* prevents wrap around numbers from being passed */
#define CALLOC_LIMIT 536870911

/* Initial table sizes to use before using 1K increments. */
/* This helps conserve memory usage when there are lots of small tables. */
static int tabsizes[] = {
    16,
    128,
    512,
    DB_TABLE_GROWTH_INCREMENT,
    0
    };

/* Returns the next size to use for table */
static long unsigned
get_new_table_size(long unsigned oldsize)
{
    long unsigned newsize = 0, n;
    if (oldsize == 0)
        newsize = tabsizes[0];
    else {
        for (n = 0; newsize = tabsizes[n++]; )
            if (oldsize == newsize) {
                newsize = tabsizes[n];  /* get next size */
                break;
            }
        if (newsize == 0)
            newsize = oldsize + DB_TABLE_GROWTH_INCREMENT;
    }
    return (newsize);
}


/* destructor */
db_free_list::~db_free_list()
{
    WRITELOCKV(this, "w db_free_list::~db_free_list");
    reset();   /* free list entries */
    DESTROYRW(free_list);
}

void
db_free_list::reset()
{
    db_free_entry *current, *nextentry;

    WRITELOCKV(this, "w db_free_list::reset");
    for (current = head; current != NULL; ) {
        nextentry = current->next;
        delete current;
        current = nextentry;
    }
    head = NULL;
    count = 0;
    WRITEUNLOCKV(this, "wu db_free_list::reset");
}

/* Returns the location of a free entry, or NULL, if there aren't any. */
entryp
db_free_list::pop()
{
    WRITELOCK(this, NULL, "w db_free_list::pop");
    if (head == NULL) {
        WRITEUNLOCK(this, NULL, "wu db_free_list::pop");
        return (NULL);
    }
    db_free_entry* old_head = head;
    entryp found = head->where;
    head = head->next;
    delete old_head;
    --count;
    WRITEUNLOCK(this, found, "wu db_free_list::pop");
    return (found);
}

/*
 * Adds given location to the free list.
 * Returns TRUE if successful, FALSE otherwise (when out of memory).
*/
bool_t
db_free_list::push(entryp tabloc)
{
    db_free_entry * newentry = new db_free_entry;

    WRITELOCK(this, FALSE, "w db_free_list::push");
    if (newentry == NULL) {
        WRITEUNLOCK(this, FALSE, "wu db_free_list::push");
        FATAL3("db_free_list::push: cannot allocation space",
            DB_MEMORY_LIMIT, FALSE);
    }
    newentry->where = tabloc;
    newentry->next = head;
    head = newentry;
    ++count;
    WRITEUNLOCK(this, TRUE, "wu db_free_list::push");
    return (TRUE);
}

/*
 * Returns in a vector the information in the free list.
 * Vector returned is of form: [n free cells][n1][n2][loc1], ..[locn].
 * Leave the first 'n' cells free.
 * n1 is the number of entries that should be in the freelist.
 * n2 is the number of entries actually found in the freelist.
 * [loc1...locn] are the entries.   n2 <= n1 because we never count beyond n1.
 * It is up to the caller to free the returned vector when he is through.
*/
long *
db_free_list::stats(int nslots)
{
    long    realcount = 0,
        i,
        liststart = nslots,     // start of freelist
        listend = nslots+count+2;   // end of freelist
    db_free_entry_p current = head;

    READLOCK(this, NULL, "r db_free_list::stats");

    long *answer = (long *)malloc((int)(listend)*sizeof (long));
    if (answer == 0) {
        READUNLOCK(this, NULL, "ru db_free_list::stats");
        FATAL3("db_free_list::stats:  cannot allocation space",
            DB_MEMORY_LIMIT, NULL);
    }

    answer[liststart] = count;  /* size of freelist */

    for (i = liststart+2; i < listend && current != NULL; i++) {
        answer[i] = current->where;
        current = current->next;
        ++realcount;
    }

    answer[liststart+1] = realcount;
    READUNLOCK(this, answer, "ru db_free_list::stats");
    return (answer);
}


/* Set default values for the mapping structure */
void
db_table::initMappingStruct(__nisdb_table_mapping_t *m) {
    if (m == 0)
        return;

    m->initTtlLo = (ldapDBTableMapping.initTtlLo > 0) ?
            ldapDBTableMapping.initTtlLo : (3600-1800);
    m->initTtlHi = (ldapDBTableMapping.initTtlHi > 0) ?
            ldapDBTableMapping.initTtlHi : (3600+1800);
    m->ttl = (ldapDBTableMapping.ttl > 0) ?
            ldapDBTableMapping.ttl : 3600;
    m->enumExpire = 0;
    m->fromLDAP = FALSE;
    m->toLDAP = FALSE;
    m->isMaster = FALSE;
    m->retrieveError = ldapDBTableMapping.retrieveError;
    m->retrieveErrorRetry.attempts =
        ldapDBTableMapping.retrieveErrorRetry.attempts;
    m->retrieveErrorRetry.timeout =
        ldapDBTableMapping.retrieveErrorRetry.timeout;
    m->storeError = ldapDBTableMapping.storeError;
    m->storeErrorRetry.attempts =
        ldapDBTableMapping.storeErrorRetry.attempts;
    m->storeErrorRetry.timeout =
        ldapDBTableMapping.storeErrorRetry.timeout;
    m->storeErrorDisp = ldapDBTableMapping.storeErrorDisp;
    m->refreshError = ldapDBTableMapping.refreshError;
    m->refreshErrorRetry.attempts =
        ldapDBTableMapping.refreshErrorRetry.attempts;
    m->refreshErrorRetry.timeout =
        ldapDBTableMapping.refreshErrorRetry.timeout;
    m->matchFetch = ldapDBTableMapping.matchFetch;

    if (mapping.expire != 0)
        free(mapping.expire);
    m->expire = 0;

    if (m->tm != 0)
        free(m->tm);
    m->tm = 0;

    /*
     * The 'objType' field obviously indicates the type of object.
     * However, we also use it to tell us if we've retrieved mapping
     * data from LDAP or not; in the latter case, 'objType' is
     * NIS_BOGUS_OBJ. For purposes of maintaining expiration times,
     * we may need to know if the object is a table or a directory
     * _before_ we've retrieved any mapping data. Hence the 'expireType'
     * field, which starts as NIS_BOGUS_OBJ (meaning, don't know, assume
     * directory for now), and later is set to NIS_DIRECTORY_OBJ
     * (always keep expiration data, in case one of the dir entries
     * is mapped) or NIS_TABLE_OBJ (only need expiration data if
     * tha table is mapped).
     */
    m->objType = NIS_BOGUS_OBJ;
    m->expireType = NIS_BOGUS_OBJ;
    if (m->objName != 0)
        free(m->objName);
    m->objName = 0;
}

void
db_table::db_table_ldap_init(void) {

    INITRW(table);

    enumMode.flag = 0;
    enumCount.flag = 0;
    enumIndex.ptr = 0;
    enumArray.ptr = 0;

    mapping.expire = 0;
    mapping.tm = 0;
    mapping.objName = 0;
    mapping.isDeferredTable = FALSE;
    (void) mutex_init(&mapping.enumLock, 0, 0);
    mapping.enumTid = 0;
    mapping.enumStat = -1;
    mapping.enumDeferred = 0;
    mapping.enumEntries = 0;
    mapping.enumTime = 0;
}

/* db_table constructor */
db_table::db_table() : freelist()
{
    tab = NULL;
    table_size = 0;
    last_used = 0;
    count = 0;

    db_table_ldap_init();
    initMappingStruct(&mapping);

/*  grow(); */
}

/*
 * db_table destructor:
 * 1.  Get rid of contents of freelist
 * 2.  delete all entries hanging off table
 * 3.  get rid of table itself
*/
db_table::~db_table()
{
    WRITELOCKV(this, "w db_table::~db_table");
    reset();
    DESTROYRW(table);
}

/* reset size and pointers */
void
db_table::reset()
{
    int i, done = 0;

    WRITELOCKV(this, "w db_table::reset");
    freelist.reset();

    /* Add sanity check in case of table corruption */
    if (tab != NULL) {
        for (i = 0;
            i <= last_used && i < table_size && done < count;
            i++) {
            if (tab[i]) {
                free_entry(tab[i]);
                ++done;
            }
        }
    }

    delete tab;
    table_size = last_used = count = 0;
    tab = NULL;
    sfree(mapping.expire);
    mapping.expire = NULL;
    mapping.objType = NIS_BOGUS_OBJ;
    mapping.expireType = NIS_BOGUS_OBJ;
    sfree(mapping.objName);
    mapping.objName = 0;
    /* Leave other values of the mapping structure unchanged */
    enumMode.flag = 0;
    enumCount.flag = 0;
    sfree(enumIndex.ptr);
    enumIndex.ptr = 0;
    sfree(enumArray.ptr);
    enumArray.ptr = 0;
    WRITEUNLOCKV(this, "wu db_table::reset");
}

db_status
db_table::allocateExpire(long oldSize, long newSize) {
    time_t          *newExpire;

    newExpire = (time_t *)realloc(mapping.expire,
                newSize * sizeof (mapping.expire[0]));
    if (newExpire != NULL) {
        /* Initialize new portion */
        (void) memset(&newExpire[oldSize], 0,
                (newSize-oldSize) * sizeof (newExpire[0]));
        mapping.expire = newExpire;
    } else {
        return (DB_MEMORY_LIMIT);
    }

    return (DB_SUCCESS);
}

db_status
db_table::allocateEnumArray(long oldSize, long newSize) {
    entry_object    **newEnumArray;
    char        *myself = "db_table::allocateEnumArray";

    if (enumCount.flag > 0) {
        if (enumIndex.ptr == 0) {
            enumIndex.ptr = (entryp *)am(myself, enumCount.flag *
                        sizeof (entryp));
            if (enumIndex.ptr == 0)
                return (DB_MEMORY_LIMIT);
        }
        oldSize = 0;
        newSize = enumCount.flag;
    }
    newEnumArray = (entry_object **)realloc(enumArray.ptr,
            newSize * sizeof (entry_object *));
    if (newEnumArray != 0 && newSize > oldSize) {
        (void) memcpy(&newEnumArray[oldSize], &tab[oldSize],
            (newSize-oldSize) * sizeof (entry_object *));
        enumArray.ptr = newEnumArray;
    } else if (newEnumArray == 0) {
        return (DB_MEMORY_LIMIT);
    }

    return (DB_SUCCESS);
}

/* Expand the table.  Fatal error if insufficient memory. */
void
db_table::grow()
{
    WRITELOCKV(this, "w db_table::grow");
    long oldsize = table_size;
    entry_object_p *oldtab = tab;
    long i;

    table_size = get_new_table_size(oldsize);

#ifdef DEBUG
    fprintf(stderr, "db_table GROWING to %d\n", table_size);
#endif

    if (table_size > CALLOC_LIMIT) {
        table_size = oldsize;
        WRITEUNLOCKV(this, "wu db_table::grow");
        FATAL("db_table::grow: table size exceeds calloc limit",
            DB_MEMORY_LIMIT);
    }

//  if ((tab = new entry_object_p[table_size]) == NULL)
    if ((tab = (entry_object_p*)
        calloc((unsigned int) table_size,
            sizeof (entry_object_p))) == NULL) {
        tab = oldtab;       // restore previous table info
        table_size = oldsize;
        WRITEUNLOCKV(this, "wu db_table::grow");
        FATAL("db_table::grow: cannot allocate space", DB_MEMORY_LIMIT);
    }

    /*
     * For directories, we may need the expire time array even if the
     * directory itself isn't mapped. If the objType and expireType both
     * are bogus, we don't  know yet if this is a table or a directory,
     * and must proceed accordingly.
     */
    if (mapping.objType == NIS_DIRECTORY_OBJ ||
            mapping.expireType != NIS_TABLE_OBJ ||
            mapping.fromLDAP) {
        db_status stat = allocateExpire(oldsize, table_size);
        if (stat != DB_SUCCESS) {
            free(tab);
            tab = oldtab;
            table_size = oldsize;
            WRITEUNLOCKV(this, "wu db_table::grow expire");
            FATAL(
        "db_table::grow: cannot allocate space for expire", stat);
        }
    }

    if (oldtab != NULL) {
        for (i = 0; i < oldsize; i++) { // transfer old to new
            tab[i] = oldtab[i];
        }
        delete oldtab;
    }

    if (enumMode.flag) {
        db_status stat = allocateEnumArray(oldsize, table_size);
        if (stat != DB_SUCCESS) {
            free(tab);
            tab = oldtab;
            table_size = oldsize;
            WRITEUNLOCKV(this, "wu db_table::grow enumArray");
            FATAL(
        "db_table::grow: cannot allocate space for enumArray", stat);
        }
    }

    WRITEUNLOCKV(this, "wu db_table::grow");
}

/*
 * Return the first entry in table, also return its position in
 * 'where'.  Return NULL in both if no next entry is found.
 */
entry_object*
db_table::first_entry(entryp * where)
{
    ASSERTRHELD(table);
    if (count == 0 || tab == NULL) {  /* empty table */
        *where = NULL;
        return (NULL);
    } else {
        entryp i;
        for (i = DB_TABLE_START;
            i < table_size && i <= last_used; i++) {
            if (tab[i] != NULL) {
                *where = i;
                return (tab[i]);
            }
        }
    }
    *where = NULL;
    return (NULL);
}

/*
 * Return the next entry in table from 'prev', also return its position in
 * 'newentry'.  Return NULL in both if no next entry is found.
 */
entry_object *
db_table::next_entry(entryp prev, entryp* newentry)
{
    long i;

    ASSERTRHELD(table);
    if (prev >= table_size || tab == NULL || tab[prev] == NULL)
        return (NULL);
    for (i = prev+1; i < table_size && i <= last_used; i++) {
        if (tab[i] != NULL) {
            *newentry = i;
            return (tab[i]);
        }
    }
    *newentry = NULL;
    return (NULL);
}

/* Return entry at location 'where', NULL if location is invalid. */
entry_object *
db_table::get_entry(entryp where)
{
    ASSERTRHELD(table);
    if (where < table_size && tab != NULL && tab[where] != NULL)
        return (tab[where]);
    else
        return (NULL);
}

void
db_table::setEntryExp(entryp where, entry_obj *obj, int initialLoad) {
    nis_object      *o;
    char            *myself = "db_table::setEntryExp";

    /*
     * If we don't know what type of object this is yet, we
     * can find out now. If it's a directory, the pseudo-object
     * in column zero will have the type "IN_DIRECTORY";
     * otherwise, it's a table object.
     */
    if (mapping.expireType == NIS_BOGUS_OBJ) {
        if (obj != 0) {
            if (obj->en_type != 0 &&
                strcmp(obj->en_type, "IN_DIRECTORY") == 0) {
                mapping.expireType = NIS_DIRECTORY_OBJ;
            } else {
                mapping.expireType = NIS_TABLE_OBJ;
                if (!mapping.fromLDAP) {
                    free(mapping.expire);
                    mapping.expire = 0;
                }
            }
        }
    }

    /* Set the entry TTL */
    if (mapping.expire != NULL) {
        struct timeval  now;
        time_t      lo, hi, ttl;

        (void) gettimeofday(&now, NULL);
        if (mapping.expireType == NIS_TABLE_OBJ) {
            lo = mapping.initTtlLo;
            hi = mapping.initTtlHi;
            ttl = mapping.ttl;
            /* TTL == 0 means always expired */
            if (ttl == 0)
                ttl = -1;
        } else {
            __nis_table_mapping_t   *t = 0;

            o = unmakePseudoEntryObj(obj, 0);
            if (o != 0) {
                __nis_buffer_t  b = {0, 0};

                bp2buf(myself, &b, "%s.%s",
                    o->zo_name, o->zo_domain);
                t = getObjMapping(b.buf, 0, 1, 0, 0);
                sfree(b.buf);
                nis_destroy_object(o);
            }

            if (t != 0) {
                lo = t->initTtlLo;
                hi = t->initTtlHi;
                ttl = t->ttl;
                /* TTL == 0 means always expired */
                if (ttl == 0)
                    ttl = -1;
            } else {
                /*
                 * No expiration time initialization
                 * data. Cook up values that will
                 * result in mapping.expire[where]
                 * set to maxTimeT.
                 */
                hi = lo = ttl = maxTimeT - now.tv_sec;
            }
        }

        if (initialLoad) {
            int interval = hi - lo + 1;
            if (interval <= 1) {
                mapping.expire[where] = now.tv_sec + lo;
            } else {
                srand48(now.tv_sec);
                mapping.expire[where] = now.tv_sec +
                            (lrand48() % interval);
            }
            if (mapping.enumExpire == 0 ||
                    mapping.expire[where] <
                            mapping.enumExpire)
                mapping.enumExpire = mapping.expire[where];
        } else {
            mapping.expire[where] = now.tv_sec + ttl;
        }
    }
}

/*
 * Add given entry to table in first available slot (either look in freelist
 * or add to end of table) and return the the position of where the record
 * is placed. 'count' is incremented if entry is added. Table may grow
 * as a side-effect of the addition. Copy is made of input.
*/
entryp
db_table::add_entry(entry_object *obj, int initialLoad) {
    /*
     * We're returning an index of the table array, so the caller
     * should hold a lock until done with the index. To save us
     * the bother of upgrading to a write lock, it might as well
     * be a write lock to begin with.
     */
    ASSERTWHELD(table);
    entryp where = freelist.pop();
    if (where == NULL) {                /* empty freelist */
        if (last_used >= (table_size-1))    /* full (> is for 0) */
            grow();
        where = ++last_used;
    }
    if (tab != NULL) {
        ++count;
        setEntryExp(where, obj, initialLoad);

        if (enumMode.flag)
            enumTouch(where);
        tab[where] = new_entry(obj);
        return (where);
    } else {
        return (NULL);
    }
}

/*
 * Replaces object at specified location by given entry.
 * Returns TRUE if replacement successful; FALSE otherwise.
 * There must something already at the specified location, otherwise,
 * replacement fails. Copy is not made of the input.
 * The pre-existing entry is freed.
 */
bool_t
db_table::replace_entry(entryp where, entry_object * obj)
{
    ASSERTWHELD(table);
    if (where < DB_TABLE_START || where >= table_size ||
        tab == NULL || tab[where] == NULL)
        return (FALSE);
    /* (Re-)set the entry TTL */
    setEntryExp(where, obj, 0);

    if (enumMode.flag)
        enumTouch(where);
    free_entry(tab[where]);
    tab[where] = obj;
    return (TRUE);
}

/*
 * Deletes entry at specified location.  Returns TRUE if location is valid;
 * FALSE if location is invalid, or the freed location cannot be added to
 * the freelist.  'count' is decremented if the deletion occurs.  The object
 * at that location is freed.
 */
bool_t
db_table::delete_entry(entryp where)
{
    bool_t  ret = TRUE;

    ASSERTWHELD(table);
    if (where < DB_TABLE_START || where >= table_size ||
        tab == NULL || tab[where] == NULL)
        return (FALSE);
    if (mapping.expire != NULL) {
        mapping.expire[where] = 0;
    }
    if (enumMode.flag)
        enumTouch(where);
    free_entry(tab[where]);
    tab[where] = NULL;    /* very important to set it to null */
    --count;
    if (where == last_used) { /* simple case, deleting from end */
        --last_used;
        return (TRUE);
    } else {
        return (freelist.push(where));
    }
    return (ret);
}

/*
 * Returns statistics of table.
 * [vector_size][table_size][last_used][count][freelist].
 * It is up to the caller to free the returned vector when his is through.
 * The free list is included if 'fl' is TRUE.
*/
long *
db_table::stats(bool_t include_freelist)
{
    long *answer;

    READLOCK(this, NULL, "r db_table::stats");
    if (include_freelist)
        answer = freelist.stats(3);
    else {
        answer = (long *)malloc(3*sizeof (long));
    }

    if (answer) {
        answer[0] = table_size;
        answer[1] = last_used;
        answer[2] = count;
    }
    READUNLOCK(this, answer, "ru db_table::stats");
    return (answer);
}

bool_t
db_table::configure(char *tablePath) {
    long        i;
    struct timeval  now;
    char        *myself = "db_table::configure";

    (void) gettimeofday(&now, NULL);

    WRITELOCK(this, FALSE, "db_table::configure w");

    /* (Re-)initialize from global info */
    initMappingStruct(&mapping);

    /* Retrieve table mapping for this table */
    mapping.tm = (__nis_table_mapping_t *)__nis_find_item_mt(
                    tablePath, &ldapMappingList, 0, 0);
    if (mapping.tm != 0) {
        __nis_object_dn_t   *odn = mapping.tm->objectDN;

        /*
         * The mapping.fromLDAP and mapping.toLDAP fields serve as
         * quick-references that tell us if mapping is enabled.
         * Hence, initialize them appropriately from the table
         * mapping objectDN.
         */
        while (odn != 0 && (!mapping.fromLDAP || !mapping.toLDAP)) {
            if (odn->read.scope != LDAP_SCOPE_UNKNOWN)
                mapping.fromLDAP = TRUE;
            if (odn->write.scope != LDAP_SCOPE_UNKNOWN)
                mapping.toLDAP = TRUE;
            odn = (__nis_object_dn_t *)odn->next;
        }

        /* Set the timeout values */
        mapping.initTtlLo = mapping.tm->initTtlLo;
        mapping.initTtlHi = mapping.tm->initTtlHi;
        mapping.ttl = mapping.tm->ttl;

        mapping.objName = sdup(myself, T, mapping.tm->objName);
        if (mapping.objName == 0 && mapping.tm->objName != 0) {
            WRITEUNLOCK(this, FALSE,
                "db_table::configure wu objName");
            FATAL3("db_table::configure objName",
                DB_MEMORY_LIMIT, FALSE);
        }
    }

    /*
     * In order to initialize the expiration times, we need to know
     * if 'this' represents a table or a directory. To that end, we
     * find an entry in the table, and invoke setEntryExp() on it.
     * As a side effect, setEntryExp() will examine the pseudo-object
     * in the entry, and set the expireType accordingly.
     */
    if (tab != 0) {
        for (i = 0; i <= last_used; i++) {
            if (tab[i] != NULL) {
                setEntryExp(i, tab[i], 1);
                break;
            }
        }
    }

    /*
     * If mapping from an LDAP repository, make sure we have the
     * expiration time array.
     */
    if ((mapping.expireType != NIS_TABLE_OBJ || mapping.fromLDAP) &&
            mapping.expire == NULL && table_size > 0 && tab != 0) {
        db_status stat = allocateExpire(0, table_size);
        if (stat != DB_SUCCESS) {
            WRITEUNLOCK(this, FALSE,
                "db_table::configure wu expire");
            FATAL3("db_table::configure expire",
                stat, FALSE);
        }
    } else if (mapping.expireType == NIS_TABLE_OBJ && !mapping.fromLDAP &&
            mapping.expire != NULL) {
        /* Not using expiration times */
        free(mapping.expire);
        mapping.expire = NULL;
    }

    /*
     * Set initial expire times for entries that don't already have one.
     * Establish the enumeration expiration time to be the minimum of
     * all expiration times in the table, though no larger than current
     * time plus initTtlHi.
     */
    if (mapping.expire != NULL) {
        int interval = mapping.initTtlHi - mapping.initTtlLo + 1;
        time_t  enumXp = now.tv_sec + mapping.initTtlHi;

        if (interval > 1)
            srand48(now.tv_sec);
        for (i = 0; i <= last_used; i++) {
            if (tab[i] != NULL && mapping.expire[i] == 0) {
                if (mapping.expireType == NIS_TABLE_OBJ) {
                    if (interval > 1)
                        mapping.expire[i] =
                            now.tv_sec +
                            (lrand48() % interval);
                    else
                        mapping.expire[i] =
                            now.tv_sec +
                            mapping.initTtlLo;
                } else {
                    setEntryExp(i, tab[i], 1);
                }
            }
            if (enumXp > mapping.expire[i])
                enumXp = mapping.expire[i];
        }
        mapping.enumExpire = enumXp;
    }

    WRITEUNLOCK(this, FALSE, "db_table::configure wu");

    return (TRUE);
}

/* Return TRUE if the entry at 'loc' hasn't expired */
bool_t
db_table::cacheValid(entryp loc) {
    bool_t      ret;
    struct timeval  now;

    (void) gettimeofday(&now, 0);

    READLOCK(this, FALSE, "db_table::cacheValid r");

    if (loc < 0 || loc >= table_size || tab == 0 || tab[loc] == 0)
        ret = FALSE;
    else if (mapping.expire == 0 || mapping.expire[loc] >= now.tv_sec)
        ret = TRUE;
    else
        ret = FALSE;

    READUNLOCK(this, ret, "db_table::cacheValid ru");

    return (ret);
}

/*
 * If the supplied object has the same content as the one at 'loc',
 * update the expiration time for the latter, and return TRUE.
 */
bool_t
db_table::dupEntry(entry_object *obj, entryp loc) {
    if (obj == 0 || loc < 0 || loc >= table_size || tab == 0 ||
            tab[loc] == 0)
        return (FALSE);

    if (sameEntry(obj, tab[loc])) {
        setEntryExp(loc, tab[loc], 0);

        if (enumMode.flag > 0)
            enumTouch(loc);
        return (TRUE);
    }

    return (FALSE);
}

/*
 * If enumeration mode is enabled, we keep a shadow array that initially
 * starts out the same as 'tab'. Any update activity (add, remove, replace,
 * or update timestamp) for an entry in the table means we delete the shadow
 * array pointer. When ending enumeration mode, we return the shadow array.
 * Any non-NULL entries in the array have not been updated since the start
 * of the enum mode.
 *
 * The indended use is for enumeration of an LDAP container, where we
 * will update all entries that currently exist in LDAP. The entries we
 * don't update are those that don't exist in LDAP, and thus should be
 * removed.
 *
 * Note that any LDAP query strictly speaking can be a partial enumeration
 * (i.e., return more than one match). Since the query might also have
 * matched multiple local DB entries, we need to do the same work as for
 * enumeration for any query. In order to avoid having to work on the
 * whole 'tab' array for simple queries (which we expect usually will
 * match just one or at most a few entries), we have a "reduced" enum mode,
 * where the caller supplies a count of the number of DB entries (derived
 * from db_mindex::satisfy_query() or similar), and then uses enumSetup()
 * to specify which 'tab' entries we're interested in.
 */
void
db_table::setEnumMode(long enumNum) {
    char    *myself = "setEnumMode";

    enumMode.flag++;
    if (enumMode.flag == 1) {
        db_status   stat;

        if (enumNum < 0)
            enumNum = 0;
        else if (enumNum >= table_size)
            enumNum = table_size;

        enumCount.flag = enumNum;

        stat = allocateEnumArray(0, table_size);

        if (stat != DB_SUCCESS) {
            enumMode.flag = 0;
            enumCount.flag = 0;
            logmsg(MSG_NOTIMECHECK, LOG_ERR,
        "%s: No memory for enum check array; entry removal disabled",
                myself);
        }
    }
}

void
db_table::clearEnumMode(void) {
    if (enumMode.flag > 0) {
        enumMode.flag--;
        if (enumMode.flag == 0) {
            sfree(enumArray.ptr);
            enumArray.ptr = 0;
            if (enumCount.flag > 0) {
                sfree(enumIndex.ptr);
                enumIndex.ptr = 0;
                enumCount.flag = 0;
            }
        }
    }
}

entry_object **
db_table::endEnumMode(long *numEa) {
    if (enumMode.flag > 0) {
        enumMode.flag--;
        if (enumMode.flag == 0) {
            entry_obj   **ea = (entry_object **)enumArray.ptr;
            long        nea;

            enumArray.ptr = 0;

            if (enumCount.flag > 0) {
                nea = enumCount.flag;
                enumCount.flag = 0;
                sfree(enumIndex.ptr);
                enumIndex.ptr = 0;
            } else {
                nea = table_size;
            }

            if (numEa != 0)
                *numEa = nea;

            return (ea);
        }
    }

    if (numEa != 0)
        *numEa = 0;

    return (0);
}

/*
 * Set the appropriate entry in the enum array to NULL.
 */
void
db_table::enumTouch(entryp loc) {
    if (loc < 0 || loc >= table_size)
        return;

    if (enumMode.flag > 0) {
        if (enumCount.flag < 1) {
            ((entry_object **)enumArray.ptr)[loc] = 0;
        } else {
            int i;

            for (i = 0; i < enumCount.flag; i++) {
                if (loc == ((entryp *)enumIndex.ptr)[i]) {
                    ((entry_object **)enumArray.ptr)[i] = 0;
                    break;
                }
            }
        }
    }
}

/*
 * Add the entry indicated by 'loc' to the enumIndex array, at 'index'.
 */
void
db_table::enumSetup(entryp loc, long index) {
    if (enumMode.flag == 0 || loc < 0 || loc >= table_size ||
            index < 0 || index >= enumCount.flag)
        return;

    ((entryp *)enumIndex.ptr)[index] = loc;
    ((entry_object **)enumArray.ptr)[index] = tab[loc];
}

/*
 * Touch, i.e., update the expiration time for the entry. Also, if enum
 * mode is in effect, mark the entry used for enum purposes.
 */
void
db_table::touchEntry(entryp loc) {
    if (loc < 0 || loc >= table_size || tab == 0 || tab[loc] == 0)
        return;

    setEntryExp(loc, tab[loc], 0);

    enumTouch(loc);
}

/* ************************* pickle_table ********************* */
/* Does the actual writing to/from file specific for db_table structure. */
/*
 * This was a static earlier with the func name being transfer_aux. The
 * backup and restore project needed this to copy files over.
 */
bool_t
transfer_aux_table(XDR* x, pptr dp)
{
    return (xdr_db_table(x, (db_table*) dp));
}

class pickle_table: public pickle_file {
    public:
    pickle_table(char *f, pickle_mode m) : pickle_file(f, m) {}

    /* Transfers db_table structure pointed to by dp to/from file. */
    int transfer(db_table* dp)
    { return (pickle_file::transfer((pptr) dp, &transfer_aux_table)); }
};

/*
 * Writes the contents of table, including the all the entries, into the
 * specified file in XDR format.  May need to change this to use APPEND
 * mode instead.
 */
int
db_table::dump(char *file)
{
    int ret;
    READLOCK(this, -1, "r db_table::dump");
    pickle_table f(file, PICKLE_WRITE);   /* may need to use APPEND mode */
    int status = f.transfer(this);

    if (status == 1)
        ret = -1;
    else
        ret = status;
    READUNLOCK(this, ret, "ru db_table::dump");
}

/* Constructor that loads in the table from the given file */
db_table::db_table(char *file)  : freelist()
{
    pickle_table f(file, PICKLE_READ);
    tab = NULL;
    table_size = last_used = count = 0;

    /* load  table */
    if (f.transfer(this) < 0) {
        /* fell through, something went wrong, initialize to null */
        tab = NULL;
        table_size = last_used = count = 0;
        freelist.init();
    }

    db_table_ldap_init();
    initMappingStruct(&mapping);
}

/* Returns whether location is valid. */
bool_t db_table::entry_exists_p(entryp i) {
    bool_t  ret = FALSE;
    READLOCK(this, FALSE, "r db_table::entry_exists_p");
    if (tab != NULL && i < table_size)
        ret = tab[i] != NULL;
    READUNLOCK(this, ret, "ru db_table::entry_exists_p");
    return (ret);
}

/* Empty free list */
void db_free_list::init() {
    WRITELOCKV(this, "w db_free_list::init");
    head = NULL;
    count = 0;
    WRITEUNLOCKV(this, "wu db_free_list::init");
}