xwords/xwords4/relay/crefmgr.cpp

/* -*-mode: C; fill-column: 78; c-basic-offset: 4; -*- */

/* 
 * Copyright 2005-2009 by Eric House (xwords@eehouse.org).  All rights
 * reserved.
 *
 * This program 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 2
 * of the License, or (at your option.
 *
 * This program 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

#include "crefmgr.h"
#include "cref.h"
#include "mlock.h"
#include "configs.h"
#include "timermgr.h"

class SocketStuff {
 public:
    SocketStuff( CookieRef* cref )
        : m_cref(cref)
        {        
            pthread_mutex_init( &m_writeMutex, NULL );
        }
    ~SocketStuff() { pthread_mutex_destroy( &m_writeMutex ); }
    CookieRef* m_cref;
    pthread_mutex_t m_writeMutex; /* so only one thread writes at a time */
};

static CRefMgr* s_instance = NULL;

/* static */ CRefMgr*
CRefMgr::Get() 
{
    if ( s_instance == NULL ) {
        s_instance = new CRefMgr();
    }
    return s_instance;
} /* Get */

CRefMgr::CRefMgr()
    : m_nRoomsFilled(0)
    , m_startTime(time(NULL))
{
    /* should be using pthread_once() here */
    /* pthread_mutex_init( &m_SocketStuffMutex, NULL ); */
    pthread_mutex_init( &m_roomsFilledMutex, NULL );
    pthread_mutex_init( &m_freeList_mutex, NULL );
    pthread_rwlock_init( &m_cookieMapRWLock, NULL );
    m_db = DBMgr::Get();
    m_cidlock = CidLock::GetInstance();
}

CRefMgr::~CRefMgr()
{
    assert( this == s_instance );

    delete m_db;
    delete m_cidlock;

    pthread_mutex_destroy( &m_freeList_mutex );
    pthread_rwlock_destroy( &m_cookieMapRWLock );

    s_instance = NULL;
}

void
CRefMgr::CloseAll()
{
    /* Get every cref instance, shut it down */

    for ( ; ; ) {
        CookieRef* cref = NULL;
        {
            RWWriteLock rwl( &m_cookieMapRWLock );
            CookieMap::iterator iter = m_cookieMap.begin();
            if ( iter == m_cookieMap.end() ) {
                break;
            }
            cref = iter->second; 
            {
                SafeCref scr( cref->GetCid(), false ); /* cref */
                scr.Shutdown();
            }
        }
    }
} /* CloseAll */

void 
CRefMgr::IncrementFullCount( void )
{
    MutexLock ml( &m_roomsFilledMutex );
    ++m_nRoomsFilled;
}

int 
CRefMgr::GetNumRoomsFilled( void )
{
    MutexLock ml(&m_roomsFilledMutex);
    return m_nRoomsFilled;
}

int 
CRefMgr::GetSize( void )
{
    return m_cookieMap.size();
}

void
CRefMgr::GetStats( CrefMgrInfo& mgrInfo )
{
    mgrInfo.m_nRoomsFilled = GetNumRoomsFilled();
    mgrInfo.m_startTimeSpawn = m_startTime;

    if ( 0 == m_ports.length() ) {
        RelayConfigs* cfg = RelayConfigs::GetConfigs();
        vector<int> ints;
        if ( cfg->GetValueFor( "GAME_PORTS", ints ) ) {
            vector<int>::const_iterator iter;
            for ( iter = ints.begin(); ; ) {
                char buf[8];
                snprintf( buf, sizeof(buf), "%d", *iter );
                m_ports += buf;
                ++iter;
                if ( iter == ints.end() ) {
                    break;
                }
                m_ports += ",";
            }
        }
    }
    mgrInfo.m_ports = m_ports.c_str();

    RWReadLock rwl( &m_cookieMapRWLock );
    mgrInfo.m_nCrefsCurrent = m_cookieMap.size();

    CookieMap::iterator iter;
    for ( iter = m_cookieMap.begin(); iter != m_cookieMap.end(); ++iter ) {
        CookieRef* cref = iter->second;

        CrefInfo info;
        info.m_cookie = cref->Cookie();
        info.m_connName = cref->ConnName();
        info.m_cid = cref->GetCid();
        info.m_curState = cref->CurState();
        info.m_nPlayersSought = cref->GetPlayersSought();
        info.m_nPlayersHere = cref->GetPlayersHere();
        info.m_startTime = cref->GetStarttime();
        info.m_langCode = cref->GetLangCode();
        
        SafeCref sc(cref->GetCid(), false );
        sc.GetHostsConnected( &info.m_hostsIds, &info.m_hostSeeds, 
                              &info.m_hostIps );
        
        mgrInfo.m_crefInfo.push_back( info );
    }
}

CookieID
CRefMgr::cookieIDForConnName( const char* connName )
{
    CookieID cid = 0;
    /* for now, just walk the existing data structure and see if the thing's
       in use.  If it isn't, return a new id. */

    RWReadLock rwl( &m_cookieMapRWLock );

    CookieMap::iterator iter = m_cookieMap.begin();
    while ( iter != m_cookieMap.end() ) {
        CookieRef* cref = iter->second;
        if ( 0 == strcmp( cref->ConnName(), connName ) ) {
            cid = iter->first;
            break;
        }
        ++iter;
    }

    return cid;
} /* cookieIDForConnName */

void
CRefMgr::addToFreeList( CookieRef* cref )
{
    MutexLock ml( &m_freeList_mutex );
    m_freeList.push_back( cref );
}

CookieRef*
CRefMgr::getFromFreeList( void )
{
    CookieRef* cref = NULL;
    MutexLock ml( &m_freeList_mutex );
    if ( m_freeList.size() > 0 ) {
        cref = m_freeList.front();
        m_freeList.pop_front();
    }
    return cref;
}

/* connect case */
CidInfo*
CRefMgr::getMakeCookieRef( const char* cookie, int nPlayersH, int nPlayersT, 
                           int langCode, int seed, int clientIndx, 
                           bool wantsPublic, bool makePublic, bool* seenSeed )
{
    CidInfo* cinfo;

    /* We have a cookie from a new connection or from a reconnect.  This may
       be the first time it's been seen, or there may be a game currently in
       the XW_ST_CONNECTING state, or it may be a dupe of a connect packet on
       the same or a different socket.  If there's a game, cool.  Otherwise add
       a new one.  Pass the connName which will be used if set, but if not set
       we'll be generating another later when the game is complete.
    */
    for ( ; ; ) {
        /* What's this for loop thing.  It's to fix a race condition.  One
           thread has "claim" on cid <N>, which is in the DB.  Another comes
           into this function and looks it up in the DB, retrieving <N>, but
           progress is blocked inside getCookieRef_impl which calls Claim().
           The first thread winds up removing <N> from the DB and deleting its
           cref before calling Relinquish so that when Claim() returns there's
           no cref.  So we test for that case and retry. */


        CookieID cid;
        char connNameBuf[MAX_CONNNAME_LEN+1] = {0};
        int alreadyHere = 0;

        *seenSeed = m_db->SeenSeed( cookie, seed, langCode, nPlayersT, 
                                    wantsPublic, connNameBuf, 
                                    sizeof(connNameBuf), &alreadyHere, &cid );
        if ( !*seenSeed ) {
            cid = m_db->FindOpen( cookie, langCode, nPlayersT, nPlayersH, 
                                  wantsPublic, connNameBuf, sizeof(connNameBuf), 
                                  &alreadyHere );
        }

        if ( cid > 0 ) {
            cinfo = m_cidlock->Claim( cid );
            if ( NULL == cinfo->GetRef() ) {
                m_cidlock->Relinquish( cinfo, true );
                continue;
            } else if ( *seenSeed ) { /* this my home? */
                logf( XW_LOGINFO, "%s: *seenSeed case", __func__ );
                break;
            } else if ( !cinfo->GetRef()->HaveRoom( nPlayersH ) ) {
                m_cidlock->Relinquish( cinfo, false );
                continue;
            }
        } else {
            cinfo = m_cidlock->Claim();
            cid = cinfo->GetCid();
            CookieRef* cref = AddNew( cookie, connNameBuf, cid, langCode, 
                                      nPlayersT, alreadyHere );
            cinfo->SetRef( cref );
            if ( !connNameBuf[0] ) { /* didn't exist in DB */
                m_db->AddNew( cookie, cref->ConnName(), cid, langCode, nPlayersT, 
                              wantsPublic || makePublic );
            } else {
                if ( !m_db->AddCID( connNameBuf, cid ) ) {
                    m_cidlock->Relinquish( cinfo, true );
                    continue;
                }
            }
        }
        break;
    }
    assert( cinfo->GetRef() );
    return cinfo;
} /* getMakeCookieRef */

/* reconnect case */
CidInfo*
CRefMgr::getMakeCookieRef( const char* connName, const char* cookie,
                           HostID hid, int nPlayersH, int nPlayersS, int seed, 
                           int langCode, bool isPublic, bool* isDead )
{
    CookieRef* cref = NULL;
    CidInfo* cinfo = NULL;

    for ( ; ; ) {               /* for: see comment above */
        /* fetch these from DB */
        char curCookie[MAX_INVITE_LEN+1];
        int curLangCode;
        int nAlreadyHere = nPlayersH;

        CookieID cid;
        if ( !m_db->FindGameFor( connName, curCookie, sizeof(curCookie),
                                 seed, hid, nPlayersH, nPlayersS,
                                 &curLangCode, isDead, &cid ) ) {
            break;
        }

        if ( 0 != cid ) {           /* already open */
            cinfo = m_cidlock->Claim( cid );
            if ( NULL == cinfo->GetRef() ) {
                m_cidlock->Relinquish( cinfo, true );
                continue;
            }
        } else {
            /* The entry may not even be in the DB, e.g. if it got deleted.
               Deal with that possibility by taking the caller's word for it. */
            cinfo = m_cidlock->Claim();
            cid = cinfo->GetCid();

            if ( !m_db->AddCID( connName, cid ) ) {
                m_cidlock->Relinquish( cinfo, true );
                continue;
            }
            cookie = curCookie;

            cref = AddNew( cookie, connName, cid, curLangCode, nPlayersS, 
                           nAlreadyHere );
            cinfo->SetRef( cref );
        }
        break;
    } /* for */
    assert( NULL == cinfo || cinfo->GetRef() );
    return cinfo;
} /* getMakeCookieRef */

CidInfo*
CRefMgr::getMakeCookieRef( const char* const connName, bool* isDead )
{
    CookieRef* cref = NULL;
    CidInfo* cinfo = NULL;
    char curCookie[MAX_INVITE_LEN+1];
    int curLangCode;
    int nPlayersT = 0;
    int nAlreadyHere = 0;

    for ( ; ; ) {               /* for: see comment above */
        CookieID cid = m_db->FindGame( connName, curCookie, sizeof(curCookie),
                                       &curLangCode, &nPlayersT, &nAlreadyHere,
                                       isDead );
        if ( 0 != cid ) {           /* already open */
            cinfo = m_cidlock->Claim( cid );
            if ( NULL == cinfo->GetRef() ) {
                m_cidlock->Relinquish( cinfo, true );
                continue;
            }
        } else {
            if ( nPlayersT == 0 ) { /* wasn't in the DB */
                /* do nothing; insufficient info to fake it */
            } else {
                cinfo = m_cidlock->Claim();
                if ( !m_db->AddCID( connName, cinfo->GetCid() ) ) {
                    m_cidlock->Relinquish( cinfo, true );
                    continue;
                }
                cref = AddNew( curCookie, connName, cinfo->GetCid(), curLangCode, 
                               nPlayersT, nAlreadyHere );
                cinfo->SetRef( cref );
            }
        }
        break;
    }
    return cinfo;
}

void 
CRefMgr::RemoveSocketRefs( const AddrInfo* addr )
{
    {    
        SafeCref scr( addr );
        scr.Remove( addr );
    }
}

void
CRefMgr::PrintSocketInfo( int sock, string& out )
{
    SafeCref scr( sock );
    const char* name = scr.Cookie();
    if ( name != NULL && name[0] != '\0' ) {
        char buf[64];

        snprintf( buf, sizeof(buf), "* socket: %d\n", sock );
        out += buf;

        snprintf( buf, sizeof(buf), "  in cookie: %s\n", name );
        out += buf;
    }
}

CidInfo*
CRefMgr::getCookieRef( CookieID cid, bool failOk /* = false */ )
{
    CidInfo* cinfo = NULL;
    for ( int count = 0; ; ++count ) {
        cinfo = m_cidlock->Claim( cid );
        if ( NULL != cinfo->GetRef() ) { /* What's it mean to get a cinfo back but have it be empty??? */
            break;
        } else if ( failOk || count > 20 ) {
            break;
        }
        m_cidlock->Relinquish( cinfo, true );
        logf( XW_LOGINFO, "%s: (count=%d) sleeping after "
              "failing to get cinfo", __func__, count );
        usleep(200000);         /* 2/10 second */
        cinfo = NULL;
    }
    return cinfo;
} /* getCookieRef */

CidInfo*
CRefMgr::getCookieRef( const AddrInfo* addr )
{
    CidInfo* cinfo = m_cidlock->ClaimSocket( addr );

    assert( NULL == cinfo || NULL != cinfo->GetRef() );
    return cinfo;
} /* getCookieRef */

#ifdef RELAY_HEARTBEAT
/* static */ void
CRefMgr::heartbeatProc( void* closure )
{
    CRefMgr* self = (CRefMgr*)closure;
    self->checkHeartbeats( ::uptime() );
} /* heartbeatProc */
#endif

CookieRef*
CRefMgr::AddNew( const char* cookie, const char* connName, CookieID cid,
                 int langCode, int nPlayers, int nAlreadyHere )
{
    if ( 0 == connName[0] ) {
        connName = NULL;
    }
    /* PENDING: should this return a locked cref? */
    logf( XW_LOGINFO, "%s( cookie=%s, connName=%s, cid=%d)", __func__,
          cookie, connName, cid );

    CookieRef* ref = getFromFreeList();

    RWWriteLock rwl( &m_cookieMapRWLock );
    logf( XW_LOGINFO, "making new cref: %d", cid );
    
    if ( !!ref ) {
        ref->ReInit( cookie, connName, cid, langCode, nPlayers, nAlreadyHere );
    } else {
        ref = new CookieRef( cookie, connName, cid, langCode, nPlayers, 
                             nAlreadyHere );
    }

    ref->assignConnName();

    pair<CookieMap::iterator,bool> result =
        m_cookieMap.insert( pair<CookieID, CookieRef*>(ref->GetCid(), ref ) );
    assert( result.second );
    logf( XW_LOGINFO, "%s: paired cookie %s/connName %s with cid %d", __func__, 
          (cookie?cookie:"NULL"), connName, ref->GetCid() );

#ifdef RELAY_HEARTBEAT
    if ( m_cookieMap.size() == 1 ) {
        RelayConfigs* cfg = RelayConfigs::GetConfigs();
        int heartbeat;
        if ( cfg->GetValueFor( "HEARTBEAT", &heartbeat ) ) {
            TimerMgr::GetTimerMgr()->SetTimer( heartbeat, heartbeatProc, this,
                                               heartbeat );
        }
    }
#endif

    logf( XW_LOGINFO, "%s=>%p", __func__, ref );
    return ref;
} /* AddNew */

void
CRefMgr::Recycle_locked( CookieRef* cref )
{
    logf( XW_LOGINFO, "%s(cref=%p,cookie=%s)", __func__, cref, cref->Cookie() );
    CookieID cid = cref->GetCid();
    DBMgr::Get()->ClearCID( cref->ConnName() );
    cref->Clear();
    addToFreeList( cref );

    cref->Unlock();

    /* don't grab this lock until after releasing cref's lock; otherwise
       deadlock happens. */
    RWWriteLock rwl( &m_cookieMapRWLock );

    CookieMap::iterator iter = m_cookieMap.begin();
    while ( iter != m_cookieMap.end() ) {
        CookieRef* ref = iter->second;
        if ( ref == cref ) {
            logf( XW_LOGINFO, "%s: erasing cref cid %d", __func__, cid );
            m_cookieMap.erase( iter );
            break;
        }
        ++iter;
    }
    assert( iter != m_cookieMap.end() ); /* we found something */

#ifdef RELAY_HEARTBEAT
    if ( m_cookieMap.size() == 0 ) {
        TimerMgr::GetTimerMgr()->ClearTimer( heartbeatProc, this );
    }
#endif
} /* CRefMgr::Recycle */

void
CRefMgr::Recycle( CookieID cid )
{
    CidInfo* cinfo = getCookieRef( cid );
    if ( cinfo != NULL ) {
        CookieRef* cref = cinfo->GetRef();
        cref->Lock();
        Recycle_locked( cref );
    }
} /* Delete */

void
CRefMgr::Recycle( const char* connName )
{
    Recycle( cookieIDForConnName( connName ) );
} /* Delete */

#ifdef RELAY_HEARTBEAT
void
CRefMgr::checkHeartbeats( time_t now )
{
    vector<CookieRef*> crefs;

    {
        RWReadLock rwl( &m_cookieMapRWLock );
        CookieMap::iterator iter = m_cookieMap.begin();
        while ( iter != m_cookieMap.end() ) {
            crefs.push_back(iter->second);
            ++iter;
        }
    }

    unsigned int ii;
    for ( ii = 0; ii < crefs.size(); ++ii ) {
        SafeCref scr( crefs[ii] );
        scr.CheckHeartbeats( now );
    }
} /* checkHeartbeats */
#endif

time_t
CRefMgr::uptime( void )
{
    return time(NULL) - m_startTime;
}

/* static */ CookieMapIterator
CRefMgr::GetCookieIterator()
{
    CookieMapIterator iter(&m_cookieMapRWLock);
    return iter;
}


CookieMapIterator::CookieMapIterator(pthread_rwlock_t* rwlock)
    : m_rwl( rwlock )
    ,_iter( CRefMgr::Get()->m_cookieMap.begin() )
{
}

CookieID
CookieMapIterator::Next()
{
    CookieID cid = 0;
    if ( _iter != CRefMgr::Get()->m_cookieMap.end() ) {
        CookieRef* cref = _iter->second;
        cid = cref->GetCid();
        ++_iter;
    }
    return cid;
}

//////////////////////////////////////////////////////////////////////////////
// SafeCref
//////////////////////////////////////////////////////////////////////////////

/* connect case */
SafeCref::SafeCref( const char* cookie, const AddrInfo* addr, int clientVers,
                    DevID* devID, int nPlayersH, int nPlayersS, 
                    unsigned short gameSeed, int clientIndx, int langCode,
                    bool wantsPublic, bool makePublic )
    : m_cinfo( NULL )
    , m_mgr( CRefMgr::Get() )
    , m_addr( *addr )
    , m_clientVersion( clientVers )
    , m_devID( devID )
    , m_isValid( false )
    , m_seenSeed( false )
{
    if ( playerCountsOk( nPlayersH, nPlayersS ) ) {
        CidInfo* cinfo;
        cinfo = m_mgr->getMakeCookieRef( cookie, nPlayersH, nPlayersS, 
                                         langCode, gameSeed, clientIndx, 
                                         wantsPublic, makePublic, &m_seenSeed );
        if ( cinfo != NULL ) {
            CookieRef* cref = cinfo->GetRef();
            m_locked = cref->Lock();
            m_cinfo = cinfo;
            m_isValid = true;
        }
    }
}

/* Reconnect case
 *
 * Device thinks it's connected, but we may disagree, e.g. if it sent an ACK
 * we didn't receive in time.  So we may actually wind up creating a new row,
 * with a new connname, in the games DB in response to this!
 *
 */
SafeCref::SafeCref( const char* connName, const char* cookie, HostID hid, 
                    const AddrInfo* addr, int clientVers, DevID* devID, 
                    int nPlayersH, int nPlayersS, unsigned short gameSeed, 
                    int clientIndx, int langCode, bool wantsPublic,
                    bool makePublic )
    : m_cinfo( NULL )
    , m_mgr( CRefMgr::Get() )
    , m_addr( *addr )
    , m_clientVersion( clientVers )
    , m_devID( devID )
    , m_hid( hid )
    , m_isValid( false )
{
    if ( playerCountsOk( nPlayersH, nPlayersS ) && hid <= 4 ) {
        CidInfo* cinfo;

        bool isDead = false;
        cinfo = m_mgr->getMakeCookieRef( connName, cookie, hid, nPlayersH, 
                                         nPlayersS, gameSeed, langCode,
                                         wantsPublic || makePublic, &isDead );

        /* If the reconnect doesn't check out, treat it as a connect. But
           preserve the existing hid. If the DB was deleted it's important
           that devices keep their places (hids) */
        if ( NULL == cinfo ) {
            logf( XW_LOGINFO, "%s: taking a second crack; (cur hid: %d)",
                  __func__, hid );
            assert( m_hid == hid );
            // m_hid = HOST_ID_NONE; /* wrong; but why was I doing it? */
            cinfo = m_mgr->getMakeCookieRef( cookie, nPlayersH, nPlayersS, 
                                             langCode, gameSeed, clientIndx,
                                             wantsPublic, makePublic, &m_seenSeed );
        }
        if ( cinfo != NULL ) {
            assert( cinfo->GetCid() == cinfo->GetRef()->GetCid() );
            m_locked = cinfo->GetRef()->Lock();
            m_cinfo = cinfo;
            m_isValid = true;
            m_dead = isDead;
        }
    }
}

/* ConnName case -- must exist (unless DB record's been removed */
SafeCref::SafeCref( const char* const connName )
    : m_cinfo( NULL )
    , m_mgr( CRefMgr::Get() )
    , m_isValid( false )
{
    bool isDead = false;
    CidInfo* cinfo = m_mgr->getMakeCookieRef( connName, &isDead );
    if ( NULL != cinfo && NULL != cinfo->GetRef() ) {
        assert( cinfo->GetCid() == cinfo->GetRef()->GetCid() );
        m_locked = cinfo->GetRef()->Lock();
        m_cinfo = cinfo;
        m_isValid = true;
        m_dead = isDead;
    }
}

SafeCref::SafeCref( CookieID cid, bool failOk /* = false */ )
    : m_cinfo( NULL )
    , m_mgr( CRefMgr::Get() )
    , m_isValid( false )
    , m_locked( false )
{
    CidInfo* cinfo = m_mgr->getCookieRef( cid, failOk );
    if ( cinfo != NULL ) {       /* known cookie? */
        CookieRef* cref = cinfo->GetRef();
        if ( NULL != cref ) {
            assert( cinfo->GetCid() == cref->GetCid() );
            m_locked = cref->Lock();
            m_isValid = m_locked && cid == cref->GetCid();
        }
        m_cinfo = cinfo;
    }
}

SafeCref::SafeCref( const AddrInfo* addr )
    : m_cinfo( NULL )
    , m_mgr( CRefMgr::Get() )
    , m_addr( *addr )
    , m_isValid( false )
{
    CidInfo* cinfo = m_mgr->getCookieRef( addr );
    if ( cinfo != NULL ) {       /* known socket? */
        CookieRef* cref = cinfo->GetRef();
        assert( cinfo->GetCid() == cref->GetCid() );
        m_locked = cref->Lock();
        m_isValid = m_locked && cref->HasSocket_locked( addr );
        m_cinfo = cinfo;
    }
}

SafeCref::~SafeCref()
{
    if ( m_cinfo != NULL ) {
        bool recycle = true;
        if ( m_locked ) {
            CookieRef* cref = m_cinfo->GetRef();
            assert( m_cinfo->GetCid() == cref->GetCid() );
            recycle = cref->ShouldDie();
            if ( recycle ) {
                m_mgr->Recycle_locked( cref );
            } else {
                cref->Unlock();
            }
        }
        m_mgr->m_cidlock->Relinquish( m_cinfo, recycle );
    }
}

bool
SafeCref::playerCountsOk( int nPlayersH, int nPlayersT )
{
    bool result = ( 0 < nPlayersH && 4 >= nPlayersH
                    && 0 < nPlayersT && 4 >= nPlayersT
                    && nPlayersH < nPlayersT );
    if ( !result ) {
        logf( XW_LOGERROR, "%s: dropping with bad player counts: here: "
              "%d; total: %d", __func__, nPlayersH, nPlayersT );
    }
    return result;
}