q3dns.cpp

奇趣公司比较新的qt/emd版本

/*!
    \class Q3Dns q3dns.h
    \brief The Q3Dns class provides asynchronous DNS lookups.

    \compat

    Both Windows and Unix provide synchronous DNS lookups; Windows
    provides some asynchronous support too. At the time of writing
    neither operating system provides asynchronous support for
    anything other than hostname-to-address mapping.

    Q3Dns rectifies this shortcoming, by providing asynchronous caching
    lookups for the record types that we expect modern GUI
    applications to need in the near future.

    The class is \e not straightforward to use (although it is much
    simpler than the native APIs); Q3Socket provides much easier to use
    TCP connection facilities. The aim of Q3Dns is to provide a correct
    and small API to the DNS and nothing more. (We use "correctness"
    to mean that the DNS information is correctly cached, and
    correctly timed out.)

    The API comprises a constructor, functions to set the DNS node
    (the domain in DNS terminology) and record type (setLabel() and
    setRecordType()), the corresponding get functions, an isWorking()
    function to determine whether Q3Dns is working or reading, a
    resultsReady() signal and query functions for the result.

    There is one query function for each RecordType, namely
    addresses(), mailServers(), servers(), hostNames() and texts().
    There are also two generic query functions: canonicalName()
    returns the name you'll presumably end up using (the exact meaning
    of this depends on the record type) and qualifiedNames() returns a
    list of the fully qualified names label() maps to.

    \sa Q3Socket
*/

/*!
    Constructs a DNS query object with invalid settings for both the
    label and the search type.
*/

Q3Dns::Q3Dns()
{
    d = new Q3DnsPrivate;
    t = None;
}




/*!
    Constructs a DNS query object that will return record type \a rr
    information about \a label.

    The DNS lookup is started the next time the application enters the
    event loop. When the result is found the signal resultsReady() is
    emitted.

    \a rr defaults to \c A, IPv4 addresses.
*/

Q3Dns::Q3Dns( const QString & label, RecordType rr )
{
    d = new Q3DnsPrivate;
    t = rr;
    setLabel( label );
    setStartQueryTimer(); // start query the next time we enter event loop
}



/*!
    Constructs a DNS query object that will return record type \a rr
    information about host address \a address. The label is set to the
    IN-ADDR.ARPA domain name. This is useful in combination with the
    \c Ptr record type (e.g. if you want to look up a hostname for a
    given address).

    The DNS lookup is started the next time the application enters the
    event loop. When the result is found the signal resultsReady() is
    emitted.

    \a rr defaults to \c Ptr, that maps addresses to hostnames.
*/

Q3Dns::Q3Dns( const QHostAddress & address, RecordType rr )
{
    d = new Q3DnsPrivate;
    t = rr;
    setLabel( address );
    setStartQueryTimer(); // start query the next time we enter event loop
}




/*!
    Destroys the DNS query object and frees its allocated resources.
*/

Q3Dns::~Q3Dns()
{
    if ( globalManager ) {
	uint q = 0;
	Q3DnsManager * m = globalManager;
	while( q < m->queries.size() ) {
	    Q3DnsQuery * query=m->queries[q];
	    if ( query && query->dns )
		    (void)query->dns->take( (void*) this );
		q++;
	}

    }

    delete d;
    d = 0;
}




/*!
    Sets this DNS query object to query for information about \a
    label.

    This does not change the recordType(), but its isWorking() status
    will probably change as a result.

    The DNS lookup is started the next time the application enters the
    event loop. When the result is found the signal resultsReady() is
    emitted.
*/

void Q3Dns::setLabel( const QString & label )
{
    l = label;
    d->noNames = false;

    // construct a list of qualified names
    n.clear();
    if ( l.length() > 1 && l[(int)l.length()-1] == QLatin1Char('.') ) {
	n.append( l.left( l.length()-1 ).lower() );
    } else {
	int i = l.length();
	int dots = 0;
	const int maxDots = 2;
	while( i && dots < maxDots ) {
	    if ( l[--i] == QLatin1Char('.') )
		dots++;
	}
	if ( dots < maxDots ) {
	    (void)Q3DnsManager::manager(); // create a Q3DnsManager, if it is not already there
	    Q3StrListIterator it( *domains );
	    const char * dom;
	    while( (dom=it.current()) != 0 ) {
		++it;
		n.append( l.lower() + QLatin1String(".") + QLatin1String(dom) );
	    }
	}
	n.append( l.lower() );
    }

#if defined(Q_DNS_SYNCHRONOUS)
    if ( d->noEventLoop ) {
	doSynchronousLookup();
    } else {
	setStartQueryTimer(); // start query the next time we enter event loop
    }
#else
    setStartQueryTimer(); // start query the next time we enter event loop
#endif
#if defined(Q3DNS_DEBUG)
    qDebug( "Q3Dns::setLabel: %d address(es) for %s", n.count(), l.ascii() );
    int i = 0;
    for( i = 0; i < (int)n.count(); i++ )
	qDebug( "Q3Dns::setLabel: %d: %s", i, n[i].ascii() );
#endif
}


/*!
    \overload

    Sets this DNS query object to query for information about the host
    address \a address. The label is set to the IN-ADDR.ARPA domain
    name. This is useful in combination with the \c Ptr record type
    (e.g. if you want to look up a hostname for a given address).
*/

void Q3Dns::setLabel( const QHostAddress & address )
{
    setLabel( toInAddrArpaDomain( address ) );
}


/*!
    \fn QStringList Q3Dns::qualifiedNames() const

    Returns a list of the fully qualified names label() maps to.

    Note that if you want to iterate over the list, you should iterate
    over a copy, e.g.
    \code
    QStringList list = myDns.qualifiedNames();
    QStringList::Iterator it = list.begin();
    while( it != list.end() ) {
        myProcessing( *it );
        ++it;
    }
    \endcode

*/


/*!
    \fn QString Q3Dns::label() const

    Returns the domain name for which this object returns information.

    \sa setLabel()
*/

/*!
    \enum Q3Dns::RecordType

    This enum type defines the record types Q3Dns can handle. The DNS
    provides many more; these are the ones we've judged to be in
    current use, useful for GUI programs and important enough to
    support right away:

    \value None  No information. This exists only so that Q3Dns can
    have a default.

    \value A  IPv4 addresses. By far the most common type.

    \value Aaaa  IPv6 addresses. So far mostly unused.

    \value Mx  Mail eXchanger names. Used for mail delivery.

    \value Srv  SeRVer names. Generic record type for finding
    servers. So far mostly unused.

    \value Cname  Canonical names. Maps from nicknames to the true
    name (the canonical name) for a host.

    \value Ptr  name PoinTeRs. Maps from IPv4 or IPv6 addresses to hostnames.

    \value Txt  arbitrary TeXT for domains.

    We expect that some support for the
    \l{http://www.rfc-editor.org/rfc/rfc2535.txt}{RFC 2535}
    extensions will be added in future versions.
*/

/*!
    Sets this object to query for record type \a rr records.

    The DNS lookup is started the next time the application enters the
    event loop. When the result is found the signal resultsReady() is
    emitted.

    \sa RecordType
*/

void Q3Dns::setRecordType( RecordType rr )
{
    t = rr;
    d->noNames = false;
    setStartQueryTimer(); // start query the next time we enter event loop
}

/*!
  \internal

  Private slot for starting the query.
*/
void Q3Dns::startQuery()
{
    // isWorking() starts the query (if necessary)
    if ( !isWorking() )
	emit resultsReady();
}

/*!
    The three functions Q3Dns::Q3Dns(QString, RecordType),
    Q3Dns::setLabel() and Q3Dns::setRecordType() may start a DNS lookup.
    This function handles setting up the single shot timer.
*/
void Q3Dns::setStartQueryTimer()
{
#if defined(Q_DNS_SYNCHRONOUS)
    if ( !d->queryTimer && !d->noEventLoop )
#else
    if ( !d->queryTimer )
#endif
    {
	// start the query the next time we enter event loop
	d->queryTimer = new QTimer( this );
	connect( d->queryTimer, SIGNAL(timeout()),
		 this, SLOT(startQuery()) );
	d->queryTimer->start( 0, true );
    }
}

/*
    Transforms the host address \a address to the IN-ADDR.ARPA domain
    name. Returns something indeterminate if you're sloppy or
    naughty. This function has an IPv4-specific name, but works for
    IPv6 too.
*/
QString Q3Dns::toInAddrArpaDomain( const QHostAddress &address )
{
    QString s;
    if ( address.isNull() ) {
	// if the address isn't valid, neither of the other two make
	// cases make sense. better to just return.
    } else if ( address.isIp4Addr() ) {
	Q_UINT32 i = address.ip4Addr();
	s.sprintf( "%d.%d.%d.%d.IN-ADDR.ARPA",
		   i & 0xff, (i >> 8) & 0xff, (i>>16) & 0xff, (i>>24) & 0xff );
    } else {
	// RFC 3152. (1886 is deprecated, and clients no longer need to
	// support it, in practice).
	Q_IPV6ADDR i = address.toIPv6Address();
	s = QLatin1String("ip6.arpa");
	uint b = 0;
	while( b < 16 ) {
	    s = QString::number( i.c[b]%16, 16 ) + QLatin1String(".") +
		QString::number( i.c[b]/16, 16 ) + QLatin1String(".") + s;
	    b++;
	}
    }
    return s;
}


/*!
    \fn Q3Dns::RecordType Q3Dns::recordType() const

    Returns the record type of this DNS query object.

    \sa setRecordType() RecordType
*/

/*!
    \fn void Q3Dns::resultsReady()

    This signal is emitted when results are available for one of the
    qualifiedNames().
*/

/*!
    Returns true if Q3Dns is doing a lookup for this object (i.e. if it
    does not already have the necessary information); otherwise
    returns false.

    Q3Dns emits the resultsReady() signal when the status changes to false.
*/

bool Q3Dns::isWorking() const
{
#if defined(Q3DNS_DEBUG)
    qDebug( "Q3Dns::isWorking (%s, %d)", l.ascii(), t );
#endif
    if ( t == None )
	return false;

#if defined(Q_DNS_SYNCHRONOUS)
    if ( d->noEventLoop )
	return true;
#endif

    Q3PtrList<Q3DnsRR> * ll = Q3DnsDomain::cached( this );
    Q_LONG queries = n.count();
    while( ll->current() != 0 ) {
	if ( ll->current()->nxdomain ) {
	    queries--;
	} else {
	    delete ll;
	    return false;
	}
	ll->next();
    }
    delete ll;

    if ( queries <= 0 )
	return false;
    if ( d->noNames )
	return false;
    return true;
}


/*!
    Returns a list of the addresses for this name if this Q3Dns object
    has a recordType() of Q3Dns::A or Q3Dns::Aaaa and the answer
    is available; otherwise returns an empty list.

    As a special case, if label() is a valid numeric IP address, this
    function returns that address.

    Note that if you want to iterate over the list, you should iterate
    over a copy, e.g.
    \code
    Q3ValueList<QHostAddress> list = myDns.addresses();
    Q3ValueList<QHostAddress>::Iterator it = list.begin();
    while( it != list.end() ) {
        myProcessing( *it );
        ++it;
    }
    \endcode

*/

Q3ValueList<QHostAddress> Q3Dns::addresses() const
{
#if defined(Q3DNS_DEBUG)
    qDebug( "Q3Dns::addresses (%s)", l.ascii() );
#endif
    Q3ValueList<QHostAddress> result;
    if ( t != A && t != Aaaa )
	return result;

    Q3PtrList<Q3DnsRR> * cached = Q3DnsDomain::cached( this );

    Q3DnsRR * rr;
    while( (rr=cached->current()) != 0 ) {
	if ( rr->current && !rr->nxdomain )
	    result.append( rr->address );
	cached->next();
    }
    delete cached;
    return result;
}


/*!
    \class Q3Dns::MailServer
    \brief The Q3Dns::MailServer class is  described in Q3Dns::mailServers().

    \internal
*/

/*!
    Returns a list of mail servers if the record type is \c Mx. The
    class Q3Dns::MailServer contains the following public variables:
    \list
    \i QString Q3Dns::MailServer::name
    \i Q_UINT16 Q3Dns::MailServer::priority
    \endlist

    Note that if you want to iterate over the list, you should iterate
    over a copy, e.g.
    \code
    Q3ValueList<Q3Dns::MailServer> list = myDns.mailServers();
    Q3ValueList<Q3Dns::MailServer>::Iterator it = list.begin();
    while( it != list.end() ) {
        myProcessing( *it );
        ++it;
    }
    \endcode

*/
Q3ValueList<Q3Dns::MailServer> Q3Dns::mailServers() const
{
#if defined(Q3DNS_DEBUG)
    qDebug( "Q3Dns::mailServers (%s)", l.ascii() );
#endif
    Q3ValueList<Q3Dns::MailServer> result;
    if ( t != Mx )
	return result;

    Q3PtrList<Q3DnsRR> * cached = Q3DnsDomain::cached( this );

    Q3DnsRR * rr;
    while( (rr=cached->current()) != 0 ) {
	if ( rr->current && !rr->nxdomain ) {
	    MailServer ms( rr->target, rr->priority );
	    result.append( ms );
	}
	cached->next();
    }
    delete cached;
    return result;
}


/*!
    \class Q3Dns::Server
    \brief The Q3Dns::Server class is described in Q3Dns::servers().

    \internal
*/

/*!
    Returns a list of servers if the record type is \c Srv. The class
    Q3Dns::Server contains the following public variables:
    \list
    \i QString Q3Dns::Server::name
    \i Q_UINT16 Q3Dns::Server::priority
    \i Q_UINT16 Q3Dns::Server::weight
    \i Q_UINT16 Q3Dns::Server::port
    \endlist

    Note that if you want to iterate over the list, you should iterate
    over a copy, e.g.
    \code
    Q3ValueList<Q3Dns::Server> list = myDns.servers();
    Q3ValueList<Q3Dns::Server>::Iterator it = list.begin();
    while( it != list.end() ) {
        myProcessing( *it );
        ++it;
    }
    \endcode
*/
Q3ValueList<Q3Dns::Server> Q3Dns::servers() const
{
#if defined(Q3DNS_DEBUG)
    qDebug( "Q3Dns::servers (%s)", l.ascii() );
#endif
    Q3ValueList<Q3Dns::Server> result;
    if ( t != Srv )
	return result;