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#include "qhostinfo.h"
#include "qhostinfo_p.h"

#include "QtCore/qscopedpointer.h"
#include <qabstracteventdispatcher.h>
#include <private/qunicodetables_p.h>
#include <qcoreapplication.h>
#include <qmetaobject.h>
#include <qregexp.h>
#include <private/qnativesocketengine_p.h>
#include <qstringlist.h>
#include <qthread.h>
#include <qtimer.h>
#include <qurl.h>

#ifdef Q_OS_UNIX
#  include <unistd.h>
#endif

QT_BEGIN_NAMESPACE

#ifndef QT_NO_THREAD
Q_GLOBAL_STATIC(QHostInfoLookupManager, theHostInfoLookupManager)
#endif

//#define QHOSTINFO_DEBUG

/*!
    \class QHostInfo
    \brief The QHostInfo class provides static functions for host name lookups.

    \reentrant
    \inmodule QtNetwork
    \ingroup network

    QHostInfo uses the lookup mechanisms provided by the operating
    system to find the IP address(es) associated with a host name,
    or the host name associated with an IP address.
    The class provides two static convenience functions: one that
    works asynchronously and emits a signal once the host is found,
    and one that blocks and returns a QHostInfo object.

    To look up a host's IP addresses asynchronously, call lookupHost(),
    which takes the host name or IP address, a receiver object, and a slot
    signature as arguments and returns an ID. You can abort the
    lookup by calling abortHostLookup() with the lookup ID.

    Example:

    \snippet doc/src/snippets/code/src_network_kernel_qhostinfo.cpp 0


    The slot is invoked when the results are ready. (If you use
    Qt for Embedded Linux and disabled multithreading support by defining
    \c QT_NO_THREAD, lookupHost() will block until the lookup has
    finished.) The results are stored in a QHostInfo object. Call
    addresses() to get the list of IP addresses for the host, and
    hostName() to get the host name that was looked up.

    If the lookup failed, error() returns the type of error that
    occurred. errorString() gives a human-readable description of the
    lookup error.

    If you want a blocking lookup, use the QHostInfo::fromName() function:

    \snippet doc/src/snippets/code/src_network_kernel_qhostinfo.cpp 1

    QHostInfo supports Internationalized Domain Names (IDNs) through the
    IDNA and Punycode standards.

    To retrieve the name of the local host, use the static
    QHostInfo::localHostName() function.

    \sa QAbstractSocket, {http://www.rfc-editor.org/rfc/rfc3492.txt}{RFC 3492}
*/

static QBasicAtomicInt theIdCounter = Q_BASIC_ATOMIC_INITIALIZER(1);

/*!
    Looks up the IP address(es) associated with host name \a name, and
    returns an ID for the lookup. When the result of the lookup is
    ready, the slot or signal \a member in \a receiver is called with
    a QHostInfo argument. The QHostInfo object can then be inspected
    to get the results of the lookup.

    The lookup is performed by a single function call, for example:

    \snippet doc/src/snippets/code/src_network_kernel_qhostinfo.cpp 2

    The implementation of the slot prints basic information about the
    addresses returned by the lookup, or reports an error if it failed:

    \snippet doc/src/snippets/code/src_network_kernel_qhostinfo.cpp 3

    If you pass a literal IP address to \a name instead of a host name,
    QHostInfo will search for the domain name for the IP (i.e., QHostInfo will
    perform a \e reverse lookup). On success, the resulting QHostInfo will
    contain both the resolved domain name and IP addresses for the host
    name. Example:

    \snippet doc/src/snippets/code/src_network_kernel_qhostinfo.cpp 4

    \note There is no guarantee on the order the signals will be emitted
    if you start multiple requests with lookupHost().

    \sa abortHostLookup(), addresses(), error(), fromName()
*/
int QHostInfo::lookupHost(const QString &name, QObject *receiver,
                          const char *member)
{
#if defined QHOSTINFO_DEBUG
    qDebug("QHostInfo::lookupHost(\"%s\", %p, %s)",
           name.toLatin1().constData(), receiver, member ? member + 1 : 0);
#endif
    if (!QAbstractEventDispatcher::instance(QThread::currentThread())) {
        qWarning("QHostInfo::lookupHost() called with no event dispatcher");
        return -1;
    }

    qRegisterMetaType<QHostInfo>("QHostInfo");

    int id = theIdCounter.fetchAndAddRelaxed(1); // generate unique ID

    if (name.isEmpty()) {
        QHostInfo hostInfo(id);
        hostInfo.setError(QHostInfo::HostNotFound);
        hostInfo.setErrorString(QObject::tr("No host name given"));
        QScopedPointer<QHostInfoResult> result(new QHostInfoResult);
        QObject::connect(result.data(), SIGNAL(resultsReady(QHostInfo)),
                         receiver, member, Qt::QueuedConnection);
        result.data()->emitResultsReady(hostInfo);
        return id;
    }

#ifdef QT_NO_THREAD
    QHostInfo hostInfo = QHostInfoAgent::fromName(name);
    hostInfo.setLookupId(id);
    QScopedPointer<QHostInfoResult> result(new QHostInfoResult);
    QObject::connect(result.data(), SIGNAL(resultsReady(QHostInfo)),
                     receiver, member, Qt::QueuedConnection);
    result.data()->emitResultsReady(hostInfo);
#else
    QHostInfoRunnable* runnable = new QHostInfoRunnable(name, id);
    QObject::connect(&runnable->resultEmitter, SIGNAL(resultsReady(QHostInfo)), receiver, member, Qt::QueuedConnection);
    theHostInfoLookupManager()->scheduleLookup(runnable);
#endif

    return id;
}

/*!
    Aborts the host lookup with the ID \a id, as returned by lookupHost().

    \sa lookupHost(), lookupId()
*/
void QHostInfo::abortHostLookup(int id)
{
#ifndef QT_NO_THREAD
    theHostInfoLookupManager()->abortLookup(id);
#else
    // we cannot abort if it was non threaded.. the result signal has already been posted
    Q_UNUSED(id);
#endif
}

/*!
    Looks up the IP address(es) for the given host \a name. The
    function blocks during the lookup which means that execution of
    the program is suspended until the results of the lookup are
    ready. Returns the result of the lookup in a QHostInfo object.

    If you pass a literal IP address to \a name instead of a host name,
    QHostInfo will search for the domain name for the IP (i.e., QHostInfo will
    perform a \e reverse lookup). On success, the returned QHostInfo will
    contain both the resolved domain name and IP addresses for the host name.

    \sa lookupHost()
*/
QHostInfo QHostInfo::fromName(const QString &name)
{
#if defined QHOSTINFO_DEBUG
    qDebug("QHostInfo::fromName(\"%s\")",name.toLatin1().constData());
#endif

    return QHostInfoAgent::fromName(name);
}

/*!
    \enum QHostInfo::HostInfoError

    This enum describes the various errors that can occur when trying
    to resolve a host name.

    \value NoError The lookup was successful.
    \value HostNotFound No IP addresses were found for the host.
    \value UnknownError An unknown error occurred.

    \sa error(), setError()
*/

/*!
    Constructs an empty host info object with lookup ID \a id.

    \sa lookupId()
*/
QHostInfo::QHostInfo(int id)
    : d(new QHostInfoPrivate)
{
    d->lookupId = id;
}

/*!
    Constructs a copy of \a other.
*/
QHostInfo::QHostInfo(const QHostInfo &other)
    : d(new QHostInfoPrivate(*other.d.data()))
{
}

/*!
    Assigns the data of the \a other object to this host info object,
    and returns a reference to it.
*/
QHostInfo &QHostInfo::operator=(const QHostInfo &other)
{
    *d.data() = *other.d.data();
    return *this;
}

/*!
    Destroys the host info object.
*/
QHostInfo::~QHostInfo()
{
}

/*!
    Returns the list of IP addresses associated with hostName(). This
    list may be empty.

    Example:

    \snippet doc/src/snippets/code/src_network_kernel_qhostinfo.cpp 5

    \sa hostName(), error()
*/
QList<QHostAddress> QHostInfo::addresses() const
{
    return d->addrs;
}

/*!
    Sets the list of addresses in this QHostInfo to \a addresses.

    \sa addresses()
*/
void QHostInfo::setAddresses(const QList<QHostAddress> &addresses)
{
    d->addrs = addresses;
}

/*!
    Returns the name of the host whose IP addresses were looked up.

    \sa localHostName()
*/
QString QHostInfo::hostName() const
{
    return d->hostName;
}

/*!
    Sets the host name of this QHostInfo to \a hostName.

    \sa hostName()
*/
void QHostInfo::setHostName(const QString &hostName)
{
    d->hostName = hostName;
}

/*!
    Returns the type of error that occurred if the host name lookup
    failed; otherwise returns NoError.

    \sa setError(), errorString()
*/
QHostInfo::HostInfoError QHostInfo::error() const
{
    return d->err;
}

/*!
    Sets the error type of this QHostInfo to \a error.

    \sa error(), errorString()
*/
void QHostInfo::setError(HostInfoError error)
{
    d->err = error;
}

/*!
    Returns the ID of this lookup.

    \sa setLookupId(), abortHostLookup(), hostName()
*/
int QHostInfo::lookupId() const
{
    return d->lookupId;
}

/*!
    Sets the ID of this lookup to \a id.

    \sa lookupId(), lookupHost()
*/
void QHostInfo::setLookupId(int id)
{
    d->lookupId = id;
}

/*!
    If the lookup failed, this function returns a human readable
    description of the error; otherwise "Unknown error" is returned.

    \sa setErrorString(), error()
*/
QString QHostInfo::errorString() const
{
    return d->errorStr;
}

/*!
    Sets the human readable description of the error that occurred to \a str
    if the lookup failed.

    \sa errorString(), setError()
*/
void QHostInfo::setErrorString(const QString &str)
{
    d->errorStr = str;
}

/*!
    \fn QString QHostInfo::localHostName()

    Returns the host name of this machine.

    \sa hostName()
*/

/*!
    \fn QString QHostInfo::localDomainName()

    Returns the DNS domain of this machine.

    Note: DNS domains are not related to domain names found in
    Windows networks.

    \sa hostName()
*/

#ifndef QT_NO_THREAD
QHostInfoRunnable::QHostInfoRunnable(QString hn, int i) : toBeLookedUp(hn), id(i)
{
    setAutoDelete(true);
}

// the QHostInfoLookupManager will at some point call this via a QThreadPool
void QHostInfoRunnable::run()
{
    QHostInfoLookupManager *manager = theHostInfoLookupManager();
    // check aborted
    if (manager->wasAborted(id)) {
        manager->lookupFinished(this);
        return;
    }

    // check cache
    // FIXME

    // if not in cache: OS lookup
    QHostInfo hostInfo = QHostInfoAgent::fromName(toBeLookedUp);

    // save to cache
    // FIXME

    // check aborted again
    if (manager->wasAborted(id)) {
        manager->lookupFinished(this);
        return;
    }

    // signal emission
    hostInfo.setLookupId(id);
    resultEmitter.emitResultsReady(hostInfo);

    manager->lookupFinished(this);

    // thread goes back to QThreadPool
}

QHostInfoLookupManager::QHostInfoLookupManager() : mutex(QMutex::Recursive), wasDeleted(false)
{
    moveToThread(QCoreApplicationPrivate::mainThread());
    threadPool.setMaxThreadCount(5); // do 5 DNS lookups in parallel
}

QHostInfoLookupManager::~QHostInfoLookupManager()
{
    wasDeleted = true;
}

void QHostInfoLookupManager::work()
{
    if (wasDeleted)
        return;

    // goals of this function:
    //  - launch new lookups via the thread pool
    //  - make sure only one lookup per host/IP is in progress

    QMutexLocker locker(&mutex);

    if (!finishedLookups.isEmpty()) {
        // remove ID from aborted if it is in there
        for (int i = 0; i < finishedLookups.length(); i++) {
           abortedLookups.removeAll(finishedLookups.at(i)->id);
        }

        finishedLookups.clear();
    }

    if (!postponedLookups.isEmpty()) {
        // try to start the postponed ones

        QMutableListIterator<QHostInfoRunnable*> iterator(postponedLookups);
        while (iterator.hasNext()) {
            QHostInfoRunnable* postponed = iterator.next();

            // check if none of the postponed hostnames is currently running
            bool alreadyRunning = false;
            for (int i = 0; i < currentLookups.length(); i++) {
                if (currentLookups.at(i)->toBeLookedUp == postponed->toBeLookedUp) {
                    alreadyRunning = true;
                    break;
                }
            }
            if (!alreadyRunning) {
                iterator.remove();
                scheduledLookups.prepend(postponed); // prepend! we want to finish it ASAP
            }
        }
    }

    if (!scheduledLookups.isEmpty()) {
        // try to start the new ones
        QMutableListIterator<QHostInfoRunnable*> iterator(scheduledLookups);
        while (iterator.hasNext()) {
            QHostInfoRunnable *scheduled = iterator.next();

            // check if a lookup for this host is already running, then postpone
            for (int i = 0; i < currentLookups.size(); i++) {
                if (currentLookups.at(i)->toBeLookedUp == scheduled->toBeLookedUp) {
                    iterator.remove();
                    postponedLookups.append(scheduled);
                    scheduled = 0;
                    break;
                }
            }

            if (scheduled && threadPool.tryStart(scheduled)) {
                // runnable now running in new thread, track this in currentLookups
                iterator.remove();
                currentLookups.append(scheduled);
            } else if (scheduled) {
                // wanted to start, but could not because thread pool is busy
                break;
            } else {
                // was postponed, continue iterating
                continue;
            }
        };
    }
}

// called by QHostInfo
void QHostInfoLookupManager::scheduleLookup(QHostInfoRunnable *r)
{
    if (wasDeleted)
        return;

    QMutexLocker locker(&this->mutex);
    scheduledLookups.enqueue(r);
    work();
}

// called by QHostInfo
void QHostInfoLookupManager::abortLookup(int id)
{
    if (wasDeleted)
        return;

    QMutexLocker locker(&this->mutex);
    if (!abortedLookups.contains(id))
        abortedLookups.append(id);
}

// called from QHostInfoRunnable
bool QHostInfoLookupManager::wasAborted(int id)
{
    if (wasDeleted)
        return true;

    QMutexLocker locker(&this->mutex);
    return abortedLookups.contains(id);
}

// called from QHostInfoRunnable
void QHostInfoLookupManager::lookupFinished(QHostInfoRunnable *r)
{
    if (wasDeleted)
        return;

    QMutexLocker locker(&this->mutex);
    currentLookups.removeOne(r);
    finishedLookups.append(r);
    work();
}

#endif // QT_NO_THREAD

QT_END_NAMESPACE