text: /****************************************************************************
  **
  ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
  ** Contact: http://www.qt-project.org/legal
  **
  ** This file is part of the QtNetwork module of the Qt Toolkit.
  **
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  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
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  ** General Public License version 2.1 as published by the Free Software
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  ** packaging of this file.  Please review the following information to
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  ** Alternatively, this file may be used under the terms of the GNU
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  ** Foundation and appearing in the file LICENSE.GPL included in the
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  ****************************************************************************/
  
  #include "qhostinfo.h"
  #include "qhostinfo_p.h"
  
  #include "QtCore/qscopedpointer.h"
  #include <qabstracteventdispatcher.h>
  #include <qcoreapplication.h>
  #include <qmetaobject.h>
  #include <qstringlist.h>
  #include <qthread.h>
  #include <qurl.h>
  #include <private/qnetworksession_p.h>
  
  #ifdef Q_OS_UNIX
  #  include <unistd.h>
  #endif
  
  QT_BEGIN_NAMESPACE
  
  //#define QHOSTINFO_DEBUG
  
  #ifndef Q_OS_SYMBIAN
  Q_GLOBAL_STATIC(QHostInfoLookupManager, theHostInfoLookupManager)
  #else
  Q_GLOBAL_STATIC(QSymbianHostInfoLookupManager, theHostInfoLookupManager)
  #endif
  
  /*!
      \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. 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.
  
      \note Since Qt 4.6.1 QHostInfo is using multiple threads for DNS lookup
      instead of one dedicated DNS thread. This improves performance,
      but also changes the order of signal emissions when using lookupHost()
      compared to previous versions of Qt.
      \note Since Qt 4.6.3 QHostInfo is using a small internal 60 second DNS cache
      for performance improvements.
  
      \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()) {
          if (!receiver)
              return -1;
  
          QHostInfo hostInfo(id);
          hostInfo.setError(QHostInfo::HostNotFound);
          hostInfo.setErrorString(QCoreApplication::translate("QHostInfo", "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;
      }
  
  #ifndef Q_OS_SYMBIAN
      QHostInfoLookupManager *manager = theHostInfoLookupManager();
  
      if (manager) {
          // the application is still alive
          if (manager->cache.isEnabled()) {
              // check cache first
              bool valid = false;
              QHostInfo info = manager->cache.get(name, &valid);
              if (valid) {
                  if (!receiver)
                      return -1;
  
                  info.setLookupId(id);
                  QHostInfoResult result;
                  QObject::connect(&result, SIGNAL(resultsReady(QHostInfo)), receiver, member, Qt::QueuedConnection);
                  result.emitResultsReady(info);
                  return id;
              }
          }
  
          // cache is not enabled or it was not in the cache, do normal lookup
          QHostInfoRunnable* runnable = new QHostInfoRunnable(name, id);
          if (receiver)
              QObject::connect(&runnable->resultEmitter, SIGNAL(resultsReady(QHostInfo)), receiver, member, Qt::QueuedConnection);
          manager->scheduleLookup(runnable);
      }
  #else
      QSymbianHostInfoLookupManager *manager = theHostInfoLookupManager();
  
      if (manager) {
          // the application is still alive
          if (manager->cache.isEnabled()) {
              // check cache first
              bool valid = false;
              QHostInfo info = manager->cache.get(name, &valid);
              if (valid) {
                  info.setLookupId(id);
                  QHostInfoResult result;
                  QObject::connect(&result, SIGNAL(resultsReady(QHostInfo)), receiver, member, Qt::QueuedConnection);
                  result.emitResultsReady(info);
                  return id;
              }
          }
  
          // cache is not enabled or it was not in the cache, do normal lookup
  #ifndef QT_NO_BEARERMANAGEMENT
          QSharedPointer<QNetworkSession> networkSession;
          QVariant v(receiver->property("_q_networksession"));
          if (v.isValid())
              networkSession = qvariant_cast< QSharedPointer<QNetworkSession> >(v);
  #endif
  
          QSymbianHostResolver *symbianResolver = 0;
          QT_TRAP_THROWING(symbianResolver = new QSymbianHostResolver(name, id, networkSession));
          QObject::connect(&symbianResolver->resultEmitter, SIGNAL(resultsReady(QHostInfo)), receiver, member, Qt::QueuedConnection);
          manager->scheduleLookup(symbianResolver);
      }
  #endif
  
      return id;
  }
  
  /*!
      Aborts the host lookup with the ID \a id, as returned by lookupHost().
  
      \sa lookupHost(), lookupId()
  */
  void QHostInfo::abortHostLookup(int id)
  {
      theHostInfoLookupManager()->abortLookup(id);
  }
  
  /*!
      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
  
      QHostInfo hostInfo = QHostInfoAgent::fromName(name);
      QAbstractHostInfoLookupManager* manager = theHostInfoLookupManager();
      manager->cache.put(name, hostInfo);
      return hostInfo;
  }
  
  #ifndef QT_NO_BEARERMANAGEMENT
  QHostInfo QHostInfoPrivate::fromName(const QString &name, QSharedPointer<QNetworkSession> session)
  {
  #if defined QHOSTINFO_DEBUG
      qDebug("QHostInfoPrivate::fromName(\"%s\") with session %p",name.toLatin1().constData(), session.data());
  #endif
  
      QHostInfo hostInfo = QHostInfoAgent::fromName(name, session);
      QAbstractHostInfoLookupManager* manager = theHostInfoLookupManager();
      manager->cache.put(name, hostInfo);
      return hostInfo;
  }
  #endif
  
  #ifndef Q_OS_SYMBIAN
  #ifndef QT_NO_BEARERMANAGEMENT
  // This function has a special implementation for symbian right now in qhostinfo_symbian.cpp but not on other OS.
  QHostInfo QHostInfoAgent::fromName(const QString &hostName, QSharedPointer<QNetworkSession>)
  {
      return QHostInfoAgent::fromName(hostName);
  }
  #endif
  #endif
  
  
  /*!
      \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 Q_OS_SYMBIAN
  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;
      }
  
      QHostInfo hostInfo;
  
      // QHostInfo::lookupHost already checks the cache. However we need to check
      // it here too because it might have been cache saved by another QHostInfoRunnable
      // in the meanwhile while this QHostInfoRunnable was scheduled but not running
      if (manager->cache.isEnabled()) {
          // check the cache first
          bool valid = false;
          hostInfo = manager->cache.get(toBeLookedUp, &valid);
          if (!valid) {
              // not in cache, we need to do the lookup and store the result in the cache
              hostInfo = QHostInfoAgent::fromName(toBeLookedUp);
              manager->cache.put(toBeLookedUp, hostInfo);
          }
      } else {
          // cache is not enabled, just do the lookup and continue
          hostInfo = QHostInfoAgent::fromName(toBeLookedUp);
      }
  
      // check aborted again
      if (manager->wasAborted(id)) {
          manager->lookupFinished(this);
          return;
      }
  
      // signal emission
      hostInfo.setLookupId(id);
      resultEmitter.emitResultsReady(hostInfo);
  
      // now also iterate through the postponed ones
      {
          QMutexLocker locker(&manager->mutex);
          QMutableListIterator<QHostInfoRunnable*> iterator(manager->postponedLookups);
          while (iterator.hasNext()) {
              QHostInfoRunnable* postponed = iterator.next();
              if (toBeLookedUp == postponed->toBeLookedUp) {
                  // we can now emit
                  iterator.remove();
                  hostInfo.setLookupId(postponed->id);
                  postponed->resultEmitter.emitResultsReady(hostInfo);
                  delete postponed;
              }
          }
      }
  
      manager->lookupFinished(this);
  
      // thread goes back to QThreadPool
  }
  
  QHostInfoLookupManager::QHostInfoLookupManager() : mutex(QMutex::Recursive), wasDeleted(false)
  {
      moveToThread(QCoreApplicationPrivate::mainThread());
      connect(QCoreApplication::instance(), SIGNAL(destroyed()), SLOT(waitForThreadPoolDone()), Qt::DirectConnection);
      threadPool.setMaxThreadCount(5); // do 5 DNS lookups in parallel
  }
  
  QHostInfoLookupManager::~QHostInfoLookupManager()
  {
      wasDeleted = true;
  
      // don't qDeleteAll currentLookups, the QThreadPool has ownership
      clear();
  }
  
  void QHostInfoLookupManager::clear()
  {
      {
          QMutexLocker locker(&mutex);
          qDeleteAll(postponedLookups);
          qDeleteAll(scheduledLookups);
          qDeleteAll(finishedLookups);
          postponedLookups.clear();
          scheduledLookups.clear();
          finishedLookups.clear();
      }
  
      threadPool.waitForDone();
      cache.clear();
  }
  
  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 && currentLookups.size() < threadPool.maxThreadCount()) {
                  // runnable now running in new thread, track this in currentLookups
                  threadPool.start(scheduled);
                  iterator.remove();
                  currentLookups.append(scheduled);
              } 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);
  
      // is postponed? delete and return
      for (int i = 0; i < postponedLookups.length(); i++) {
          if (postponedLookups.at(i)->id == id) {
              delete postponedLookups.takeAt(i);
              return;
          }
      }
  
      // is scheduled? delete and return
      for (int i = 0; i < scheduledLookups.length(); i++) {
          if (scheduledLookups.at(i)->id == id) {
              delete scheduledLookups.takeAt(i);
              return;
          }
      }
  
      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
  
  // This function returns immediately when we had a result in the cache, else it will later emit a signal
  QHostInfo qt_qhostinfo_lookup(const QString &name, QObject *receiver, const char *member, bool *valid, int *id)
  {
      *valid = false;
      *id = -1;
  
      // check cache
      QAbstractHostInfoLookupManager* manager = theHostInfoLookupManager();
      if (manager && manager->cache.isEnabled()) {
          QHostInfo info = manager->cache.get(name, valid);
          if (*valid) {
              return info;
          }
      }
  
      // was not in cache, trigger lookup
      *id = QHostInfo::lookupHost(name, receiver, member);
  
      // return empty response, valid==false
      return QHostInfo();
  }
  
  void qt_qhostinfo_clear_cache()
  {
      QAbstractHostInfoLookupManager* manager = theHostInfoLookupManager();
      if (manager) {
          manager->clear();
      }
  }
  
  void Q_AUTOTEST_EXPORT qt_qhostinfo_enable_cache(bool e)
  {
      QAbstractHostInfoLookupManager* manager = theHostInfoLookupManager();
      if (manager) {
          manager->cache.setEnabled(e);
      }
  }
  
  // cache for 60 seconds
  // cache 128 items
  QHostInfoCache::QHostInfoCache() : max_age(60), enabled(true), cache(128)
  {
  #ifdef QT_QHOSTINFO_CACHE_DISABLED_BY_DEFAULT
      enabled = false;
  #endif
  }
  
  bool QHostInfoCache::isEnabled()
  {
      return enabled;
  }
  
  // this function is currently only used for the auto tests
  // and not usable by public API
  void QHostInfoCache::setEnabled(bool e)
  {
      enabled = e;
  }
  
  
  QHostInfo QHostInfoCache::get(const QString &name, bool *valid)
  {
      QMutexLocker locker(&this->mutex);
  
      *valid = false;
      if (cache.contains(name)) {
          QHostInfoCacheElement *element = cache.object(name);
          if (element->age.elapsed() < max_age*1000)
              *valid = true;
          return element->info;
  
          // FIXME idea:
          // if too old but not expired, trigger a new lookup
          // to freshen our cache
      }
  
      return QHostInfo();
  }
  
  void QHostInfoCache::put(const QString &name, const QHostInfo &info)
  {
      // if the lookup failed, don't cache
      if (info.error() != QHostInfo::NoError)
          return;
  
      QHostInfoCacheElement* element = new QHostInfoCacheElement();
      element->info = info;
      element->age = QElapsedTimer();
      element->age.start();
  
      QMutexLocker locker(&this->mutex);
      cache.insert(name, element); // cache will take ownership
  }
  
  void QHostInfoCache::clear()
  {
      QMutexLocker locker(&this->mutex);
      cache.clear();
  }
  
  QAbstractHostInfoLookupManager* QAbstractHostInfoLookupManager::globalInstance()
  {
      return theHostInfoLookupManager();
  }
  
  QT_END_NAMESPACE
  