qhostinfo.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
//#define QHOSTINFO_DEBUG
 
#include "qhostinfo.h"
#include "qhostinfo_p.h"
#include <qplatformdefs.h>
 
#include "QtCore/qapplicationstatic.h"
#include "QtCore/qscopedpointer.h"
#include <qabstracteventdispatcher.h>
#include <qcoreapplication.h>
#include <qmetaobject.h>
#include <qscopeguard.h>
#include <qstringlist.h>
#include <qthread.h>
#include <qurl.h>
 
#include <algorithm>
 
#ifdef Q_OS_UNIX
#  include <unistd.h>
#  include <netdb.h>
#  include <netinet/in.h>
#  if defined(AI_ADDRCONFIG) && !defined(Q_OS_WASM)
#    define Q_ADDRCONFIG          AI_ADDRCONFIG
#  endif
#elif defined Q_OS_WIN
#  include <ws2tcpip.h>
 
#  define QT_SOCKLEN_T int
#endif
 
QT_BEGIN_NAMESPACE
 
using namespace Qt::StringLiterals;
 
//#define QHOSTINFO_DEBUG
 
QT_IMPL_METATYPE_EXTERN(QHostInfo)
 
namespace {
struct ToBeLookedUpEquals {
    typedef bool result_type;
    explicit ToBeLookedUpEquals(const QString &toBeLookedUp) noexcept : m_toBeLookedUp(toBeLookedUp) {}
    result_type operator()(QHostInfoRunnable* lookup) const noexcept
    {
        return m_toBeLookedUp == lookup->toBeLookedUp;
    }
private:
    QString m_toBeLookedUp;
};
 
template <typename InputIt, typename OutputIt1, typename OutputIt2, typename UnaryPredicate>
std::pair<OutputIt1, OutputIt2> separate_if(InputIt first, InputIt last, OutputIt1 dest1, OutputIt2 dest2, UnaryPredicate p)
{
    while (first != last) {
        if (p(*first)) {
            *dest1 = *first;
            ++dest1;
        } else {
            *dest2 = *first;
            ++dest2;
        }
        ++first;
    }
    return std::make_pair(dest1, dest2);
}
 
Q_APPLICATION_STATIC(QHostInfoLookupManager, theHostInfoLookupManager)
 
}
 
/*
    The calling thread is likely the one that executes the lookup via
    QHostInfoRunnable. Unless we operate with a queued connection already,
    posts the QHostInfo to a dedicated QHostInfoResult object that lives in
    the same thread as the user-provided receiver, or (if there is none) in
    the thread that made the call to lookupHost. That QHostInfoResult object
    then calls the user code in the correct thread.
 
    The 'result' object deletes itself (via deleteLater) when the metacall
    event is received.
*/
void QHostInfoResult::postResultsReady(const QHostInfo &info)
{
    // queued connection will take care of dispatching to right thread
    if (!slotObj) {
        emit resultsReady(info);
        return;
    }
    // we used to have a context object, but it's already destroyed
    if (withContextObject && !receiver)
        return;
 
    static const int signal_index = []() -> int {
        auto senderMetaObject = &QHostInfoResult::staticMetaObject;
        auto signal = &QHostInfoResult::resultsReady;
        int signal_index = -1;
        void *args[] = { &signal_index, &signal };
        senderMetaObject->static_metacall(QMetaObject::IndexOfMethod, 0, args);
        return signal_index + QMetaObjectPrivate::signalOffset(senderMetaObject);
    }();
 
    // a long-living version of this
    auto result = new QHostInfoResult(this);
    Q_CHECK_PTR(result);
 
    auto metaCallEvent = QMetaCallEvent::create(slotObj, nullptr, signal_index, info);
    Q_CHECK_PTR(metaCallEvent);
    qApp->postEvent(result, metaCallEvent);
}
 
/*
    Receives the event posted by postResultsReady, and calls the functor.
*/
bool QHostInfoResult::event(QEvent *event)
{
    if (event->type() == QEvent::MetaCall) {
        Q_ASSERT(slotObj);
        auto metaCallEvent = static_cast<QMetaCallEvent *>(event);
        auto args = metaCallEvent->args();
        // we didn't have a context object, or it's still alive
        if (!withContextObject || receiver)
            slotObj->call(const_cast<QObject*>(receiver.data()), args);
        slotObj->destroyIfLastRef();
 
        deleteLater();
        return true;
    }
    return QObject::event(event);
}
 
static int nextId()
{
    Q_CONSTINIT static QBasicAtomicInt counter = Q_BASIC_ATOMIC_INITIALIZER(0);
    return 1 + counter.fetchAndAddRelaxed(1);
}
 
int QHostInfo::lookupHost(const QString &name, QObject *receiver, const char *member)
{
    return QHostInfo::lookupHostImpl(name, receiver, nullptr, member);
}
 
void QHostInfo::abortHostLookup(int id)
{
    theHostInfoLookupManager()->abortLookup(id);
}
 
QHostInfo QHostInfo::fromName(const QString &name)
{
#if defined QHOSTINFO_DEBUG
    qDebug("QHostInfo::fromName(\"%s\")",name.toLatin1().constData());
#endif
 
#ifdef Q_OS_WASM
    return QHostInfoAgent::lookup(name);
#else
    QHostInfo hostInfo = QHostInfoAgent::fromName(name);
    QHostInfoLookupManager* manager = theHostInfoLookupManager();
    manager->cache.put(name, hostInfo);
    return hostInfo;
#endif
}
 
 
QHostInfo QHostInfoAgent::reverseLookup(const QHostAddress &address)
{
    QHostInfo results;
    // Reverse lookup
    sockaddr_in sa4;
    sockaddr_in6 sa6;
    sockaddr *sa = nullptr;
    QT_SOCKLEN_T saSize;
    if (address.protocol() == QAbstractSocket::IPv4Protocol) {
        sa = reinterpret_cast<sockaddr *>(&sa4);
        saSize = sizeof(sa4);
        memset(&sa4, 0, sizeof(sa4));
        sa4.sin_family = AF_INET;
        sa4.sin_addr.s_addr = htonl(address.toIPv4Address());
    } else {
        sa = reinterpret_cast<sockaddr *>(&sa6);
        saSize = sizeof(sa6);
        memset(&sa6, 0, sizeof(sa6));
        sa6.sin6_family = AF_INET6;
        memcpy(&sa6.sin6_addr, address.toIPv6Address().c, sizeof(sa6.sin6_addr));
    }
 
    char hbuf[NI_MAXHOST];
    if (sa && getnameinfo(sa, saSize, hbuf, sizeof(hbuf), nullptr, 0, 0) == 0)
        results.setHostName(QString::fromLatin1(hbuf));
 
    if (results.hostName().isEmpty())
        results.setHostName(address.toString());
    results.setAddresses(QList<QHostAddress>() << address);
 
    return results;
}
 
/*
    Call getaddrinfo, and returns the results as QHostInfo::addresses
*/
QHostInfo QHostInfoAgent::lookup(const QString &hostName)
{
    QHostInfo results;
 
    // IDN support
    QByteArray aceHostname = QUrl::toAce(hostName);
    results.setHostName(hostName);
    if (aceHostname.isEmpty()) {
        results.setError(QHostInfo::HostNotFound);
        results.setErrorString(hostName.isEmpty() ?
                               QCoreApplication::translate("QHostInfoAgent", "No host name given") :
                               QCoreApplication::translate("QHostInfoAgent", "Invalid hostname"));
        return results;
    }
 
    addrinfo *res = nullptr;
    struct addrinfo hints;
    memset(&hints, 0, sizeof(hints));
    hints.ai_family = PF_UNSPEC;
#ifdef Q_ADDRCONFIG
    hints.ai_flags = Q_ADDRCONFIG;
#endif
 
    int result = getaddrinfo(aceHostname.constData(), nullptr, &hints, &res);
# ifdef Q_ADDRCONFIG
    if (result == EAI_BADFLAGS) {
        // if the lookup failed with AI_ADDRCONFIG set, try again without it
        hints.ai_flags = 0;
        result = getaddrinfo(aceHostname.constData(), nullptr, &hints, &res);
    }
# endif
 
    if (result == 0) {
        addrinfo *node = res;
        QList<QHostAddress> addresses;
        while (node) {
#ifdef QHOSTINFO_DEBUG
            qDebug() << "getaddrinfo node: flags:" << node->ai_flags << "family:" << node->ai_family
                     << "ai_socktype:" << node->ai_socktype << "ai_protocol:" << node->ai_protocol
                     << "ai_addrlen:" << node->ai_addrlen;
#endif
            switch (node->ai_family) {
            case AF_INET: {
                QHostAddress addr;
                addr.setAddress(ntohl(((sockaddr_in *) node->ai_addr)->sin_addr.s_addr));
                if (!addresses.contains(addr))
                    addresses.append(addr);
                break;
            }
            case AF_INET6: {
                QHostAddress addr;
                sockaddr_in6 *sa6 = (sockaddr_in6 *) node->ai_addr;
                addr.setAddress(sa6->sin6_addr.s6_addr);
                if (sa6->sin6_scope_id)
                    addr.setScopeId(QString::number(sa6->sin6_scope_id));
                if (!addresses.contains(addr))
                    addresses.append(addr);
                break;
            }
            default:
                results.setError(QHostInfo::UnknownError);
                results.setErrorString(QCoreApplication::translate("QHostInfoAgent", "Unknown address type"));
            }
            node = node->ai_next;
        }
        if (addresses.isEmpty()) {
            // Reached the end of the list, but no addresses were found; this
            // means the list contains one or more unknown address types.
            results.setError(QHostInfo::UnknownError);
            results.setErrorString(QCoreApplication::translate("QHostInfoAgent", "Unknown address type"));
        }
 
        results.setAddresses(addresses);
        freeaddrinfo(res);
    } else {
        switch (result) {
#ifdef Q_OS_WIN
        case WSAHOST_NOT_FOUND: //authoritative not found
        case WSATRY_AGAIN: //non authoritative not found
        case WSANO_DATA: //valid name, no associated address
#else
        case EAI_NONAME:
        case EAI_FAIL:
#  ifdef EAI_NODATA // EAI_NODATA is deprecated in RFC 3493
        case EAI_NODATA:
#  endif
#endif
            results.setError(QHostInfo::HostNotFound);
            results.setErrorString(QCoreApplication::translate("QHostInfoAgent", "Host not found"));
            break;
        default:
            results.setError(QHostInfo::UnknownError);
#ifdef Q_OS_WIN
            results.setErrorString(QString::fromWCharArray(gai_strerror(result)));
#else
            results.setErrorString(QString::fromLocal8Bit(gai_strerror(result)));
#endif
            break;
        }
    }
 
#if defined(QHOSTINFO_DEBUG)
    if (results.error() != QHostInfo::NoError) {
        qDebug("QHostInfoAgent::fromName(): error #%d %s",
               h_errno, results.errorString().toLatin1().constData());
    } else {
        QString tmp;
        QList<QHostAddress> addresses = results.addresses();
        for (int i = 0; i < addresses.count(); ++i) {
            if (i != 0) tmp += ", "_L1;
            tmp += addresses.at(i).toString();
        }
        qDebug("QHostInfoAgent::fromName(): found %i entries for \"%s\": {%s}",
               addresses.count(), aceHostname.constData(),
               tmp.toLatin1().constData());
    }
#endif
 
    return results;
}
 
QHostInfo::QHostInfo(int id)
    : d_ptr(new QHostInfoPrivate)
{
    Q_D(QHostInfo);
    d->lookupId = id;
}
 
QHostInfo::QHostInfo(const QHostInfo &other)
    : d_ptr(new QHostInfoPrivate(*other.d_ptr))
{
}
 
QHostInfo &QHostInfo::operator=(const QHostInfo &other)
{
    if (this == &other)
      return *this;
 
    Q_ASSERT(d_ptr && other.d_ptr);
    *d_ptr = *other.d_ptr;
    return *this;
}
 
QHostInfo::~QHostInfo()
{
    delete d_ptr;
}
 
QList<QHostAddress> QHostInfo::addresses() const
{
    Q_D(const QHostInfo);
    return d->addrs;
}
 
void QHostInfo::setAddresses(const QList<QHostAddress> &addresses)
{
    Q_D(QHostInfo);
    d->addrs = addresses;
}
 
QString QHostInfo::hostName() const
{
    Q_D(const QHostInfo);
    return d->hostName;
}
 
void QHostInfo::setHostName(const QString &hostName)
{
    Q_D(QHostInfo);
    d->hostName = hostName;
}
 
QHostInfo::HostInfoError QHostInfo::error() const
{
    Q_D(const QHostInfo);
    return d->err;
}
 
void QHostInfo::setError(HostInfoError error)
{
    Q_D(QHostInfo);
    d->err = error;
}
 
int QHostInfo::lookupId() const
{
    Q_D(const QHostInfo);
    return d->lookupId;
}
 
void QHostInfo::setLookupId(int id)
{
    Q_D(QHostInfo);
    d->lookupId = id;
}
 
QString QHostInfo::errorString() const
{
    Q_D(const QHostInfo);
    return d->errorStr;
}
 
void QHostInfo::setErrorString(const QString &str)
{
    Q_D(QHostInfo);
    d->errorStr = str;
}
 
QString QHostInfo::localHostName()
{
    return QSysInfo::machineHostName();
}
 
int QHostInfo::lookupHostImpl(const QString &name,
                              const QObject *receiver,
                              QtPrivate::QSlotObjectBase *slotObj,
                              const char *member)
{
#if defined QHOSTINFO_DEBUG
    qDebug("QHostInfo::lookupHostImpl(\"%s\", %p, %p, %s)",
           name.toLatin1().constData(), receiver, slotObj, member ? member + 1 : 0);
#endif
    Q_ASSERT(!member != !slotObj); // one of these must be set, but not both
    Q_ASSERT(receiver || slotObj);
 
    if (!QAbstractEventDispatcher::instance(QThread::currentThread())) {
        qWarning("QHostInfo::lookupHost() called with no event dispatcher");
        return -1;
    }
 
    qRegisterMetaType<QHostInfo>();
 
    int id = nextId(); // generate unique ID
 
    if (Q_UNLIKELY(name.isEmpty())) {
        QHostInfo hostInfo(id);
        hostInfo.setError(QHostInfo::HostNotFound);
        hostInfo.setErrorString(QCoreApplication::translate("QHostInfo", "No host name given"));
 
        QHostInfoResult result(receiver, slotObj);
        if (receiver && member)
            QObject::connect(&result, SIGNAL(resultsReady(QHostInfo)),
                            receiver, member, Qt::QueuedConnection);
        result.postResultsReady(hostInfo);
 
        return id;
    }
 
#ifdef Q_OS_WASM
    // Resolve the host name directly without using a thread or cache,
    // since Emscripten's host lookup is fast. Emscripten maintains an internal
    // mapping of hosts and addresses for the purposes of WebSocket socket
    // tunnelling, and does not perform an actual host lookup.
    QHostInfo hostInfo = QHostInfoAgent::lookup(name);
    hostInfo.setLookupId(id);
 
    QHostInfoResult result(receiver, slotObj);
    if (receiver && member)
        QObject::connect(&result, SIGNAL(resultsReady(QHostInfo)),
                        receiver, member, Qt::QueuedConnection);
    result.postResultsReady(hostInfo);
#else
    QHostInfoLookupManager *manager = theHostInfoLookupManager();
 
    if (Q_LIKELY(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(receiver, slotObj);
                if (receiver && member)
                    QObject::connect(&result, SIGNAL(resultsReady(QHostInfo)),
                                    receiver, member, Qt::QueuedConnection);
                result.postResultsReady(info);
                return id;
            }
        }
 
        // cache is not enabled or it was not in the cache, do normal lookup
        QHostInfoRunnable *runnable = new QHostInfoRunnable(name, id, receiver, slotObj);
        if (receiver && member)
            QObject::connect(&runnable->resultEmitter, SIGNAL(resultsReady(QHostInfo)),
                                receiver, member, Qt::QueuedConnection);
        manager->scheduleLookup(runnable);
    }
#endif // Q_OS_WASM
    return id;
}
 
QHostInfoRunnable::QHostInfoRunnable(const QString &hn, int i, const QObject *receiver,
                                     QtPrivate::QSlotObjectBase *slotObj) :
    toBeLookedUp(hn), id(i), resultEmitter(receiver, slotObj)
{
    setAutoDelete(true);
}
 
// the QHostInfoLookupManager will at some point call this via a QThreadPool
void QHostInfoRunnable::run()
{
    QHostInfoLookupManager *manager = theHostInfoLookupManager();
    const auto sg = qScopeGuard([&] { manager->lookupFinished(this); });
    // check aborted
    if (manager->wasAborted(id))
        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))
        return;
 
    // signal emission
    hostInfo.setLookupId(id);
    resultEmitter.postResultsReady(hostInfo);
 
#if QT_CONFIG(thread)
    // now also iterate through the postponed ones
    {
        QMutexLocker locker(&manager->mutex);
        const auto partitionBegin = std::stable_partition(manager->postponedLookups.rbegin(), manager->postponedLookups.rend(),
                                                          ToBeLookedUpEquals(toBeLookedUp)).base();
        const auto partitionEnd = manager->postponedLookups.end();
        for (auto it = partitionBegin; it != partitionEnd; ++it) {
            QHostInfoRunnable* postponed = *it;
            // we can now emit
            hostInfo.setLookupId(postponed->id);
            postponed->resultEmitter.postResultsReady(hostInfo);
            delete postponed;
        }
        manager->postponedLookups.erase(partitionBegin, partitionEnd);
    }
 
#endif
    // thread goes back to QThreadPool
}
 
QHostInfoLookupManager::QHostInfoLookupManager() : wasDeleted(false)
{
#if QT_CONFIG(thread)
    QObject::connect(QCoreApplication::instance(), &QObject::destroyed,
                     &threadPool, [&](QObject *) { threadPool.waitForDone(); },
                     Qt::DirectConnection);
    threadPool.setMaxThreadCount(20); // do up to 20 DNS lookups in parallel
#endif
}
 
QHostInfoLookupManager::~QHostInfoLookupManager()
{
    QMutexLocker locker(&mutex);
    wasDeleted = true;
    locker.unlock();
 
    // don't qDeleteAll currentLookups, the QThreadPool has ownership
    clear();
}
 
void QHostInfoLookupManager::clear()
{
    {
        QMutexLocker locker(&mutex);
        qDeleteAll(scheduledLookups);
        qDeleteAll(finishedLookups);
#if QT_CONFIG(thread)
        qDeleteAll(postponedLookups);
        postponedLookups.clear();
#endif
        scheduledLookups.clear();
        finishedLookups.clear();
    }
 
#if QT_CONFIG(thread)
    threadPool.waitForDone();
#endif
    cache.clear();
}
 
// assumes mutex is locked by caller
void QHostInfoLookupManager::rescheduleWithMutexHeld()
{
    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
 
    if (!finishedLookups.isEmpty()) {
        // remove ID from aborted if it is in there
        for (int i = 0; i < finishedLookups.size(); i++) {
           abortedLookups.removeAll(finishedLookups.at(i)->id);
        }
 
        finishedLookups.clear();
    }
 
#if QT_CONFIG(thread)
    auto isAlreadyRunning = [this](QHostInfoRunnable *lookup) {
        return std::any_of(currentLookups.cbegin(), currentLookups.cend(), ToBeLookedUpEquals(lookup->toBeLookedUp));
    };
 
    // Transfer any postponed lookups that aren't currently running to the scheduled list, keeping already-running lookups:
    postponedLookups.erase(separate_if(postponedLookups.begin(),
                                       postponedLookups.end(),
                                       postponedLookups.begin(),
                                       std::front_inserter(scheduledLookups), // prepend! we want to finish it ASAP
                                       isAlreadyRunning).first,
                           postponedLookups.end());
 
    // Unschedule and postpone any that are currently running:
    scheduledLookups.erase(separate_if(scheduledLookups.begin(),
                                       scheduledLookups.end(),
                                       std::back_inserter(postponedLookups),
                                       scheduledLookups.begin(),
                                       isAlreadyRunning).second,
                           scheduledLookups.end());
 
    const int availableThreads = threadPool.maxThreadCount() - currentLookups.size();
    if (availableThreads > 0) {
        int readyToStartCount = qMin(availableThreads, scheduledLookups.size());
        auto it = scheduledLookups.begin();
        while (readyToStartCount--) {
            // runnable now running in new thread, track this in currentLookups
            threadPool.start(*it);
            currentLookups.push_back(std::move(*it));
            ++it;
        }
        scheduledLookups.erase(scheduledLookups.begin(), it);
    }
#else
    if (!scheduledLookups.isEmpty())
        scheduledLookups.takeFirst()->run();
#endif
}
 
// called by QHostInfo
void QHostInfoLookupManager::scheduleLookup(QHostInfoRunnable *r)
{
    QMutexLocker locker(&this->mutex);
 
    if (wasDeleted)
        return;
 
    scheduledLookups.enqueue(r);
    rescheduleWithMutexHeld();
}
 
// called by QHostInfo
void QHostInfoLookupManager::abortLookup(int id)
{
    QMutexLocker locker(&this->mutex);
 
    if (wasDeleted)
        return;
 
#if QT_CONFIG(thread)
    // is postponed? delete and return
    for (int i = 0; i < postponedLookups.size(); i++) {
        if (postponedLookups.at(i)->id == id) {
            delete postponedLookups.takeAt(i);
            return;
        }
    }
#endif
 
    // is scheduled? delete and return
    for (int i = 0; i < scheduledLookups.size(); 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)
{
    QMutexLocker locker(&this->mutex);
 
    if (wasDeleted)
        return true;
 
    return abortedLookups.contains(id);
}
 
// called from QHostInfoRunnable
void QHostInfoLookupManager::lookupFinished(QHostInfoRunnable *r)
{
    QMutexLocker locker(&this->mutex);
 
    if (wasDeleted)
        return;
 
#if QT_CONFIG(thread)
    currentLookups.removeOne(r);
#endif
    finishedLookups.append(r);
    rescheduleWithMutexHeld();
}
 
// 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
    QHostInfoLookupManager* 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::lookupHostImpl(name, receiver, nullptr, member);
 
    // return empty response, valid==false
    return QHostInfo();
}
 
void qt_qhostinfo_clear_cache()
{
    QHostInfoLookupManager* manager = theHostInfoLookupManager();
    if (manager) {
        manager->clear();
    }
}
 
#ifdef QT_BUILD_INTERNAL
void Q_AUTOTEST_EXPORT qt_qhostinfo_enable_cache(bool e)
{
    QHostInfoLookupManager* manager = theHostInfoLookupManager();
    if (manager) {
        manager->cache.setEnabled(e);
    }
}
 
void qt_qhostinfo_cache_inject(const QString &hostname, const QHostInfo &resolution)
{
    QHostInfoLookupManager* manager = theHostInfoLookupManager();
    if (!manager || !manager->cache.isEnabled())
        return;
 
    manager->cache.put(hostname, resolution);
}
#endif
 
// cache for 60 seconds
// cache 128 items
QHostInfoCache::QHostInfoCache() : max_age(60), enabled(true), cache(128)
{
#ifdef QT_QHOSTINFO_CACHE_DISABLED_BY_DEFAULT
    enabled.store(false, std::memory_order_relaxed);
#endif
}
 
QHostInfo QHostInfoCache::get(const QString &name, bool *valid)
{
    QMutexLocker locker(&this->mutex);
 
    *valid = false;
    if (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();
}
 
QT_END_NAMESPACE
 
#include "moc_qhostinfo_p.cpp"