k3resolver.h

/*  -*- mode: C++; coding: utf-8; -*-
 *  Copyright (C) 2003,2005 Thiago Macieira <[email protected]>
 *
 *
 *  Permission is hereby granted, free of charge, to any person obtaining
 *  a copy of this software and associated documentation files (the
 *  "Software"), to deal in the Software without restriction, including
 *  without limitation the rights to use, copy, modify, merge, publish,
 *  distribute, sublicense, and/or sell copies of the Software, and to
 *  permit persons to whom the Software is furnished to do so, subject to
 *  the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included
 *  in all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef KRESOLVER_H
#define KRESOLVER_H

//////////////////
// Needed includes
#include <QList>
#include <QObject>
#include <QSharedDataPointer>
#include "k3socketaddress.h"
#include "kdemacros.h"

////////////////////////
// Forward declarations
struct sockaddr;
class QString;
class QByteArray;
template<typename T> class QSet;

//////////////////
// Our definitions

namespace KNetwork
{

namespace Internal
{
class KResolverManager;
}

class KResolverEntryPrivate;
/** @class KResolverEntry k3resolver.h k3resolver.h
 *  @brief One resolution entry.
 *
 * This class is one element in the resolution results list.
 * It contains the socket address for connecting, as well as
 * a bit more of information: the socket type, address family
 * and protocol numbers.
 *
 * This class contains all the information required for creating,
 * binding and connecting a socket.
 *
 * KResolverEntry objects implicitly share data, so copying them
 * is quite efficient.
 *
 * @author Thiago Macieira <[email protected]>
 * @deprecated Use KSocketFactory or KLocalSocket instead
 */
class KDELIBS4SUPPORT_DEPRECATED_EXPORT KResolverEntry
{
public:
    /**
     * Default constructor
     *
     */
    KResolverEntry();

    /**
     * Constructs a new KResolverEntry from a KSocketAddress
     * and other data.
     *
     * The KSocketAddress @p addr parameter will be deep-copied.
     *
     * @param addr    the address that was resolved
     * @param socktype    the socket type of the resolved address
     * @param protocol    the protocol of the resolved address
     * @param canonName   the canonical name of the resolved hostname
     * @param encodedName the ASCII-compatible encoding of the hostname
     */
    KResolverEntry(const KSocketAddress &addr, int socktype, int protocol,
                   const QString &canonName = QString(),
                   const QByteArray &encodedName = QByteArray());

    /**
     * Constructs a new KResolverEntry from raw forms of
     * socket addresses and other data.
     *
     * This constructor instead creates an internal KSocketAddress object.
     *
     * @param sa      the sockaddr structure containing the raw address
     * @param salen   the length of the sockaddr structure
     * @param socktype    the socket type of the resolved address
     * @param protocol    the protocol of the resolved address
     * @param canonName   the canonical name of the resolved hostname
     * @param encodedName the ASCII-compatible encoding of the hostname
     */
    KResolverEntry(const struct sockaddr *sa, quint16 salen, int socktype,
                   int protocol, const QString &canonName = QString(),
                   const QByteArray &encodedName = QByteArray());

    /**
     * Copy constructor.
     *
     * This constructor performs a shallow-copy of the other object.
     */
    KResolverEntry(const KResolverEntry &other);

    /**
     * Destructor.
     *
     * The destructor frees associated resources with this object. It does
     * not destroy shared data.
     */
    ~KResolverEntry();

    /**
     * Retrieves the socket address associated with this entry.
     */
    KSocketAddress address() const;

    /**
     * Retrieves the length of the socket address structure.
     */
    quint16 length() const;

    /**
     * Retrieves the family associated with this socket address.
     */
    int family() const;

    /**
     * Retrieves the canonical name associated with this entry, if there is any.
     * If the canonical name was not found, this function returns QString().
     */
    QString canonicalName() const;

    /**
     * Retrieves the encoded domain name associated with this entry, if there is
     * any. If this domain has been resolved through DNS, this will be the
     * the ACE-encoded hostname.
     *
     * Returns a null QByteArray if such information is not available.
     *
     * Please note that this information is NOT to be presented to the user,
     * unless requested.
     */
    QByteArray encodedName() const;

    /**
     * Retrieves the socket type associated with this entry.
     */
    int socketType() const;

    /**
     * Retrieves the protocol associated with this entry.
     */
    int protocol() const;

    /**
     * Assignment operator
     *
     * This function copies the contents of the other object into this one.
     * Data will be shared between the two of them.
     */
    KResolverEntry &operator=(const KResolverEntry &other);

    /**
     * Dummy operator== for compilers which need a complete
     * instantiated class when exporting to a shared lib
     */
    KDE_DUMMY_COMPARISON_OPERATOR(KResolverEntry)

private:
    QSharedDataPointer<KResolverEntryPrivate> d;
};

KDE_DUMMY_QHASH_FUNCTION(KResolverEntry)

class KResolverResultsPrivate;
/**
 * @class KResolverResults k3resolver.h k3resolver.h
 * @brief Name and service resolution results.
 *
 * This object contains the results of a name and service resolution, as
 * those performed by KResolver. It is also a descendant of QValueList, so
 * you may use all its member functions here to access the elements.
 *
 * A KResolverResults object is associated with a resolution, so, in addition
 * to the resolved elements, you can also retrieve information about the
 * resolution process itself, like the nodename that was resolved or an error
 * code.
 *
 * Note Resolver also uses KResolverResults objects to indicate failure, so
 * you should test for failure.
 *
 * @author Thiago Macieira <[email protected]>
 * @deprecated Use KSocketFactory or KLocalSocket instead
 */
class KDELIBS4SUPPORT_DEPRECATED_EXPORT KResolverResults: public QList<KResolverEntry>
{
public:
    /**
     * Default constructor.
     *
     * Constructs an empty list.
     */
    KResolverResults();

    /**
     * Copy constructor
     *
     * Creates a new object with the contents of the other one. Data will be
     * shared by the two objects, like QValueList
     */
    KResolverResults(const KResolverResults &other);

    /**
     * Destructor
     *
     * Destroys the object and frees associated resources.
     */
    virtual ~KResolverResults();

    /**
     * Assignment operator
     *
     * Copies the contents of the other container into this one, discarding
     * our current values.
     */
    KResolverResults &operator=(const KResolverResults &other);

    /**
     * Retrieves the error code associated with this resolution. The values
     * here are the same as in KResolver::ErrorCodes.
     */
    int error() const;

    /**
     * Retrieves the system error code, if any.
     * @see KResolver::systemError for more information
     */
    int systemError() const;

    /**
     * Sets the error codes
     *
     * @param errorcode       the error code in KResolver::ErrorCodes
     * @param systemerror the system error code associated, if any
     */
    void setError(int errorcode, int systemerror = 0);

    /**
     * The nodename to which the resolution was performed.
     */
    QString nodeName() const;

    /**
     * The service name to which the resolution was performed.
     */
    QString serviceName() const;

    /**
     * Sets the new nodename and service name
     */
    void setAddress(const QString &host, const QString &service);

protected:
    /** Standard hack to add virtuals later. @internal */
    virtual void virtual_hook(int id, void *data);
private:
    QSharedDataPointer<KResolverResultsPrivate> d;
};

class KResolverPrivate;
/**
 * @class KResolver k3resolver.h k3resolver.h
 * @brief Name and service resolution class.
 *
 * This class provides support for doing name-to-binary resolution
 * for nodenames and service ports. You should use this class if you
 * need specific resolution techniques when creating a socket or if you
 * want to inspect the results before calling the socket functions.
 *
 * You can either create an object and set the options you want in it
 * or you can simply call the static member functions, which will create
 * standard Resolver objects and dispatch the resolution for you. Normally,
 * the static functions will be used, except in cases where specific options
 * must be set.
 *
 * A Resolver object defaults to the following:
 * @li address family: any address family
 * @li socket type: streaming socket
 * @li protocol: implementation-defined. Generally, TCP
 * @li host and service: unset
 *
 * @author Thiago Macieira <[email protected]>
 * @deprecated Use KSocketFactory or KLocalSocket instead
 */
class KDELIBS4SUPPORT_DEPRECATED_EXPORT KResolver: public QObject
{
    Q_OBJECT

public:

    /**
     * Address family selection types
     *
     * These values can be OR-ed together to form a composite family selection.
     *
     * @li UnknownFamily: a family that is unknown to the current implementation
     * @li KnownFamily: a family that is known to the implementation (the exact
     *        opposite of UnknownFamily)
     * @li AnyFamilies: any address family is acceptable
     * @li InternetFamily: an address for connecting to the Internet
     * @li InetFamily: alias for InternetFamily
     * @li IPv6Family: an IPv6 address only
     * @li IPv4Family: an IPv4 address only
     * @li UnixFamily: an address for the local Unix namespace (i.e., Unix sockets)
     * @li LocalFamily: alias for UnixFamily
     */
    enum SocketFamilies {
        UnknownFamily = 0x0001,

        UnixFamily = 0x0002,
        LocalFamily = UnixFamily,

        IPv4Family = 0x0004,
        IPv6Family = 0x0008,
        InternetFamily = IPv4Family | IPv6Family,
        InetFamily = InternetFamily,

        KnownFamily = ~UnknownFamily,
        AnyFamily = KnownFamily | UnknownFamily
    };

    /**
     * Flags for the resolution.
     *
     * These flags are used for setting the resolution behaviour for this
     * object:
     * @li Passive: resolve to a passive socket (i.e., one that can be used for
     *        binding to a local interface)
     * @li CanonName: request that the canonical name for the given nodename
     *        be found and recorded
     * @li NoResolve: request that no external resolution be performed. The given
     *        nodename and servicename will be resolved locally only.
     * @li NoSrv: don't try to use SRV-based name-resolution.
     * @li Multiport: the port/service argument is a list of port numbers and
     *        ranges. (future extension)
     *
     * @note SRV-based lookup and Multiport are not implemented yet.
     */
    enum Flags {
        Passive = 0x01,
        CanonName = 0x02,
        NoResolve = 0x04,
        NoSrv = 0x08,
        Multiport = 0x10
    };

    /**
     * Error codes
     *
     * These are the possible error values that objects of this class
     * may return. See errorString() for getting a string representation
     * for these errors.
     *
     * @li AddrFamily: Address family for the given nodename is not supported.
     * @li TryAgain: Temporary failure in name resolution. You should try again.
     * @li NonRecoverable: Non-recoverable failure in name resolution.
     * @li BadFlags: Invalid flags were given.
     * @li Memory: Memory allocation failure.
     * @li NoName: The specified name or service doesn't exist.
     * @li UnsupportedFamily: The requested socket family is not supported.
     * @li UnsupportedService: The requested service is not supported for this
     *        socket type (i.e., a datagram service in a streaming socket).
     * @li UnsupportedSocketType: The requested socket type is not supported.
     * @li UnknownError: An unknown, unexpected error occurred.
     * @li SystemError: A system error occurred. See systemError().
     * @li Canceled: This request was canceled by the user.
     */
    enum ErrorCodes {
        // note: if you change this enum, take a look at KResolver::errorString
        NoError = 0,
        AddrFamily = -1,
        TryAgain = -2,
        NonRecoverable = -3,
        BadFlags = -4,
        Memory = -5,
        NoName = -6,
        UnsupportedFamily = -7,
        UnsupportedService = -8,
        UnsupportedSocketType = -9,
        UnknownError = -10,
        SystemError = -11,
        Canceled = -100
    };

    /**
     * Status codes.
     *
     * These are the possible status for a Resolver object. A value
     * greater than zero indicates normal behaviour, while negative
     * values either indicate failure or error.
     *
     * @li Idle: resolution has not yet been started.
     * @li Queued: resolution is queued but not yet in progress.
     * @li InProgress: resolution is in progress.
     * @li PostProcessing: resolution is in progress.
     * @li Success: resolution is done; you can retrieve the results.
     * @li Canceled: request canceled by the user.
     * @li Failed: resolution is done, but failed.
     *
     * Note: the status Canceled and the error code Canceled are the same.
     *
     * Note 2: the status Queued and InProgress might not be distinguishable.
     * Some implementations might not differentiate one from the other.
     */
    enum StatusCodes {
        Idle = 0,
        Queued = 1,
        InProgress = 5,
        PostProcessing = 6,
        Success = 10,
        //Canceled = -100,    // already defined above
        Failed = -101
    };

    /**
     * Default constructor.
     *
     * Creates an empty Resolver object. You should set the wanted
     * names and flags using the member functions before starting
     * the name resolution.
     *
     * @param parent the parent object (see QObject)
     */
    KResolver(QObject *parent = nullptr);

    /**
     * Constructor with host and service names.
     *
     * Creates a Resolver object with the given host and
     * service names. Flags are initialised to 0 and any address family
     * will be accepted.
     *
     * @param nodename    the host name we want resolved
     * @param servicename the service name associated, like "http"
     * @param parent      the parent object (see QObject)
     */
    KDELIBS4SUPPORT_DEPRECATED explicit KResolver(const QString &nodename, const QString &servicename = QString(),
                       QObject *parent = nullptr);

    /**
     * Destructor.
     *
     * When this object is deleted, it'll destroy all associated
     * resources. If the resolution is still in progress, it will be
     * canceled and the signal will \b not be emitted.
     */
    ~KResolver() override;

    /**
     * Retrieve the current status of this object.
     *
     * @see StatusCodes for the possible status codes.
     */
    int status() const;

    /**
     * Retrieve the error code in this object.
     *
     * This function will return NoError if we are not in
     * an error condition. See status() and StatusCodes to
     * find out what the current status is.
     *
     * @see errorString for getting a textual representation of
     * this error
     */
    int error() const;

    /**
     * Retrieve the associated system error code in this object.
     *
     * Many resolution operations may generate an extra error code
     * as given by the C errno variable. That value is stored in the
     * object and can be retrieved by this function.
     */
    int systemError() const;

    /**
     * Returns the textual representation of the error in this object.
     */
    QString errorString() const;

    /**
     * Returns true if this object is currently running
     */
    bool isRunning() const;

    /**
     * The nodename to which the resolution was/is to be performed.
     */
    QString nodeName() const;

    /**
     * The service name to which the resolution was/is to be performed.
     */
    QString serviceName() const;

    /**
     * Sets the nodename for the resolution.
     *
     * Set the nodename to QString() to unset it.
     * @param nodename        The nodename to be resolved.
     */
    void setNodeName(const QString &nodename);

    /**
     * Sets the service name to be resolved.
     *
     * Set it to QString() to unset it.
     * @param service     The service to be resolved.
     */
    void setServiceName(const QString &service);

    /**
     * Sets both the host and the service names.
     *
     * Setting either value to QString() will unset them.
     * @param node        The nodename
     * @param service     The service name
     */
    void setAddress(const QString &node, const QString &service);

    /**
     * Retrieves the flags set for the resolution.
     *
     * @see Flags for an explanation on what flags are possible
     */
    int flags() const;

    /**
     * Sets the flags.
     *
     * @param flags       the new flags
     * @return            the old flags
     * @see Flags for an explanation on the flags
     */
    int setFlags(int flags);

    /**
     * Sets the allowed socket families.
     *
     * @param families        the families that we want/accept
     * @see SocketFamilies for possible values
     */
    void setFamily(int families);

    /**
     * Sets the socket type we want.
     *
     * The values for the @p type parameter are the SOCK_*
     * constants, defined in <sys/socket.h>. The most common
     * values are:
     *  @li SOCK_STREAM       streaming socket (= reliable, sequenced,
     *                connection-based)
     *  @li SOCK_DGRAM        datagram socket (= unreliable, connectionless)
     *  @li SOCK_RAW      raw socket, with direct access to the
     *                container protocol (such as IP)
     *
     * These three are the only values to which it is guaranteed that
     * resolution will work. Some systems may define other constants (such as
     * SOCK_RDM for reliable datagrams), but support is implementation-defined.
     *
     * @param type        the wanted socket type (SOCK_* constants). Set
     *                0 to use the default.
     */
    void setSocketType(int type);

    /**
     * Sets the protocol we want.
     *
     * Protocols are dependent on the selected address family, so you should know
     * what you are doing if you use this function. Besides, protocols generally
     * are either stream-based or datagram-based, so the value of the socket
     * type is also important. The resolution will fail if these values don't match.
     *
     * When using an Internet socket, the values for the protocol are the
     * IPPROTO_* constants, defined in <netinet/in.h>.
     *
     * You may choose to set the protocol either by its number or by its name, or
     * by both. If you set:
     * @li the number and the name: both values will be stored internally; you
     *        may set the name to an empty value, if wanted
     * @li the number only (name = NULL): the name will be searched in the
     *        protocols database
     * @li the name only (number = 0): the number will be searched in the
     *        database
     * @li neither name nor number: reset to default behaviour
     *
     * @param protonum        the protocol number we want
     * @param name        the protocol name
     */
    void setProtocol(int protonum, const char *name = nullptr);

    /**
     * Starts the name resolution asynchronously.
     *
     * This function will queue this object for resolution
     * and will return immediately. The status upon exit will either be
     * Queued or InProgress or Failed.
     *
     * This function does nothing if the object is already queued. But if
     * it had already succeeded or failed, this function will re-start it.
     *
     * Note: if both the nodename and the servicename are unset, this function
     * will not queue, but will set a success state and emit the signal. Also
     * note that in this case and maybe others, the signal finished() might
     * be emitted before this function returns.
     *
     * @return true if this request was successfully queued for asynchronous
     *        resolution
     */
    bool start();

    /**
     * Waits for a request to finish resolving.
     *
     * This function will wait on a running request for its termination. The
     * status upon exit will either be Success or Failed or Canceled.
     *
     * This function may be called from any thread, even one that is not the
     * GUI thread or the one that started the resolution process. But note this
     * function is not thread-safe nor reentrant: i.e., only one thread can be
     * waiting on one given object.
     *
     * Also note that this function ensures that the finished() signal is
     * emitted before it returns. That means that, as a side-effect, whenever
     * wait() is called, the signal is emitted on the thread calling wait().
     *
     * @param msec        the time to wait, in milliseconds or 0 to
     *                wait forever
     * @return true if the resolution has finished processing, even when it
     *         failed or was canceled. False means the wait timed out and
     *         the resolution is still running.
     */
    bool wait(int msec = 0);

    /**
     * Cancels a running request
     *
     * This function will cancel a running request. If the request is not
     * currently running or queued, this function does nothing.
     *
     * Note: if you tell the signal to be emitted, be aware that it might
     * or might not be emitted before this function returns.
     *
     * @param emitSignal  whether to emit the finished() signal or not
     */
    void cancel(bool emitSignal = true);

    /**
     * Retrieves the results of this resolution
     *
     * Use this function to retrieve the results of the resolution. If no
     * data was resolved (yet) or if we failed, this function will return
     * an empty object.
     *
     * @return the resolved data
     * @see status for information on finding out if the resolution was successful
     */
    KResolverResults results() const;

    /**
     * Handles events. Reimplemented from QObject.
     *
     * This function handles the events generated by the manager indicating that
     * this object has finished processing.
     *
     * Do not post events to this object.
     */
    bool event(QEvent *) override;

Q_SIGNALS:
    // signals

    /**
     * This signal is emitted whenever the resolution is finished, one
     * way or another (success or failure). The @p results parameter
     * will contain the resolved data.
     *
     * Note: if you are doing multiple resolutions, you can use the
     * QObject::sender() function to distinguish one Resolver object from
     * another.
     *
     * @param results     the resolved data; might be empty if the resolution
     *            failed
     * @see results for information on what the results are
     *
     * @note This signal is @b always delivered in the GUI event thread, even for
     *       resolutions that were started in secondary threads.
     */
    void finished(const KNetwork::KResolverResults &results);

private:
    void emitFinished();

public:
    // Static functions

    /**
     * Returns the string representation of this error code.
     *
     * @param errorcode   the error code. See ErrorCodes.
     * @param syserror    the system error code associated.
     * @return        the string representation. This is already
     *            i18n'ed.
     */
    static QString errorString(int errorcode, int syserror = 0);

    /**
     * Resolve the nodename and service name synchronously
     *
     * This static function is provided as convenience for simplifying
     * name resolution. It resolves the given host and service names synchronously
     * and returns the results it found. It is equivalent to the following code:
     *
     * \code
     *   KResolver qres(host, service);
     *   qres.setFlags(flags);
     *   qres.setFamily(families)
     *   qres.start();
     *   qres.wait();
     *   return qres.results();
     * \endcode
     *
     * @param host        the nodename to resolve
     * @param service     the service to resolve
     * @param flags       flags to be used
     * @param families        the families to be searched
     * @return a KResolverResults object containing the results
     * @see KResolverResults for information on how to obtain the error code
     */
    static KResolverResults resolve(const QString &host, const QString &service,
                                    int flags = 0, int families = KResolver::InternetFamily);

    /**
     * Start an asynchronous name resolution
     *
     * This function is provided as a convenience to simplify the resolution
     * process. It creates an internal KResolver object, connects the
     * finished() signal to the given slot and starts the resolution
     * asynchronously. It is more or less equivalent to the following code:
     *
     * \b Note: this function may trigger the signal before it returns, so
     * your code must be prepared for this situation.
     *
     * \code
     *   KResolver* qres = new KResolver(host, service);
     *   QObject::connect(qres, SIGNAL(finished(const KNetwork::KResolverResults&)),
     *                userObj, userSlot);
     *   qres->setFlags(flags);
     *   qres->setFamily(families);
     *   return qres->start();
     * \endcode
     *
     * You should use it like this in your code:
     * \code
     *   KResolver::resolveAsync(myObj, SLOT(mySlot(KResolverResults)), host, service);
     * \endcode
     *
     * @param userObj     the object whose slot @p userSlot we will connect
     * @param userSlot        the slot to which we'll connect
     * @param host        the nodename to resolve
     * @param service     the service to resolve
     * @param flags       flags to be used
     * @param families        families to be searcheed
     * @return true if the queuing was successful, false if not
     * @see KResolverResults for information on how to obtain the error code
     */
    static bool resolveAsync(QObject *userObj, const char *userSlot,
                             const QString &host, const QString &service,
                             int flags = 0, int families = KResolver::InternetFamily);

    /**
     * Returns the domain name in an ASCII Compatible Encoding form, suitable
     * for DNS lookups. This is the base for International Domain Name support
     * over the Internet.
     *
     * Note this function may fail, in which case it'll return a null
     * QByteArray. Reasons for failure include use of unknown code
     * points (Unicode characters).
     *
     * Note that the encoding is illegible and, thus, should not be presented
     * to the user, except if requested.
     *
     * @param unicodeDomain   the domain name to be encoded
     * @return the ACE-encoded suitable for DNS queries if successful, a null
     *         QByteArray if failure.
     */
    static QByteArray domainToAscii(const QString &unicodeDomain);

    /**
     * Does the inverse of domainToAscii() and return an Unicode domain
     * name from the given ACE-encoded domain.
     *
     * This function may fail if the given domain cannot be successfully
     * converted back to Unicode. Reasons for failure include a malformed
     * domain name or good ones whose reencoding back to ACE don't match
     * the form given here (e.g., ACE-encoding of an already
     * ASCII-compatible domain).
     *
     * It is, however, guaranteed that domains returned
     * by domainToAscii() will work.
     *
     * @param asciiDomain the ACE-encoded domain name to be decoded
     * @return the Unicode representation of the given domain name
     * if successful, the original string if not
     * @note ACE = ASCII-Compatible Encoding, i.e., 7-bit
     */
    static QString domainToUnicode(const QByteArray &asciiDomain);

    /**
     * The same as above, but taking a QString argument.
     *
     * @param asciiDomain the ACE-encoded domain name to be decoded
     * @return the Unicode representation of the given domain name
     * if successful, QString() if not.
     */
    static QString domainToUnicode(const QString &asciiDomain);

    /**
     * Normalise a domain name.
     *
     * In order to prevent simple mistakes in International Domain
     * Names (IDN), it has been decided that certain code points
     * (characters in Unicode) would be instead converted to others.
     * This includes turning them all to lower case, as well certain
     * other specific operations, as specified in the documents.
     *
     * For instance, the German 'ß' will be changed into 'ss', while
     * the micro symbol 'µ' will be changed to the Greek mu 'μ'.
     *
     * Two equivalent domains have the same normalised form. And the
     * normalised form of a normalised domain is itself (i.e., if
     * d is normalised, the following is true: d == normalizeDomain(d) )
     *
     * This operation is equivalent to encoding and the decoding a Unicode
     * hostname.
     *
     * @param domain      a domain to be normalised
     * @return the normalised domain, or QString() if the domain is
     * invalid.
     */
    static QString normalizeDomain(const QString &domain);

    /**
     * Resolves a protocol number to its names
     *
     * Note: the returned QStrList operates on deep-copies.
     *
     * @param protonum    the protocol number to be looked for
     * @return all the protocol names in a list. The first is the "proper"
     *        name.
     */
    static QList<QByteArray> protocolName(int protonum);

    /**
     * Finds all aliases for a given protocol name
     *
     * @param protoname   the protocol name to be looked for
     * @return all the protocol names in a list. The first is the "proper"
     *        name.
     */
    static QList<QByteArray> protocolName(const char *protoname);

    /**
     * Resolves a protocol name to its number
     *
     * @param protoname   the protocol name to be looked for
     * @return the protocol number or -1 if we couldn't locate it
     */
    static int protocolNumber(const char *protoname);

    /**
     * Resolves a service name to its port number
     *
     * @param servname        the service name to be looked for
     * @param protoname       the protocol it is associated with
     * @return the port number in host byte-order or -1 in case of error
     */
    static int servicePort(const char *servname, const char *protoname);

    /**
     * Finds all the aliases for a given service name
     *
     * Note: the returned QList<QByteArray> operates on deep-copies.
     *
     * @param servname        the service alias to be looked for
     * @param protoname       the protocol it is associated with
     * @return all the service names in a list. The first is the "proper"
     *        name.
     */
    static QList<QByteArray> serviceName(const char *servname, const char *protoname);

    /**
     * Resolves a port number to its names
     *
     * Note: the returned QList<QByteArray> operates on deep copies.
     *
     * @param port        the port number, in host byte-order
     * @param protoname       the protocol it is associated with
     * @return all the service names in a list. The first is the "proper"
     *        name.
     */
    static QList<QByteArray> serviceName(int port, const char *protoname);

    /**
     * Returns this machine's local hostname.
     *
     * @return this machine's local hostname
     */
    static QString localHostName();

protected:

    /**
     * Sets the error codes
     */
    void setError(int errorcode, int systemerror = 0);

    /** Standard hack to add virtuals later. @internal */
    virtual void virtual_hook(int id, void *data);
private:
    KResolverPrivate *const d;
    friend class KResolverResults;
    friend class ::KNetwork::Internal::KResolverManager;
};

}               // namespace KNetwork

#endif