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 * Copyright (c) 1995, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.net;

import java.io.IOException;

import java.io.InputStream;

import java.io.File;

import java.io.OutputStream;

import java.util.Hashtable;

import java.util.Objects;

import sun.net.util.IPAddressUtil;

import sun.net.www.ParseUtil;

/**

 * The abstract class {@code URLStreamHandler} is the common

 * superclass for all stream protocol handlers. A stream protocol

 * handler knows how to make a connection for a particular protocol

 * type, such as {@code http} or {@code https}.

 * <p>

 * In most cases, an instance of a {@code URLStreamHandler}

 * subclass is not created directly by an application. Rather, the

 * first time a protocol name is encountered when constructing a

 * {@code URL}, the appropriate stream protocol handler is

 * automatically loaded.

 *

 * @author  James Gosling

 * @see     java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)

 * @since   1.0

 */

public abstract class URLStreamHandler {

    /**

     * Opens a connection to the object referenced by the

     * {@code URL} argument.

     * This method should be overridden by a subclass.

     *

     * <p>If for the handler's protocol (such as HTTP or JAR), there

     * exists a public, specialized URLConnection subclass belonging

     * to one of the following packages or one of their subpackages:

     * java.lang, java.io, java.util, java.net, the connection

     * returned will be of that subclass. For example, for HTTP an

     * HttpURLConnection will be returned, and for JAR a

     * JarURLConnection will be returned.

     *

     * @param      u   the URL that this connects to.

     * @return     a {@code URLConnection} object for the {@code URL}.

     * @throws     IOException  if an I/O error occurs while opening the

     *               connection.

     */

    protected abstract URLConnection openConnection(URL u) throws IOException;

    /**

     * Same as openConnection(URL), except that the connection will be

     * made through the specified proxy; Protocol handlers that do not

     * support proxying will ignore the proxy parameter and make a

     * normal connection.

     *

     * <p> Calling this method preempts the system's default

     * {@link java.net.ProxySelector ProxySelector} settings.

     *

     * @implSpec

     * The default implementation of this method first checks that the given

     * {@code URL} and {@code Proxy} are not null, then throws {@code

     * UnsupportedOperationException}. Subclasses should override this method

     * with an appropriate implementation.

     *

     * @param      u   the URL that this connects to.

     * @param      p   the proxy through which the connection will be made.

     *                 If direct connection is desired, Proxy.NO_PROXY

     *                 should be specified.

     * @return     a {@code URLConnection} object for the {@code URL}.

     * @throws     IOException  if an I/O error occurs while opening the

     *               connection.

     * @throws     IllegalArgumentException if either u or p is null,

     *               or p has the wrong type.

     * @throws     UnsupportedOperationException if the subclass that

     *               implements the protocol doesn't support this method.

     * @since      1.5

     */

    protected URLConnection openConnection(URL u, Proxy p) throws IOException {

        if (u == null || p == null)

            throw new IllegalArgumentException("null " + (u == null ? "url" : "proxy"));

        throw new UnsupportedOperationException("Method not implemented.");

    }

    /**

     * Parses the string representation of a {@code URL} into a

     * {@code URL} object.

     * <p>

     * If there is any inherited context, then it has already been

     * copied into the {@code URL} argument.

     * <p>

     * The {@code parseURL} method of {@code URLStreamHandler}

     * parses the string representation as if it were an

     * {@code http} specification. Most URL protocol families have a

     * similar parsing. A stream protocol handler for a protocol that has

     * a different syntax must override this routine.

     *

     * @param   u       the {@code URL} to receive the result of parsing

     *                  the spec.

     * @param   spec    the {@code String} representing the URL that

     *                  must be parsed.

     * @param   start   the character index at which to begin parsing. This is

     *                  just past the '{@code :}' (if there is one) that

     *                  specifies the determination of the protocol name.

     * @param   limit   the character position to stop parsing at. This is the

     *                  end of the string or the position of the

     *                  "{@code #}" character, if present. All information

     *                  after the sharp sign indicates an anchor.

     */

    protected void parseURL(URL u, String spec, int start, int limit) {

        // These fields may receive context content if this was relative URL

        String protocol = u.getProtocol();

        String authority = u.getAuthority();

        String userInfo = u.getUserInfo();

        String host = u.getHost();

        int port = u.getPort();

        String path = u.getPath();

        String query = u.getQuery();

        // This field has already been parsed

        String ref = u.getRef();

        boolean isRelPath = false;

        boolean queryOnly = false;

// FIX: should not assume query if opaque

        // Strip off the query part

        if (start < limit) {

            int queryStart = spec.indexOf('?');

            queryOnly = queryStart == start;

            if ((queryStart != -1) && (queryStart < limit)) {

                query = spec.substring(queryStart+1, limit);

                if (limit > queryStart)

                    limit = queryStart;

                spec = spec.substring(0, queryStart);

            }

        }

        int i = 0;

        // Parse the authority part if any

        boolean isUNCName = (start <= limit - 4) &&

                        (spec.charAt(start) == '/') &&

                        (spec.charAt(start + 1) == '/') &&

                        (spec.charAt(start + 2) == '/') &&

                        (spec.charAt(start + 3) == '/');

        if (!isUNCName && (start <= limit - 2) && (spec.charAt(start) == '/') &&

            (spec.charAt(start + 1) == '/')) {

            start += 2;

            i = spec.indexOf('/', start);

            if (i < 0 || i > limit) {

                i = spec.indexOf('?', start);

                if (i < 0 || i > limit)

                    i = limit;

            }

            host = authority = spec.substring(start, i);

            int ind = authority.indexOf('@');

            if (ind != -1) {

                if (ind != authority.lastIndexOf('@')) {

                    // more than one '@' in authority. This is not server based

                    userInfo = null;

                    host = null;

                } else {

                    userInfo = authority.substring(0, ind);

                    host = authority.substring(ind+1);

                }

            } else {

                userInfo = null;

            }

            if (host != null) {

                // If the host is surrounded by [ and ] then its an IPv6

                // literal address as specified in RFC2732

                if (host.length()>0 && (host.charAt(0) == '[')) {

                    if ((ind = host.indexOf(']')) > 2) {

                        String nhost = host ;

                        host = nhost.substring(0,ind+1);

                        if (!IPAddressUtil.

                            isIPv6LiteralAddress(host.substring(1, ind))) {

                            throw new IllegalArgumentException(

                                "Invalid host: "+ host);

                        }

                        port = -1 ;

                        if (nhost.length() > ind+1) {

                            if (nhost.charAt(ind+1) == ':') {

                                ++ind ;

                                // port can be null according to RFC2396

                                if (nhost.length() > (ind + 1)) {

                                    port = Integer.parseInt(nhost, ind + 1,

                                        nhost.length(), 10);

                                }

                            } else {

                                throw new IllegalArgumentException(

                                    "Invalid authority field: " + authority);

                            }

                        }

                    } else {

                        throw new IllegalArgumentException(

                            "Invalid authority field: " + authority);

                    }

                } else {

                    ind = host.indexOf(':');

                    port = -1;

                    if (ind >= 0) {

                        // port can be null according to RFC2396

                        if (host.length() > (ind + 1)) {

                            port = Integer.parseInt(host, ind + 1,

                                    host.length(), 10);

                        }

                        host = host.substring(0, ind);

                    }

                }

            } else {

                host = "";

            }

            if (port < -1)

                throw new IllegalArgumentException("Invalid port number :" +

                                                   port);

            start = i;

            // If the authority is defined then the path is defined by the

            // spec only; See RFC 2396 Section 5.2.4.

            if (authority != null && !authority.isEmpty())

                path = "";

        }

        if (host == null) {

            host = "";

        }

        // Parse the file path if any

        if (start < limit) {

            if (spec.charAt(start) == '/') {

                path = spec.substring(start, limit);

            } else if (path != null && !path.isEmpty()) {

                isRelPath = true;

                int ind = path.lastIndexOf('/');

                String separator = "";

                if (ind == -1 && authority != null)

                    separator = "/";

                path = path.substring(0, ind + 1) + separator +

                         spec.substring(start, limit);

            } else {

                String separator = (authority != null) ? "/" : "";

                path = separator + spec.substring(start, limit);

            }

        } else if (queryOnly && path != null) {

            int ind = path.lastIndexOf('/');

            if (ind < 0)

                ind = 0;

            path = path.substring(0, ind) + "/";

        }

        if (path == null)

            path = "";

        if (isRelPath) {

            // Remove embedded /./

            while ((i = path.indexOf("/./")) >= 0) {

                path = path.substring(0, i) + path.substring(i + 2);

            }

            // Remove embedded /../ if possible

            i = 0;

            while ((i = path.indexOf("/../", i)) >= 0) {

                /*

                 * A "/../" will cancel the previous segment and itself,

                 * unless that segment is a "/../" itself

                 * i.e. "/a/b/../c" becomes "/a/c"

                 * but "/../../a" should stay unchanged

                 */

                if (i > 0 && (limit = path.lastIndexOf('/', i - 1)) >= 0 &&

                    (path.indexOf("/../", limit) != 0)) {

                    path = path.substring(0, limit) + path.substring(i + 3);

                    i = 0;

                } else {

                    i = i + 3;

                }

            }

            // Remove trailing .. if possible

            while (path.endsWith("/..")) {

                i = path.indexOf("/..");

                if ((limit = path.lastIndexOf('/', i - 1)) >= 0) {

                    path = path.substring(0, limit+1);

                } else {

                    break;

                }

            }

            // Remove starting .

            if (path.startsWith("./") && path.length() > 2)

                path = path.substring(2);

            // Remove trailing .

            if (path.endsWith("/."))

                path = path.substring(0, path.length() -1);

        }

        setURL(u, protocol, host, port, authority, userInfo, path, query, ref);

    }

    /**

     * Returns the default port for a URL parsed by this handler. This method

     * is meant to be overridden by handlers with default port numbers.

     * @return the default port for a {@code URL} parsed by this handler.

     * @since 1.3

     */

    protected int getDefaultPort() {

        return -1;

    }

    /**

     * Provides the default equals calculation. May be overridden by handlers

     * for other protocols that have different requirements for equals().

     * This method requires that none of its arguments is null. This is

     * guaranteed by the fact that it is only called by java.net.URL class.

     * @param u1 a URL object

     * @param u2 a URL object

     * @return {@code true} if the two urls are

     * considered equal, i.e. they refer to the same

     * fragment in the same file.

     * @since 1.3

     */

    protected boolean equals(URL u1, URL u2) {

        return Objects.equals(u1.getRef(), u2.getRef()) && sameFile(u1, u2);

    }

    /**

     * Provides the default hash calculation. May be overridden by handlers for

     * other protocols that have different requirements for hashCode

     * calculation.

     * @param u a URL object

     * @return an {@code int} suitable for hash table indexing

     * @since 1.3

     */

    protected int hashCode(URL u) {

        int h = 0;

        // Generate the protocol part.

        String protocol = u.getProtocol();

        if (protocol != null)

            h += protocol.hashCode();

        // Generate the host part.

        InetAddress addr = getHostAddress(u);

        if (addr != null) {

            h += addr.hashCode();

        } else {

            String host = u.getHost();

            if (host != null)

                h += host.toLowerCase().hashCode();

        }

        // Generate the file part.

        String file = u.getFile();

        if (file != null)

            h += file.hashCode();

        // Generate the port part.

        if (u.getPort() == -1)

            h += getDefaultPort();

        else

            h += u.getPort();

        // Generate the ref part.

        String ref = u.getRef();

        if (ref != null)

            h += ref.hashCode();

        return h;

    }

    /**

     * Compare two urls to see whether they refer to the same file,

     * i.e., having the same protocol, host, port, and path.

     * This method requires that none of its arguments is null. This is

     * guaranteed by the fact that it is only called indirectly

     * by java.net.URL class.

     * @param u1 a URL object

     * @param u2 a URL object

     * @return true if u1 and u2 refer to the same file

     * @since 1.3

     */

    protected boolean sameFile(URL u1, URL u2) {

        // Compare the protocols.

        if (!((u1.getProtocol() == u2.getProtocol()) ||

              (u1.getProtocol() != null &&

               u1.getProtocol().equalsIgnoreCase(u2.getProtocol()))))

            return false;

        // Compare the files.

        if (!(u1.getFile() == u2.getFile() ||

              (u1.getFile() != null && u1.getFile().equals(u2.getFile()))))

            return false;

        // Compare the ports.

        int port1, port2;

        port1 = (u1.getPort() != -1) ? u1.getPort() : u1.handler.getDefaultPort();

        port2 = (u2.getPort() != -1) ? u2.getPort() : u2.handler.getDefaultPort();

        if (port1 != port2)

            return false;

        // Compare the hosts.

        if (!hostsEqual(u1, u2))

            return false;

        return true;

    }

    /**

     * Get the IP address of our host. An empty host field or a DNS failure

     * will result in a null return.

     *

     * @param u a URL object

     * @return an {@code InetAddress} representing the host

     * IP address.

     * @since 1.3

     */

    protected synchronized InetAddress getHostAddress(URL u) {

        if (u.hostAddress != null)

            return u.hostAddress;

        String host = u.getHost();

        if (host == null || host.isEmpty()) {

            return null;

        } else {

            try {

                u.hostAddress = InetAddress.getByName(host);

            } catch (UnknownHostException ex) {

                return null;

            } catch (SecurityException se) {

                return null;

            }

        }

        return u.hostAddress;

    }

    /**

     * Compares the host components of two URLs.

     * @param u1 the URL of the first host to compare

     * @param u2 the URL of the second host to compare

     * @return  {@code true} if and only if they

     * are equal, {@code false} otherwise.

     * @since 1.3

     */

    protected boolean hostsEqual(URL u1, URL u2) {

        InetAddress a1 = getHostAddress(u1);

        InetAddress a2 = getHostAddress(u2);

        // if we have internet address for both, compare them

        if (a1 != null && a2 != null) {

            return a1.equals(a2);

        // else, if both have host names, compare them

        } else if (u1.getHost() != null && u2.getHost() != null)

            return u1.getHost().equalsIgnoreCase(u2.getHost());

         else

            return u1.getHost() == null && u2.getHost() == null;

    }

    /**

     * Converts a {@code URL} of a specific protocol to a

     * {@code String}.

     *

     * @param   u   the URL.

     * @return  a string representation of the {@code URL} argument.

     */

    protected String toExternalForm(URL u) {

        String s;

        return u.getProtocol()

            + ':'

            + ((s = u.getAuthority()) != null && !s.isEmpty()

               ? "//" + s : "")

            + ((s = u.getPath()) != null ? s : "")

            + ((s = u.getQuery()) != null ? '?' + s : "")

            + ((s = u.getRef()) != null ? '#' + s : "");

    }

    /**

     * Sets the fields of the {@code URL} argument to the indicated values.

     * Only classes derived from URLStreamHandler are able

     * to use this method to set the values of the URL fields.

     *

     * @param   u         the URL to modify.

     * @param   protocol  the protocol name.

     * @param   host      the remote host value for the URL.

     * @param   port      the port on the remote machine.

     * @param   authority the authority part for the URL.

     * @param   userInfo the userInfo part of the URL.

     * @param   path      the path component of the URL.

     * @param   query     the query part for the URL.

     * @param   ref       the reference.

     * @throws          SecurityException       if the protocol handler of the URL is

     *                                  different from this one

     * @since 1.3