/*

  * Copyright (c) 1995, 2006, 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;

 /**

  * The abstract class <code>URLStreamHandler</code> 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</code>, <code>ftp</code>, or

  * <code>gopher</code>.

  * <p>

  * In most cases, an instance of a <code>URLStreamHandler</code>

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

  * first time a protocol name is encountered when constructing a

  * <code>URL</code>, 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   JDK1.0

  */

 public abstract class URLStreamHandler {

     /**

      * Opens a connection to the object referenced by the

      * <code>URL</code> 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</code> object for the <code>URL</code>.

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

      *               connection.

      */

     abstract protected 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.

      *

      * Calling this method preempts the system's default ProxySelector

      * settings.

      *

      * @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</code> object for the <code>URL</code>.

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

      *               connection.

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

      *               or p has the wrong type.

      * @exception  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 {

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

 //    }

     /**

      * Parses the string representation of a <code>URL</code> into a

      * <code>URL</code> object.

      * <p>

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

      * copied into the <code>URL</code> argument.

      * <p>

      * The <code>parseURL</code> method of <code>URLStreamHandler</code>

      * parses the string representation as if it were an

      * <code>http</code> 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</code> to receive the result of parsing

      *                  the spec.

      * @param   spec    the <code>String</code> representing the URL that

      *                  must be parsed.

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

      *                  just past the '<code>:</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>#</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 = spec.indexOf('?', start);

                 if (i < 0)

                     i = limit;

             }

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

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

             if (ind != -1) {

                 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.substring(ind+1));

                                 }

                             } 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.substring(ind + 1));

                         }

                         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.length() > 0)

                 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.length() > 0) {

                 isRelPath = true;

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

                 String seperator = "";

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

                     seperator = "/";

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

                          spec.substring(start, limit);

             } else {

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

                 path = seperator + 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 overidden by handlers with default port numbers.

      * @return the default port for a <code>URL</code> parsed by this handler.

      * @since 1.3

      */

     protected int getDefaultPort() {

         return -1;

     }

     /**

      * Provides the default equals calculation. May be overidden 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 <tt>true</tt> if the two urls are

      * considered equal, ie. they refer to the same

      * fragment in the same file.

      * @since 1.3

      */

     protected boolean equals(URL u1, URL u2) {

         String ref1 = u1.getRef();

         String ref2 = u2.getRef();

         return (ref1 == ref2 || (ref1 != null && ref1.equals(ref2))) &&

                sameFile(u1, u2);

     }

     /**

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

      * other protocols that have different requirements for hashCode

      * calculation.

      * @param u a URL object

      * @return an <tt>int</tt> 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.

         Object 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</code> representing the host

      * IP address.

      * @since 1.3

      */

     private synchronized Object getHostAddress(URL u) {

         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  <tt>true</tt> if and only if they

      * are equal, <tt>false</tt> otherwise.

      * @since 1.3

      */

     protected boolean hostsEqual(URL u1, URL u2) {

         Object a1 = getHostAddress(u1);

         Object 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</code> of a specific protocol to a

      * <code>String</code>.

      *

      * @param   u   the URL.

      * @return  a string representation of the <code>URL</code> argument.

      */

     protected String toExternalForm(URL u) {

         // pre-compute length of StringBuffer

         int len = u.getProtocol().length() + 1;

         if (u.getAuthority() != null && u.getAuthority().length() > 0)

             len += 2 + u.getAuthority().length();

         if (u.getPath() != null) {

             len += u.getPath().length();

         }

         if (u.getQuery() != null) {

             len += 1 + u.getQuery().length();

         }

         if (u.getRef() != null)

             len += 1 + u.getRef().length();

         StringBuffer result = new StringBuffer(len);

         result.append(u.getProtocol());

         result.append(":");

         if (u.getAuthority() != null && u.getAuthority().length() > 0) {

             result.append("//");

             result.append(u.getAuthority());

         }

         if (u.getPath() != null) {

             result.append(u.getPath());

         }

         if (u.getQuery() != null) {

             result.append('?');

             result.append(u.getQuery());

         }

         if (u.getRef() != null) {

             result.append("#");

             result.append(u.getRef());

         }

         return result.toString();

     }

     /**

      * Sets the fields of the <code>URL</code> argument to the indicated values.

      * Only classes derived from URLStreamHandler are supposed to be able

      * to call the set method on a URL.

      *

      * @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.

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

      *                                  different from this one

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

      * @since 1.3

      */

        protected void setURL(URL u, String protocol, String host, int port,

                              String authority, String userInfo, String path,

                              String query, String ref) {

         if (this != u.handler) {

             throw new SecurityException("handler for url different from " +

                                         "this handler");

         }

         // ensure that no one can reset the protocol on a given URL.

         u.set(u.getProtocol(), host, port, authority, userInfo, path, query, ref);

     }

     /**

      * Sets the fields of the <code>URL</code> argument to the indicated values.

      * Only classes derived from URLStreamHandler are supposed to be able

      * to call the set method on a URL.

      *

      * @param   u         the URL to modify.

      * @param   protocol  the protocol name. This value is ignored since 1.2.

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

      * @param   port      the port on the remote machine.

      * @param   file      the file.

      * @param   ref       the reference.

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

      *                                  different from this one

      * @deprecated Use setURL(URL, String, String, int, String, String, String,

      *             String);

      */

     @Deprecated

     protected void setURL(URL u, String protocol, String host, int port,

                           String file, String ref) {

         /*

          * Only old URL handlers call this, so assume that the host

          * field might contain "user:passwd@host". Fix as necessary.

          */

         String authority = null;

         String userInfo = null;

         if (host != null && host.length() != 0) {

             authority = (port == -1) ? host : host + ":" + port;

             int at = host.lastIndexOf('@');

             if (at != -1) {

                 userInfo = host.substring(0, at);

                 host = host.substring(at+1);

             }

         }

         /*

          * Assume file might contain query part. Fix as necessary.

          */

         String path = null;

         String query = null;

         if (file != null) {

             int q = file.lastIndexOf('?');

             if (q != -1) {

                 query = file.substring(q+1);

                 path = file.substring(0, q);

             } else

                 path = file;

         }

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

     }

 }