content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package mf.org.apache.xerces.util;
  
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.Locale;
  
  /**********************************************************************
   * A class to represent a Uniform Resource Identifier (URI). This class
   * is designed to handle the parsing of URIs and provide access to
   * the various components (scheme, host, port, userinfo, path, query
   * string and fragment) that may constitute a URI.
   * <p/>
   * Parsing of a URI specification is done according to the URI
   * syntax described in
   * <a href="http://www.ietf.org/rfc/rfc2396.txt?number=2396">RFC 2396</a>,
   * and amended by
   * <a href="http://www.ietf.org/rfc/rfc2732.txt?number=2732">RFC 2732</a>.
   * <p/>
   * Every absolute URI consists of a scheme, followed by a colon (':'),
   * followed by a scheme-specific part. For URIs that follow the
   * "generic URI" syntax, the scheme-specific part begins with two
   * slashes ("//") and may be followed by an authority segment (comprised
   * of user information, host, and port), path segment, query segment
   * and fragment. Note that RFC 2396 no longer specifies the use of the
   * parameters segment and excludes the "user:password" syntax as part of
   * the authority segment. If "user:password" appears in a URI, the entire
   * user/password string is stored as userinfo.
   * <p/>
   * For URIs that do not follow the "generic URI" syntax (e.g. mailto),
   * the entire scheme-specific part is treated as the "path" portion
   * of the URI.
   * <p/>
   * Note that, unlike the java.net.URL class, this class does not provide
   * any built-in network access functionality nor does it provide any
   * scheme-specific functionality (for example, it does not know a
   * default port for a specific scheme). Rather, it only knows the
   * grammar and basic set of operations that can be applied to a URI.
   *
   * @version $Id: URI.java 712351 2008-11-08 05:45:12Z mrglavas $
   **********************************************************************/
  public class URI implements Serializable {
  
      /**
       * Serialization version.
       */
      static final long serialVersionUID = 1601921774685357214L;
      private static final byte[] fgLookupTable = new byte[128];
      /**
       * reserved characters ;/?:@&=+$,[]
       */
      //RFC 2732 added '[' and ']' as reserved characters
      private static final int RESERVED_CHARACTERS = 0x01;
  
      /**
       * Character Classes
       */
      /**
       * URI punctuation mark characters: -_.!~*'() - these, combined with
       * alphanumerics, constitute the "unreserved" characters
       */
      private static final int MARK_CHARACTERS = 0x02;
      /**
       * scheme can be composed of alphanumerics and these characters: +-.
       */
      private static final int SCHEME_CHARACTERS = 0x04;
      /**
       * userinfo can be composed of unreserved, escaped and these
       * characters: ;:&=+$,
       */
      private static final int USERINFO_CHARACTERS = 0x08;
      /**
       * ASCII letter characters
       */
      private static final int ASCII_ALPHA_CHARACTERS = 0x10;
      /**
       * ASCII digit characters
       */
      private static final int ASCII_DIGIT_CHARACTERS = 0x20;
      /**
       * ASCII hex characters
       */
      private static final int ASCII_HEX_CHARACTERS = 0x40;
      /**
       * Path characters
       */
      private static final int PATH_CHARACTERS = 0x80;
      /**
       * Mask for alpha-numeric characters
       */
      private static final int MASK_ALPHA_NUMERIC = ASCII_ALPHA_CHARACTERS | ASCII_DIGIT_CHARACTERS;
      /**
       * Mask for unreserved characters
       */
      private static final int MASK_UNRESERVED_MASK = MASK_ALPHA_NUMERIC | MARK_CHARACTERS;
      /**
       * Mask for URI allowable characters except for %
       */
      private static final int MASK_URI_CHARACTER = MASK_UNRESERVED_MASK | RESERVED_CHARACTERS;
      /**
       * Mask for scheme characters
       */
      private static final int MASK_SCHEME_CHARACTER = MASK_ALPHA_NUMERIC | SCHEME_CHARACTERS;
      /**
       * Mask for userinfo characters
       */
      private static final int MASK_USERINFO_CHARACTER = MASK_UNRESERVED_MASK | USERINFO_CHARACTERS;
      /**
       * Mask for path characters
       */
      private static final int MASK_PATH_CHARACTER = MASK_UNRESERVED_MASK | PATH_CHARACTERS;
      private static boolean DEBUG = false;
  
      static {
          // Add ASCII Digits and ASCII Hex Numbers
          for (int i = '0'; i <= '9'; ++i) {
              fgLookupTable[i] |= ASCII_DIGIT_CHARACTERS | ASCII_HEX_CHARACTERS;
          }
  
          // Add ASCII Letters and ASCII Hex Numbers
          for (int i = 'A'; i <= 'F'; ++i) {
              fgLookupTable[i] |= ASCII_ALPHA_CHARACTERS | ASCII_HEX_CHARACTERS;
              fgLookupTable[i + 0x00000020] |= ASCII_ALPHA_CHARACTERS | ASCII_HEX_CHARACTERS;
          }
  
          // Add ASCII Letters
          for (int i = 'G'; i <= 'Z'; ++i) {
              fgLookupTable[i] |= ASCII_ALPHA_CHARACTERS;
              fgLookupTable[i + 0x00000020] |= ASCII_ALPHA_CHARACTERS;
          }
  
          // Add Reserved Characters
          fgLookupTable[';'] |= RESERVED_CHARACTERS;
          fgLookupTable['/'] |= RESERVED_CHARACTERS;
          fgLookupTable['?'] |= RESERVED_CHARACTERS;
          fgLookupTable[':'] |= RESERVED_CHARACTERS;
          fgLookupTable['@'] |= RESERVED_CHARACTERS;
          fgLookupTable['&'] |= RESERVED_CHARACTERS;
          fgLookupTable['='] |= RESERVED_CHARACTERS;
          fgLookupTable['+'] |= RESERVED_CHARACTERS;
          fgLookupTable['$'] |= RESERVED_CHARACTERS;
          fgLookupTable[','] |= RESERVED_CHARACTERS;
          fgLookupTable['['] |= RESERVED_CHARACTERS;
          fgLookupTable[']'] |= RESERVED_CHARACTERS;
  
          // Add Mark Characters
          fgLookupTable['-'] |= MARK_CHARACTERS;
          fgLookupTable['_'] |= MARK_CHARACTERS;
          fgLookupTable['.'] |= MARK_CHARACTERS;
          fgLookupTable['!'] |= MARK_CHARACTERS;
          fgLookupTable['~'] |= MARK_CHARACTERS;
          fgLookupTable['*'] |= MARK_CHARACTERS;
          fgLookupTable['\''] |= MARK_CHARACTERS;
          fgLookupTable['('] |= MARK_CHARACTERS;
          fgLookupTable[')'] |= MARK_CHARACTERS;
  
          // Add Scheme Characters
          fgLookupTable['+'] |= SCHEME_CHARACTERS;
          fgLookupTable['-'] |= SCHEME_CHARACTERS;
          fgLookupTable['.'] |= SCHEME_CHARACTERS;
  
          // Add Userinfo Characters
          fgLookupTable[';'] |= USERINFO_CHARACTERS;
          fgLookupTable[':'] |= USERINFO_CHARACTERS;
          fgLookupTable['&'] |= USERINFO_CHARACTERS;
          fgLookupTable['='] |= USERINFO_CHARACTERS;
          fgLookupTable['+'] |= USERINFO_CHARACTERS;
          fgLookupTable['$'] |= USERINFO_CHARACTERS;
          fgLookupTable[','] |= USERINFO_CHARACTERS;
  
          // Add Path Characters
          fgLookupTable[';'] |= PATH_CHARACTERS;
          fgLookupTable['/'] |= PATH_CHARACTERS;
          fgLookupTable[':'] |= PATH_CHARACTERS;
          fgLookupTable['@'] |= PATH_CHARACTERS;
          fgLookupTable['&'] |= PATH_CHARACTERS;
          fgLookupTable['='] |= PATH_CHARACTERS;
          fgLookupTable['+'] |= PATH_CHARACTERS;
          fgLookupTable['$'] |= PATH_CHARACTERS;
          fgLookupTable[','] |= PATH_CHARACTERS;
      }
  
      /**
       * Stores the scheme (usually the protocol) for this URI.
       */
      private String m_scheme = null;
  
      /**
       * If specified, stores the userinfo for this URI; otherwise null
       */
      private String m_userinfo = null;
  
      /**
       * If specified, stores the host for this URI; otherwise null
       */
      private String m_host = null;
  
      /**
       * If specified, stores the port for this URI; otherwise -1
       */
      private int m_port = -1;
  
      /**
       * If specified, stores the registry based authority for this URI; otherwise -1
       */
      private String m_regAuthority = null;
  
      /**
       * If specified, stores the path for this URI; otherwise null
       */
      private String m_path = null;
  
      /**
       * If specified, stores the query string for this URI; otherwise
       * null.
       */
      private String m_queryString = null;
  
      /**
       * If specified, stores the fragment for this URI; otherwise null
       */
      private String m_fragment = null;
  
      /**
       * Construct a new and uninitialized URI.
       */
      public URI() {
      }
  
      /**
       * Construct a new URI from another URI. All fields for this URI are
       * set equal to the fields of the URI passed in.
       *
       * @param p_other the URI to copy (cannot be null)
       */
      public URI(URI p_other) {
          initialize(p_other);
      }
  
      /**
       * Construct a new URI from a URI specification string. If the
       * specification follows the "generic URI" syntax, (two slashes
       * following the first colon), the specification will be parsed
       * accordingly - setting the scheme, userinfo, host,port, path, query
       * string and fragment fields as necessary. If the specification does
       * not follow the "generic URI" syntax, the specification is parsed
       * into a scheme and scheme-specific part (stored as the path) only.
       *
       * @param p_uriSpec the URI specification string (cannot be null or
       *                  empty)
       * @throws MalformedURIException if p_uriSpec violates any syntax
       *                               rules
       */
      public URI(String p_uriSpec) throws MalformedURIException {
          this((URI) null, p_uriSpec);
      }
  
      /**
       * Construct a new URI from a URI specification string. If the
       * specification follows the "generic URI" syntax, (two slashes
       * following the first colon), the specification will be parsed
       * accordingly - setting the scheme, userinfo, host,port, path, query
       * string and fragment fields as necessary. If the specification does
       * not follow the "generic URI" syntax, the specification is parsed
       * into a scheme and scheme-specific part (stored as the path) only.
       * Construct a relative URI if boolean is assigned to "true"
       * and p_uriSpec is not valid absolute URI, instead of throwing an exception.
       *
       * @param p_uriSpec           the URI specification string (cannot be null or
       *                            empty)
       * @param allowNonAbsoluteURI true to permit non-absolute URIs,
       *                            false otherwise.
       * @throws MalformedURIException if p_uriSpec violates any syntax
       *                               rules
       */
      public URI(String p_uriSpec, boolean allowNonAbsoluteURI) throws MalformedURIException {
          this(null, p_uriSpec, allowNonAbsoluteURI);
      }
  
      /**
       * Construct a new URI from a base URI and a URI specification string.
       * The URI specification string may be a relative URI.
       *
       * @param p_base    the base URI (cannot be null if p_uriSpec is null or
       *                  empty)
       * @param p_uriSpec the URI specification string (cannot be null or
       *                  empty if p_base is null)
       * @throws MalformedURIException if p_uriSpec violates any syntax
       *                               rules
       */
      public URI(URI p_base, String p_uriSpec) throws MalformedURIException {
          initialize(p_base, p_uriSpec);
      }
  
      /**
       * Construct a new URI from a base URI and a URI specification string.
       * The URI specification string may be a relative URI.
       * Construct a relative URI if boolean is assigned to "true"
       * and p_uriSpec is not valid absolute URI and p_base is null
       * instead of throwing an exception.
       *
       * @param p_base              the base URI (cannot be null if p_uriSpec is null or
       *                            empty)
       * @param p_uriSpec           the URI specification string (cannot be null or
       *                            empty if p_base is null)
       * @param allowNonAbsoluteURI true to permit non-absolute URIs,
       *                            false otherwise.
       * @throws MalformedURIException if p_uriSpec violates any syntax
       *                               rules
       */
      public URI(URI p_base, String p_uriSpec, boolean allowNonAbsoluteURI) throws MalformedURIException {
          initialize(p_base, p_uriSpec, allowNonAbsoluteURI);
      }
  
      /**
       * Construct a new URI that does not follow the generic URI syntax.
       * Only the scheme and scheme-specific part (stored as the path) are
       * initialized.
       *
       * @param p_scheme             the URI scheme (cannot be null or empty)
       * @param p_schemeSpecificPart the scheme-specific part (cannot be
       *                             null or empty)
       * @throws MalformedURIException if p_scheme violates any
       *                               syntax rules
       */
      public URI(String p_scheme, String p_schemeSpecificPart)
              throws MalformedURIException {
          if (p_scheme == null || p_scheme.trim().length() == 0) {
              throw new MalformedURIException(
                      "Cannot construct URI with null/empty scheme!");
          }
          if (p_schemeSpecificPart == null ||
                  p_schemeSpecificPart.trim().length() == 0) {
              throw new MalformedURIException(
                      "Cannot construct URI with null/empty scheme-specific part!");
          }
          setScheme(p_scheme);
          setPath(p_schemeSpecificPart);
      }
  
      /**
       * Construct a new URI that follows the generic URI syntax from its
       * component parts. Each component is validated for syntax and some
       * basic semantic checks are performed as well.  See the individual
       * setter methods for specifics.
       *
       * @param p_scheme      the URI scheme (cannot be null or empty)
       * @param p_host        the hostname, IPv4 address or IPv6 reference for the URI
       * @param p_path        the URI path - if the path contains '?' or '#',
       *                      then the query string and/or fragment will be
       *                      set from the path; however, if the query and
       *                      fragment are specified both in the path and as
       *                      separate parameters, an exception is thrown
       * @param p_queryString the URI query string (cannot be specified
       *                      if path is null)
       * @param p_fragment    the URI fragment (cannot be specified if path
       *                      is null)
       * @throws MalformedURIException if any of the parameters violates
       *                               syntax rules or semantic rules
       */
      public URI(String p_scheme, String p_host, String p_path,
                 String p_queryString, String p_fragment)
              throws MalformedURIException {
          this(p_scheme, null, p_host, -1, p_path, p_queryString, p_fragment);
      }
  
      /**
       * Construct a new URI that follows the generic URI syntax from its
       * component parts. Each component is validated for syntax and some
       * basic semantic checks are performed as well.  See the individual
       * setter methods for specifics.
       *
       * @param p_scheme      the URI scheme (cannot be null or empty)
       * @param p_userinfo    the URI userinfo (cannot be specified if host
       *                      is null)
       * @param p_host        the hostname, IPv4 address or IPv6 reference for the URI
       * @param p_port        the URI port (may be -1 for "unspecified"; cannot
       *                      be specified if host is null)
       * @param p_path        the URI path - if the path contains '?' or '#',
       *                      then the query string and/or fragment will be
       *                      set from the path; however, if the query and
       *                      fragment are specified both in the path and as
       *                      separate parameters, an exception is thrown
       * @param p_queryString the URI query string (cannot be specified
       *                      if path is null)
       * @param p_fragment    the URI fragment (cannot be specified if path
       *                      is null)
       * @throws MalformedURIException if any of the parameters violates
       *                               syntax rules or semantic rules
       */
      public URI(String p_scheme, String p_userinfo,
                 String p_host, int p_port, String p_path,
                 String p_queryString, String p_fragment)
              throws MalformedURIException {
          if (p_scheme == null || p_scheme.trim().length() == 0) {
              throw new MalformedURIException("Scheme is required!");
          }
  
          if (p_host == null) {
              if (p_userinfo != null) {
                  throw new MalformedURIException(
                          "Userinfo may not be specified if host is not specified!");
              }
              if (p_port != -1) {
                  throw new MalformedURIException(
                          "Port may not be specified if host is not specified!");
              }
          }
  
          if (p_path != null) {
              if (p_path.indexOf('?') != -1 && p_queryString != null) {
                  throw new MalformedURIException(
                          "Query string cannot be specified in path and query string!");
              }
  
              if (p_path.indexOf('#') != -1 && p_fragment != null) {
                  throw new MalformedURIException(
                          "Fragment cannot be specified in both the path and fragment!");
              }
          }
  
          setScheme(p_scheme);
          setHost(p_host);
          setPort(p_port);
          setUserinfo(p_userinfo);
          setPath(p_path);
          setQueryString(p_queryString);
          setFragment(p_fragment);
      }
  
      /**
       * Determine whether a scheme conforms to the rules for a scheme name.
       * A scheme is conformant if it starts with an alphanumeric, and
       * contains only alphanumerics, '+','-' and '.'.
       *
       * @return true if the scheme is conformant, false otherwise
       */
      public static boolean isConformantSchemeName(String p_scheme) {
          if (p_scheme == null || p_scheme.trim().length() == 0) {
              return false;
          }
  
          if (!isAlpha(p_scheme.charAt(0))) {
              return false;
          }
  
          char testChar;
          int schemeLength = p_scheme.length();
          for (int i = 1; i < schemeLength; ++i) {
              testChar = p_scheme.charAt(i);
              if (!isSchemeCharacter(testChar)) {
                  return false;
              }
          }
  
          return true;
      }
  
      /**
       * Determine whether a string is syntactically capable of representing
       * a valid IPv4 address, IPv6 reference or the domain name of a network host.
       * A valid IPv4 address consists of four decimal digit groups separated by a
       * '.'. Each group must consist of one to three digits. See RFC 2732 Section 3,
       * and RFC 2373 Section 2.2, for the definition of IPv6 references. A hostname
       * consists of domain labels (each of which must begin and end with an alphanumeric
       * but may contain '-') separated & by a '.'. See RFC 2396 Section 3.2.2.
       *
       * @return true if the string is a syntactically valid IPv4 address,
       * IPv6 reference or hostname
       */
      public static boolean isWellFormedAddress(String address) {
          if (address == null) {
              return false;
          }
  
          int addrLength = address.length();
          if (addrLength == 0) {
              return false;
          }
  
          // Check if the host is a valid IPv6reference.
          if (address.startsWith("[")) {
              return isWellFormedIPv6Reference(address);
          }
  
          // Cannot start with a '.', '-', or end with a '-'.
          if (address.startsWith(".") ||
                  address.startsWith("-") ||
                  address.endsWith("-")) {
              return false;
          }
  
          // rightmost domain label starting with digit indicates IP address
          // since top level domain label can only start with an alpha
          // see RFC 2396 Section 3.2.2
          int index = address.lastIndexOf('.');
          if (address.endsWith(".")) {
              index = address.substring(0, index).lastIndexOf('.');
          }
  
          if (index + 1 < addrLength && isDigit(address.charAt(index + 1))) {
              return isWellFormedIPv4Address(address);
          } else {
              // hostname      = *( domainlabel "." ) toplabel [ "." ]
              // domainlabel   = alphanum | alphanum *( alphanum | "-" ) alphanum
              // toplabel      = alpha | alpha *( alphanum | "-" ) alphanum
  
              // RFC 2396 states that hostnames take the form described in
              // RFC 1034 (Section 3) and RFC 1123 (Section 2.1). According
              // to RFC 1034, hostnames are limited to 255 characters.
              if (addrLength > 255) {
                  return false;
              }
  
              // domain labels can contain alphanumerics and '-"
              // but must start and end with an alphanumeric
              char testChar;
              int labelCharCount = 0;
  
              for (int i = 0; i < addrLength; i++) {
                  testChar = address.charAt(i);
                  if (testChar == '.') {
                      if (!isAlphanum(address.charAt(i - 1))) {
                          return false;
                      }
                      if (i + 1 < addrLength && !isAlphanum(address.charAt(i + 1))) {
                          return false;
                      }
                      labelCharCount = 0;
                  } else if (!isAlphanum(testChar) && testChar != '-') {
                      return false;
                  }
                  // RFC 1034: Labels must be 63 characters or less.
                  else if (++labelCharCount > 63) {
                      return false;
                  }
              }
          }
          return true;
      }
  
      /**
       * <p>Determines whether a string is an IPv4 address as defined by
       * RFC 2373, and under the further constraint that it must be a 32-bit
       * address. Though not expressed in the grammar, in order to satisfy
       * the 32-bit address constraint, each segment of the address cannot
       * be greater than 255 (8 bits of information).</p>
       * <p/>
       * <p><code>IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT</code></p>
       *
       * @return true if the string is a syntactically valid IPv4 address
       */
      public static boolean isWellFormedIPv4Address(String address) {
  
          int addrLength = address.length();
          char testChar;
          int numDots = 0;
          int numDigits = 0;
  
          // make sure that 1) we see only digits and dot separators, 2) that
          // any dot separator is preceded and followed by a digit and
          // 3) that we find 3 dots
          //
          // RFC 2732 amended RFC 2396 by replacing the definition
          // of IPv4address with the one defined by RFC 2373. - mrglavas
          //
          // IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
          //
          // One to three digits must be in each segment.
          for (int i = 0; i < addrLength; i++) {
              testChar = address.charAt(i);
              if (testChar == '.') {
                  if ((i > 0 && !isDigit(address.charAt(i - 1))) ||
                          (i + 1 < addrLength && !isDigit(address.charAt(i + 1)))) {
                      return false;
                  }
                  numDigits = 0;
                  if (++numDots > 3) {
                      return false;
                  }
              } else if (!isDigit(testChar)) {
                  return false;
              }
              // Check that that there are no more than three digits
              // in this segment.
              else if (++numDigits > 3) {
                  return false;
              }
              // Check that this segment is not greater than 255.
              else if (numDigits == 3) {
                  char first = address.charAt(i - 2);
                  char second = address.charAt(i - 1);
                  if (!(first < '2' ||
                          (first == '2' &&
                                  (second < '5' ||
                                          (second == '5' && testChar <= '5'))))) {
                      return false;
                  }
              }
          }
          return (numDots == 3);
      }
  
      /**
       * <p>Determines whether a string is an IPv6 reference as defined
       * by RFC 2732, where IPv6address is defined in RFC 2373. The
       * IPv6 address is parsed according to Section 2.2 of RFC 2373,
       * with the additional constraint that the address be composed of
       * 128 bits of information.</p>
       * <p/>
       * <p><code>IPv6reference = "[" IPv6address "]"</code></p>
       * <p/>
       * <p>Note: The BNF expressed in RFC 2373 Appendix B does not
       * accurately describe section 2.2, and was in fact removed from
       * RFC 3513, the successor of RFC 2373.</p>
       *
       * @return true if the string is a syntactically valid IPv6 reference
       */
      public static boolean isWellFormedIPv6Reference(String address) {
  
          int addrLength = address.length();
          int index = 1;
          int end = addrLength - 1;
  
          // Check if string is a potential match for IPv6reference.
          if (!(addrLength > 2 && address.charAt(0) == '['
                  && address.charAt(end) == ']')) {
              return false;
          }
  
          // Counter for the number of 16-bit sections read in the address.
          int[] counter = new int[1];
  
          // Scan hex sequence before possible '::' or IPv4 address.
          index = scanHexSequence(address, index, end, counter);
          if (index == -1) {
              return false;
          }
          // Address must contain 128-bits of information.
          else if (index == end) {
              return (counter[0] == 8);
          }
  
          if (index + 1 < end && address.charAt(index) == ':') {
              if (address.charAt(index + 1) == ':') {
                  // '::' represents at least one 16-bit group of zeros.
                  if (++counter[0] > 8) {
                      return false;
                  }
                  index += 2;
                  // Trailing zeros will fill out the rest of the address.
                  if (index == end) {
                      return true;
                  }
              }
              // If the second character wasn't ':', in order to be valid,
              // the remainder of the string must match IPv4Address,
              // and we must have read exactly 6 16-bit groups.
              else {
                  return (counter[0] == 6) &&
                          isWellFormedIPv4Address(address.substring(index + 1, end));
              }
          } else {
              return false;
          }
  
          // 3. Scan hex sequence after '::'.
          int prevCount = counter[0];
          index = scanHexSequence(address, index, end, counter);
  
          // We've either reached the end of the string, the address ends in
          // an IPv4 address, or it is invalid. scanHexSequence has already
          // made sure that we have the right number of bits.
          return (index == end) ||
                  (index != -1 && isWellFormedIPv4Address(
                          address.substring((counter[0] > prevCount) ? index + 1 : index, end)));
      }
  
      /**
       * Helper method for isWellFormedIPv6Reference which scans the
       * hex sequences of an IPv6 address. It returns the index of the
       * next character to scan in the address, or -1 if the string
       * cannot match a valid IPv6 address.
       *
       * @param address the string to be scanned
       * @param index   the beginning index (inclusive)
       * @param end     the ending index (exclusive)
       * @param counter a counter for the number of 16-bit sections read
       *                in the address
       * @return the index of the next character to scan, or -1 if the
       * string cannot match a valid IPv6 address
       */
      private static int scanHexSequence(String address, int index, int end, int[] counter) {
  
          char testChar;
          int numDigits = 0;
          int start = index;
  
          // Trying to match the following productions:
          // hexseq = hex4 *( ":" hex4)
          // hex4   = 1*4HEXDIG
          for (; index < end; ++index) {
              testChar = address.charAt(index);
              if (testChar == ':') {
                  // IPv6 addresses are 128-bit, so there can be at most eight sections.
                  if (numDigits > 0 && ++counter[0] > 8) {
                      return -1;
                  }
                  // This could be '::'.
                  if (numDigits == 0 || ((index + 1 < end) && address.charAt(index + 1) == ':')) {
                      return index;
                  }
                  numDigits = 0;
              }
              // This might be invalid or an IPv4address. If it's potentially an IPv4address,
              // backup to just after the last valid character that matches hexseq.
              else if (!isHex(testChar)) {
                  if (testChar == '.' && numDigits < 4 && numDigits > 0 && counter[0] <= 6) {
                      int back = index - numDigits - 1;
                      return (back >= start) ? back : (back + 1);
                  }
                  return -1;
              }
              // There can be at most 4 hex digits per group.
              else if (++numDigits > 4) {
                  return -1;
              }
          }
          return (numDigits > 0 && ++counter[0] <= 8) ? end : -1;
      }
  
      /**
       * Determine whether a char is a digit.
       *
       * @return true if the char is betweeen '0' and '9', false otherwise
       */
      private static boolean isDigit(char p_char) {
          return p_char >= '0' && p_char <= '9';
      }
  
      /**
       * Determine whether a character is a hexadecimal character.
       *
       * @return true if the char is betweeen '0' and '9', 'a' and 'f'
       * or 'A' and 'F', false otherwise
       */
      private static boolean isHex(char p_char) {
          return (p_char <= 'f' && (fgLookupTable[p_char] & ASCII_HEX_CHARACTERS) != 0);
      }
  
      /**
       * Determine whether a char is an alphabetic character: a-z or A-Z
       *
       * @return true if the char is alphabetic, false otherwise
       */
      private static boolean isAlpha(char p_char) {
          return ((p_char >= 'a' && p_char <= 'z') || (p_char >= 'A' && p_char <= 'Z'));
      }
  
      /**
       * Determine whether a char is an alphanumeric: 0-9, a-z or A-Z
       *
       * @return true if the char is alphanumeric, false otherwise
       */
      private static boolean isAlphanum(char p_char) {
          return (p_char <= 'z' && (fgLookupTable[p_char] & MASK_ALPHA_NUMERIC) != 0);
      }
  
      /**
       * Determine whether a character is a reserved character:
       * ';', '/', '?', ':', '@', '&', '=', '+', '$', ',', '[', or ']'
       *
       * @return true if the string contains any reserved characters
       */
      private static boolean isReservedCharacter(char p_char) {
          return (p_char <= ']' && (fgLookupTable[p_char] & RESERVED_CHARACTERS) != 0);
      }
  
      /**
       * Determine whether a char is an unreserved character.
       *
       * @return true if the char is unreserved, false otherwise
       */
      private static boolean isUnreservedCharacter(char p_char) {
          return (p_char <= '~' && (fgLookupTable[p_char] & MASK_UNRESERVED_MASK) != 0);
      }
  
      /**
       * Determine whether a char is a URI character (reserved or
       * unreserved, not including '%' for escaped octets).
       *
       * @return true if the char is a URI character, false otherwise
       */
      private static boolean isURICharacter(char p_char) {
          return (p_char <= '~' && (fgLookupTable[p_char] & MASK_URI_CHARACTER) != 0);
      }
  
      /**
       * Determine whether a char is a scheme character.
       *
       * @return true if the char is a scheme character, false otherwise
       */
      private static boolean isSchemeCharacter(char p_char) {
          return (p_char <= 'z' && (fgLookupTable[p_char] & MASK_SCHEME_CHARACTER) != 0);
      }
  
      /**
       * Determine whether a char is a userinfo character.
       *
       * @return true if the char is a userinfo character, false otherwise
       */
      private static boolean isUserinfoCharacter(char p_char) {
          return (p_char <= 'z' && (fgLookupTable[p_char] & MASK_USERINFO_CHARACTER) != 0);
      }
  
      /**
       * Determine whether a char is a path character.
       *
       * @return true if the char is a path character, false otherwise
       */
      private static boolean isPathCharacter(char p_char) {
          return (p_char <= '~' && (fgLookupTable[p_char] & MASK_PATH_CHARACTER) != 0);
      }
  
      /**
       * Determine whether a given string contains only URI characters (also
       * called "uric" in RFC 2396). uric consist of all reserved
       * characters, unreserved characters and escaped characters.
       *
       * @return true if the string is comprised of uric, false otherwise
       */
      private static boolean isURIString(String p_uric) {
          if (p_uric == null) {
              return false;
          }
          int end = p_uric.length();
          char testChar = '\0';
          for (int i = 0; i < end; i++) {
              testChar = p_uric.charAt(i);
              if (testChar == '%') {
                  if (i + 2 >= end ||
                          !isHex(p_uric.charAt(i + 1)) ||
                          !isHex(p_uric.charAt(i + 2))) {
                      return false;
                  } else {
                      i += 2;
                      continue;
                  }
              }
              if (isURICharacter(testChar)) {
                  continue;
              } else {
                  return false;
              }
          }
          return true;
      }
  
      /**
       * Initialize all fields of this URI from another URI.
       *
       * @param p_other the URI to copy (cannot be null)
       */
      private void initialize(URI p_other) {
          m_scheme = p_other.getScheme();
          m_userinfo = p_other.getUserinfo();
          m_host = p_other.getHost();
          m_port = p_other.getPort();
          m_regAuthority = p_other.getRegBasedAuthority();
          m_path = p_other.getPath();
          m_queryString = p_other.getQueryString();
          m_fragment = p_other.getFragment();
      }
  
      /**
       * Initializes this URI from a base URI and a URI specification string.
       * See RFC 2396 Section 4 and Appendix B for specifications on parsing
       * the URI and Section 5 for specifications on resolving relative URIs
       * and relative paths.
       *
       * @param p_base              the base URI (may be null if p_uriSpec is an absolute
       *                            URI)
       * @param p_uriSpec           the URI spec string which may be an absolute or
       *                            relative URI (can only be null/empty if p_base
       *                            is not null)
       * @param allowNonAbsoluteURI true to permit non-absolute URIs,
       *                            in case of relative URI, false otherwise.
       * @throws MalformedURIException if p_base is null and p_uriSpec
       *                               is not an absolute URI or if
       *                               p_uriSpec violates syntax rules
       */
      private void initialize(URI p_base, String p_uriSpec, boolean allowNonAbsoluteURI)
              throws MalformedURIException {
  
          String uriSpec = p_uriSpec;
          int uriSpecLen = (uriSpec != null) ? uriSpec.length() : 0;
  
          if (p_base == null && uriSpecLen == 0) {
              if (allowNonAbsoluteURI) {
                  m_path = "";
                  return;
              }
              throw new MalformedURIException("Cannot initialize URI with empty parameters.");
          }
  
          // just make a copy of the base if spec is empty
          if (uriSpecLen == 0) {
              initialize(p_base);
              return;
          }
  
          int index = 0;
  
          // Check for scheme, which must be before '/', '?' or '#'.
          int colonIdx = uriSpec.indexOf(':');
          if (colonIdx != -1) {
              final int searchFrom = colonIdx - 1;
              // search backwards starting from character before ':'.
              int slashIdx = uriSpec.lastIndexOf('/', searchFrom);
              int queryIdx = uriSpec.lastIndexOf('?', searchFrom);
              int fragmentIdx = uriSpec.lastIndexOf('#', searchFrom);
  
              if (colonIdx == 0 || slashIdx != -1 ||
                      queryIdx != -1 || fragmentIdx != -1) {
                  // A standalone base is a valid URI according to spec
                  if (colonIdx == 0 || (p_base == null && fragmentIdx != 0 && !allowNonAbsoluteURI)) {
                      throw new MalformedURIException("No scheme found in URI.");
                  }
              } else {
                  initializeScheme(uriSpec);
                  index = m_scheme.length() + 1;
  
                  // Neither 'scheme:' or 'scheme:#fragment' are valid URIs.
                  if (colonIdx == uriSpecLen - 1 || uriSpec.charAt(colonIdx + 1) == '#') {
                      throw new MalformedURIException("Scheme specific part cannot be empty.");
                  }
              }
          } else if (p_base == null && uriSpec.indexOf('#') != 0 && !allowNonAbsoluteURI) {
              throw new MalformedURIException("No scheme found in URI.");
          }
  
          // Two slashes means we may have authority, but definitely means we're either
          // matching net_path or abs_path. These two productions are ambiguous in that
          // every net_path (except those containing an IPv6Reference) is an abs_path.
          // RFC 2396 resolves this ambiguity by applying a greedy left most matching rule.
          // Try matching net_path first, and if that fails we don't have authority so
          // then attempt to match abs_path.
          //
          // net_path = "//" authority [ abs_path ]
          // abs_path = "/"  path_segments
          if (((index + 1) < uriSpecLen) &&
                  (uriSpec.charAt(index) == '/' && uriSpec.charAt(index + 1) == '/')) {
              index += 2;
              int startPos = index;
  
              // Authority will be everything up to path, query or fragment
              char testChar = '\0';
              while (index < uriSpecLen) {
                  testChar = uriSpec.charAt(index);
                  if (testChar == '/' || testChar == '?' || testChar == '#') {
                      break;
                  }
                  index++;
              }
  
              // Attempt to parse authority. If the section is an empty string
              // this is a valid server based authority, so set the host to this
              // value.
              if (index > startPos) {
                  // If we didn't find authority we need to back up. Attempt to
                  // match against abs_path next.
                  if (!initializeAuthority(uriSpec.substring(startPos, index))) {
                      index = startPos - 2;
                  }
              } else {
                  m_host = "";
              }
          }
  
          initializePath(uriSpec, index);
  
          // Resolve relative URI to base URI - see RFC 2396 Section 5.2
          // In some cases, it might make more sense to throw an exception
          // (when scheme is specified is the string spec and the base URI
          // is also specified, for example), but we're just following the
          // RFC specifications
          if (p_base != null) {
              absolutize(p_base);
          }
      }
  
      /**
       * Initializes this URI from a base URI and a URI specification string.
       * See RFC 2396 Section 4 and Appendix B for specifications on parsing
       * the URI and Section 5 for specifications on resolving relative URIs
       * and relative paths.
       *
       * @param p_base    the base URI (may be null if p_uriSpec is an absolute
       *                  URI)
       * @param p_uriSpec the URI spec string which may be an absolute or
       *                  relative URI (can only be null/empty if p_base
       *                  is not null)
       * @throws MalformedURIException if p_base is null and p_uriSpec
       *                               is not an absolute URI or if
       *                               p_uriSpec violates syntax rules
       */
      private void initialize(URI p_base, String p_uriSpec)
              throws MalformedURIException {
  
          String uriSpec = p_uriSpec;
          int uriSpecLen = (uriSpec != null) ? uriSpec.length() : 0;
  
          if (p_base == null && uriSpecLen == 0) {
              throw new MalformedURIException(
                      "Cannot initialize URI with empty parameters.");
          }
  
          // just make a copy of the base if spec is empty
          if (uriSpecLen == 0) {
              initialize(p_base);
              return;
          }
  
          int index = 0;
  
          // Check for scheme, which must be before '/', '?' or '#'.
          int colonIdx = uriSpec.indexOf(':');
          if (colonIdx != -1) {
              final int searchFrom = colonIdx - 1;
              // search backwards starting from character before ':'.
              int slashIdx = uriSpec.lastIndexOf('/', searchFrom);
              int queryIdx = uriSpec.lastIndexOf('?', searchFrom);
              int fragmentIdx = uriSpec.lastIndexOf('#', searchFrom);
  
              if (colonIdx == 0 || slashIdx != -1 ||
                      queryIdx != -1 || fragmentIdx != -1) {
                  // A standalone base is a valid URI according to spec
                  if (colonIdx == 0 || (p_base == null && fragmentIdx != 0)) {
                      throw new MalformedURIException("No scheme found in URI.");
                  }
              } else {
                  initializeScheme(uriSpec);
                  index = m_scheme.length() + 1;
  
                  // Neither 'scheme:' or 'scheme:#fragment' are valid URIs.
                  if (colonIdx == uriSpecLen - 1 || uriSpec.charAt(colonIdx + 1) == '#') {
                      throw new MalformedURIException("Scheme specific part cannot be empty.");
                  }
              }
          } else if (p_base == null && uriSpec.indexOf('#') != 0) {
              throw new MalformedURIException("No scheme found in URI.");
          }
  
          // Two slashes means we may have authority, but definitely means we're either
          // matching net_path or abs_path. These two productions are ambiguous in that
          // every net_path (except those containing an IPv6Reference) is an abs_path.
          // RFC 2396 resolves this ambiguity by applying a greedy left most matching rule.
          // Try matching net_path first, and if that fails we don't have authority so
          // then attempt to match abs_path.
          //
          // net_path = "//" authority [ abs_path ]
          // abs_path = "/"  path_segments
          if (((index + 1) < uriSpecLen) &&
                  (uriSpec.charAt(index) == '/' && uriSpec.charAt(index + 1) == '/')) {
              index += 2;
              int startPos = index;
  
              // Authority will be everything up to path, query or fragment
              char testChar = '\0';
              while (index < uriSpecLen) {
                  testChar = uriSpec.charAt(index);
                  if (testChar == '/' || testChar == '?' || testChar == '#') {
                      break;
                  }
                  index++;
              }
  
              // Attempt to parse authority. If the section is an empty string
              // this is a valid server based authority, so set the host to this
              // value.
              if (index > startPos) {
                  // If we didn't find authority we need to back up. Attempt to
                  // match against abs_path next.
                  if (!initializeAuthority(uriSpec.substring(startPos, index))) {
                      index = startPos - 2;
                  }
              } else {
                  m_host = "";
              }
          }
  
          initializePath(uriSpec, index);
  
          // Resolve relative URI to base URI - see RFC 2396 Section 5.2
          // In some cases, it might make more sense to throw an exception
          // (when scheme is specified is the string spec and the base URI
          // is also specified, for example), but we're just following the
          // RFC specifications
          if (p_base != null) {
              absolutize(p_base);
          }
      }
  
      /**
       * Absolutize URI with given base URI.
       *
       * @param p_base base URI for absolutization
       */
      public void absolutize(URI p_base) {
  
          // check to see if this is the current doc - RFC 2396 5.2 #2
          // note that this is slightly different from the RFC spec in that
          // we don't include the check for query string being null
          // - this handles cases where the urispec is just a query
          // string or a fragment (e.g. "?y" or "#s") -
          // see <http://www.ics.uci.edu/~fielding/url/test1.html> which
          // identified this as a bug in the RFC
          if (m_path.length() == 0 && m_scheme == null &&
                  m_host == null && m_regAuthority == null) {
              m_scheme = p_base.getScheme();
              m_userinfo = p_base.getUserinfo();
              m_host = p_base.getHost();
              m_port = p_base.getPort();
              m_regAuthority = p_base.getRegBasedAuthority();
              m_path = p_base.getPath();
  
              if (m_queryString == null) {
                  m_queryString = p_base.getQueryString();
  
                  if (m_fragment == null) {
                      m_fragment = p_base.getFragment();
                  }
              }
              return;
          }
  
          // check for scheme - RFC 2396 5.2 #3
          // if we found a scheme, it means absolute URI, so we're done
          if (m_scheme == null) {
              m_scheme = p_base.getScheme();
          } else {
              return;
          }
  
          // check for authority - RFC 2396 5.2 #4
          // if we found a host, then we've got a network path, so we're done
          if (m_host == null && m_regAuthority == null) {
              m_userinfo = p_base.getUserinfo();
              m_host = p_base.getHost();
              m_port = p_base.getPort();
              m_regAuthority = p_base.getRegBasedAuthority();
          } else {
              return;
          }
  
          // check for absolute path - RFC 2396 5.2 #5
          if (m_path.length() > 0 &&
                  m_path.startsWith("/")) {
              return;
          }
  
          // if we get to this point, we need to resolve relative path
          // RFC 2396 5.2 #6
          String path = "";
          String basePath = p_base.getPath();
  
          // 6a - get all but the last segment of the base URI path
          if (basePath != null && basePath.length() > 0) {
              int lastSlash = basePath.lastIndexOf('/');
              if (lastSlash != -1) {
                  path = basePath.substring(0, lastSlash + 1);
              }
          } else if (m_path.length() > 0) {
              path = "/";
          }
  
          // 6b - append the relative URI path
          path = path.concat(m_path);
  
          // 6c - remove all "./" where "." is a complete path segment
          int index = -1;
          while ((index = path.indexOf("/./")) != -1) {
              path = path.substring(0, index + 1).concat(path.substring(index + 3));
          }
  
          // 6d - remove "." if path ends with "." as a complete path segment
          if (path.endsWith("/.")) {
              path = path.substring(0, path.length() - 1);
          }
  
          // 6e - remove all "<segment>/../" where "<segment>" is a complete
          // path segment not equal to ".."
          index = 1;
          int segIndex = -1;
          String tempString = null;
  
          while ((index = path.indexOf("/../", index)) > 0) {
              tempString = path.substring(0, path.indexOf("/../"));
              segIndex = tempString.lastIndexOf('/');
              if (segIndex != -1) {
                  if (!tempString.substring(segIndex).equals("..")) {
                      path = path.substring(0, segIndex + 1).concat(path.substring(index + 4));
                      index = segIndex;
                  } else {
                      index += 4;
                  }
              } else {
                  index += 4;
              }
          }
  
          // 6f - remove ending "<segment>/.." where "<segment>" is a
          // complete path segment
          if (path.endsWith("/..")) {
              tempString = path.substring(0, path.length() - 3);
              segIndex = tempString.lastIndexOf('/');
              if (segIndex != -1) {
                  path = path.substring(0, segIndex + 1);
              }
          }
          m_path = path;
      }
  
      /**
       * Initialize the scheme for this URI from a URI string spec.
       *
       * @param p_uriSpec the URI specification (cannot be null)
       * @throws MalformedURIException if URI does not have a conformant
       *                               scheme
       */
      private void initializeScheme(String p_uriSpec)
              throws MalformedURIException {
          int uriSpecLen = p_uriSpec.length();
          int index = 0;
          String scheme = null;
          char testChar = '\0';
  
          while (index < uriSpecLen) {
              testChar = p_uriSpec.charAt(index);
              if (testChar == ':' || testChar == '/' ||
                      testChar == '?' || testChar == '#') {
                  break;
              }
              index++;
          }
          scheme = p_uriSpec.substring(0, index);
  
          if (scheme.length() == 0) {
              throw new MalformedURIException("No scheme found in URI.");
          } else {
              setScheme(scheme);
          }
      }
  
      /**
       * Initialize the authority (either server or registry based)
       * for this URI from a URI string spec.
       *
       * @param p_uriSpec the URI specification (cannot be null)
       * @return true if the given string matched server or registry
       * based authority
       */
      private boolean initializeAuthority(String p_uriSpec) {
  
          int index = 0;
          int start = 0;
          int end = p_uriSpec.length();
  
          char testChar = '\0';
          String userinfo = null;
  
          // userinfo is everything up to @
          if (p_uriSpec.indexOf('@', start) != -1) {
              while (index < end) {
                  testChar = p_uriSpec.charAt(index);
                  if (testChar == '@') {
                      break;
                  }
                  index++;
              }
              userinfo = p_uriSpec.substring(start, index);
              index++;
          }
  
          // host is everything up to last ':', or up to
          // and including ']' if followed by ':'.
          String host = null;
          start = index;
          boolean hasPort = false;
          if (index < end) {
              if (p_uriSpec.charAt(start) == '[') {
                  int bracketIndex = p_uriSpec.indexOf(']', start);
                  index = (bracketIndex != -1) ? bracketIndex : end;
                  if (index + 1 < end && p_uriSpec.charAt(index + 1) == ':') {
                      ++index;
                      hasPort = true;
                  } else {
                      index = end;
                  }
              } else {
                  int colonIndex = p_uriSpec.lastIndexOf(':', end);
                  index = (colonIndex > start) ? colonIndex : end;
                  hasPort = (index != end);
              }
          }
          host = p_uriSpec.substring(start, index);
          int port = -1;
          if (host.length() > 0) {
              // port
              if (hasPort) {
                  index++;
                  start = index;
                  while (index < end) {
                      index++;
                  }
                  String portStr = p_uriSpec.substring(start, index);
                  if (portStr.length() > 0) {
                      // REVISIT: Remove this code.
                      /** for (int i = 0; i < portStr.length(); i++) {
                       if (!isDigit(portStr.charAt(i))) {
                       throw new MalformedURIException(
                       portStr +
                       " is invalid. Port should only contain digits!");
                       }
                       }**/
                      // REVISIT: Remove this code.
                      // Store port value as string instead of integer.
                      try {
                          port = Integer.parseInt(portStr);
                          if (port == -1) --port;
                      } catch (NumberFormatException nfe) {
                          port = -2;
                      }
                  }
              }
          }
  
          if (isValidServerBasedAuthority(host, port, userinfo)) {
              m_host = host;
              m_port = port;
              m_userinfo = userinfo;
              return true;
          }
          // Note: Registry based authority is being removed from a
          // new spec for URI which would obsolete RFC 2396. If the
          // spec is added to XML errata, processing of reg_name
          // needs to be removed. - mrglavas.
          else if (isValidRegistryBasedAuthority(p_uriSpec)) {
              m_regAuthority = p_uriSpec;
              return true;
          }
          return false;
      }
  
      /**
       * Determines whether the components host, port, and user info
       * are valid as a server authority.
       *
       * @param host     the host component of authority
       * @param port     the port number component of authority
       * @param userinfo the user info component of authority
       * @return true if the given host, port, and userinfo compose
       * a valid server authority
       */
      private boolean isValidServerBasedAuthority(String host, int port, String userinfo) {
  
          // Check if the host is well formed.
          if (!isWellFormedAddress(host)) {
              return false;
          }
  
          // Check that port is well formed if it exists.
          // REVISIT: There's no restriction on port value ranges, but
          // perform the same check as in setPort to be consistent. Pass
          // in a string to this method instead of an integer.
          if (port < -1 || port > 65535) {
              return false;
          }
  
          // Check that userinfo is well formed if it exists.
          if (userinfo != null) {
              // Userinfo can contain alphanumerics, mark characters, escaped
              // and ';',':','&','=','+','$',','
              int index = 0;
              int end = userinfo.length();
              char testChar = '\0';
              while (index < end) {
                  testChar = userinfo.charAt(index);
                  if (testChar == '%') {
                      if (index + 2 >= end ||
                              !isHex(userinfo.charAt(index + 1)) ||
                              !isHex(userinfo.charAt(index + 2))) {
                          return false;
                      }
                      index += 2;
                  } else if (!isUserinfoCharacter(testChar)) {
                      return false;
                  }
                  ++index;
              }
          }
          return true;
      }
  
      /**
       * Determines whether the given string is a registry based authority.
       *
       * @param authority the authority component of a URI
       * @return true if the given string is a registry based authority
       */
      private boolean isValidRegistryBasedAuthority(String authority) {
          int index = 0;
          int end = authority.length();
          char testChar;
  
          while (index < end) {
              testChar = authority.charAt(index);
  
              // check for valid escape sequence
              if (testChar == '%') {
                  if (index + 2 >= end ||
                          !isHex(authority.charAt(index + 1)) ||
                          !isHex(authority.charAt(index + 2))) {
                      return false;
                  }
                  index += 2;
              }
              // can check against path characters because the set
              // is the same except for '/' which we've already excluded.
              else if (!isPathCharacter(testChar)) {
                  return false;
              }
              ++index;
          }
          return true;
      }
  
      /**
       * Initialize the path for this URI from a URI string spec.
       *
       * @param p_uriSpec     the URI specification (cannot be null)
       * @param p_nStartIndex the index to begin scanning from
       * @throws MalformedURIException if p_uriSpec violates syntax rules
       */
      private void initializePath(String p_uriSpec, int p_nStartIndex)
              throws MalformedURIException {
          if (p_uriSpec == null) {
              throw new MalformedURIException(
                      "Cannot initialize path from null string!");
          }
  
          int index = p_nStartIndex;
          int start = p_nStartIndex;
          int end = p_uriSpec.length();
          char testChar = '\0';
  
          // path - everything up to query string or fragment
          if (start < end) {
              // RFC 2732 only allows '[' and ']' to appear in the opaque part.
              if (getScheme() == null || p_uriSpec.charAt(start) == '/') {
  
                  // Scan path.
                  // abs_path = "/"  path_segments
                  // rel_path = rel_segment [ abs_path ]
                  while (index < end) {
                      testChar = p_uriSpec.charAt(index);
  
                      // check for valid escape sequence
                      if (testChar == '%') {
                          if (index + 2 >= end ||
                                  !isHex(p_uriSpec.charAt(index + 1)) ||
                                  !isHex(p_uriSpec.charAt(index + 2))) {
                              throw new MalformedURIException(
                                      "Path contains invalid escape sequence!");
                          }
                          index += 2;
                      }
                      // Path segments cannot contain '[' or ']' since pchar
                      // production was not changed by RFC 2732.
                      else if (!isPathCharacter(testChar)) {
                          if (testChar == '?' || testChar == '#') {
                              break;
                          }
                          throw new MalformedURIException(
                                  "Path contains invalid character: " + testChar);
                      }
                      ++index;
                  }
              } else {
  
                  // Scan opaque part.
                  // opaque_part = uric_no_slash *uric
                  while (index < end) {
                      testChar = p_uriSpec.charAt(index);
  
                      if (testChar == '?' || testChar == '#') {
                          break;
                      }
  
                      // check for valid escape sequence
                      if (testChar == '%') {
                          if (index + 2 >= end ||
                                  !isHex(p_uriSpec.charAt(index + 1)) ||
                                  !isHex(p_uriSpec.charAt(index + 2))) {
                              throw new MalformedURIException(
                                      "Opaque part contains invalid escape sequence!");
                          }
                          index += 2;
                      }
                      // If the scheme specific part is opaque, it can contain '['
                      // and ']'. uric_no_slash wasn't modified by RFC 2732, which
                      // I've interpreted as an error in the spec, since the
                      // production should be equivalent to (uric - '/'), and uric
                      // contains '[' and ']'. - mrglavas
                      else if (!isURICharacter(testChar)) {
                          throw new MalformedURIException(
                                  "Opaque part contains invalid character: " + testChar);
                      }
                      ++index;
                  }
              }
          }
          m_path = p_uriSpec.substring(start, index);
  
          // query - starts with ? and up to fragment or end
          if (testChar == '?') {
              index++;
              start = index;
              while (index < end) {
                  testChar = p_uriSpec.charAt(index);
                  if (testChar == '#') {
                      break;
                  }
                  if (testChar == '%') {
                      if (index + 2 >= end ||
                              !isHex(p_uriSpec.charAt(index + 1)) ||
                              !isHex(p_uriSpec.charAt(index + 2))) {
                          throw new MalformedURIException(
                                  "Query string contains invalid escape sequence!");
                      }
                      index += 2;
                  } else if (!isURICharacter(testChar)) {
                      throw new MalformedURIException(
                              "Query string contains invalid character: " + testChar);
                  }
                  index++;
              }
              m_queryString = p_uriSpec.substring(start, index);
          }
  
          // fragment - starts with #
          if (testChar == '#') {
              index++;
              start = index;
              while (index < end) {
                  testChar = p_uriSpec.charAt(index);
  
                  if (testChar == '%') {
                      if (index + 2 >= end ||
                              !isHex(p_uriSpec.charAt(index + 1)) ||
                              !isHex(p_uriSpec.charAt(index + 2))) {
                          throw new MalformedURIException(
                                  "Fragment contains invalid escape sequence!");
                      }
                      index += 2;
                  } else if (!isURICharacter(testChar)) {
                      throw new MalformedURIException(
                              "Fragment contains invalid character: " + testChar);
                  }
                  index++;
              }
              m_fragment = p_uriSpec.substring(start, index);
          }
      }
  
      /**
       * Get the scheme for this URI.
       *
       * @return the scheme for this URI
       */
      public String getScheme() {
          return m_scheme;
      }
  
      /**
       * Set the scheme for this URI. The scheme is converted to lowercase
       * before it is set.
       *
       * @param p_scheme the scheme for this URI (cannot be null)
       * @throws MalformedURIException if p_scheme is not a conformant
       *                               scheme name
       */
      public void setScheme(String p_scheme) throws MalformedURIException {
          if (p_scheme == null) {
              throw new MalformedURIException(
                      "Cannot set scheme from null string!");
          }
          if (!isConformantSchemeName(p_scheme)) {
              throw new MalformedURIException("The scheme is not conformant.");
          }
  
          m_scheme = p_scheme.toLowerCase(Locale.ENGLISH);
      }
  
      /**
       * Get the scheme-specific part for this URI (everything following the
       * scheme and the first colon). See RFC 2396 Section 5.2 for spec.
       *
       * @return the scheme-specific part for this URI
       */
      public String getSchemeSpecificPart() {
          StringBuffer schemespec = new StringBuffer();
  
          if (m_host != null || m_regAuthority != null) {
              schemespec.append("//");
  
              // Server based authority.
              if (m_host != null) {
  
                  if (m_userinfo != null) {
                      schemespec.append(m_userinfo);
                      schemespec.append('@');
                  }
  
                  schemespec.append(m_host);
  
                  if (m_port != -1) {
                      schemespec.append(':');
                      schemespec.append(m_port);
                  }
              }
              // Registry based authority.
              else {
                  schemespec.append(m_regAuthority);
              }
          }
  
          if (m_path != null) {
              schemespec.append((m_path));
          }
  
          if (m_queryString != null) {
              schemespec.append('?');
              schemespec.append(m_queryString);
          }
  
          if (m_fragment != null) {
              schemespec.append('#');
              schemespec.append(m_fragment);
          }
  
          return schemespec.toString();
      }
  
      /**
       * Get the userinfo for this URI.
       *
       * @return the userinfo for this URI (null if not specified).
       */
      public String getUserinfo() {
          return m_userinfo;
      }
  
      /**
       * Set the userinfo for this URI. If a non-null value is passed in and
       * the host value is null, then an exception is thrown.
       *
       * @param p_userinfo the userinfo for this URI
       * @throws MalformedURIException if p_userinfo contains invalid
       *                               characters
       */
      public void setUserinfo(String p_userinfo) throws MalformedURIException {
          if (p_userinfo == null) {
              m_userinfo = null;
              return;
          } else {
              if (m_host == null) {
                  throw new MalformedURIException(
                          "Userinfo cannot be set when host is null!");
              }
  
              // userinfo can contain alphanumerics, mark characters, escaped
              // and ';',':','&','=','+','$',','
              int index = 0;
              int end = p_userinfo.length();
              char testChar = '\0';
              while (index < end) {
                  testChar = p_userinfo.charAt(index);
                  if (testChar == '%') {
                      if (index + 2 >= end ||
                              !isHex(p_userinfo.charAt(index + 1)) ||
                              !isHex(p_userinfo.charAt(index + 2))) {
                          throw new MalformedURIException(
                                  "Userinfo contains invalid escape sequence!");
                      }
                  } else if (!isUserinfoCharacter(testChar)) {
                      throw new MalformedURIException(
                              "Userinfo contains invalid character:" + testChar);
                  }
                  index++;
              }
          }
          m_userinfo = p_userinfo;
      }
  
      /**
       * Get the host for this URI.
       *
       * @return the host for this URI (null if not specified).
       */
      public String getHost() {
          return m_host;
      }
  
      /**
       * <p>Set the host for this URI. If null is passed in, the userinfo
       * field is also set to null and the port is set to -1.</p>
       * <p/>
       * <p>Note: This method overwrites registry based authority if it
       * previously existed in this URI.</p>
       *
       * @param p_host the host for this URI
       * @throws MalformedURIException if p_host is not a valid IP
       *                               address or DNS hostname.
       */
      public void setHost(String p_host) throws MalformedURIException {
          if (p_host == null || p_host.length() == 0) {
              if (p_host != null) {
                  m_regAuthority = null;
              }
              m_host = p_host;
              m_userinfo = null;
              m_port = -1;
              return;
          } else if (!isWellFormedAddress(p_host)) {
              throw new MalformedURIException("Host is not a well formed address!");
          }
          m_host = p_host;
          m_regAuthority = null;
      }
  
      /**
       * Get the port for this URI.
       *
       * @return the port for this URI (-1 if not specified).
       */
      public int getPort() {
          return m_port;
      }
  
      /**
       * Set the port for this URI. -1 is used to indicate that the port is
       * not specified, otherwise valid port numbers are  between 0 and 65535.
       * If a valid port number is passed in and the host field is null,
       * an exception is thrown.
       *
       * @param p_port the port number for this URI
       * @throws MalformedURIException if p_port is not -1 and not a
       *                               valid port number
       */
      public void setPort(int p_port) throws MalformedURIException {
          if (p_port >= 0 && p_port <= 65535) {
              if (m_host == null) {
                  throw new MalformedURIException(
                          "Port cannot be set when host is null!");
              }
          } else if (p_port != -1) {
              throw new MalformedURIException("Invalid port number!");
          }
          m_port = p_port;
      }
  
      /**
       * Get the registry based authority for this URI.
       *
       * @return the registry based authority (null if not specified).
       */
      public String getRegBasedAuthority() {
          return m_regAuthority;
      }
  
      /**
       * <p>Sets the registry based authority for this URI.</p>
       * <p/>
       * <p>Note: This method overwrites server based authority
       * if it previously existed in this URI.</p>
       *
       * @param authority the registry based authority for this URI
       * @throws MalformedURIException it authority is not a
       *                               well formed registry based authority
       */
      public void setRegBasedAuthority(String authority)
              throws MalformedURIException {
  
          if (authority == null) {
              m_regAuthority = null;
              return;
          }
          // reg_name = 1*( unreserved | escaped | "$" | "," |
          //            ";" | ":" | "@" | "&" | "=" | "+" )
          else if (authority.length() < 1 ||
                  !isValidRegistryBasedAuthority(authority) ||
                  authority.indexOf('/') != -1) {
              throw new MalformedURIException("Registry based authority is not well formed.");
          }
          m_regAuthority = authority;
          m_host = null;
          m_userinfo = null;
          m_port = -1;
      }
  
      /**
       * Get the authority for this URI.
       *
       * @return the authority
       */
      public String getAuthority() {
          StringBuffer authority = new StringBuffer();
          if (m_host != null || m_regAuthority != null) {
              authority.append("//");
  
              // Server based authority.
              if (m_host != null) {
  
                  if (m_userinfo != null) {
                      authority.append(m_userinfo);
                      authority.append('@');
                  }
  
                  authority.append(m_host);
  
                  if (m_port != -1) {
                      authority.append(':');
                      authority.append(m_port);
                  }
              }
              // Registry based authority.
              else {
                  authority.append(m_regAuthority);
              }
          }
          return authority.toString();
      }
  
      /**
       * Get the path for this URI (optionally with the query string and
       * fragment).
       *
       * @param p_includeQueryString if true (and query string is not null),
       *                             then a "?" followed by the query string
       *                             will be appended
       * @param p_includeFragment    if true (and fragment is not null),
       *                             then a "#" followed by the fragment
       *                             will be appended
       * @return the path for this URI possibly including the query string
       * and fragment
       */
      public String getPath(boolean p_includeQueryString,
                            boolean p_includeFragment) {
          StringBuffer pathString = new StringBuffer(m_path);
  
          if (p_includeQueryString && m_queryString != null) {
              pathString.append('?');
              pathString.append(m_queryString);
          }
  
          if (p_includeFragment && m_fragment != null) {
              pathString.append('#');
              pathString.append(m_fragment);
          }
          return pathString.toString();
      }
  
      /**
       * Get the path for this URI. Note that the value returned is the path
       * only and does not include the query string or fragment.
       *
       * @return the path for this URI.
       */
      public String getPath() {
          return m_path;
      }
  
      /**
       * Set the path for this URI. If the supplied path is null, then the
       * query string and fragment are set to null as well. If the supplied
       * path includes a query string and/or fragment, these fields will be
       * parsed and set as well. Note that, for URIs following the "generic
       * URI" syntax, the path specified should start with a slash.
       * For URIs that do not follow the generic URI syntax, this method
       * sets the scheme-specific part.
       *
       * @param p_path the path for this URI (may be null)
       * @throws MalformedURIException if p_path contains invalid
       *                               characters
       */
      public void setPath(String p_path) throws MalformedURIException {
          if (p_path == null) {
              m_path = null;
              m_queryString = null;
              m_fragment = null;
          } else {
              initializePath(p_path, 0);
          }
      }
  
      /**
       * Get the query string for this URI.
       *
       * @return the query string for this URI. Null is returned if there
       * was no "?" in the URI spec, empty string if there was a
       * "?" but no query string following it.
       */
      public String getQueryString() {
          return m_queryString;
      }
  
      /**
       * Set the query string for this URI. A non-null value is valid only
       * if this is an URI conforming to the generic URI syntax and
       * the path value is not null.
       *
       * @param p_queryString the query string for this URI
       * @throws MalformedURIException if p_queryString is not null and this
       *                               URI does not conform to the generic
       *                               URI syntax or if the path is null
       */
      public void setQueryString(String p_queryString) throws MalformedURIException {
          if (p_queryString == null) {
              m_queryString = null;
          } else if (!isGenericURI()) {
              throw new MalformedURIException(
                      "Query string can only be set for a generic URI!");
          } else if (getPath() == null) {
              throw new MalformedURIException(
                      "Query string cannot be set when path is null!");
          } else if (!isURIString(p_queryString)) {
              throw new MalformedURIException(
                      "Query string contains invalid character!");
          } else {
              m_queryString = p_queryString;
          }
      }
  
      /**
       * Get the fragment for this URI.
       *
       * @return the fragment for this URI. Null is returned if there
       * was no "#" in the URI spec, empty string if there was a
       * "#" but no fragment following it.
       */
      public String getFragment() {
          return m_fragment;
      }
  
      /**
       * Set the fragment for this URI. A non-null value is valid only
       * if this is a URI conforming to the generic URI syntax and
       * the path value is not null.
       *
       * @param p_fragment the fragment for this URI
       * @throws MalformedURIException if p_fragment is not null and this
       *                               URI does not conform to the generic
       *                               URI syntax or if the path is null
       */
      public void setFragment(String p_fragment) throws MalformedURIException {
          if (p_fragment == null) {
              m_fragment = null;
          } else if (!isGenericURI()) {
              throw new MalformedURIException(
                      "Fragment can only be set for a generic URI!");
          } else if (getPath() == null) {
              throw new MalformedURIException(
                      "Fragment cannot be set when path is null!");
          } else if (!isURIString(p_fragment)) {
              throw new MalformedURIException(
                      "Fragment contains invalid character!");
          } else {
              m_fragment = p_fragment;
          }
      }
  
      /**
       * Append to the end of the path of this URI. If the current path does
       * not end in a slash and the path to be appended does not begin with
       * a slash, a slash will be appended to the current path before the
       * new segment is added. Also, if the current path ends in a slash
       * and the new segment begins with a slash, the extra slash will be
       * removed before the new segment is appended.
       *
       * @param p_addToPath the new segment to be added to the current path
       * @throws MalformedURIException if p_addToPath contains syntax
       *                               errors
       */
      public void appendPath(String p_addToPath)
              throws MalformedURIException {
          if (p_addToPath == null || p_addToPath.trim().length() == 0) {
              return;
          }
  
          if (!isURIString(p_addToPath)) {
              throw new MalformedURIException(
                      "Path contains invalid character!");
          }
  
          if (m_path == null || m_path.trim().length() == 0) {
              if (p_addToPath.startsWith("/")) {
                  m_path = p_addToPath;
              } else {
                  m_path = "/" + p_addToPath;
              }
          } else if (m_path.endsWith("/")) {
              if (p_addToPath.startsWith("/")) {
                  m_path = m_path.concat(p_addToPath.substring(1));
              } else {
                  m_path = m_path.concat(p_addToPath);
              }
          } else {
              if (p_addToPath.startsWith("/")) {
                  m_path = m_path.concat(p_addToPath);
              } else {
                  m_path = m_path.concat("/" + p_addToPath);
              }
          }
      }
  
      /**
       * Determines if the passed-in Object is equivalent to this URI.
       *
       * @param p_test the Object to test for equality.
       * @return true if p_test is a URI with all values equal to this
       * URI, false otherwise
       */
      @Override
      public boolean equals(Object p_test) {
          if (p_test instanceof URI) {
              URI testURI = (URI) p_test;
              if (((m_scheme == null && testURI.m_scheme == null) ||
                      (m_scheme != null && testURI.m_scheme != null &&
                              m_scheme.equals(testURI.m_scheme))) &&
                      ((m_userinfo == null && testURI.m_userinfo == null) ||
                              (m_userinfo != null && testURI.m_userinfo != null &&
                                      m_userinfo.equals(testURI.m_userinfo))) &&
                      ((m_host == null && testURI.m_host == null) ||
                              (m_host != null && testURI.m_host != null &&
                                      m_host.equals(testURI.m_host))) &&
                      m_port == testURI.m_port &&
                      ((m_path == null && testURI.m_path == null) ||
                              (m_path != null && testURI.m_path != null &&
                                      m_path.equals(testURI.m_path))) &&
                      ((m_queryString == null && testURI.m_queryString == null) ||
                              (m_queryString != null && testURI.m_queryString != null &&
                                      m_queryString.equals(testURI.m_queryString))) &&
                      ((m_fragment == null && testURI.m_fragment == null) ||
                              (m_fragment != null && testURI.m_fragment != null &&
                                      m_fragment.equals(testURI.m_fragment)))) {
                  return true;
              }
          }
          return false;
      }
  
      /**
       * Get the URI as a string specification. See RFC 2396 Section 5.2.
       *
       * @return the URI string specification
       */
      @Override
      public String toString() {
          StringBuffer uriSpecString = new StringBuffer();
  
          if (m_scheme != null) {
              uriSpecString.append(m_scheme);
              uriSpecString.append(':');
          }
          uriSpecString.append(getSchemeSpecificPart());
          return uriSpecString.toString();
      }
  
      /**
       * Get the indicator as to whether this URI uses the "generic URI"
       * syntax.
       *
       * @return true if this URI uses the "generic URI" syntax, false
       * otherwise
       */
      public boolean isGenericURI() {
          // presence of the host (whether valid or empty) means
          // double-slashes which means generic uri
          return (m_host != null);
      }
  
      /**
       * Returns whether this URI represents an absolute URI.
       *
       * @return true if this URI represents an absolute URI, false
       * otherwise
       */
      public boolean isAbsoluteURI() {
          // presence of the scheme means absolute uri
          return (m_scheme != null);
      }
  
      /*******************************************************************
       * MalformedURIExceptions are thrown in the process of building a URI
       * or setting fields on a URI when an operation would result in an
       * invalid URI specification.
       ********************************************************************/
      public static class MalformedURIException extends IOException {
  
          /**
           * Serialization version.
           */
          static final long serialVersionUID = -6695054834342951930L;
  
          /******************************************************************
           * Constructs a <code>MalformedURIException</code> with no specified
           * detail message.
           ******************************************************************/
          public MalformedURIException() {
              super();
          }
  
          /*****************************************************************
           * Constructs a <code>MalformedURIException</code> with the
           * specified detail message.
           *
           * @param p_msg the detail message.
           ******************************************************************/
          public MalformedURIException(String p_msg) {
              super(p_msg);
          }
      }
  }
  