**** Merged from MCS ****

[mono-project.git] / mcs / class / System / System / Uri.cs

//
// System.Uri
//
// Authors:
//    Lawrence Pit (loz@cable.a2000.nl)
//    Garrett Rooney (rooneg@electricjellyfish.net)
//    Ian MacLean (ianm@activestate.com)
//    Ben Maurer (bmaurer@users.sourceforge.net)
//    Atsushi Enomoto (atsushi@ximian.com)
//
// (C) 2001 Garrett Rooney
// (C) 2003 Ian MacLean
// (C) 2003 Ben Maurer
// (C) 2003 Novell inc.
//

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

// See RFC 2396 for more info on URI's.

// TODO: optimize by parsing host string only once

namespace System 
{
        [Serializable]
        public class Uri : MarshalByRefObject, ISerializable 
        {
                // NOTES:
                // o  scheme excludes the scheme delimiter
                // o  port is -1 to indicate no port is defined
                // o  path is empty or starts with / when scheme delimiter == "://"
                // o  query is empty or starts with ? char, escaped.
                // o  fragment is empty or starts with # char, unescaped.
                // o  all class variables are in escaped format when they are escapable,
                //    except cachedToString.
                // o  UNC is supported, as starts with "\\" for windows,
                //    or "//" with unix.

                private bool isUnixFilePath = false;
                private string source;
                private string scheme = String.Empty;
                private string host = String.Empty;
                private int port = -1;
                private string path = String.Empty;
                private string query = String.Empty;
                private string fragment = String.Empty;
                private string userinfo = String.Empty;
                private bool isUnc = false;
                private bool isOpaquePart = false;

                private string [] segments;
                
                private bool userEscaped = false;
                private string cachedAbsoluteUri = null;
                private string cachedToString = null;
                private string cachedLocalPath = null;
                private int cachedHashCode = 0;
                
                private static readonly string hexUpperChars = "0123456789ABCDEF";
        
                // Fields
                
                public static readonly string SchemeDelimiter = "://";
                public static readonly string UriSchemeFile = "file";
                public static readonly string UriSchemeFtp = "ftp";
                public static readonly string UriSchemeGopher = "gopher";
                public static readonly string UriSchemeHttp = "http";
                public static readonly string UriSchemeHttps = "https";
                public static readonly string UriSchemeMailto = "mailto";
                public static readonly string UriSchemeNews = "news";
                public static readonly string UriSchemeNntp = "nntp";

                // Constructors         

                public Uri (string uriString) : this (uriString, false) 
                {
                }

                protected Uri (SerializationInfo serializationInfo, 
                               StreamingContext streamingContext) :
                        this (serializationInfo.GetString ("AbsoluteUri"), true)
                {
                }

                public Uri (string uriString, bool dontEscape) 
                {
                        userEscaped = dontEscape;
                        source = uriString;
                        Parse ();
                }

                public Uri (Uri baseUri, string relativeUri) 
                        : this (baseUri, relativeUri, false) 
                {                       
                }

                public Uri (Uri baseUri, string relativeUri, bool dontEscape) 
                {
                        if (baseUri == null)
                                throw new NullReferenceException ("baseUri");

                        // See RFC 2396 Par 5.2 and Appendix C

                        userEscaped = dontEscape;

                        if (relativeUri == null)
                                throw new NullReferenceException ("relativeUri");

                        // Check Windows UNC (for // it is scheme/host separator)
                        if (relativeUri.StartsWith ("\\\\")) {
                                source = relativeUri;
                                Parse ();
                                return;
                        }

                        int pos = relativeUri.IndexOf (':');
                        if (pos != -1) {

                                int pos2 = relativeUri.IndexOfAny (new char [] {'/', '\\', '?'});

                                // pos2 < 0 ... e.g. mailto
                                // pos2 > pos ... to block ':' in query part
                                if (pos2 > pos || pos2 < 0) {
                                        // equivalent to new Uri (relativeUri, dontEscape)
                                        source = relativeUri;
                                        Parse ();

                                        return;
                                }
                        }

                        this.scheme = baseUri.scheme;
                        this.host = baseUri.host;
                        this.port = baseUri.port;
                        this.userinfo = baseUri.userinfo;
                        this.isUnc = baseUri.isUnc;
                        this.isUnixFilePath = baseUri.isUnixFilePath;
                        this.isOpaquePart = baseUri.isOpaquePart;

                        if (relativeUri == String.Empty) {
                                this.path = baseUri.path;
                                this.query = baseUri.query;
                                this.fragment = baseUri.fragment;
                                return;
                        }
                        
                        // 8 fragment
                        // Note that in relative constructor, file URI cannot handle '#' as a filename character, but just regarded as a fragment identifier.
                        pos = relativeUri.IndexOf ('#');
                        if (pos != -1) {
                                fragment = relativeUri.Substring (pos);
                                // fragment is not escaped.
                                relativeUri = relativeUri.Substring (0, pos);
                        }

                        // 6 query
                        pos = relativeUri.IndexOf ('?');
                        if (pos != -1) {
                                query = relativeUri.Substring (pos);
                                if (!userEscaped)
                                        query = EscapeString (query);
                                relativeUri = relativeUri.Substring (0, pos);
                        }

                        if (relativeUri.Length > 0 && relativeUri [0] == '/') {
                                if (relativeUri.Length > 1 && relativeUri [1] == '/') {
                                        source = scheme + ':' + relativeUri;
                                        Parse ();
                                        return;
                                } else {
                                        path = relativeUri;
                                        if (!userEscaped)
                                                path = EscapeString (path);
                                        return;
                                }
                        }
                        
                        // par 5.2 step 6 a)
                        path = baseUri.path;
                        if (relativeUri.Length > 0 || query.Length > 0) {
                                pos = path.LastIndexOf ('/');
                                if (pos >= 0) 
                                        path = path.Substring (0, pos + 1);
                        }

                        if(relativeUri.Length == 0)
                                return;
        
                        // 6 b)
                        path += relativeUri;

                        // 6 c)
                        int startIndex = 0;
                        while (true) {
                                pos = path.IndexOf ("./", startIndex);
                                if (pos == -1)
                                        break;
                                if (pos == 0)
                                        path = path.Remove (0, 2);
                                else if (path [pos - 1] != '.')
                                        path = path.Remove (pos, 2);
                                else
                                        startIndex = pos + 1;
                        }
                        
                        // 6 d)
                        if (path.Length > 1 && 
                            path [path.Length - 1] == '.' &&
                            path [path.Length - 2] == '/')
                                path = path.Remove (path.Length - 1, 1);
                        
                        // 6 e)
                        startIndex = 0;
                        while (true) {
                                pos = path.IndexOf ("/../", startIndex);
                                if (pos == -1)
                                        break;
                                if (pos == 0) {
                                        startIndex = 3;
                                        continue;
                                }
                                int pos2 = path.LastIndexOf ('/', pos - 1);
                                if (pos2 == -1) {
                                        startIndex = pos + 1;
                                } else {
                                        if (path.Substring (pos2 + 1, pos - pos2 - 1) != "..")
                                                path = path.Remove (pos2 + 1, pos - pos2 + 3);
                                        else
                                                startIndex = pos + 1;
                                }
                        }
                        
                        // 6 f)
                        if (path.Length > 3 && path.EndsWith ("/..")) {
                                pos = path.LastIndexOf ('/', path.Length - 4);
                                if (pos != -1)
                                        if (path.Substring (pos + 1, path.Length - pos - 4) != "..")
                                                path = path.Remove (pos + 1, path.Length - pos - 1);
                        }
                        
                        if (!userEscaped)
                                path = EscapeString (path);
                }               
                
                // Properties
                
                public string AbsolutePath { 
                        get { return path; } 
                }

                public string AbsoluteUri { 
                        get { 
                                if (cachedAbsoluteUri == null) {
                                        cachedAbsoluteUri = GetLeftPart (UriPartial.Path) + query + fragment;
                                }
                                return cachedAbsoluteUri;
                        } 
                }

                public string Authority { 
                        get { 
                                return (GetDefaultPort (scheme) == port)
                                     ? host : host + ":" + port;
                        } 
                }

                public string Fragment { 
                        get { return fragment; } 
                }

                public string Host { 
                        get { return host; } 
                }

                public UriHostNameType HostNameType { 
                        get {
                                UriHostNameType ret = CheckHostName (host);
                                if (ret != UriHostNameType.Unknown)
                                        return ret;

                                // looks it always returns Basic...
                                return UriHostNameType.Basic; //.Unknown;
                        } 
                }

                public bool IsDefaultPort { 
                        get { return GetDefaultPort (scheme) == port; } 
                }

                public bool IsFile { 
                        get { return (scheme == UriSchemeFile); }
                }

                public bool IsLoopback { 
                        get { 
                                if (host == String.Empty)
                                        return false;
                                        
                                if (host == "loopback" || host == "localhost") 
                                        return true;
                                        
                                try {
                                        if (IPAddress.Loopback.Equals (IPAddress.Parse (host)))
                                                return true;
                                } catch (FormatException) {}

                                try {
                                        return IPv6Address.IsLoopback (IPv6Address.Parse (host));
                                } catch (FormatException) {}
                                
                                return false;
                        } 
                }

                public bool IsUnc {
                        // rule: This should be true only if
                        //   - uri string starts from "\\", or
                        //   - uri string starts from "//" (Samba way)
                        get { return isUnc; } 
                }

                public string LocalPath { 
                        get {
                                if (cachedLocalPath != null)
                                        return cachedLocalPath;
                                if (!IsFile)
                                        return AbsolutePath;

                                bool windows = (path.Length > 3 && path [1] == ':' &&
                                                (path [2] == '\\' || path [2] == '/'));

                                if (!IsUnc) {
                                        string p = Unescape (path);
                                        if (System.IO.Path.DirectorySeparatorChar == '\\' || windows)
                                                cachedLocalPath = p.Replace ('/', '\\');
                                        else
                                                cachedLocalPath = p;
                                } else {
                                        // support *nix and W32 styles
                                        if (path.Length > 1 && path [1] == ':')
                                                cachedLocalPath = Unescape (path.Replace (Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar));

                                        // LAMESPEC: ok, now we cannot determine
                                        // if such URI like "file://foo/bar" is
                                        // Windows UNC or unix file path, so
                                        // they should be handled differently.
                                        else if (System.IO.Path.DirectorySeparatorChar == '\\')
                                                cachedLocalPath = "\\\\" + Unescape (host + path.Replace ('/', '\\'));
                                        else
                                                cachedLocalPath = Unescape (path);
                                }
                                if (cachedLocalPath == String.Empty)
                                        cachedLocalPath = Path.DirectorySeparatorChar.ToString ();
                                return cachedLocalPath;
                        } 
                }

                public string PathAndQuery { 
                        get { return path + query; } 
                }

                public int Port { 
                        get { return port; } 
                }

                public string Query { 
                        get { return query; } 
                }

                public string Scheme { 
                        get { return scheme; } 
                }

                public string [] Segments { 
                        get { 
                                if (segments != null)
                                        return segments;

                                if (path == "") {
                                        segments = new string [0];
                                        return segments;
                                }

                                string [] parts = path.Split ('/');
                                segments = parts;
                                bool endSlash = path.EndsWith ("/");
                                if (parts.Length > 0 && endSlash) {
                                        string [] newParts = new string [parts.Length - 1];
                                        Array.Copy (parts, 0, newParts, 0, parts.Length - 1);
                                        parts = newParts;
                                }

                                int i = 0;
                                if (IsFile && path.Length > 1 && path [1] == ':') {
                                        string [] newParts = new string [parts.Length + 1];
                                        Array.Copy (parts, 1, newParts, 2, parts.Length - 1);
                                        parts = newParts;
                                        parts [0] = path.Substring (0, 2);
                                        parts [1] = "";
                                        i++;
                                }
                                
                                int end = parts.Length;
                                for (; i < end; i++) 
                                        if (i != end - 1 || endSlash)
                                                parts [i] += '/';

                                segments = parts;
                                return segments;
                        } 
                }

                public bool UserEscaped { 
                        get { return userEscaped; } 
                }

                public string UserInfo { 
                        get { return userinfo; }
                }
                

                // Methods              
                
                public static UriHostNameType CheckHostName (string name) 
                {
                        if (name == null || name.Length == 0)
                                return UriHostNameType.Unknown;

                        if (IsIPv4Address (name)) 
                                return UriHostNameType.IPv4;
                                
                        if (IsDomainAddress (name))
                                return UriHostNameType.Dns;                             
                                
                        try {
                                IPv6Address.Parse (name);
                                return UriHostNameType.IPv6;
                        } catch (FormatException) {}
                        
                        return UriHostNameType.Unknown;
                }
                
                internal static bool IsIPv4Address (string name)
                {               
                        string [] captures = name.Split (new char [] {'.'});
                        if (captures.Length != 4)
                                return false;
                        for (int i = 0; i < 4; i++) {
                                try {
                                        int d = Int32.Parse (captures [i], CultureInfo.InvariantCulture);
                                        if (d < 0 || d > 255)
                                                return false;
                                } catch (Exception) {
                                        return false;
                                }
                        }
                        return true;
                }                       
                                
                internal static bool IsDomainAddress (string name)
                {
                        int len = name.Length;
                        
                        if (name [len - 1] == '.')
                                return false;
                                
                        int count = 0;
                        for (int i = 0; i < len; i++) {
                                char c = name [i];
                                if (count == 0) {
                                        if (!Char.IsLetterOrDigit (c))
                                                return false;
                                } else if (c == '.') {
                                        count = 0;
                                } else if (!Char.IsLetterOrDigit (c) && c != '-' && c != '_') {
                                        return false;
                                }
                                if (++count == 64)
                                        return false;
                        }
                        
                        return true;
                }

                [MonoTODO ("Find out what this should do")]
                protected virtual void Canonicalize ()
                {
                }

                public static bool CheckSchemeName (string schemeName) 
                {
                        if (schemeName == null || schemeName.Length == 0)
                                return false;
                        
                        if (!Char.IsLetter (schemeName [0]))
                                return false;

                        int len = schemeName.Length;
                        for (int i = 1; i < len; i++) {
                                char c = schemeName [i];
                                if (!Char.IsLetterOrDigit (c) && c != '.' && c != '+' && c != '-')
                                        return false;
                        }
                        
                        return true;
                }

                [MonoTODO ("Find out what this should do")]
                protected virtual void CheckSecurity ()
                {
                }

                public override bool Equals (object comparant) 
                {
                        if (comparant == null) 
                                return false;
                                
                        Uri uri = comparant as Uri;
                        if (uri == null) {
                                string s = comparant as String;
                                if (s == null)
                                        return false;
                                uri = new Uri (s);
                        }

                        CultureInfo inv = CultureInfo.InvariantCulture;
                        return ((this.scheme.ToLower (inv) == uri.scheme.ToLower (inv)) &&
                                (this.userinfo.ToLower (inv) == uri.userinfo.ToLower (inv)) &&
                                (this.host.ToLower (inv) == uri.host.ToLower (inv)) &&
                                (this.port == uri.port) &&
                                (this.path == uri.path) &&
                                (this.query.ToLower (inv) == uri.query.ToLower (inv)));
                }               
                
                public override int GetHashCode () 
                {
                        if (cachedHashCode == 0)                        
                                cachedHashCode = scheme.GetHashCode ()
                                               + userinfo.GetHashCode ()
                                               + host.GetHashCode ()
                                               + port
                                               + path.GetHashCode ()
                                               + query.GetHashCode ();                             
                        return cachedHashCode;                          
                }
                
                public string GetLeftPart (UriPartial part) 
                {
                        int defaultPort;
                        switch (part) {                         
                        case UriPartial.Scheme : 
                                return scheme + GetOpaqueWiseSchemeDelimiter ();
                        case UriPartial.Authority :
                                if (host == String.Empty ||
                                    scheme == Uri.UriSchemeMailto ||
                                    scheme == Uri.UriSchemeNews)
                                        return String.Empty;
                                        
                                StringBuilder s = new StringBuilder ();
                                s.Append (scheme);
                                s.Append (GetOpaqueWiseSchemeDelimiter ());
                                if (path.Length > 1 && path [1] == ':' && (Uri.UriSchemeFile == scheme)) 
                                        s.Append ('/');  // win32 file
                                if (userinfo.Length > 0) 
                                        s.Append (userinfo).Append ('@');
                                s.Append (host);
                                defaultPort = GetDefaultPort (scheme);
                                if ((port != -1) && (port != defaultPort))
                                        s.Append (':').Append (port);                    
                                return s.ToString ();                           
                        case UriPartial.Path :                  
                                StringBuilder sb = new StringBuilder ();
                                sb.Append (scheme);
                                sb.Append (GetOpaqueWiseSchemeDelimiter ());
                                if (path.Length > 1 && path [1] == ':' && (Uri.UriSchemeFile == scheme)) 
                                        sb.Append ('/');  // win32 file
                                if (userinfo.Length > 0) 
                                        sb.Append (userinfo).Append ('@');
                                sb.Append (host);
                                defaultPort = GetDefaultPort (scheme);
                                if ((port != -1) && (port != defaultPort))
                                        sb.Append (':').Append (port);                   
                                sb.Append (path);
                                return sb.ToString ();
                        }
                        return null;
                }

                public static int FromHex (char digit) 
                {
                        if ('0' <= digit && digit <= '9') {
                                return (int) (digit - '0');
                        }
                                
                        if ('a' <= digit && digit <= 'f')
                                return (int) (digit - 'a' + 10);

                        if ('A' <= digit && digit <= 'F')
                                return (int) (digit - 'A' + 10);
                                
                        throw new ArgumentException ("digit");
                }

                public static string HexEscape (char character) 
                {
                        if (character > 255) {
                                throw new ArgumentOutOfRangeException ("character");
                        }
                        
                        return "%" + hexUpperChars [((character & 0xf0) >> 4)] 
                                   + hexUpperChars [((character & 0x0f))];
                }

                public static char HexUnescape (string pattern, ref int index) 
                {
                        if (pattern == null) 
                                throw new ArgumentException ("pattern");
                                
                        if (index < 0 || index >= pattern.Length)
                                throw new ArgumentOutOfRangeException ("index");

                        int stage = 0;
                        int c = 0;
                        byte [] bytes = new byte [6];
                        do {
                                if (((index + 3) > pattern.Length) ||
                                    (pattern [index] != '%') || 
                                    !IsHexDigit (pattern [index + 1]) || 
                                    !IsHexDigit (pattern [index + 2]))
                                {
                                        if (stage == 0)
                                                return pattern [index++];
                                        break;
                                }

                                index++;
                                int msb = FromHex (pattern [index++]);
                                int lsb = FromHex (pattern [index++]);
                                int b = (msb << 4) + lsb;

                                if (stage == 0) {
                                        if (b < 0xc0)
                                                return (char) b;
                                        else if (b < 0xE0) {
                                                c = b - 0xc0;
                                                stage = 2;
                                        } else if (b < 0xF0) {
                                                c = b - 0xe0;
                                                stage = 3;
                                        } else if (b < 0xF8) {
                                                c = b - 0xf0;
                                                stage = 4;
                                        } else if (b < 0xFB) {
                                                c = b - 0xf8;
                                                stage = 5;
                                        } else if (b < 0xFE) {
                                                c = b - 0xfc;
                                                stage = 6;
                                        }
                                        c <<= (stage - 1) * 6;
                                }
                                else
                                        c += (b - 0x80) << ((stage - 1) * 6);
//Console.WriteLine ("stage {0}: {5:X04} <-- {1:X02}|{2:X01},{3:X01} {4}", new object [] {stage, b, msb, lsb, pattern.Substring (index), c});
                                stage--;
                        } while (stage > 0);
                        
                        return (char) c;
                }

                public static bool IsHexDigit (char digit) 
                {
                        return (('0' <= digit && digit <= '9') ||
                                ('a' <= digit && digit <= 'f') ||
                                ('A' <= digit && digit <= 'F'));
                }

                public static bool IsHexEncoding (string pattern, int index) 
                {
                        if ((index + 3) > pattern.Length)
                                return false;

                        return ((pattern [index++] == '%') &&
                                IsHexDigit (pattern [index++]) &&
                                IsHexDigit (pattern [index]));
                }

                public string MakeRelative (Uri toUri) 
                {
                        if ((this.Scheme != toUri.Scheme) ||
                            (this.Authority != toUri.Authority))
                                return toUri.ToString ();
                                
                        if (this.path == toUri.path)
                                return String.Empty;
                                
                        string [] segments = this.Segments;
                        string [] segments2 = toUri.Segments;
                        
                        int k = 0;
                        int max = Math.Min (segments.Length, segments2.Length);
                        for (; k < max; k++)
                                if (segments [k] != segments2 [k]) 
                                        break;
                        
                        string result = String.Empty;
                        for (int i = k + 1; i < segments.Length; i++)
                                result += "../";
                        for (int i = k; i < segments2.Length; i++)
                                result += segments2 [i];
                        
                        return result;
                }

                public override string ToString () 
                {
                        if (cachedToString != null) 
                                return cachedToString;
                        string q = query.StartsWith ("?") ? '?' + Unescape (query.Substring (1)) : Unescape (query);
                        cachedToString = Unescape (GetLeftPart (UriPartial.Path), true) + q + fragment;
                        return cachedToString;
                }

                void ISerializable.GetObjectData (SerializationInfo info, 
                                          StreamingContext context)
                {
                        info.AddValue ("AbsoluteUri", this.AbsoluteUri);
                }


                // Internal Methods             

                protected virtual void Escape ()
                {
                        path = EscapeString (path);
                }

                protected static string EscapeString (string str) 
                {
                        return EscapeString (str, false, true, true);
                }
                
                internal static string EscapeString (string str, bool escapeReserved, bool escapeHex, bool escapeBrackets) 
                {
                        if (str == null)
                                return String.Empty;
                        
                        byte [] data = Encoding.UTF8.GetBytes (str.ToCharArray ());
                        StringBuilder s = new StringBuilder ();
                        int len = data.Length;  
                        for (int i = 0; i < len; i++) {
                                char c = (char) data [i];
                                // reserved    = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" | "$" | ","
                                // mark        = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
                                // control     = <US-ASCII coded characters 00-1F and 7F hexadecimal>
                                // space       = <US-ASCII coded character 20 hexadecimal>
                                // delims      = "<" | ">" | "#" | "%" | <">
                                // unwise      = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"

                                // check for escape code already placed in str, 
                                // i.e. for encoding that follows the pattern 
                // "%hexhex" in a string, where "hex" is a digit from 0-9 
                                // or a letter from A-F (case-insensitive).
                                if('%'.Equals(c) && IsHexEncoding(str,i))
                                {
                                        // if ,yes , copy it as is
                                        s.Append(c);
                                        s.Append(str[++i]);
                                        s.Append(str[++i]);
                                        continue;
                                }

                                if ((c <= 0x20) || (c >= 0x7f) || 
                                    ("<>%\"{}|\\^`".IndexOf (c) != -1) ||
                                    (escapeHex && (c == '#')) ||
                                    (escapeBrackets && (c == '[' || c == ']')) ||
                                    (escapeReserved && (";/?:@&=+$,".IndexOf (c) != -1))) {
                                        s.Append (HexEscape (c));
                                        continue;
                                }
                                
                                        
                                s.Append (c);
                        }
                        
                        return s.ToString ();
                }

                // This method is called from .ctor(). When overriden, we can
                // avoid the "absolute uri" constraints of the .ctor() by
                // overriding with custom code.
                protected virtual void Parse ()
                {
                        Parse (source);

                        if (userEscaped) 
                                return;

                        host = EscapeString (host, false, true, false);
                        path = EscapeString (path);
                }
                
                protected virtual string Unescape (string str)
                {
                        return Unescape (str, false);
                }
                
                private string Unescape (string str, bool excludeSharp) 
                {
                        if (str == null)
                                return String.Empty;
                        StringBuilder s = new StringBuilder ();
                        int len = str.Length;
                        for (int i = 0; i < len; i++) {
                                char c = str [i];
                                if (c == '%') {
                                        char x = HexUnescape (str, ref i);
                                        if (excludeSharp && x == '#')
                                                s.Append ("%23");
                                        else
                                                s.Append (x);
                                        i--;
                                } else
                                        s.Append (c);
                        }
                        return s.ToString ();
                }

                
                // Private Methods
                
                private void ParseAsWindowsUNC (string uriString)
                {
                        scheme = UriSchemeFile;
                        port = -1;
                        fragment = String.Empty;
                        query = String.Empty;
                        isUnc = true;

                        uriString = uriString.TrimStart (new char [] {'\\'});
                        int pos = uriString.IndexOf ('\\');
                        if (pos > 0) {
                                path = uriString.Substring (pos);
                                host = uriString.Substring (0, pos);
                        } else { // "\\\\server"
                                host = uriString;
                                path = String.Empty;
                        }
                        path = path.Replace ("\\", "/");
                }

                private void ParseAsWindowsAbsoluteFilePath (string uriString)
                {
                        if (uriString.Length > 2 && uriString [2] != '\\'
                                        && uriString [2] != '/')
                                throw new UriFormatException ("Relative file path is not allowed.");
                        scheme = UriSchemeFile;
                        host = String.Empty;
                        port = -1;
                        path = uriString.Replace ("\\", "/");
                        fragment = String.Empty;
                        query = String.Empty;
                }

                private void ParseAsUnixAbsoluteFilePath (string uriString)
                {
                        isUnixFilePath = true;
                        scheme = UriSchemeFile;
                        port = -1;
                        fragment = String.Empty;
                        query = String.Empty;
                        host = String.Empty;
                        path = null;

                        if (uriString.StartsWith ("//")) {
                                uriString = uriString.TrimStart (new char [] {'/'});
                                // Now we don't regard //foo/bar as "foo" host.
                                /* 
                                int pos = uriString.IndexOf ('/');
                                if (pos > 0) {
                                        path = '/' + uriString.Substring (pos + 1);
                                        host = uriString.Substring (0, pos);
                                } else { // "///server"
                                        host = uriString;
                                        path = String.Empty;
                                }
                                */
                                path = '/' + uriString;
                        }
                        if (path == null)
                                path = uriString;
                }

                // this parse method is as relaxed as possible about the format
                // it will hardly ever throw a UriFormatException
                private void Parse (string uriString)
                {                       
                        //
                        // From RFC 2396 :
                        //
                        //      ^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
                        //       12            3  4          5       6  7        8 9
                        //                      
                        
                        if (uriString == null)
                                throw new ArgumentNullException ("uriString");

                        int len = uriString.Length;
                        if (len <= 1) 
                                throw new UriFormatException ();

                        int pos = 0;

                        // 1, 2
                        // Identify Windows path, unix path, or standard URI.
                        pos = uriString.IndexOf (':');
                        if (pos < 0) {
                                // It must be Unix file path or Windows UNC
                                if (uriString [0] == '/')
                                        ParseAsUnixAbsoluteFilePath (uriString);
                                else if (uriString.StartsWith ("\\\\"))
                                        ParseAsWindowsUNC (uriString);
                                else
                                        throw new UriFormatException ("URI scheme was not recognized, nor input string is not recognized as an absolute file path.");
                                return;
                        }
                        else if (pos == 1) {
                                if (!Char.IsLetter (uriString [0]))
                                        throw new UriFormatException ("URI scheme must start with alphabet character.");
                                // This means 'a:' == windows full path.
                                ParseAsWindowsAbsoluteFilePath (uriString);
                                return;
                        }

                        // scheme
                        scheme = uriString.Substring (0, pos).ToLower (CultureInfo.InvariantCulture);
                        // Check scheme name characters as specified in RFC2396.
                        if (!Char.IsLetter (scheme [0]))
                                        throw new UriFormatException ("URI scheme must start with alphabet character.");
                        for (int i = 1; i < scheme.Length; i++) {
                                if (!Char.IsLetterOrDigit (scheme, i)) {
                                        switch (scheme [i]) {
                                        case '+':
                                        case '-':
                                        case '.':
                                                break;
                                        default:
                                                throw new UriFormatException ("URI scheme must consist of one of alphabet, digits, '+', '-' or '.' character.");
                                        }
                                }
                        }
                        uriString = uriString.Substring (pos + 1);

                        // 8 fragment
                        pos = uriString.IndexOf ('#');
                        if (!IsUnc && pos != -1) {
                                fragment = uriString.Substring (pos);
                                uriString = uriString.Substring (0, pos);
                        }

                        // 6 query
                        pos = uriString.IndexOf ('?');
                        if (pos != -1) {
                                query = uriString.Substring (pos);
                                uriString = uriString.Substring (0, pos);
                                if (!userEscaped)
                                        query = EscapeString (query);
                        }

                        // 3
                        bool unixAbsPath = scheme == UriSchemeFile && uriString.StartsWith ("///");
                        if (uriString.StartsWith ("//")) {
                                if (uriString.StartsWith ("////"))
                                        unixAbsPath = false;
                                uriString = uriString.TrimStart (new char [] {'/'});
                                if (uriString.Length > 1 && uriString [1] == ':')
                                        unixAbsPath = false;
                        } else if (!IsPredefinedScheme (scheme)) {
                                path = uriString;
                                isOpaquePart = true;
                                return;
                        }
                        
                        // 5 path
                        pos = uriString.IndexOfAny (new char[] {'/'});
                        if (unixAbsPath)
                                pos = -1;
                        if (pos == -1) {
                                if ((scheme != Uri.UriSchemeMailto) &&
                                    (scheme != Uri.UriSchemeNews) &&
                                        (scheme != Uri.UriSchemeFile))
                                        path = "/";
                        } else {
                                path = uriString.Substring (pos);
                                uriString = uriString.Substring (0, pos);
                        }

                        // 4.a user info
                        pos = uriString.IndexOf ("@");
                        if (pos != -1) {
                                userinfo = uriString.Substring (0, pos);
                                uriString = uriString.Remove (0, pos + 1);
                        }

                        // 4.b port
                        port = -1;
                        pos = uriString.LastIndexOf (":");
                        if (unixAbsPath)
                                pos = -1;
                        if (pos != -1 && pos != (uriString.Length - 1)) {
                                string portStr = uriString.Remove (0, pos + 1);
                                if (portStr.Length > 1 && portStr [portStr.Length - 1] != ']') {
                                        try {
                                                port = (int) UInt32.Parse (portStr, CultureInfo.InvariantCulture);
                                                uriString = uriString.Substring (0, pos);
                                        } catch (Exception) {
                                                throw new UriFormatException ("Invalid URI: invalid port number");
                                        }
                                }
                        }
                        if (port == -1) {
                                port = GetDefaultPort (scheme);
                        }
                        
                        // 4 authority
                        host = uriString;
                        if (host.Length > 1 && host [0] == '[' && host [host.Length - 1] == ']') {
                                try {
                                        host = "[" + IPv6Address.Parse (host).ToString () + "]";
                                } catch (Exception) {
                                        throw new UriFormatException ("Invalid URI: The hostname could not be parsed");
                                }
                        }

                        if (unixAbsPath) {
                                path = '/' + uriString;
                                host = String.Empty;
                        } else if (host.Length == 2 && host [1] == ':') {
                                // windows filepath
                                path = host + path;
                                host = String.Empty;
                        } else if (isUnixFilePath) {
                                uriString = "//" + uriString;
                                host = String.Empty;
                        } else if (host.Length == 0) {
                                throw new UriFormatException ("Invalid URI: The hostname could not be parsed");
                        } else if (scheme == UriSchemeFile) {
                                isUnc = true;
                        }

                        if ((scheme != Uri.UriSchemeMailto) &&
                                        (scheme != Uri.UriSchemeNews) &&
                                        (scheme != Uri.UriSchemeFile))
                        path = Reduce (path);
                }

                private static string Reduce (string path)
                {
                        path = path.Replace ('\\','/');
                        string [] parts = path.Split ('/');
                        ArrayList result = new ArrayList ();

                        int end = parts.Length;
                        for (int i = 0; i < end; i++) {
                                string current = parts [i];
                                if (current == "" || current == "." )
                                        continue;

                                if (current == "..") {
                                        if (result.Count == 0) {
                                                if (i == 1) // see bug 52599
                                                        continue;
                                                throw new Exception ("Invalid path.");
                                        }

                                        result.RemoveAt (result.Count - 1);
                                        continue;
                                }

                                result.Add (current);
                        }

                        if (result.Count == 0)
                                return "/";

                        result.Insert (0, "");

                        string res = String.Join ("/", (string []) result.ToArray (typeof (string)));
                        if (path.EndsWith ("/"))
                                res += '/';
                                
                        return res;
                }
                                
                private struct UriScheme 
                {
                        public string scheme;
                        public string delimiter;
                        public int defaultPort;

                        public UriScheme (string s, string d, int p) 
                        {
                                scheme = s;
                                delimiter = d;
                                defaultPort = p;
                        }
                };

                static UriScheme [] schemes = new UriScheme [] {
                        new UriScheme (UriSchemeHttp, SchemeDelimiter, 80),
                        new UriScheme (UriSchemeHttps, SchemeDelimiter, 443),
                        new UriScheme (UriSchemeFtp, SchemeDelimiter, 21),
                        new UriScheme (UriSchemeFile, SchemeDelimiter, -1),
                        new UriScheme (UriSchemeMailto, ":", 25),
                        new UriScheme (UriSchemeNews, ":", -1),
                        new UriScheme (UriSchemeNntp, SchemeDelimiter, 119),
                        new UriScheme (UriSchemeGopher, SchemeDelimiter, 70),
                };
                                
                internal static string GetSchemeDelimiter (string scheme) 
                {
                        for (int i = 0; i < schemes.Length; i++) 
                                if (schemes [i].scheme == scheme)
                                        return schemes [i].delimiter;
                        return Uri.SchemeDelimiter;
                }
                
                internal static int GetDefaultPort (string scheme)
                {
                        for (int i = 0; i < schemes.Length; i++) 
                                if (schemes [i].scheme == scheme)
                                        return schemes [i].defaultPort;
                        return -1;                      
                }

                private string GetOpaqueWiseSchemeDelimiter ()
                {
                        if (isOpaquePart)
                                return ":";
                        else
                                return GetSchemeDelimiter (scheme);
                }

                protected virtual bool IsBadFileSystemCharacter (char ch)
                {
                        // It does not always overlap with InvalidPathChars.
                        int chInt = (int) ch;
                        if (chInt < 32 || (chInt < 64 && chInt > 57))
                                return true;
                        switch (chInt) {
                        case 0:
                        case 34: // "
                        case 38: // &
                        case 42: // *
                        case 44: // ,
                        case 47: // /
                        case 92: // \
                        case 94: // ^
                        case 124: // |
                                return true;
                        }

                        return false;
                }

                
                protected static bool IsExcludedCharacter (char ch)
                {
                        if (ch <= 32 || ch >= 127)
                                return true;
                        
                        if (ch == '"' || ch == '#' || ch == '%' || ch == '<' ||
                            ch == '>' || ch == '[' || ch == '\\' || ch == ']' ||
                            ch == '^' || ch == '`' || ch == '{' || ch == '|' ||
                            ch == '}')
                                return true;
                        return false;
                }

                private static bool IsPredefinedScheme (string scheme)
                {
                        switch (scheme) {
                        case "http":
                        case "https":
                        case "file":
                        case "ftp":
                        case "nntp":
                        case "gopher":
                        case "mailto":
                        case "news":
                                return true;
                        default:
                                return false;
                        }
                }

                protected virtual bool IsReservedCharacter (char ch)
                {
                        if (ch == '$' || ch == '&' || ch == '+' || ch == ',' ||
                            ch == '/' || ch == ':' || ch == ';' || ch == '=' ||
                            ch == '@')
                                return true;
                        return false;
                }
        }
}