New tests.
[mono.git] / mcs / class / corlib / System.IO / Path.cs
index 649d011eacf2636aee309874ad2adb5fc6a21f41..1dd4706255704a3b4e12c75dac0b901b66ecb8b6 100644 (file)
 //                 Dan Lewis (dihlewis@yahoo.co.uk)
 //                 Gonzalo Paniagua Javier (gonzalo@ximian.com)
 //                 Ben Maurer (bmaurer@users.sourceforge.net)
+//                 Sebastien Pouliot  <sebastien@ximian.com>
 // Created:        Saturday, August 11, 2001 
 //
 //------------------------------------------------------------------------------
 
 //
-// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
+// Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
 //
 // Permission is hereby granted, free of charge, to any person obtaining
 // a copy of this software and associated documentation files (the
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
 
-using System;
+using System.Globalization;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Security;
+using System.Security.Cryptography;
+using System.Security.Permissions;
+using System.Text;
 
-namespace System.IO
-{
-       public sealed class Path
-       {
+namespace System.IO {
+
+       [ComVisible (true)]
+       public static class Path {
+
+               [Obsolete ("see GetInvalidPathChars and GetInvalidFileNameChars methods.")]
+               public static readonly char[] InvalidPathChars;
                public static readonly char AltDirectorySeparatorChar;
                public static readonly char DirectorySeparatorChar;
-               public static readonly char[] InvalidPathChars;
                public static readonly char PathSeparator;
                internal static readonly string DirectorySeparatorStr;
                public static readonly char VolumeSeparatorChar;
 
-               private static readonly char[] PathSeparatorChars;
+               internal static readonly char[] PathSeparatorChars;
                private static readonly bool dirEqualsVolume;
 
-               private Path ()
-               {
-               }
-
                // class methods
                public static string ChangeExtension (string path, string extension)
                {
@@ -65,13 +69,13 @@ namespace System.IO
                                return null;
 
                        if (path.IndexOfAny (InvalidPathChars) != -1)
-                               throw new ArgumentException ("Illegal characters in path", "path");
+                               throw new ArgumentException ("Illegal characters in path.");
 
                        int iExt = findExtension (path);
 
                        if (extension == null)
                                return iExt < 0 ? path : path.Substring (0, iExt);
-                       else if (extension == String.Empty)
+                       else if (extension.Length == 0)
                                return iExt < 0 ? path + '.' : path.Substring (0, iExt + 1);
 
                        else if (path.Length != 0) {
@@ -98,43 +102,114 @@ namespace System.IO
                        if (path2 == null)
                                throw new ArgumentNullException ("path2");
 
-                       if (path1 == String.Empty)
+                       if (path1.Length == 0)
                                return path2;
 
-                       if (path2 == String.Empty)
+                       if (path2.Length == 0)
                                return path1;
 
                        if (path1.IndexOfAny (InvalidPathChars) != -1)
-                               throw new ArgumentException ("Illegal characters in path", "path1");
+                               throw new ArgumentException ("Illegal characters in path.");
 
                        if (path2.IndexOfAny (InvalidPathChars) != -1)
-                               throw new ArgumentException ("Illegal characters in path", "path2");
+                               throw new ArgumentException ("Illegal characters in path.");
 
                        //TODO???: UNC names
-                       // LAMESPEC: MS says that if path1 is not empty and path2 is a full path
-                       // it should throw ArgumentException
                        if (IsPathRooted (path2))
                                return path2;
                        
                        char p1end = path1 [path1.Length - 1];
                        if (p1end != DirectorySeparatorChar && p1end != AltDirectorySeparatorChar && p1end != VolumeSeparatorChar)
-                               return path1 + DirectorySeparatorChar + path2;
+                               return path1 + DirectorySeparatorStr + path2;
 
                        return path1 + path2;
                }
+       
+               //
+               // This routine:
+               //   * Removes duplicat path separators from a string
+               //   * If the string starts with \\, preserves the first two (hostname on Windows)
+               //   * Removes the trailing path separator.
+               //   * Returns the DirectorySeparatorChar for the single input DirectorySeparatorChar or AltDirectorySeparatorChar
+               //
+               // Unlike CanonicalizePath, this does not do any path resolution
+               // (which GetDirectoryName is not supposed to do).
+               //
+               internal static string CleanPath (string s)
+               {
+                       int l = s.Length;
+                       int sub = 0;
+                       int start = 0;
+
+                       // Host prefix?
+                       char s0 = s [0];
+                       if (l > 2 && s0 == '\\' && s [1] == '\\'){
+                               start = 2;
+                       }
+
+                       // We are only left with root
+                       if (l == 1 && (s0 == DirectorySeparatorChar || s0 == AltDirectorySeparatorChar))
+                               return s;
+
+                       // Cleanup
+                       for (int i = start; i < l; i++){
+                               char c = s [i];
+                               
+                               if (c != DirectorySeparatorChar && c != AltDirectorySeparatorChar)
+                                       continue;
+                               if (i+1 == l)
+                                       sub++;
+                               else {
+                                       c = s [i + 1];
+                                       if (c == DirectorySeparatorChar || c == AltDirectorySeparatorChar)
+                                               sub++;
+                               }
+                       }
+
+                       if (sub == 0)
+                               return s;
+
+                       char [] copy = new char [l-sub];
+                       if (start != 0){
+                               copy [0] = '\\';
+                               copy [1] = '\\';
+                       }
+                       for (int i = start, j = start; i < l && j < copy.Length; i++){
+                               char c = s [i];
+
+                               if (c != DirectorySeparatorChar && c != AltDirectorySeparatorChar){
+                                       copy [j++] = c;
+                                       continue;
+                               }
+
+                               // For non-trailing cases.
+                               if (j+1 != copy.Length){
+                                       copy [j++] = DirectorySeparatorChar;
+                                       for (;i < l-1; i++){
+                                               c = s [i+1];
+                                               if (c != DirectorySeparatorChar && c != AltDirectorySeparatorChar)
+                                                       break;
+                                       }
+                               }
+                       }
+                       return new String (copy);
+               }
 
                public static string GetDirectoryName (string path)
                {
                        // LAMESPEC: For empty string MS docs say both
                        // return null AND throw exception.  Seems .NET throws.
                        if (path == String.Empty)
-                               throw new ArgumentException();
+                               throw new ArgumentException("Invalid path");
 
                        if (path == null || GetPathRoot (path) == path)
                                return null;
 
-                       CheckArgument.WhitespaceOnly (path);
-                       CheckArgument.PathChars (path);
+                       if (path.Trim ().Length == 0)
+                               throw new ArgumentException ("Argument string consists of whitespace characters only.");
+
+                       if (path.IndexOfAny (System.IO.Path.InvalidPathChars) > -1)
+                               throw new ArgumentException ("Path contains invalid characters");
 
                        int nLast = path.LastIndexOfAny (PathSeparatorChars);
                        if (nLast == 0)
@@ -143,10 +218,17 @@ namespace System.IO
                        if (nLast > 0) {
                                string ret = path.Substring (0, nLast);
                                int l = ret.Length;
-                               if (l >= 2 && ret [l - 1] == VolumeSeparatorChar)
+
+                               if (l >= 2 && DirectorySeparatorChar == '\\' && ret [l - 1] == VolumeSeparatorChar)
                                        return ret + DirectorySeparatorChar;
-                               else
-                                       return ret;
+                               else {
+                                       //
+                                       // Important: do not use CanonicalizePath here, use
+                                       // the custom CleanPath here, as this should not
+                                       // return absolute paths
+                                       //
+                                       return CleanPath (ret);
+                               }
                        }
 
                        return String.Empty;
@@ -158,7 +240,7 @@ namespace System.IO
                                return null;
 
                        if (path.IndexOfAny (InvalidPathChars) != -1)
-                               throw new ArgumentException ("Illegal characters in path", "path");
+                               throw new ArgumentException ("Illegal characters in path.");
 
                        int iExt = findExtension (path);
 
@@ -172,11 +254,11 @@ namespace System.IO
 
                public static string GetFileName (string path)
                {
-                       if (path == null || path == String.Empty)
+                       if (path == null || path.Length == 0)
                                return path;
 
                        if (path.IndexOfAny (InvalidPathChars) != -1)
-                               throw new ArgumentException ("Illegal characters in path", "path");
+                               throw new ArgumentException ("Illegal characters in path.");
 
                        int nLast = path.LastIndexOfAny (PathSeparatorChars);
                        if (nLast >= 0)
@@ -191,40 +273,109 @@ namespace System.IO
                }
 
                public static string GetFullPath (string path)
+               {
+                       string fullpath = InsecureGetFullPath (path);
+
+                       SecurityManager.EnsureElevatedPermissions (); // this is a no-op outside moonlight
+
+#if !NET_2_1
+                       if (SecurityManager.SecurityEnabled) {
+                               new FileIOPermission (FileIOPermissionAccess.PathDiscovery, fullpath).Demand ();
+                       }
+#endif
+                       return fullpath;
+               }
+
+               internal static string WindowsDriveAdjustment (string path)
+               {
+                       // two special cases to consider when a drive is specified
+                       if (path.Length < 2)
+                               return path;
+                       if ((path [1] != ':') || !Char.IsLetter (path [0]))
+                               return path;
+
+                       string current = Directory.GetCurrentDirectory ();
+                       // first, only the drive is specified
+                       if (path.Length == 2) {
+                               // then if the current directory is on the same drive
+                               if (current [0] == path [0])
+                                       path = current; // we return it
+                               else
+                                       path += '\\';
+                       } else if ((path [2] != Path.DirectorySeparatorChar) && (path [2] != Path.AltDirectorySeparatorChar)) {
+                               // second, the drive + a directory is specified *without* a separator between them (e.g. C:dir).
+                               // If the current directory is on the specified drive...
+                               if (current [0] == path [0]) {
+                                       // then specified directory is appended to the current drive directory
+                                       path = Path.Combine (current, path.Substring (2, path.Length - 2));
+                               } else {
+                                       // if not, then just pretend there was a separator (Path.Combine won't work in this case)
+                                       path = String.Concat (path.Substring (0, 2), DirectorySeparatorStr, path.Substring (2, path.Length - 2));
+                               }
+                       }
+                       return path;
+               }
+
+               // insecure - do not call directly
+               internal static string InsecureGetFullPath (string path)
                {
                        if (path == null)
-                               throw (new ArgumentNullException (
-                                       "path",
-                                       "You must specify a path when calling System.IO.Path.GetFullPath"));
+                               throw new ArgumentNullException ("path");
+
+                       if (path.Trim ().Length == 0) {
+                               string msg = Locale.GetText ("The specified path is not of a legal form (empty).");
+                               throw new ArgumentException (msg);
+                       }
 
-                       if (path.Trim () == String.Empty)
-                               throw new ArgumentException ("The path is not of a legal form", "path");
+                       // adjust for drives, i.e. a special case for windows
+                       if (Environment.IsRunningOnWindows)
+                               path = WindowsDriveAdjustment (path);
 
+                       // if the supplied path ends with a separator...
+                       char end = path [path.Length - 1];
+
+                       var canonicalize = true;
                        if (path.Length >= 2 &&
                                IsDsc (path [0]) &&
                                IsDsc (path [1])) {
                                if (path.Length == 2 || path.IndexOf (path [0], 2) < 0)
                                        throw new ArgumentException ("UNC pass should be of the form \\\\server\\share.");
-                               else
-                                       if (path [0] == DirectorySeparatorChar)
-                                               return path; // UNC
+
+                               if (path [0] != DirectorySeparatorChar)
+                                       path = path.Replace (AltDirectorySeparatorChar, DirectorySeparatorChar);
+
+                       } else {
+                               if (!IsPathRooted (path)) {
+                                       
+                                       // avoid calling expensive CanonicalizePath when possible
+                                       var start = 0;
+                                       while ((start = path.IndexOf ('.', start)) != -1) {
+                                               if (++start == path.Length || path [start] == DirectorySeparatorChar || path [start] == AltDirectorySeparatorChar)
+                                                       break;
+                                       }
+                                       canonicalize = start > 0;
+                                       
+                                       path = Directory.GetCurrentDirectory () + DirectorySeparatorStr + path;
+                               } else if (DirectorySeparatorChar == '\\' &&
+                                       path.Length >= 2 &&
+                                       IsDsc (path [0]) &&
+                                       !IsDsc (path [1])) { // like `\abc\def'
+                                       string current = Directory.GetCurrentDirectory ();
+                                       if (current [1] == VolumeSeparatorChar)
+                                               path = current.Substring (0, 2) + path;
                                        else
-                                               return path.Replace (AltDirectorySeparatorChar, DirectorySeparatorChar);
+                                               path = current.Substring (0, current.IndexOf ('\\', current.IndexOf ("\\\\") + 1));
+                               }
                        }
+                       
+                       if (canonicalize)
+                           path = CanonicalizePath (path);
 
-                       if (!IsPathRooted (path))
-                               path = Directory.GetCurrentDirectory () + DirectorySeparatorStr + path;
-                       else if (DirectorySeparatorChar == '\\' &&
-                               path.Length >= 2 &&
-                               IsDsc (path [0]) &&
-                               !IsDsc (path [1])) { // like `\abc\def'
-                               string current = Directory.GetCurrentDirectory ();
-                               if (current [1] == VolumeSeparatorChar)
-                                       path = current.Substring (0, 2) + path;
-                               else
-                                       path = current.Substring (0, current.IndexOf ('\\', current.IndexOf ("\\\\") + 1));
-                       }
-                       return CanonicalizePath (path);
+                       // if the original ended with a [Alt]DirectorySeparatorChar then ensure the full path also ends with one
+                       if (IsDsc (end) && (path [path.Length - 1] != DirectorySeparatorChar))
+                               path += DirectorySeparatorChar;
+
+                       return path;
                }
 
                static bool IsDsc (char c) {
@@ -236,8 +387,8 @@ namespace System.IO
                        if (path == null)
                                return null;
 
-                       if (path == String.Empty)
-                               throw new ArgumentException ("This specified path is invalid.");
+                       if (path.Trim ().Length == 0)
+                               throw new ArgumentException ("The specified path is not of a legal form.");
 
                        if (!IsPathRooted (path))
                                return String.Empty;
@@ -258,11 +409,16 @@ namespace System.IO
                                        // UNC: \\server or \\server\share
                                        // Get server
                                        while (len < path.Length && !IsDsc (path [len])) len++;
+
                                        // Get share
-                                       while (len < path.Length && !IsDsc (path [len])) len++;
+                                       if (len < path.Length) {
+                                               len++;
+                                               while (len < path.Length && !IsDsc (path [len])) len++;
+                                       }
+
                                        return DirectorySeparatorStr +
                                                DirectorySeparatorStr +
-                                               path.Substring (2).Replace (AltDirectorySeparatorChar, DirectorySeparatorChar);
+                                               path.Substring (2, len - 2).Replace (AltDirectorySeparatorChar, DirectorySeparatorChar);
                                } else if (IsDsc (path [0])) {
                                        // path starts with '\' or '/'
                                        return DirectorySeparatorStr;
@@ -275,6 +431,8 @@ namespace System.IO
                        }
                }
 
+               // FIXME: Further limit the assertion when imperative Assert is implemented
+               [FileIOPermission (SecurityAction.Assert, Unrestricted = true)]
                public static string GetTempFileName ()
                {
                        FileStream f = null;
@@ -282,15 +440,27 @@ namespace System.IO
                        Random rnd;
                        int num = 0;
 
+                       SecurityManager.EnsureElevatedPermissions (); // this is a no-op outside moonlight
+
                        rnd = new Random ();
                        do {
                                num = rnd.Next ();
                                num++;
-                               path = Path.Combine (GetTempPath(), "tmp" + num.ToString("x"));
+                               path = Path.Combine (GetTempPath(), "tmp" + num.ToString("x") + ".tmp");
 
                                try {
-                                       f = new FileStream (path, FileMode.CreateNew);
-                               } catch {
+                                       f = new FileStream (path, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.Read,
+                                                           8192, false, (FileOptions) 1);
+                               }
+                               catch (SecurityException) {
+                                       // avoid an endless loop
+                                       throw;
+                               }
+                               catch (UnauthorizedAccessException) {
+                                       // This can happen if we don't have write permission to /tmp
+                                       throw;
+                               }
+                               catch {
                                }
                        } while (f == null);
                        
@@ -298,11 +468,11 @@ namespace System.IO
                        return path;
                }
 
-               /// <summary>
-               /// Returns the path of the current systems temp directory
-               /// </summary>
+               [EnvironmentPermission (SecurityAction.Demand, Unrestricted = true)]
                public static string GetTempPath ()
                {
+                       SecurityManager.EnsureElevatedPermissions (); // this is a no-op outside moonlight
+
                        string p = get_temp_path ();
                        if (p.Length > 0 && p [p.Length - 1] != DirectorySeparatorChar)
                                return p + DirectorySeparatorChar;
@@ -314,10 +484,13 @@ namespace System.IO
                private static extern string get_temp_path ();
 
                public static bool HasExtension (string path)
-               {  
-                       if (path == null || path.Trim () == String.Empty)
+               {
+                       if (path == null || path.Trim ().Length == 0)
                                return false;
 
+                       if (path.IndexOfAny (InvalidPathChars) != -1)
+                               throw new ArgumentException ("Illegal characters in path.");
+
                        int pos = findExtension (path);
                        return 0 <= pos && pos < path.Length - 1;
                }
@@ -328,7 +501,7 @@ namespace System.IO
                                return false;
 
                        if (path.IndexOfAny (InvalidPathChars) != -1)
-                               throw new ArgumentException ("Illegal characters in path", "path");
+                               throw new ArgumentException ("Illegal characters in path.");
 
                        char c = path [0];
                        return (c == DirectorySeparatorChar     ||
@@ -336,6 +509,54 @@ namespace System.IO
                                (!dirEqualsVolume && path.Length > 1 && path [1] == VolumeSeparatorChar));
                }
 
+               public static char[] GetInvalidFileNameChars ()
+               {
+                       // return a new array as we do not want anyone to be able to change the values
+                       if (Environment.IsRunningOnWindows) {
+                               return new char [41] { '\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07',
+                                       '\x08', '\x09', '\x0A', '\x0B', '\x0C', '\x0D', '\x0E', '\x0F', '\x10', '\x11', '\x12', 
+                                       '\x13', '\x14', '\x15', '\x16', '\x17', '\x18', '\x19', '\x1A', '\x1B', '\x1C', '\x1D', 
+                                       '\x1E', '\x1F', '\x22', '\x3C', '\x3E', '\x7C', ':', '*', '?', '\\', '/' };
+                       } else {
+                               return new char [2] { '\x00', '/' };
+                       }
+               }
+
+               public static char[] GetInvalidPathChars ()
+               {
+                       // return a new array as we do not want anyone to be able to change the values
+                       if (Environment.IsRunningOnWindows) {
+                               return new char [36] { '\x22', '\x3C', '\x3E', '\x7C', '\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07',
+                                       '\x08', '\x09', '\x0A', '\x0B', '\x0C', '\x0D', '\x0E', '\x0F', '\x10', '\x11', '\x12', 
+                                       '\x13', '\x14', '\x15', '\x16', '\x17', '\x18', '\x19', '\x1A', '\x1B', '\x1C', '\x1D', 
+                                       '\x1E', '\x1F' };
+                       } else {
+                               return new char [1] { '\x00' };
+                       }
+               }
+
+               public static string GetRandomFileName ()
+               {
+                       // returns a 8.3 filename (total size 12)
+                       StringBuilder sb = new StringBuilder (12);
+                       // using strong crypto but without creating the file
+                       RandomNumberGenerator rng = RandomNumberGenerator.Create ();
+                       byte [] buffer = new byte [11];
+                       rng.GetBytes (buffer);
+
+                       for (int i = 0; i < buffer.Length; i++) {
+                               if (sb.Length == 8)
+                                       sb.Append ('.');
+
+                               // restrict to length of range [a..z0..9]
+                               int b = (buffer [i] % 36);
+                               char c = (char) (b < 26 ? (b + 'a') : (b - 26 + '0'));
+                               sb.Append (c);
+                       }
+
+                       return sb.ToString ();
+               }
+
                // private class methods
 
                private static int findExtension (string path)
@@ -352,14 +573,15 @@ namespace System.IO
                        return -1;
                }
 
-               static Path () {
+               static Path ()
+               {
                        VolumeSeparatorChar = MonoIO.VolumeSeparatorChar;
                        DirectorySeparatorChar = MonoIO.DirectorySeparatorChar;
                        AltDirectorySeparatorChar = MonoIO.AltDirectorySeparatorChar;
 
                        PathSeparator = MonoIO.PathSeparator;
-                       InvalidPathChars = MonoIO.InvalidPathChars;
-
+                       // this copy will be modifiable ("by design")
+                       InvalidPathChars = GetInvalidPathChars ();
                        // internal fields
 
                        DirectorySeparatorStr = DirectorySeparatorChar.ToString ();
@@ -371,64 +593,220 @@ namespace System.IO
 
                        dirEqualsVolume = (DirectorySeparatorChar == VolumeSeparatorChar);
                }
-               
-               
-               static string CanonicalizePath (string path) {
+
+               // returns the server and share part of a UNC. Assumes "path" is a UNC.
+               static string GetServerAndShare (string path)
+               {
+                       int len = 2;
+                       while (len < path.Length && !IsDsc (path [len])) len++;
+
+                       if (len < path.Length) {
+                               len++;
+                               while (len < path.Length && !IsDsc (path [len])) len++;
+                       }
+
+                       return path.Substring (2, len - 2).Replace (AltDirectorySeparatorChar, DirectorySeparatorChar);
+               }
+
+               // assumes Environment.IsRunningOnWindows == true
+               static bool SameRoot (string root, string path)
+               {
+                       // compare root - if enough details are available
+                       if ((root.Length < 2) || (path.Length < 2))
+                               return false;
+
+                       // UNC handling
+                       if (IsDsc (root[0]) && IsDsc (root[1])) {
+                               if (!(IsDsc (path[0]) && IsDsc (path[1])))
+                                       return false;
+
+                               string rootShare = GetServerAndShare (root);
+                               string pathShare = GetServerAndShare (path);
+
+                               return String.Compare (rootShare, pathShare, true, CultureInfo.InvariantCulture) == 0;
+                       }
                        
+                       // same volume/drive
+                       if (!root [0].Equals (path [0]))
+                               return false;
+                       // presence of the separator
+                       if (path[1] != Path.VolumeSeparatorChar)
+                               return false;
+                       if ((root.Length > 2) && (path.Length > 2)) {
+                               // but don't directory compare the directory separator
+                               return (IsDsc (root[2]) && IsDsc (path[2]));
+                       }
+                       return true;
+               }
+
+               static string CanonicalizePath (string path)
+               {
                        // STEP 1: Check for empty string
-                       if (path == null) return path;
-                       path = path.Trim ();
-                       if (path == String.Empty) return path;
-                       
+                       if (path == null)
+                               return path;
+                       if (Environment.IsRunningOnWindows)
+                               path = path.Trim ();
+
+                       if (path.Length == 0)
+                               return path;
+
                        // STEP 2: Check to see if this is only a root
-                       string root = GetPathRoot (path);
+                       string root = Path.GetPathRoot (path);
                        // it will return '\' for path '\', while it should return 'c:\' or so.
-                       // Note: commenting this out makes the ened for the (target == 1...) check in step 5
+                       // Note: commenting this out makes the need for the (target == 1...) check in step 5
                        //if (root == path) return path;
-                               
+
                        // STEP 3: split the directories, this gets rid of consecutative "/"'s
-                       string [] dirs = path.Split (DirectorySeparatorChar, AltDirectorySeparatorChar);
+                       string[] dirs = path.Split (Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
                        // STEP 4: Get rid of directories containing . and ..
                        int target = 0;
-                       
+
+                       bool isUnc = Environment.IsRunningOnWindows &&
+                               root.Length > 2 && IsDsc (root[0]) && IsDsc (root[1]);
+
+                       // Set an overwrite limit for UNC paths since '\' + server + share
+                       // must not be eliminated by the '..' elimination algorithm.
+                       int limit = isUnc ? 3 : 0;
+
                        for (int i = 0; i < dirs.Length; i++) {
-                               if (dirs [i] == "." || (i != 0 && dirs [i] == String.Empty)) continue;
-                               else if (dirs [i] == "..") {
-                                       if (target != 0) target--;
-                               }
-                               else
-                                       dirs [target++] = dirs [i];
+                               // WIN32 path components must be trimmed
+                               if (Environment.IsRunningOnWindows)
+                                       dirs[i] = dirs[i].TrimEnd ();
+                               
+                               if (dirs[i] == "." || (i != 0 && dirs[i].Length == 0))
+                                       continue;
+                               else if (dirs[i] == "..") {
+                                       // don't overwrite path segments below the limit
+                                       if (target > limit)
+                                               target--;
+                               } else
+                                       dirs[target++] = dirs[i];
                        }
 
                        // STEP 5: Combine everything.
-                       if (target == 0 || (target == 1 && dirs [0] == ""))
+                       if (target == 0 || (target == 1 && dirs[0] == ""))
                                return root;
                        else {
                                string ret = String.Join (DirectorySeparatorStr, dirs, 0, target);
-                               switch (DirectorySeparatorChar) {
-                               case '\\': // Windows
-                                       // In GetFullPath(), it is assured that here never comes UNC. So this must only applied to such path that starts with '\', without drive specification.
-                                       if (path [0] != DirectorySeparatorChar && path.StartsWith (root)) {
+                               if (Environment.IsRunningOnWindows) {
+                                       // append leading '\' of the UNC path that was lost in STEP 3.
+                                       if (isUnc)
+                                               ret = Path.DirectorySeparatorStr + ret;
+
+                                       if (!SameRoot (root, ret))
+                                               ret = root + ret;
+
+                                       if (isUnc) {
+                                               return ret;
+                                       } else if (!IsDsc (path[0]) && SameRoot (root, path)) {
                                                if (ret.Length <= 2 && !ret.EndsWith (DirectorySeparatorStr)) // '\' after "c:"
-                                                       ret += DirectorySeparatorChar;
+                                                       ret += Path.DirectorySeparatorChar;
                                                return ret;
                                        } else {
                                                string current = Directory.GetCurrentDirectory ();
-                                               if (current.Length > 1 && current [1] == VolumeSeparatorChar) {
+                                               if (current.Length > 1 && current[1] == Path.VolumeSeparatorChar) {
                                                        // DOS local file path
-                                                       if (ret.Length == 0 || IsDsc (ret [0]))
+                                                       if (ret.Length == 0 || IsDsc (ret[0]))
                                                                ret += '\\';
                                                        return current.Substring (0, 2) + ret;
-                                               }
-                                               else if (IsDsc (current [current.Length - 1]) && IsDsc (ret [0]))
+                                               } else if (IsDsc (current[current.Length - 1]) && IsDsc (ret[0]))
                                                        return current + ret.Substring (1);
                                                else
                                                        return current + ret;
                                        }
-                               default: // Unix/Mac
-                                       return ret;
                                }
+                               return ret;
+                       }
+               }
+
+               // required for FileIOPermission (and most proibably reusable elsewhere too)
+               // both path MUST be "full paths"
+               static internal bool IsPathSubsetOf (string subset, string path)
+               {
+                       if (subset.Length > path.Length)
+                               return false;
+
+                       // check that everything up to the last separator match
+                       int slast = subset.LastIndexOfAny (PathSeparatorChars);
+                       if (String.Compare (subset, 0, path, 0, slast) != 0)
+                               return false;
+
+                       slast++;
+                       // then check if the last segment is identical
+                       int plast = path.IndexOfAny (PathSeparatorChars, slast);
+                       if (plast >= slast) {
+                               return String.Compare (subset, slast, path, slast, path.Length - plast) == 0;
+                       }
+                       if (subset.Length != path.Length)
+                               return false;
+
+                       return String.Compare (subset, slast, path, slast, subset.Length - slast) == 0;
+               }
+
+#if NET_4_0 || MOONLIGHT
+               public static string Combine (params string [] paths)
+               {
+                       if (paths == null)
+                               throw new ArgumentNullException ("paths");
+
+                       int l = 0;
+                       bool need_sep = false;
+                       foreach (var s in paths){
+                               if (s == null)
+                                       throw new ArgumentNullException ("One of the paths contains a null value", "paths");
+                               if (s.IndexOfAny (InvalidPathChars) != -1)
+                                       throw new ArgumentException ("Illegal characters in path.");
+                               if (l == 0 && s.Length > 0){
+                                       char p1end = s [s.Length - 1];
+                                       if (p1end != DirectorySeparatorChar && p1end != AltDirectorySeparatorChar && p1end != VolumeSeparatorChar){
+                                               need_sep = true;
+                                               l += DirectorySeparatorStr.Length;
+                                       }
+                               }
+                       }
+                       var ret = new StringBuilder (l);
+                       l = 0;
+                       foreach (var s in paths){
+                               if (IsPathRooted (s))
+                                       ret.Length = l = 0;
+                               ret.Append (s);
+                               if (l == 0 && need_sep)
+                                       ret.Append (DirectorySeparatorStr);
+                               l = 1;
+                       }
+
+                       return ret.ToString ();
+               }
+
+               public static string Combine (string path1, string path2, string path3)
+               {
+                       return Combine (new string [] { path1, path2, path3 });
+               }
+
+               public static string Combine (string path1, string path2, string path3, string path4)
+               {
+                       return Combine (new string [] { path1, path2, path3, path4 });
+               }
+#endif
+
+               internal static void Validate (string path)
+               {
+                       Validate (path, "path");
+               }
+
+               internal static void Validate (string path, string parameterName)
+               {
+                       if (path == null)
+                               throw new ArgumentNullException (parameterName);
+                       if (String.IsNullOrWhiteSpace (path))
+                               throw new ArgumentException (Locale.GetText ("Path is empty"));
+                       if (path.IndexOfAny (Path.InvalidPathChars) != -1)
+                               throw new ArgumentException (Locale.GetText ("Path contains invalid chars"));
+#if MOONLIGHT
+                       // On Moonlight (SL4+) there are some limitations in "Elevated Trust"
+                       if (SecurityManager.HasElevatedPermissions) {
                        }
+#endif
                }
        }
 }