context: //
  // UniqueId.cs
  //
  // Author:
  //	Atsushi Enomoto <atsushi@ximian.com>
  //	Jonathan Pryor <jpryor@novell.com>
  //
  // Copyright (C) 2005,2007,2009 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
  // "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.
  //
  #if NET_2_0
  using System;
  using System.Collections.Generic;
  using System.Security;
  
  namespace System.Xml
  {
  	public class UniqueId
  	{
  		Guid guid;
  		string id;
  
  		public UniqueId ()
  			: this (Guid.NewGuid ())
  		{
  		}
  
  		public UniqueId (byte [] id)
  			: this (id, 0)
  		{
  		}
  
  		public UniqueId (Guid id)
  		{
  			this.guid = id;
  		}
  
  #if !NET_2_1
  		[SecurityCritical]
  		[SecurityTreatAsSafe]
  #endif
  		public UniqueId (string value)
  		{
  			if (value == null)
  				throw new ArgumentNullException ("value cannot be null", "value");
  
  			if (value.Length == 0)
  				throw new FormatException ("UniqueId cannot be zero length");
  
  			this.id = value;
  		}
  
  #if !NET_2_1
  		[SecurityCritical]
  		[SecurityTreatAsSafe]
  #endif
  		public UniqueId (byte [] id, int offset)
  		{
  			if (id == null)
  				throw new ArgumentNullException ();
  			if (offset < 0)
  				throw new ArgumentOutOfRangeException ("offset");
  			if (offset >= id.Length)
  				throw new ArgumentException ("id too small.", "offset");
  
  			if (id.Length - offset != 16)
  				throw new ArgumentException ("id and offset provide less than 16 bytes");
  
  			if (offset == 0)
  				guid = new Guid (id);
  			else {
  				List<byte> buf = new List<byte> (id);
  				buf.RemoveRange (0, offset);
  				guid = new Guid (buf.ToArray ());
  			}
  		}
  
  #if !NET_2_1
  		[SecurityCritical]
  		[SecurityTreatAsSafe]
  #endif
  		public UniqueId (char [] id, int offset, int count)
  		{
  			if (id == null)
  				throw new ArgumentNullException ("id");
  			if (offset < 0 || offset >= id.Length)
  				throw new ArgumentOutOfRangeException ("offset");
  			if (count < 0 || id.Length - offset < count)
  				throw new ArgumentOutOfRangeException ("count");
  			if (count == 0)
  				throw new FormatException ();
  
  			// Does it start with "urn:uuid:"?  If so, it's a Guid.
  			if (count > 8 && id [offset] == 'u' && id [offset+1] == 'r' && 
  					id [offset+2] == 'n' && id [offset+3] == ':' &&
  					id [offset+4] == 'u' && id [offset+5] == 'u' &&
  					id [offset+6] == 'i' && id [offset+7] == 'd' &&
  					id [offset+8] == ':') {
  				if (count != 45)
  					throw new ArgumentOutOfRangeException ("Invalid Guid");
  				this.guid = new Guid (new string (id, offset+9, count-9));
  			} else
  				this.id = new string (id, offset, count);
  		}
  
  		public int CharArrayLength {
  #if !NET_2_1
  			[SecurityCritical]
  			[SecurityTreatAsSafe]
  #endif
  			get {return id != null ? id.Length : 45;}
  		}
  
  		public bool IsGuid {
  			get { return guid != default (Guid); }
  		}
  
  		public override bool Equals (Object obj)
  		{
  			UniqueId other = obj as UniqueId;
  
  			if (other == null)
  				return false;
  
  			if (IsGuid && other.IsGuid) {
  				return guid.Equals (other.guid);
  			}
  
  			return id == other.id;
  		}
  
  		[MonoTODO ("Determine semantics when IsGuid==true")]
  		public override int GetHashCode ()
  		{
  			return id != null ? id.GetHashCode () : guid.GetHashCode ();
  		}
  
  		public static bool operator == (UniqueId id1, UniqueId id2)
  		{
  			return object.Equals (id1, id2);
  		}
  
  		public static bool operator != (UniqueId id1, UniqueId id2)
  		{
  			return ! (id1 == id2);
  		}
  
  #if !NET_2_1
  		[SecurityCritical]
  		[SecurityTreatAsSafe]
  #endif
  		public int ToCharArray (char [] array, int offset)
  		{
  			if (array == null)
  				throw new ArgumentNullException ("array");
  			if (offset < 0 || offset >= array.Length)
  				throw new ArgumentOutOfRangeException ("offset");
  
  			string s = ToString ();
  			s.CopyTo (0, array, offset, s.Length);
  			return s.Length;
  		}
  
  #if !NET_2_1
  		[SecurityCritical]
  		[SecurityTreatAsSafe]
  #endif
  		public override string ToString ()
  		{
  			if (id == null)
  				return "urn:uuid:" + guid;
  
  			return id;
  		}
  
  		public bool TryGetGuid (out Guid guid)
  		{
  			if (IsGuid) {
  				guid = this.guid;
  				return true;
  			} else {
  				guid = default (Guid);
  				return false;
  			}
  		}
  
  #if !NET_2_1
  		[SecurityCritical]
  		[SecurityTreatAsSafe]
  #endif
  		public bool TryGetGuid (byte [] buffer, int offset)
  		{
  			if (!IsGuid)
  				return false;
  
  			if (buffer == null)
  
gt: 				throw new ArgumentNullException ("buffer");