mcs/class/System.XML/Mono.Xml.Xsl/XslFunctions.cs

   1 //
   2 // XsltCompiledContext.cs
   3 //
   4 // Authors:
   5 //      Ben Maurer (bmaurer@users.sourceforge.net)
   6 //      Atsushi Enomoto (atsushi@ximian.com)
   7 // (C) 2003 Ben Maurer
   8 // (C) 2004 Atsushi Enomoto
   9 //
  10
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31 using System;
  32 using System.Collections;
  33 using System.Globalization;
  34 using System.Reflection;
  35 using System.Text;
  36 using System.Xml;
  37 using System.Xml.XPath;
  38 using System.Xml.Xsl;
  39 using Mono.Xml.Xsl;
  40
  41 using QName = System.Xml.XmlQualifiedName;
  42
  43 namespace Mono.Xml.Xsl
  44 {
  45         internal abstract class XPFuncImpl : IXsltContextFunction
  46         {
  47                 int minargs, maxargs;
  48                 XPathResultType returnType;
  49                 XPathResultType [] argTypes;
  50
  51                 public XPFuncImpl () {}
  52                 public XPFuncImpl (int minArgs, int maxArgs, XPathResultType returnType, XPathResultType[] argTypes)
  53                 {
  54                         this.Init(minArgs, maxArgs, returnType, argTypes);
  55                 }
  56
  57                 protected void Init (int minArgs, int maxArgs, XPathResultType returnType, XPathResultType[] argTypes)
  58                 {
  59                         this.minargs    = minArgs;
  60                         this.maxargs    = maxArgs;
  61                         this.returnType = returnType;
  62                         this.argTypes   = argTypes;
  63                 }
  64
  65                 public int Minargs { get { return this.minargs; }}
  66                 public int Maxargs { get { return this.maxargs; }}
  67                 public XPathResultType ReturnType { get { return this.returnType; }}
  68                 public XPathResultType [] ArgTypes { get { return this.argTypes; }}
  69                 public object Invoke (XsltContext xsltContext, object [] args, XPathNavigator docContext)
  70                 {
  71                         return Invoke ((XsltCompiledContext)xsltContext, args, docContext);
  72                 }
  73
  74                 public abstract object Invoke (XsltCompiledContext xsltContext, object [] args, XPathNavigator docContext);
  75
  76                 public static XPathResultType GetXPathType (Type type, XPathNavigator node) {
  77                         switch (Type.GetTypeCode(type)) {
  78                         case TypeCode.String:
  79                                 return XPathResultType.String;
  80                         case TypeCode.Boolean:
  81                                 return XPathResultType.Boolean;
  82                         case TypeCode.Object:
  83                                 if (typeof (XPathNavigator).IsAssignableFrom (type) || typeof (IXPathNavigable).IsAssignableFrom (type))
  84                                         return XPathResultType.Navigator;
  85
  86                                 if (typeof (XPathNodeIterator).IsAssignableFrom (type))
  87                                         return XPathResultType.NodeSet;
  88
  89                                 return XPathResultType.Any;
  90                         case TypeCode.DateTime :
  91                                 throw new XsltException ("Invalid type DateTime was specified.", null, node);
  92                         default: // Numeric
  93                                 return XPathResultType.Number;
  94                         }
  95                 }
  96         }
  97
  98         class XsltExtensionFunction : XPFuncImpl
  99         {
 100                 private object extension;
 101                 private MethodInfo method;
 102                 private TypeCode [] typeCodes;
 103
 104                 public XsltExtensionFunction (object extension, MethodInfo method, XPathNavigator currentNode)
 105                 {
 106                         this.extension = extension;
 107                         this.method = method;
 108
 109                         ParameterInfo [] parameters = method.GetParameters ();
 110                         int minArgs = parameters.Length;
 111                         int maxArgs = parameters.Length;
 112
 113                         this.typeCodes = new TypeCode [parameters.Length];
 114                         XPathResultType[] argTypes = new XPathResultType [parameters.Length];
 115
 116                         bool canBeOpt = true;
 117                         for (int i = parameters.Length - 1; 0 <= i; i--) { // optionals at the end
 118                                 typeCodes [i] = Type.GetTypeCode (parameters [i].ParameterType);
 119                                 argTypes [i] = GetXPathType (parameters [i].ParameterType, currentNode);
 120                                 if (canBeOpt) {
 121                                         if (parameters[i].IsOptional)
 122                                                 minArgs --;
 123                                         else
 124                                                 canBeOpt = false;
 125                                 }
 126                         }
 127                         base.Init (minArgs, maxArgs, GetXPathType (method.ReturnType, currentNode), argTypes);
 128                 }
 129
 130                 public override object Invoke (XsltCompiledContext xsltContext, object [] args, XPathNavigator docContext)
 131                 {
 132                         try {
 133                                 ParameterInfo [] pis = method.GetParameters ();
 134                                 object [] castedArgs = new object [pis.Length];
 135                                 for (int i = 0; i < args.Length; i++) {
 136                                         Type t = pis [i].ParameterType;
 137                                         switch (t.FullName) {
 138                                         case "System.Int16":
 139                                         case "System.UInt16":
 140                                         case "System.Int32":
 141                                         case "System.UInt32":
 142                                         case "System.Int64":
 143                                         case "System.UInt64":
 144                                         case "System.Single":
 145                                         case "System.Decimal":
 146                                                 castedArgs [i] = Convert.ChangeType (args [i], t);
 147                                                 break;
 148                                         default:
 149                                                 castedArgs [i] = args [i];
 150                                                 break;
 151                                         }
 152                                 }
 153
 154                                 object result = null;
 155                                 switch (method.ReturnType.FullName) {
 156                                 case "System.Int16":
 157                                 case "System.UInt16":
 158                                 case "System.Int32":
 159                                 case "System.UInt32":
 160                                 case "System.Int64":
 161                                 case "System.UInt64":
 162                                 case "System.Single":
 163                                 case "System.Decimal":
 164                                         result = Convert.ChangeType (method.Invoke (extension, castedArgs), typeof (double));
 165                                         break;
 166                                 default:
 167                                         result = method.Invoke(extension, castedArgs);
 168                                         break;
 169                                 }
 170                                 IXPathNavigable navigable = result as IXPathNavigable;
 171                                 if (navigable != null)
 172                                         return navigable.CreateNavigator ();
 173
 174                                 return result;
 175                         } catch (Exception ex) {
 176                                 throw new XsltException ("Custom function reported an error.", ex);
 177 //                              Debug.WriteLine ("****** INCORRECT RESOLUTION **********");
 178                         }
 179                 }
 180         }
 181
 182         class XsltCurrent : XPathFunction
 183         {
 184                 public XsltCurrent (FunctionArguments args) : base (args)
 185                 {
 186                         if (args != null)
 187                                 throw new XPathException ("current takes 0 args");
 188                 }
 189
 190                 public override XPathResultType ReturnType { get { return XPathResultType.NodeSet; }}
 191
 192                 public override object Evaluate (BaseIterator iter)
 193                 {
 194                         XsltCompiledContext ctx = (XsltCompiledContext) iter.NamespaceManager;
 195                         return new SelfIterator ((ctx).Processor.CurrentNode, ctx);
 196                 }
 197
 198                 internal override bool Peer {
 199                         get { return false; }
 200                 }
 201
 202                 public override string ToString ()
 203                 {
 204                         return "current()";
 205                 }
 206         }
 207
 208         class XsltDocument : XPathFunction
 209         {
 210                 Expression arg0, arg1;
 211                 XPathNavigator doc;
 212
 213                 public XsltDocument (FunctionArguments args, Compiler c) : base (args)
 214                 {
 215                         if (args == null || (args.Tail != null && args.Tail.Tail != null))
 216                                 throw new XPathException ("document takes one or two args");
 217
 218                         arg0 = args.Arg;
 219                         if (args.Tail != null)
 220                                 arg1 = args.Tail.Arg;
 221                         doc = c.Input.Clone ();
 222                 }
 223                 public override XPathResultType ReturnType { get { return XPathResultType.NodeSet; }}
 224
 225                 internal override bool Peer {
 226                         get { return arg0.Peer && (arg1 != null ? arg1.Peer : true); }
 227                 }
 228
 229                 public override object Evaluate (BaseIterator iter)
 230                 {
 231                         string baseUri = null;
 232                         if (arg1 != null) {
 233                                 XPathNodeIterator it = arg1.EvaluateNodeSet (iter);
 234                                 if (it.MoveNext())
 235                                         baseUri = it.Current.BaseURI;
 236                                 else
 237                                         baseUri = VoidBaseUriFlag;
 238                         }
 239
 240                         object o = arg0.Evaluate (iter);
 241                         if (o is XPathNodeIterator)
 242                                 return GetDocument ((iter.NamespaceManager as XsltCompiledContext), (XPathNodeIterator)o, baseUri);
 243                         else
 244                                 return GetDocument ((iter.NamespaceManager as XsltCompiledContext), o is IFormattable ? ((IFormattable) o).ToString (null, CultureInfo.InvariantCulture) : o.ToString (), baseUri);
 245                 }
 246
 247                 static string VoidBaseUriFlag = "&^)(*&%*^$&$VOID!BASE!URI!";
 248
 249                 Uri Resolve (string thisUri, string baseUri, XslTransformProcessor p)
 250                 {
 251 //                      Debug.WriteLine ("THIS: " + thisUri);
 252 //                      Debug.WriteLine ("BASE: " + baseUri);
 253                         XmlResolver r = p.Resolver;
 254                         if (r == null)
 255                                 return null;
 256                         Uri uriBase = null;
 257                         if (! object.ReferenceEquals (baseUri, VoidBaseUriFlag) && baseUri != String.Empty)
 258                                 uriBase = r.ResolveUri (null, baseUri);
 259
 260                         return r.ResolveUri (uriBase, thisUri);
 261                 }
 262
 263                 XPathNodeIterator GetDocument (XsltCompiledContext xsltContext, XPathNodeIterator itr, string baseUri)
 264                 {
 265                         ArrayList list = new ArrayList ();
 266                         try {
 267                                 Hashtable got = new Hashtable ();
 268
 269                                 while (itr.MoveNext()) {
 270                                         Uri uri = Resolve (itr.Current.Value, baseUri != null ? baseUri : /*itr.Current.BaseURI*/doc.BaseURI, xsltContext.Processor);
 271                                         if (!got.ContainsKey (uri)) {
 272                                                 got.Add (uri, null);
 273                                                 if (uri != null && uri.ToString () == "") {
 274                                                         XPathNavigator n = doc.Clone ();
 275                                                         n.MoveToRoot ();
 276                                                         list.Add (n);
 277                                                 } else
 278                                                         list.Add (xsltContext.Processor.GetDocument (uri));
 279                                         }
 280                                 }
 281                         } catch (Exception) {
 282                                 // Error recovery.
 283                                 // See http://www.w3.org/TR/xslt#document and
 284                                 // bug #75663.
 285                                 list.Clear ();
 286                         }
 287                         return new ListIterator (list, xsltContext);
 288                 }
 289
 290                 XPathNodeIterator GetDocument (XsltCompiledContext xsltContext, string arg0, string baseUri)
 291                 {
 292                         try {
 293                                 Uri uri = Resolve (arg0, baseUri != null ? baseUri : doc.BaseURI, xsltContext.Processor);
 294                                 XPathNavigator n;
 295                                 if (uri != null && uri.ToString () == "") {
 296                                         n = doc.Clone ();
 297                                         n.MoveToRoot ();
 298                                 } else
 299                                         n = xsltContext.Processor.GetDocument (uri);
 300
 301                                 return new SelfIterator (n, xsltContext);
 302                         } catch (Exception) {
 303                                 return new ListIterator (new ArrayList (), xsltContext);
 304                         }
 305                 }
 306
 307                 public override string ToString ()
 308                 {
 309                         return String.Concat ("document(",
 310                                 arg0.ToString (),
 311                                 arg1 != null ? "," : String.Empty,
 312                                 arg1 != null ? arg1.ToString () : String.Empty,
 313                                 ")");
 314                 }
 315         }
 316
 317         class XsltElementAvailable : XPathFunction
 318         {
 319                 Expression arg0;
 320                 IStaticXsltContext ctx;
 321
 322                 public XsltElementAvailable (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 323                 {
 324                         if (args == null || args.Tail != null)
 325                                 throw new XPathException ("element-available takes 1 arg");
 326
 327                         arg0 = args.Arg;
 328                         this.ctx = ctx;
 329                 }
 330
 331                 public override XPathResultType ReturnType { get { return XPathResultType.Boolean; }}
 332
 333                 internal override bool Peer {
 334                         get { return arg0.Peer; }
 335                 }
 336
 337                 public override object Evaluate (BaseIterator iter)
 338                 {
 339                         QName name = XslNameUtil.FromString (arg0.EvaluateString (iter), ctx);
 340
 341                         return (
 342                                 (name.Namespace == Compiler.XsltNamespace) &&
 343                                 (
 344                                         //
 345                                         // A list of all the instructions (does not include top-level-elements)
 346                                         //
 347                                         name.Name == "apply-imports" ||
 348                                         name.Name == "apply-templates" ||
 349                                         name.Name == "call-template" ||
 350                                         name.Name == "choose" ||
 351                                         name.Name == "comment" ||
 352                                         name.Name == "copy" ||
 353                                         name.Name == "copy-of" ||
 354                                         name.Name == "element" ||
 355                                         name.Name == "fallback" ||
 356                                         name.Name == "for-each" ||
 357                                         name.Name == "message" ||
 358                                         name.Name == "number" ||
 359                                         name.Name == "processing-instruction" ||
 360                                         name.Name == "text" ||
 361                                         name.Name == "value-of" ||
 362                                         name.Name == "variable"
 363                                 )
 364                         );
 365                 }
 366         }
 367
 368         class XsltFormatNumber : XPathFunction
 369         {
 370                 Expression arg0, arg1, arg2;
 371                 IStaticXsltContext ctx;
 372
 373                 public XsltFormatNumber (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 374                 {
 375                         if (args == null || args.Tail == null || (args.Tail.Tail != null && args.Tail.Tail.Tail != null))
 376                                 throw new XPathException ("format-number takes 2 or 3 args");
 377
 378                         arg0 = args.Arg;
 379                         arg1 = args.Tail.Arg;
 380                         if (args.Tail.Tail != null) {
 381                                 arg2= args.Tail.Tail.Arg;
 382                                 this.ctx = ctx;
 383                         }
 384                 }
 385                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 386
 387                 internal override bool Peer {
 388                         get { return arg0.Peer && arg1.Peer && (arg2 != null ? arg2.Peer : true); }
 389                 }
 390
 391                 public override object Evaluate (BaseIterator iter)
 392                 {
 393                         double d = arg0.EvaluateNumber (iter);
 394                         string s = arg1.EvaluateString (iter);
 395                         QName nm = QName.Empty;
 396
 397                         if (arg2 != null)
 398                                 nm = XslNameUtil.FromString (arg2.EvaluateString (iter), ctx);
 399
 400                         try {
 401                                 return ((XsltCompiledContext) iter.NamespaceManager).Processor.CompiledStyle
 402                                 .LookupDecimalFormat (nm).FormatNumber (d, s);
 403                         } catch (ArgumentException ex) {
 404                                 throw new XsltException (ex.Message, ex, iter.Current);
 405                         }
 406                 }
 407         }
 408
 409         class XsltFunctionAvailable : XPathFunction
 410         {
 411                 Expression arg0;
 412                 IStaticXsltContext ctx;
 413
 414                 public XsltFunctionAvailable (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 415                 {
 416                         if (args == null || args.Tail != null)
 417                                 throw new XPathException ("element-available takes 1 arg");
 418
 419                         arg0 = args.Arg;
 420                         this.ctx = ctx;
 421                 }
 422
 423                 public override XPathResultType ReturnType { get { return XPathResultType.Boolean; }}
 424
 425                 internal override bool Peer {
 426                         get { return arg0.Peer; }
 427                 }
 428
 429                 public override object Evaluate (BaseIterator iter)
 430                 {
 431
 432                         string name = arg0.EvaluateString (iter);
 433                         int colon = name.IndexOf (':');
 434                         // extension function
 435                         if (colon > 0)
 436                                 return (iter.NamespaceManager as XsltCompiledContext).ResolveFunction (
 437                                         XslNameUtil.FromString (name, ctx),
 438                                         null) != null;
 439
 440                         return (
 441                                 //
 442                                 // XPath
 443                                 //
 444                                 name == "boolean" ||
 445                                 name == "ceiling" ||
 446                                 name == "concat" ||
 447                                 name == "contains" ||
 448                                 name == "count" ||
 449                                 name == "false" ||
 450                                 name == "floor" ||
 451                                 name == "id"||
 452                                 name == "lang" ||
 453                                 name == "last" ||
 454                                 name == "local-name" ||
 455                                 name == "name" ||
 456                                 name == "namespace-uri" ||
 457                                 name == "normalize-space" ||
 458                                 name == "not" ||
 459                                 name == "number" ||
 460                                 name == "position" ||
 461                                 name == "round" ||
 462                                 name == "starts-with" ||
 463                                 name == "string" ||
 464                                 name == "string-length" ||
 465                                 name == "substring" ||
 466                                 name == "substring-after" ||
 467                                 name == "substring-before" ||
 468                                 name == "sum" ||
 469                                 name == "translate" ||
 470                                 name == "true" ||
 471                                 // XSLT
 472                                 name == "document" ||
 473                                 name == "format-number" ||
 474                                 name == "function-available" ||
 475                                 name == "generate-id" ||
 476                                 name == "key" ||
 477                                 name == "current" ||
 478                                 name == "unparsed-entity-uri" ||
 479                                 name == "element-available" ||
 480                                 name == "system-property"
 481                         );
 482                 }
 483         }
 484
 485         class XsltGenerateId : XPathFunction
 486         {
 487                 //FIXME: generate short string, not the huge thing it makes now
 488                 Expression arg0;
 489                 public XsltGenerateId (FunctionArguments args) : base (args)
 490                 {
 491                         if (args != null) {
 492                                 if (args.Tail != null)
 493                                         throw new XPathException ("generate-id takes 1 or no args");
 494                                 arg0 = args.Arg;
 495                         }
 496                 }
 497
 498                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 499
 500                 internal override bool Peer {
 501                         get { return arg0.Peer; }
 502                 }
 503
 504                 public override object Evaluate (BaseIterator iter)
 505                 {
 506                         XPathNavigator n;
 507                         if (arg0 != null) {
 508                                 XPathNodeIterator itr = arg0.EvaluateNodeSet (iter);
 509                                 if (itr.MoveNext ())
 510                                         n = itr.Current.Clone ();
 511                                 else
 512                                         return string.Empty; // empty nodeset == empty string
 513                         } else
 514                                 n = iter.Current.Clone ();
 515
 516                         StringBuilder sb = new StringBuilder ("Mono"); // Ensure begins with alpha
 517                         sb.Append (XmlConvert.EncodeLocalName (n.BaseURI));
 518                         sb.Replace ('_', 'm'); // remove underscores from EncodeLocalName
 519                         sb.Append (n.NodeType);
 520                         sb.Append ('m');
 521
 522                         do {
 523                                 sb.Append (IndexInParent (n));
 524                                 sb.Append ('m');
 525                         } while (n.MoveToParent ());
 526
 527                         return sb.ToString ();
 528                 }
 529
 530                 int IndexInParent (XPathNavigator nav)
 531                 {
 532                         int n = 0;
 533                         while (nav.MoveToPrevious ())
 534                                 n++;
 535
 536                         return n;
 537                 }
 538         }
 539
 540         class XsltKey : XPathFunction
 541         {
 542                 Expression arg0, arg1;
 543                 IStaticXsltContext staticContext;
 544
 545                 public XsltKey (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 546                 {
 547                         staticContext = ctx;
 548                         if (args == null || args.Tail == null)
 549                                 throw new XPathException ("key takes 2 args");
 550                         arg0 = args.Arg;
 551                         arg1 = args.Tail.Arg;
 552                 }
 553                 public Expression KeyName { get { return arg0; } }
 554                 public Expression Field { get { return arg1; } }
 555                 public override XPathResultType ReturnType { get { return XPathResultType.NodeSet; }}
 556
 557                 internal override bool Peer {
 558                         get { return arg0.Peer && arg1.Peer; }
 559                 }
 560
 561                 public bool PatternMatches (XPathNavigator nav, XsltContext nsmgr)
 562                 {
 563                         XsltCompiledContext ctx = nsmgr as XsltCompiledContext;
 564                         // for key pattern, it must contain literal value
 565                         return ctx.MatchesKey (nav, staticContext,
 566                                 arg0.StaticValueAsString,
 567                                 arg1.StaticValueAsString);
 568                 }
 569
 570                 public override object Evaluate (BaseIterator iter)
 571                 {
 572                         XsltCompiledContext ctx = iter.NamespaceManager
 573                                 as XsltCompiledContext;
 574                         return ctx.EvaluateKey (staticContext, iter, arg0, arg1);
 575                 }
 576         }
 577
 578         class XsltSystemProperty : XPathFunction
 579         {
 580                 Expression arg0;
 581                 IStaticXsltContext ctx;
 582
 583                 public XsltSystemProperty (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 584                 {
 585                         if (args == null || args.Tail != null)
 586                                 throw new XPathException ("system-property takes 1 arg");
 587
 588                         arg0 = args.Arg;
 589                         this.ctx = ctx;
 590                 }
 591
 592                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 593
 594                 internal override bool Peer {
 595                         get { return arg0.Peer; }
 596                 }
 597
 598                 public override object Evaluate (BaseIterator iter)
 599                 {
 600                         QName name = XslNameUtil.FromString (arg0.EvaluateString (iter), ctx);
 601
 602                         if (name.Namespace == Compiler.XsltNamespace) {
 603                                 switch (name.Name) {
 604                                         case "version": return "1.0";
 605                                         case "vendor": return "Mono";
 606                                         case "vendor-url": return "http://www.go-mono.com/";
 607                                 }
 608                         }
 609
 610                         return "";
 611                 }
 612         }
 613
 614         class XsltUnparsedEntityUri : XPathFunction
 615         {
 616                 Expression arg0;
 617
 618                 public XsltUnparsedEntityUri (FunctionArguments args) : base (args)
 619                 {
 620                         if (args == null || args.Tail != null)
 621                                 throw new XPathException ("unparsed-entity-uri takes 1 arg");
 622
 623                         arg0 = args.Arg;
 624                 }
 625
 626                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 627
 628                 internal override bool Peer {
 629                         get { return arg0.Peer; }
 630                 }
 631
 632                 public override object Evaluate (BaseIterator iter)
 633                 {
 634                         IHasXmlNode xn = iter.Current as IHasXmlNode;
 635                         if (xn == null)
 636                                 return String.Empty;
 637                         XmlNode n = xn.GetNode ();
 638                         if (n.OwnerDocument == null)
 639                                 return String.Empty;
 640                         XmlDocumentType doctype = n.OwnerDocument.DocumentType;
 641                         if (doctype == null)
 642                                 return String.Empty;
 643                         XmlEntity ent = doctype.Entities.GetNamedItem (arg0.EvaluateString (iter)) as XmlEntity;
 644                         if (ent == null)
 645                                 return String.Empty;
 646                         return ent.SystemId != null ? ent.SystemId : String.Empty;
 647                 }
 648         }
 649
 650         class MSXslNodeSet : XPathFunction
 651         {
 652                 Expression arg0;
 653
 654                 public MSXslNodeSet (FunctionArguments args) : base (args)
 655                 {
 656                         if (args == null || args.Tail != null)
 657                                 throw new XPathException ("element-available takes 1 arg");
 658
 659                         arg0 = args.Arg;
 660                 }
 661
 662                 public override XPathResultType ReturnType {
 663                         get {
 664                                 return XPathResultType.NodeSet;
 665                         }
 666                 }
 667
 668                 internal override bool Peer {
 669                         get { return arg0.Peer; }
 670                 }
 671
 672                 public override object Evaluate (BaseIterator iter)
 673                 {
 674                         XsltCompiledContext ctx = iter.NamespaceManager as XsltCompiledContext;
 675                         XPathNavigator loc = iter.Current != null ? iter.Current.Clone () : null;
 676                         XPathNavigator nav = arg0.EvaluateAs (iter, XPathResultType.Navigator) as XPathNavigator;
 677                         if (nav == null) {
 678                                 if (loc != null)
 679                                         return new XsltException ("Cannot convert the XPath argument to a result tree fragment.", null, loc);
 680                                 else
 681                                         return new XsltException ("Cannot convert the XPath argument to a result tree fragment.", null);
 682                         }
 683                         ArrayList al = new ArrayList ();
 684                         al.Add (nav);
 685                         return new ListIterator (al, ctx);
 686                 }
 687         }
 688 }