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 = (double) method.Invoke (extension, castedArgs);
 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                         return new SelfIterator ((iter.NamespaceManager as XsltCompiledContext).Processor.CurrentNode, null);
 195                 }
 196         }
 197
 198         class XsltDocument : XPathFunction
 199         {
 200                 Expression arg0, arg1;
 201                 XPathNavigator doc;
 202
 203                 public XsltDocument (FunctionArguments args, Compiler c) : base (args)
 204                 {
 205                         if (args == null || (args.Tail != null && args.Tail.Tail != null))
 206                                 throw new XPathException ("document takes one or two args");
 207
 208                         arg0 = args.Arg;
 209                         if (args.Tail != null)
 210                                 arg1 = args.Tail.Arg;
 211                         doc = c.Input.Clone ();
 212                 }
 213                 public override XPathResultType ReturnType { get { return XPathResultType.NodeSet; }}
 214
 215                 public override object Evaluate (BaseIterator iter)
 216                 {
 217                         string baseUri = null;
 218                         if (arg1 != null) {
 219                                 XPathNodeIterator it = arg1.EvaluateNodeSet (iter);
 220                                 if (it.MoveNext())
 221                                         baseUri = it.Current.BaseURI;
 222                                 else
 223                                         baseUri = VoidBaseUriFlag;
 224                         }
 225
 226                         object o = arg0.Evaluate (iter);
 227                         if (o is XPathNodeIterator)
 228                                 return GetDocument ((iter.NamespaceManager as XsltCompiledContext), (XPathNodeIterator)o, baseUri);
 229                         else
 230                                 return GetDocument ((iter.NamespaceManager as XsltCompiledContext), o is IFormattable ? ((IFormattable) o).ToString (null, CultureInfo.InvariantCulture) : o.ToString (), baseUri);
 231                 }
 232
 233                 static string VoidBaseUriFlag = "&^)(*&%*^$&$VOID!BASE!URI!";
 234
 235                 Uri Resolve (string thisUri, string baseUri, XslTransformProcessor p)
 236                 {
 237 //                      Debug.WriteLine ("THIS: " + thisUri);
 238 //                      Debug.WriteLine ("BASE: " + baseUri);
 239                         XmlResolver r = p.Resolver;
 240
 241                         Uri uriBase = null;
 242                         if (! object.ReferenceEquals (baseUri, VoidBaseUriFlag) && baseUri != String.Empty)
 243                                 uriBase = r.ResolveUri (null, baseUri);
 244
 245                         return r.ResolveUri (uriBase, thisUri);
 246                 }
 247
 248                 XPathNodeIterator GetDocument (XsltCompiledContext xsltContext, XPathNodeIterator itr, string baseUri)
 249                 {
 250                         ArrayList list = new ArrayList ();
 251                         Hashtable got = new Hashtable ();
 252
 253                         while (itr.MoveNext()) {
 254                                 Uri uri = Resolve (itr.Current.Value, baseUri != null ? baseUri : /*itr.Current.BaseURI*/doc.BaseURI, xsltContext.Processor);
 255                                 if (!got.ContainsKey (uri)) {
 256                                         got.Add (uri, null);
 257                                         if (uri.ToString () == "") {
 258                                                 XPathNavigator n = doc.Clone ();
 259                                                 n.MoveToRoot ();
 260                                                 list.Add (n);
 261                                         } else
 262                                                 list.Add (xsltContext.Processor.GetDocument (uri));
 263                                 }
 264                         }
 265
 266                         return new ListIterator (list, xsltContext, false);
 267                 }
 268
 269                 XPathNodeIterator GetDocument (XsltCompiledContext xsltContext, string arg0, string baseUri)
 270                 {
 271                         Uri uri = Resolve (arg0, baseUri != null ? baseUri : doc.BaseURI, xsltContext.Processor);
 272                         XPathNavigator n;
 273                         if (uri.ToString () == "") {
 274                                 n = doc.Clone ();
 275                                 n.MoveToRoot ();
 276                         } else
 277                                 n = xsltContext.Processor.GetDocument (uri);
 278
 279                         return new SelfIterator (n, xsltContext);
 280                 }
 281         }
 282
 283         class XsltElementAvailable : XPathFunction
 284         {
 285                 Expression arg0;
 286                 XmlNamespaceManager nsm;
 287
 288                 public XsltElementAvailable (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 289                 {
 290                         if (args == null || args.Tail != null)
 291                                 throw new XPathException ("element-available takes 1 arg");
 292
 293                         arg0 = args.Arg;
 294                         nsm = ctx.GetNsm ();
 295                 }
 296
 297                 public override XPathResultType ReturnType { get { return XPathResultType.Boolean; }}
 298
 299                 public override object Evaluate (BaseIterator iter)
 300                 {
 301                         QName name = XslNameUtil.FromString (arg0.EvaluateString (iter), nsm);
 302
 303                         return (
 304                                 (name.Namespace == Compiler.XsltNamespace) &&
 305                                 (
 306                                         //
 307                                         // A list of all the instructions (does not include top-level-elements)
 308                                         //
 309                                         name.Name == "apply-imports" ||
 310                                         name.Name == "apply-templates" ||
 311                                         name.Name == "call-template" ||
 312                                         name.Name == "choose" ||
 313                                         name.Name == "comment" ||
 314                                         name.Name == "copy" ||
 315                                         name.Name == "copy-of" ||
 316                                         name.Name == "element" ||
 317                                         name.Name == "fallback" ||
 318                                         name.Name == "for-each" ||
 319                                         name.Name == "message" ||
 320                                         name.Name == "number" ||
 321                                         name.Name == "processing-instruction" ||
 322                                         name.Name == "text" ||
 323                                         name.Name == "value-of" ||
 324                                         name.Name == "variable"
 325                                 )
 326                         );
 327                 }
 328         }
 329
 330         class XsltFormatNumber : XPathFunction
 331         {
 332                 Expression arg0, arg1, arg2;
 333                 XmlNamespaceManager nsm;
 334
 335                 public XsltFormatNumber (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 336                 {
 337                         if (args == null || args.Tail == null || (args.Tail.Tail != null && args.Tail.Tail.Tail != null))
 338                                 throw new XPathException ("format-number takes 2 or 3 args");
 339
 340                         arg0 = args.Arg;
 341                         arg1 = args.Tail.Arg;
 342                         if (args.Tail.Tail != null) {
 343                                 arg2= args.Tail.Tail.Arg;
 344                                 nsm = ctx.GetNsm ();
 345                         }
 346                 }
 347                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 348
 349                 public override object Evaluate (BaseIterator iter)
 350                 {
 351                         double d = arg0.EvaluateNumber (iter);
 352                         string s = arg1.EvaluateString (iter);
 353                         QName nm = QName.Empty;
 354
 355                         if (arg2 != null)
 356                                 nm = XslNameUtil.FromString (arg2.EvaluateString (iter), nsm);
 357
 358                         try {
 359                                 return (iter.NamespaceManager as XsltCompiledContext).Processor.CompiledStyle
 360                                 .LookupDecimalFormat (nm).FormatNumber (d, s);
 361                         } catch (ArgumentException ex) {
 362                                 throw new XsltException (ex.Message, ex, iter.Current);
 363                         }
 364                 }
 365         }
 366
 367         class XsltFunctionAvailable : XPathFunction
 368         {
 369                 Expression arg0;
 370                 XmlNamespaceManager nsm;
 371
 372                 public XsltFunctionAvailable (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 373                 {
 374                         if (args == null || args.Tail != null)
 375                                 throw new XPathException ("element-available takes 1 arg");
 376
 377                         arg0 = args.Arg;
 378                         nsm = ctx.GetNsm ();
 379                 }
 380
 381                 public override XPathResultType ReturnType { get { return XPathResultType.Boolean; }}
 382
 383                 public override object Evaluate (BaseIterator iter)
 384                 {
 385
 386                         string name = arg0.EvaluateString (iter);
 387                         int colon = name.IndexOf (':');
 388                         // extension function
 389                         if (colon > 0)
 390                                 return (iter.NamespaceManager as XsltCompiledContext).ResolveFunction (
 391                                         XslNameUtil.FromString (name, nsm),
 392                                         null) != null;
 393
 394                         return (
 395                                 //
 396                                 // XPath
 397                                 //
 398                                 name == "boolean" ||
 399                                 name == "ceiling" ||
 400                                 name == "concat" ||
 401                                 name == "contains" ||
 402                                 name == "count" ||
 403                                 name == "false" ||
 404                                 name == "floor" ||
 405                                 name == "id"||
 406                                 name == "lang" ||
 407                                 name == "last" ||
 408                                 name == "local-name" ||
 409                                 name == "name" ||
 410                                 name == "namespace-uri" ||
 411                                 name == "normalize-space" ||
 412                                 name == "not" ||
 413                                 name == "number" ||
 414                                 name == "position" ||
 415                                 name == "round" ||
 416                                 name == "starts-with" ||
 417                                 name == "string" ||
 418                                 name == "string-length" ||
 419                                 name == "substring" ||
 420                                 name == "substring-after" ||
 421                                 name == "substring-before" ||
 422                                 name == "sum" ||
 423                                 name == "translate" ||
 424                                 name == "true" ||
 425                                 // XSLT
 426                                 name == "document" ||
 427                                 name == "format-number" ||
 428                                 name == "function-available" ||
 429                                 name == "generate-id" ||
 430                                 name == "key" ||
 431                                 name == "current" ||
 432                                 name == "unparsed-entity-uri" ||
 433                                 name == "element-available" ||
 434                                 name == "system-property"
 435                         );
 436                 }
 437         }
 438
 439         class XsltGenerateId : XPathFunction
 440         {
 441                 Expression arg0;
 442                 public XsltGenerateId (FunctionArguments args) : base (args)
 443                 {
 444                         if (args != null) {
 445                                 if (args.Tail != null)
 446                                         throw new XPathException ("generate-id takes 1 or no args");
 447                                 arg0 = args.Arg;
 448                         }
 449                 }
 450
 451                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 452                 public override object Evaluate (BaseIterator iter)
 453                 {
 454                         XPathNavigator n;
 455                         if (arg0 != null) {
 456                                 XPathNodeIterator itr = arg0.EvaluateNodeSet (iter);
 457                                 if (itr.MoveNext ())
 458                                         n = itr.Current.Clone ();
 459                                 else
 460                                         return string.Empty; // empty nodeset == empty string
 461                         } else
 462                                 n = iter.Current.Clone ();
 463
 464                         StringBuilder sb = new StringBuilder ("Mono"); // Ensure begins with alpha
 465                         sb.Append (XmlConvert.EncodeLocalName (n.BaseURI));
 466                         sb.Replace ('_', 'm'); // remove underscores from EncodeLocalName
 467                         sb.Append (n.NodeType);
 468                         sb.Append ('m');
 469
 470                         do {
 471                                 sb.Append (IndexInParent (n));
 472                                 sb.Append ('m');
 473                         } while (n.MoveToParent ());
 474
 475                         return sb.ToString ();
 476                 }
 477
 478                 int IndexInParent (XPathNavigator nav)
 479                 {
 480                         int n = 0;
 481                         while (nav.MoveToPrevious ())
 482                                 n++;
 483
 484                         return n;
 485                 }
 486         }
 487
 488         class XsltKey : XPathFunction
 489         {
 490                 Expression arg0, arg1;
 491                 XmlNamespaceManager nsm;
 492                 XslKey key;
 493
 494                 public XsltKey (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 495                 {
 496                         if (args == null || args.Tail == null)
 497                                 throw new XPathException ("key takes 2 args");
 498                         arg0 = args.Arg;
 499                         arg1 = args.Tail.Arg;
 500                         nsm = ctx.GetNsm ();
 501                 }
 502                 public Expression KeyName { get { return arg0; } }
 503                 public Expression Field { get { return arg1; } }
 504                 public XmlNamespaceManager NamespaceManager { get { return nsm; } }
 505                 public override XPathResultType ReturnType { get { return XPathResultType.NodeSet; }}
 506
 507                 public override object Evaluate (BaseIterator iter)
 508                 {
 509                         QName name = XslNameUtil.FromString (arg0.EvaluateString (iter), nsm);
 510                         XsltCompiledContext ctx = iter.NamespaceManager as XsltCompiledContext;
 511                         if (key == null)
 512                                 key = ctx.Processor.CompiledStyle.Style.FindKey (name);
 513
 514                         ArrayList result = new ArrayList ();
 515                         object o = arg1.Evaluate (iter);
 516                         XPathNodeIterator it = o as XPathNodeIterator;
 517
 518                         if (it != null) {
 519                                 while (it.MoveNext())
 520                                         FindKeyMatch (ctx, it.Current.Value, result, iter.Current);
 521                         } else {
 522                                 FindKeyMatch (ctx, XPathFunctions.ToString (o), result, iter.Current);
 523                         }
 524
 525                         return new ListIterator (result, (iter.NamespaceManager as XsltCompiledContext), true);
 526                 }
 527
 528                 void FindKeyMatch (XsltCompiledContext xsltContext, string value, ArrayList result, XPathNavigator context)
 529                 {
 530                         XPathNavigator searchDoc = context.Clone ();
 531                         searchDoc.MoveToRoot ();
 532                         if (key != null) {
 533                                 XPathNodeIterator desc = searchDoc.SelectDescendants (XPathNodeType.All, true);
 534
 535                                 while (desc.MoveNext ()) {
 536                                         if (key.Matches (desc.Current, xsltContext, value))
 537                                                 AddResult (result, desc.Current);
 538
 539                                         if (desc.Current.MoveToFirstAttribute ()) {
 540                                                 do {
 541                                                         if (key.Matches (desc.Current, xsltContext, value))
 542                                                                 AddResult (result, desc.Current);
 543                                                 } while (desc.Current.MoveToNextAttribute ());
 544
 545                                                 desc.Current.MoveToParent ();
 546                                         }
 547                                 }
 548                         }
 549                 }
 550
 551                 void AddResult (ArrayList result, XPathNavigator nav)
 552                 {
 553                         for (int i = 0; i < result.Count; i++) {
 554                                 XmlNodeOrder docOrder = nav.ComparePosition (((XPathNavigator)result [i]));
 555                                 if (docOrder == XmlNodeOrder.Same)
 556                                         return;
 557
 558                                 if (docOrder == XmlNodeOrder.Before) {
 559                                         result.Insert(i, nav.Clone ());
 560                                         return;
 561                                 }
 562                         }
 563                         result.Add (nav.Clone ());
 564                 }
 565         }
 566
 567         class XsltSystemProperty : XPathFunction
 568         {
 569                 Expression arg0;
 570                 XmlNamespaceManager nsm;
 571
 572                 public XsltSystemProperty (FunctionArguments args, IStaticXsltContext ctx) : base (args)
 573                 {
 574                         if (args == null || args.Tail != null)
 575                                 throw new XPathException ("system-property takes 1 arg");
 576
 577                         arg0 = args.Arg;
 578                         nsm = ctx.GetNsm ();
 579                 }
 580
 581                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 582                 public override object Evaluate (BaseIterator iter)
 583                 {
 584                         QName name = XslNameUtil.FromString (arg0.EvaluateString (iter), nsm);
 585
 586                         if (name.Namespace == Compiler.XsltNamespace) {
 587                                 switch (name.Name) {
 588                                         case "version": return "1.0";
 589                                         case "vendor": return "Mono";
 590                                         case "vendor-url": return "http://www.go-mono.com/";
 591                                 }
 592                         }
 593
 594                         return "";
 595                 }
 596         }
 597
 598         class XsltUnparsedEntityUri : XPathFunction
 599         {
 600                 Expression arg0;
 601
 602                 public XsltUnparsedEntityUri (FunctionArguments args) : base (args)
 603                 {
 604                         if (args == null || args.Tail != null)
 605                                 throw new XPathException ("unparsed-entity-uri takes 1 arg");
 606
 607                         arg0 = args.Arg;
 608                 }
 609
 610                 public override XPathResultType ReturnType { get { return XPathResultType.String; }}
 611                 public override object Evaluate (BaseIterator iter)
 612                 {
 613                         IHasXmlNode xn = iter.Current as IHasXmlNode;
 614                         if (xn == null)
 615                                 return String.Empty;
 616                         XmlNode n = xn.GetNode ();
 617                         XmlDocumentType doctype = n.OwnerDocument.DocumentType;
 618                         if (doctype == null)
 619                                 return String.Empty;
 620                         XmlEntity ent = doctype.Entities.GetNamedItem (arg0.EvaluateString (iter)) as XmlEntity;
 621                         if (ent == null)
 622                                 return String.Empty;
 623                         else
 624                                 return ent.BaseURI;
 625                 }
 626         }
 627
 628         class MSXslNodeSet : XPathFunction
 629         {
 630                 Expression arg0;
 631
 632                 public MSXslNodeSet (FunctionArguments args) : base (args)
 633                 {
 634                         if (args == null || args.Tail != null)
 635                                 throw new XPathException ("element-available takes 1 arg");
 636
 637                         arg0 = args.Arg;
 638                 }
 639 \r
 640                 public override XPathResultType ReturnType {\r
 641                         get {\r
 642                                 return XPathResultType.NodeSet;\r
 643                         }\r
 644                 }\r
 645
 646                 public override object Evaluate (BaseIterator iter)\r
 647                 {\r
 648                         XsltCompiledContext ctx = iter.NamespaceManager as XsltCompiledContext;\r
 649                         XPathNavigator loc = iter.Current != null ? iter.Current.Clone () : null;\r
 650                         XPathNavigator nav = arg0.EvaluateAs (iter, XPathResultType.Navigator) as XPathNavigator;\r
 651                         if (nav == null) {\r
 652                                 if (loc != null)\r
 653                                         return new XsltException ("Cannot convert the XPath argument to a result tree fragment.", null, loc);\r
 654                                 else\r
 655                                         return new XsltException ("Cannot convert the XPath argument to a result tree fragment.", null);\r
 656                         }\r
 657                         ArrayList al = new ArrayList ();\r
 658                         al.Add (nav);\r
 659                         return new ListIterator (al, ctx, false);\r
 660                 }
 661         }
 662 }