mcs/mcs/context.cs

   1 //
   2 // context.cs: Various compiler contexts.
   3 //
   4 // Author:
   5 //   Marek Safar (marek.safar@gmail.com)
   6 //   Miguel de Icaza (miguel@ximian.com)
   7 //
   8 // Copyright 2001, 2002, 2003 Ximian, Inc.
   9 // Copyright 2004-2009 Novell, Inc.
  10 // Copyright 2011 Xamarin Inc.
  11 //
  12
  13 using System;
  14 using System.Collections.Generic;
  15 using System.IO;
  16 using System.Security.Cryptography;
  17 using System.Diagnostics;
  18
  19 namespace Mono.CSharp
  20 {
  21         public enum LookupMode
  22         {
  23                 Normal = 0,
  24                 Probing = 1,
  25                 IgnoreAccessibility = 2
  26         }
  27
  28         //
  29         // Implemented by elements which can act as independent contexts
  30         // during resolve phase. Used mostly for lookups.
  31         //
  32         public interface IMemberContext : IModuleContext
  33         {
  34                 //
  35                 // A scope type context, it can be inflated for generic types
  36                 //
  37                 TypeSpec CurrentType { get; }
  38
  39                 //
  40                 // A scope type parameters either VAR or MVAR
  41                 //
  42                 TypeParameters CurrentTypeParameters { get; }
  43
  44                 //
  45                 // A member definition of the context. For partial types definition use
  46                 // CurrentTypeDefinition.PartialContainer otherwise the context is local
  47                 //
  48                 // TODO: Obsolete it in this context, dynamic context cannot guarantee sensible value
  49                 //
  50                 MemberCore CurrentMemberDefinition { get; }
  51
  52                 bool IsObsolete { get; }
  53                 bool IsUnsafe { get; }
  54                 bool IsStatic { get; }
  55
  56                 string GetSignatureForError ();
  57
  58                 ExtensionMethodCandidates LookupExtensionMethod (string name, int arity);
  59                 FullNamedExpression LookupNamespaceOrType (string name, int arity, LookupMode mode, Location loc);
  60                 FullNamedExpression LookupNamespaceAlias (string name);
  61         }
  62
  63         public interface IModuleContext
  64         {
  65                 ModuleContainer Module { get; }
  66         }
  67
  68         //
  69         // Block or statement resolving context
  70         //
  71         public class BlockContext : ResolveContext
  72         {
  73                 readonly TypeSpec return_type;
  74
  75                 //
  76                 // Tracks the last offset used by VariableInfo
  77                 //
  78                 public int AssignmentInfoOffset;
  79
  80                 public BlockContext (IMemberContext mc, ExplicitBlock block, TypeSpec returnType)
  81                         : base (mc)
  82                 {
  83                         if (returnType == null)
  84                                 throw new ArgumentNullException ("returnType");
  85
  86                         this.return_type = returnType;
  87
  88                         // TODO: check for null value
  89                         CurrentBlock = block;
  90                 }
  91
  92                 public BlockContext (ResolveContext rc, ExplicitBlock block, TypeSpec returnType)
  93                         : this (rc.MemberContext, block, returnType)
  94                 {
  95                         if (rc.IsUnsafe)
  96                                 flags |= ResolveContext.Options.UnsafeScope;
  97
  98                         if (rc.HasSet (ResolveContext.Options.CheckedScope))
  99                                 flags |= ResolveContext.Options.CheckedScope;
 100
 101                         if (!rc.ConstantCheckState)
 102                                 flags &= ~Options.ConstantCheckState;
 103
 104                         if (rc.IsInProbingMode)
 105                                 flags |= ResolveContext.Options.ProbingMode;
 106
 107                         if (rc.HasSet (ResolveContext.Options.FieldInitializerScope))
 108                                 flags |= ResolveContext.Options.FieldInitializerScope;
 109
 110                         if (rc.HasSet (ResolveContext.Options.ExpressionTreeConversion))
 111                                 flags |= ResolveContext.Options.ExpressionTreeConversion;
 112
 113                         if (rc.HasSet (ResolveContext.Options.BaseInitializer))
 114                                 flags |= ResolveContext.Options.BaseInitializer;
 115                 }
 116
 117                 public ExceptionStatement CurrentTryBlock { get; set; }
 118
 119                 public LoopStatement EnclosingLoop { get; set; }
 120
 121                 public LoopStatement EnclosingLoopOrSwitch { get; set; }
 122
 123                 public Switch Switch { get; set; }
 124
 125                 public TypeSpec ReturnType {
 126                         get { return return_type; }
 127                 }
 128         }
 129
 130         //
 131         // Expression resolving context
 132         //
 133         public class ResolveContext : IMemberContext
 134         {
 135                 [Flags]
 136                 public enum Options
 137                 {
 138                         /// <summary>
 139                         ///   This flag tracks the `checked' state of the compilation,
 140                         ///   it controls whether we should generate code that does overflow
 141                         ///   checking, or if we generate code that ignores overflows.
 142                         ///
 143                         ///   The default setting comes from the command line option to generate
 144                         ///   checked or unchecked code plus any source code changes using the
 145                         ///   checked/unchecked statements or expressions.   Contrast this with
 146                         ///   the ConstantCheckState flag.
 147                         /// </summary>
 148                         CheckedScope = 1 << 0,
 149
 150                         /// <summary>
 151                         ///   The constant check state is always set to `true' and cant be changed
 152                         ///   from the command line.  The source code can change this setting with
 153                         ///   the `checked' and `unchecked' statements and expressions.
 154                         /// </summary>
 155                         ConstantCheckState = 1 << 1,
 156
 157                         AllCheckStateFlags = CheckedScope | ConstantCheckState,
 158
 159                         //
 160                         // unsafe { ... } scope
 161                         //
 162                         UnsafeScope = 1 << 2,
 163                         CatchScope = 1 << 3,
 164                         FinallyScope = 1 << 4,
 165                         FieldInitializerScope = 1 << 5,
 166                         CompoundAssignmentScope = 1 << 6,
 167                         FixedInitializerScope = 1 << 7,
 168                         BaseInitializer = 1 << 8,
 169
 170                         //
 171                         // Inside an enum definition, we do not resolve enumeration values
 172                         // to their enumerations, but rather to the underlying type/value
 173                         // This is so EnumVal + EnumValB can be evaluated.
 174                         //
 175                         // There is no "E operator + (E x, E y)", so during an enum evaluation
 176                         // we relax the rules
 177                         //
 178                         EnumScope = 1 << 9,
 179
 180                         ConstantScope = 1 << 10,
 181
 182                         ConstructorScope = 1 << 11,
 183
 184                         UsingInitializerScope = 1 << 12,
 185
 186                         LockScope = 1 << 13,
 187
 188                         TryScope = 1 << 14,
 189
 190                         TryWithCatchScope = 1 << 15,
 191
 192                         DontSetConditionalAccessReceiver = 1 << 16,
 193
 194                         NameOfScope = 1 << 17,
 195
 196                         ///
 197                         /// Indicates the current context is in probing mode, no errors are reported.
 198                         ///
 199                         ProbingMode = 1 << 22,
 200
 201                         //
 202                         // Return and ContextualReturn statements will set the ReturnType
 203                         // value based on the expression types of each return statement
 204                         // instead of the method return type which is initially null.
 205                         //
 206                         InferReturnType = 1 << 23,
 207
 208                         OmitDebuggingInfo = 1 << 24,
 209
 210                         ExpressionTreeConversion = 1 << 25,
 211
 212                         InvokeSpecialName = 1 << 26
 213                 }
 214
 215                 // utility helper for CheckExpr, UnCheckExpr, Checked and Unchecked statements
 216                 // it's public so that we can use a struct at the callsite
 217                 public struct FlagsHandle : IDisposable
 218                 {
 219                         readonly ResolveContext ec;
 220                         readonly Options invmask, oldval;
 221
 222                         public FlagsHandle (ResolveContext ec, Options flagsToSet)
 223                                 : this (ec, flagsToSet, flagsToSet)
 224                         {
 225                         }
 226
 227                         internal FlagsHandle (ResolveContext ec, Options mask, Options val)
 228                         {
 229                                 this.ec = ec;
 230                                 invmask = ~mask;
 231                                 oldval = ec.flags & mask;
 232                                 ec.flags = (ec.flags & invmask) | (val & mask);
 233
 234 //                              if ((mask & Options.ProbingMode) != 0)
 235 //                                      ec.Report.DisableReporting ();
 236                         }
 237
 238                         public void Dispose ()
 239                         {
 240 //                              if ((invmask & Options.ProbingMode) == 0)
 241 //                                      ec.Report.EnableReporting ();
 242
 243                                 ec.flags = (ec.flags & invmask) | oldval;
 244                         }
 245                 }
 246
 247                 protected Options flags;
 248
 249                 //
 250                 // Whether we are inside an anonymous method.
 251                 //
 252                 public AnonymousExpression CurrentAnonymousMethod;
 253
 254                 //
 255                 // Holds a varible used during collection or object initialization.
 256                 //
 257                 public Expression CurrentInitializerVariable;
 258
 259                 public Block CurrentBlock;
 260
 261                 public readonly IMemberContext MemberContext;
 262
 263                 public ResolveContext (IMemberContext mc)
 264                 {
 265                         if (mc == null)
 266                                 throw new ArgumentNullException ();
 267
 268                         MemberContext = mc;
 269
 270                         //
 271                         // The default setting comes from the command line option
 272                         //
 273                         if (mc.Module.Compiler.Settings.Checked)
 274                                 flags |= Options.CheckedScope;
 275
 276                         //
 277                         // The constant check state is always set to true
 278                         //
 279                         flags |= Options.ConstantCheckState;
 280                 }
 281
 282                 public ResolveContext (IMemberContext mc, Options options)
 283                         : this (mc)
 284                 {
 285                         flags |= options;
 286                 }
 287
 288                 #region Properties
 289
 290                 public BuiltinTypes BuiltinTypes {
 291                         get {
 292                                 return MemberContext.Module.Compiler.BuiltinTypes;
 293                         }
 294                 }
 295
 296                 public virtual ExplicitBlock ConstructorBlock {
 297                         get {
 298                                 return CurrentBlock.Explicit;
 299                         }
 300                 }
 301
 302                 //
 303                 // The current iterator
 304                 //
 305                 public Iterator CurrentIterator {
 306                         get { return CurrentAnonymousMethod as Iterator; }
 307                 }
 308
 309                 public TypeSpec CurrentType {
 310                         get { return MemberContext.CurrentType; }
 311                 }
 312
 313                 public TypeParameters CurrentTypeParameters {
 314                         get { return MemberContext.CurrentTypeParameters; }
 315                 }
 316
 317                 public MemberCore CurrentMemberDefinition {
 318                         get { return MemberContext.CurrentMemberDefinition; }
 319                 }
 320
 321                 public bool ConstantCheckState {
 322                         get { return (flags & Options.ConstantCheckState) != 0; }
 323                 }
 324
 325                 public bool IsInProbingMode {
 326                         get {
 327                                 return (flags & Options.ProbingMode) != 0;
 328                         }
 329                 }
 330
 331                 public bool IsObsolete {
 332                         get {
 333                                 // Disables obsolete checks when probing is on
 334                                 return MemberContext.IsObsolete;
 335                         }
 336                 }
 337
 338                 public bool IsStatic {
 339                         get {
 340                                 return MemberContext.IsStatic;
 341                         }
 342                 }
 343
 344                 public bool IsUnsafe {
 345                         get {
 346                                 return HasSet (Options.UnsafeScope) || MemberContext.IsUnsafe;
 347                         }
 348                 }
 349
 350                 public bool IsRuntimeBinder {
 351                         get {
 352                                 return Module.Compiler.IsRuntimeBinder;
 353                         }
 354                 }
 355
 356                 public bool IsVariableCapturingRequired {
 357                         get {
 358                                 return !IsInProbingMode;
 359                         }
 360                 }
 361
 362                 public ModuleContainer Module {
 363                         get {
 364                                 return MemberContext.Module;
 365                         }
 366                 }
 367
 368                 public Report Report {
 369                         get {
 370                                 return Module.Compiler.Report;
 371                         }
 372                 }
 373
 374                 #endregion
 375
 376                 public bool MustCaptureVariable (INamedBlockVariable local)
 377                 {
 378                         if (CurrentAnonymousMethod == null)
 379                                 return false;
 380
 381                         //
 382                         // Capture only if this or any of child blocks contain yield
 383                         // or it's a parameter
 384                         //
 385                         if (CurrentAnonymousMethod.IsIterator)
 386                                 return local.IsParameter || local.Block.Explicit.HasYield;
 387
 388                         //
 389                         // Capture only if this or any of child blocks contain await
 390                         // or it's a parameter or we need to access variable from
 391                         // different parameter block
 392                         //
 393                         if (CurrentAnonymousMethod is AsyncInitializer)
 394                                 return local.IsParameter || local.Block.Explicit.HasAwait || CurrentBlock.Explicit.HasAwait ||
 395                                         local.Block.ParametersBlock != CurrentBlock.ParametersBlock.Original;
 396
 397                         return local.Block.ParametersBlock != CurrentBlock.ParametersBlock.Original;
 398                 }
 399
 400                 public bool HasSet (Options options)
 401                 {
 402                         return (this.flags & options) == options;
 403                 }
 404
 405                 public bool HasAny (Options options)
 406                 {
 407                         return (this.flags & options) != 0;
 408                 }
 409
 410
 411                 // Temporarily set all the given flags to the given value.  Should be used in an 'using' statement
 412                 public FlagsHandle Set (Options options)
 413                 {
 414                         return new FlagsHandle (this, options);
 415                 }
 416
 417                 public FlagsHandle With (Options options, bool enable)
 418                 {
 419                         return new FlagsHandle (this, options, enable ? options : 0);
 420                 }
 421
 422                 #region IMemberContext Members
 423
 424                 public string GetSignatureForError ()
 425                 {
 426                         return MemberContext.GetSignatureForError ();
 427                 }
 428
 429                 public ExtensionMethodCandidates LookupExtensionMethod (string name, int arity)
 430                 {
 431                         return MemberContext.LookupExtensionMethod (name, arity);
 432                 }
 433
 434                 public FullNamedExpression LookupNamespaceOrType (string name, int arity, LookupMode mode, Location loc)
 435                 {
 436                         return MemberContext.LookupNamespaceOrType (name, arity, mode, loc);
 437                 }
 438
 439                 public FullNamedExpression LookupNamespaceAlias (string name)
 440                 {
 441                         return MemberContext.LookupNamespaceAlias (name);
 442                 }
 443
 444                 #endregion
 445         }
 446
 447         public class FlowAnalysisContext
 448         {
 449                 readonly CompilerContext ctx;
 450
 451                 public FlowAnalysisContext (CompilerContext ctx, ParametersBlock parametersBlock, int definiteAssignmentLength)
 452                 {
 453                         this.ctx = ctx;
 454                         this.ParametersBlock = parametersBlock;
 455
 456                         DefiniteAssignment = definiteAssignmentLength == 0 ?
 457                                 DefiniteAssignmentBitSet.Empty :
 458                                 new DefiniteAssignmentBitSet (definiteAssignmentLength);
 459                 }
 460
 461                 public DefiniteAssignmentBitSet DefiniteAssignment { get; set; }
 462
 463                 public DefiniteAssignmentBitSet DefiniteAssignmentOnTrue { get; set; }
 464
 465                 public DefiniteAssignmentBitSet DefiniteAssignmentOnFalse { get; set; }
 466
 467                 Dictionary<Statement, List<DefiniteAssignmentBitSet>> LabelStack { get; set; }
 468
 469                 public ParametersBlock ParametersBlock { get; set; }
 470
 471                 public Report Report {
 472                         get {
 473                                 return ctx.Report;
 474                         }
 475                 }
 476
 477                 public DefiniteAssignmentBitSet SwitchInitialDefinitiveAssignment { get; set; }
 478
 479                 public TryFinally TryFinally { get; set; }
 480
 481                 public bool UnreachableReported { get; set; }
 482
 483                 public bool AddReachedLabel (Statement label)
 484                 {
 485                         List<DefiniteAssignmentBitSet> das;
 486                         if (LabelStack == null) {
 487                                 LabelStack = new Dictionary<Statement, List<DefiniteAssignmentBitSet>> ();
 488                                 das = null;
 489                         } else {
 490                                 LabelStack.TryGetValue (label, out das);
 491                         }
 492
 493                         if (das == null) {
 494                                 das = new List<DefiniteAssignmentBitSet> ();
 495                                 das.Add (new DefiniteAssignmentBitSet (DefiniteAssignment));
 496                                 LabelStack.Add (label, das);
 497                                 return false;
 498                         }
 499
 500                         foreach (var existing in das) {
 501                                 if (DefiniteAssignmentBitSet.IsIncluded (existing, DefiniteAssignment))
 502                                         return true;
 503                         }
 504
 505                         if (DefiniteAssignment == DefiniteAssignmentBitSet.Empty)
 506                                 das.Add (DefiniteAssignment);
 507                         else
 508                                 das.Add (new DefiniteAssignmentBitSet (DefiniteAssignment));
 509
 510                         return false;
 511                 }
 512
 513                 public DefiniteAssignmentBitSet BranchDefiniteAssignment ()
 514                 {
 515                         return BranchDefiniteAssignment (DefiniteAssignment);
 516                 }
 517
 518                 public DefiniteAssignmentBitSet BranchDefiniteAssignment (DefiniteAssignmentBitSet da)
 519                 {
 520                         if (da != DefiniteAssignmentBitSet.Empty) {
 521                                 DefiniteAssignment = new DefiniteAssignmentBitSet (da);
 522                         }
 523
 524                         return da;
 525                 }
 526
 527                 public bool IsDefinitelyAssigned (VariableInfo variable)
 528                 {
 529                         return variable.IsAssigned (DefiniteAssignment);
 530                 }
 531
 532                 public bool IsStructFieldDefinitelyAssigned (VariableInfo variable, string name)
 533                 {
 534                         return variable.IsStructFieldAssigned (DefiniteAssignment, name);
 535                 }
 536
 537                 public void SetVariableAssigned (VariableInfo variable, bool generatedAssignment = false)
 538                 {
 539                         variable.SetAssigned (DefiniteAssignment, generatedAssignment);
 540                 }
 541
 542                 public void SetStructFieldAssigned (VariableInfo variable, string name)
 543                 {
 544                         variable.SetStructFieldAssigned (DefiniteAssignment, name);
 545                 }
 546         }
 547
 548
 549         //
 550         // This class is used during the Statement.Clone operation
 551         // to remap objects that have been cloned.
 552         //
 553         // Since blocks are cloned by Block.Clone, we need a way for
 554         // expressions that must reference the block to be cloned
 555         // pointing to the new cloned block.
 556         //
 557         public class CloneContext
 558         {
 559                 Dictionary<Block, Block> block_map = new Dictionary<Block, Block> ();
 560
 561                 public void AddBlockMap (Block from, Block to)
 562                 {
 563                         block_map.Add (from, to);
 564                 }
 565
 566                 public Block LookupBlock (Block from)
 567                 {
 568                         Block result;
 569                         if (!block_map.TryGetValue (from, out result)) {
 570                                 result = (Block) from.Clone (this);
 571                         }
 572
 573                         return result;
 574                 }
 575
 576                 ///
 577                 /// Remaps block to cloned copy if one exists.
 578                 ///
 579                 public Block RemapBlockCopy (Block from)
 580                 {
 581                         Block mapped_to;
 582                         if (!block_map.TryGetValue (from, out mapped_to))
 583                                 return from;
 584
 585                         return mapped_to;
 586                 }
 587         }
 588
 589         //
 590         // Main compiler context
 591         //
 592         public class CompilerContext
 593         {
 594                 static readonly TimeReporter DisabledTimeReporter = new TimeReporter (false);
 595
 596                 readonly Report report;
 597                 readonly BuiltinTypes builtin_types;
 598                 readonly CompilerSettings settings;
 599
 600                 Dictionary<string, SourceFile> all_source_files;
 601
 602                 public CompilerContext (CompilerSettings settings, ReportPrinter reportPrinter)
 603                 {
 604                         this.settings = settings;
 605                         this.report = new Report (this, reportPrinter);
 606                         this.builtin_types = new BuiltinTypes ();
 607                         this.TimeReporter = DisabledTimeReporter;
 608                 }
 609
 610                 #region Properties
 611
 612                 public BuiltinTypes BuiltinTypes {
 613                         get {
 614                                 return builtin_types;
 615                         }
 616                 }
 617
 618                 // Used for special handling of runtime dynamic context mostly
 619                 // by error reporting but also by member accessibility checks
 620                 public bool IsRuntimeBinder {
 621                         get; set;
 622                 }
 623
 624                 public Report Report {
 625                         get {
 626                                 return report;
 627                         }
 628                 }
 629
 630                 public CompilerSettings Settings {
 631                         get {
 632                                 return settings;
 633                         }
 634                 }
 635
 636                 public List<SourceFile> SourceFiles {
 637                         get {
 638                                 return settings.SourceFiles;
 639                         }
 640                 }
 641
 642                 internal TimeReporter TimeReporter {
 643                         get; set;
 644                 }
 645
 646                 #endregion
 647
 648                 //
 649                 // This is used when we encounter a #line preprocessing directive during parsing
 650                 // to register additional source file names
 651                 //
 652                 public SourceFile LookupFile (CompilationSourceFile comp_unit, string name)
 653                 {
 654                         if (all_source_files == null) {
 655                                 all_source_files = new Dictionary<string, SourceFile> ();
 656                                 foreach (var source in SourceFiles)
 657                                         all_source_files[source.FullPathName] = source;
 658                         }
 659
 660                         string path;
 661                         if (!Path.IsPathRooted (name)) {
 662                                 var loc = comp_unit.SourceFile;
 663                                 string root = Path.GetDirectoryName (loc.FullPathName);
 664                                 path = Path.GetFullPath (Path.Combine (root, name));
 665                                 var dir = Path.GetDirectoryName (loc.Name);
 666                                 if (!string.IsNullOrEmpty (dir))
 667                                         name = Path.Combine (dir, name);
 668                         } else
 669                                 path = name;
 670
 671                         SourceFile retval;
 672                         if (all_source_files.TryGetValue (path, out retval))
 673                                 return retval;
 674
 675                         retval = new SourceFile (name, path, all_source_files.Count + 1);
 676                         Location.AddFile (retval);
 677                         all_source_files.Add (path, retval);
 678                         return retval;
 679                 }
 680         }
 681
 682         //
 683         // Generic code emitter context
 684         //
 685         public class BuilderContext
 686         {
 687                 [Flags]
 688                 public enum Options
 689                 {
 690                         /// <summary>
 691                         ///   This flag tracks the `checked' state of the compilation,
 692                         ///   it controls whether we should generate code that does overflow
 693                         ///   checking, or if we generate code that ignores overflows.
 694                         ///
 695                         ///   The default setting comes from the command line option to generate
 696                         ///   checked or unchecked code plus any source code changes using the
 697                         ///   checked/unchecked statements or expressions.   Contrast this with
 698                         ///   the ConstantCheckState flag.
 699                         /// </summary>
 700                         CheckedScope = 1 << 0,
 701
 702                         AccurateDebugInfo = 1 << 1,
 703
 704                         OmitDebugInfo = 1 << 2,
 705
 706                         ConstructorScope = 1 << 3,
 707
 708                         AsyncBody = 1 << 4,
 709                 }
 710
 711                 // utility helper for CheckExpr, UnCheckExpr, Checked and Unchecked statements
 712                 // it's public so that we can use a struct at the callsite
 713                 public struct FlagsHandle : IDisposable
 714                 {
 715                         readonly BuilderContext ec;
 716                         readonly Options invmask, oldval;
 717
 718                         public FlagsHandle (BuilderContext ec, Options flagsToSet)
 719                                 : this (ec, flagsToSet, flagsToSet)
 720                         {
 721                         }
 722
 723                         internal FlagsHandle (BuilderContext ec, Options mask, Options val)
 724                         {
 725                                 this.ec = ec;
 726                                 invmask = ~mask;
 727                                 oldval = ec.flags & mask;
 728                                 ec.flags = (ec.flags & invmask) | (val & mask);
 729                         }
 730
 731                         public void Dispose ()
 732                         {
 733                                 ec.flags = (ec.flags & invmask) | oldval;
 734                         }
 735                 }
 736
 737                 protected Options flags;
 738
 739                 public bool HasSet (Options options)
 740                 {
 741                         return (this.flags & options) == options;
 742                 }
 743
 744                 // Temporarily set all the given flags to the given value.  Should be used in an 'using' statement
 745                 public FlagsHandle With (Options options, bool enable)
 746                 {
 747                         return new FlagsHandle (this, options, enable ? options : 0);
 748                 }
 749         }
 750
 751         //
 752         // Parser session objects. We could recreate all these objects for each parser
 753         // instance but the best parser performance the session object can be reused
 754         //
 755         public class ParserSession
 756         {
 757                 MD5 md5;
 758
 759                 public readonly char[] StreamReaderBuffer = new char[SeekableStreamReader.DefaultReadAheadSize * 2];
 760                 public readonly Dictionary<char[], string>[] Identifiers = new Dictionary<char[], string>[Tokenizer.MaxIdentifierLength + 1];
 761                 public readonly List<Parameter> ParametersStack = new List<Parameter> (4);
 762                 public readonly char[] IDBuilder = new char[Tokenizer.MaxIdentifierLength];
 763                 public readonly char[] NumberBuilder = new char[Tokenizer.MaxNumberLength];
 764
 765                 public LocationsBag LocationsBag { get; set; }
 766                 public bool UseJayGlobalArrays { get; set; }
 767                 public LocatedToken[] LocatedTokens { get; set; }
 768
 769                 public MD5 GetChecksumAlgorithm ()
 770                 {
 771                         return md5 ?? (md5 = MD5.Create ());
 772                 }
 773         }
 774 }