mcs/mcs/flowanalysis.cs

   1 //
   2 // flowanalyis.cs: The control flow analysis code
   3 //
   4 // Author:
   5 //   Martin Baulig (martin@ximian.com)
   6 //   Raja R Harinath (rharinath@novell.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 using System;
  12 using System.Text;
  13 using System.Collections;
  14 using System.Reflection;
  15 using System.Reflection.Emit;
  16 using System.Diagnostics;
  17
  18 namespace Mono.CSharp
  19 {
  20         // <summary>
  21         //   A new instance of this class is created every time a new block is resolved
  22         //   and if there's branching in the block's control flow.
  23         // </summary>
  24         public abstract class FlowBranching
  25         {
  26                 // <summary>
  27                 //   The type of a FlowBranching.
  28                 // </summary>
  29                 public enum BranchingType : byte {
  30                         // Normal (conditional or toplevel) block.
  31                         Block,
  32
  33                         // Conditional.
  34                         Conditional,
  35
  36                         // A loop block.
  37                         Loop,
  38
  39                         // The statement embedded inside a loop
  40                         Embedded,
  41
  42                         // part of a block headed by a jump target
  43                         Labeled,
  44
  45                         // Try/Catch block.
  46                         Exception,
  47
  48                         // Switch block.
  49                         Switch,
  50
  51                         // Switch section.
  52                         SwitchSection,
  53
  54                         // The toplevel block of a function
  55                         Toplevel
  56                 }
  57
  58                 // <summary>
  59                 //   The type of one sibling of a branching.
  60                 // </summary>
  61                 public enum SiblingType : byte {
  62                         Block,
  63                         Conditional,
  64                         SwitchSection,
  65                         Try,
  66                         Catch,
  67                         Finally
  68                 }
  69
  70                 public static FlowBranching CreateBranching (FlowBranching parent, BranchingType type, Block block, Location loc)
  71                 {
  72                         switch (type) {
  73                         case BranchingType.Exception:
  74                         case BranchingType.Labeled:
  75                         case BranchingType.Toplevel:
  76                                 throw new InvalidOperationException ();
  77
  78                         case BranchingType.Switch:
  79                                 return new FlowBranchingBreakable (parent, type, SiblingType.SwitchSection, block, loc);
  80
  81                         case BranchingType.SwitchSection:
  82                                 return new FlowBranchingBlock (parent, type, SiblingType.Block, block, loc);
  83
  84                         case BranchingType.Block:
  85                                 return new FlowBranchingBlock (parent, type, SiblingType.Block, block, loc);
  86
  87                         case BranchingType.Loop:
  88                                 return new FlowBranchingBreakable (parent, type, SiblingType.Conditional, block, loc);
  89
  90                         case BranchingType.Embedded:
  91                                 return new FlowBranchingContinuable (parent, type, SiblingType.Conditional, block, loc);
  92
  93                         default:
  94                                 return new FlowBranchingBlock (parent, type, SiblingType.Conditional, block, loc);
  95                         }
  96                 }
  97
  98                 // <summary>
  99                 //   The type of this flow branching.
 100                 // </summary>
 101                 public readonly BranchingType Type;
 102
 103                 // <summary>
 104                 //   The block this branching is contained in.  This may be null if it's not
 105                 //   a top-level block and it doesn't declare any local variables.
 106                 // </summary>
 107                 public readonly Block Block;
 108
 109                 // <summary>
 110                 //   The parent of this branching or null if this is the top-block.
 111                 // </summary>
 112                 public readonly FlowBranching Parent;
 113
 114                 // <summary>
 115                 //   Start-Location of this flow branching.
 116                 // </summary>
 117                 public readonly Location Location;
 118
 119                 static int next_id = 0;
 120                 int id;
 121
 122                 // <summary>
 123                 //   The vector contains a BitArray with information about which local variables
 124                 //   and parameters are already initialized at the current code position.
 125                 // </summary>
 126                 public class UsageVector {
 127                         // <summary>
 128                         //   The type of this branching.
 129                         // </summary>
 130                         public readonly SiblingType Type;
 131
 132                         // <summary>
 133                         //   Start location of this branching.
 134                         // </summary>
 135                         public Location Location;
 136
 137                         // <summary>
 138                         //   This is only valid for SwitchSection, Try, Catch and Finally.
 139                         // </summary>
 140                         public readonly Block Block;
 141
 142                         // <summary>
 143                         //   The number of locals in this block.
 144                         // </summary>
 145                         public readonly int CountLocals;
 146
 147                         // <summary>
 148                         //   If not null, then we inherit our state from this vector and do a
 149                         //   copy-on-write.  If null, then we're the first sibling in a top-level
 150                         //   block and inherit from the empty vector.
 151                         // </summary>
 152                         public readonly UsageVector InheritsFrom;
 153
 154                         // <summary>
 155                         //   This is used to construct a list of UsageVector's.
 156                         // </summary>
 157                         public UsageVector Next;
 158
 159                         //
 160                         // Private.
 161                         //
 162                         MyBitVector locals;
 163                         bool is_unreachable;
 164
 165                         static int next_id = 0;
 166                         int id;
 167
 168                         //
 169                         // Normally, you should not use any of these constructors.
 170                         //
 171                         public UsageVector (SiblingType type, UsageVector parent, Block block, Location loc, int num_locals)
 172                         {
 173                                 this.Type = type;
 174                                 this.Block = block;
 175                                 this.Location = loc;
 176                                 this.InheritsFrom = parent;
 177                                 this.CountLocals = num_locals;
 178
 179                                 locals = num_locals == 0
 180                                         ? MyBitVector.Empty
 181                                         : new MyBitVector (parent == null ? MyBitVector.Empty : parent.locals, num_locals);
 182
 183                                 if (parent != null)
 184                                         is_unreachable = parent.is_unreachable;
 185
 186                                 id = ++next_id;
 187
 188                         }
 189
 190                         public UsageVector (SiblingType type, UsageVector parent, Block block, Location loc)
 191                                 : this (type, parent, block, loc, parent.CountLocals)
 192                         { }
 193
 194                         private UsageVector (MyBitVector locals, bool is_unreachable, Block block, Location loc)
 195                         {
 196                                 this.Type = SiblingType.Block;
 197                                 this.Location = loc;
 198                                 this.Block = block;
 199
 200                                 this.is_unreachable = is_unreachable;
 201
 202                                 this.locals = locals;
 203
 204                                 id = ++next_id;
 205
 206                         }
 207
 208                         // <summary>
 209                         //   This does a deep copy of the usage vector.
 210                         // </summary>
 211                         public UsageVector Clone ()
 212                         {
 213                                 UsageVector retval = new UsageVector (Type, null, Block, Location, CountLocals);
 214
 215                                 retval.locals = locals.Clone ();
 216                                 retval.is_unreachable = is_unreachable;
 217
 218                                 return retval;
 219                         }
 220
 221                         public bool IsAssigned (VariableInfo var, bool ignoreReachability)
 222                         {
 223                                 if (!ignoreReachability && !var.IsParameter && IsUnreachable)
 224                                         return true;
 225
 226                                 return var.IsAssigned (locals);
 227                         }
 228
 229                         public void SetAssigned (VariableInfo var)
 230                         {
 231                                 if (!var.IsParameter && IsUnreachable)
 232                                         return;
 233
 234                                 var.SetAssigned (locals);
 235                         }
 236
 237                         public bool IsFieldAssigned (VariableInfo var, string name)
 238                         {
 239                                 if (!var.IsParameter && IsUnreachable)
 240                                         return true;
 241
 242                                 return var.IsFieldAssigned (locals, name);
 243                         }
 244
 245                         public void SetFieldAssigned (VariableInfo var, string name)
 246                         {
 247                                 if (!var.IsParameter && IsUnreachable)
 248                                         return;
 249
 250                                 var.SetFieldAssigned (locals, name);
 251                         }
 252
 253                         public bool IsUnreachable {
 254                                 get { return is_unreachable; }
 255                         }
 256
 257                         public void ResetBarrier ()
 258                         {
 259                                 is_unreachable = false;
 260                         }
 261
 262                         public void Goto ()
 263                         {
 264                                 is_unreachable = true;
 265                         }
 266
 267                         public static UsageVector MergeSiblings (UsageVector sibling_list, Location loc)
 268                         {
 269                                 if (sibling_list.Next == null)
 270                                         return sibling_list;
 271
 272                                 MyBitVector locals = null;
 273                                 bool is_unreachable = sibling_list.is_unreachable;
 274
 275                                 if (!sibling_list.IsUnreachable)
 276                                         locals &= sibling_list.locals;
 277
 278                                 for (UsageVector child = sibling_list.Next; child != null; child = child.Next) {
 279                                         is_unreachable &= child.is_unreachable;
 280
 281                                         if (!child.IsUnreachable)
 282                                                 locals &= child.locals;
 283                                 }
 284
 285                                 return new UsageVector (locals, is_unreachable, null, loc);
 286                         }
 287
 288                         // <summary>
 289                         //   Merges a child branching.
 290                         // </summary>
 291                         public UsageVector MergeChild (UsageVector child, bool overwrite)
 292                         {
 293                                 Report.Debug (2, "    MERGING CHILD EFFECTS", this, child, Type);
 294
 295                                 bool new_isunr = child.is_unreachable;
 296
 297                                 //
 298                                 // We've now either reached the point after the branching or we will
 299                                 // never get there since we always return or always throw an exception.
 300                                 //
 301                                 // If we can reach the point after the branching, mark all locals and
 302                                 // parameters as initialized which have been initialized in all branches
 303                                 // we need to look at (see above).
 304                                 //
 305
 306                                 if ((Type == SiblingType.SwitchSection) && !new_isunr) {
 307                                         Report.Error (163, Location,
 308                                                       "Control cannot fall through from one " +
 309                                                       "case label to another");
 310                                         return child;
 311                                 }
 312
 313                                 locals |= child.locals;
 314
 315                                 if (overwrite)
 316                                         is_unreachable = new_isunr;
 317                                 else
 318                                         is_unreachable |= new_isunr;
 319
 320                                 return child;
 321                         }
 322
 323                         public void MergeOrigins (UsageVector o_vectors)
 324                         {
 325                                 Report.Debug (1, "  MERGING BREAK ORIGINS", this);
 326
 327                                 if (o_vectors == null)
 328                                         return;
 329
 330                                 if (IsUnreachable && locals != null)
 331                                         locals.SetAll (true);
 332
 333                                 for (UsageVector vector = o_vectors; vector != null; vector = vector.Next) {
 334                                         Report.Debug (1, "    MERGING BREAK ORIGIN", vector);
 335                                         if (vector.IsUnreachable)
 336                                                 continue;
 337                                         locals &= vector.locals;
 338                                         is_unreachable &= vector.is_unreachable;
 339                                 }
 340
 341                                 Report.Debug (1, "  MERGING BREAK ORIGINS DONE", this);
 342                         }
 343
 344                         //
 345                         // Debugging stuff.
 346                         //
 347
 348                         public override string ToString ()
 349                         {
 350                                 return String.Format ("Vector ({0},{1},{2}-{3})", Type, id, is_unreachable, locals);
 351                         }
 352                 }
 353
 354                 // <summary>
 355                 //   Creates a new flow branching which is contained in `parent'.
 356                 //   You should only pass non-null for the `block' argument if this block
 357                 //   introduces any new variables - in this case, we need to create a new
 358                 //   usage vector with a different size than our parent's one.
 359                 // </summary>
 360                 protected FlowBranching (FlowBranching parent, BranchingType type, SiblingType stype,
 361                                          Block block, Location loc)
 362                 {
 363                         Parent = parent;
 364                         Block = block;
 365                         Location = loc;
 366                         Type = type;
 367                         id = ++next_id;
 368
 369                         UsageVector vector;
 370                         if (Block != null) {
 371                                 UsageVector parent_vector = parent != null ? parent.CurrentUsageVector : null;
 372                                 vector = new UsageVector (stype, parent_vector, Block, loc, Block.AssignableSlots);
 373                         } else {
 374                                 vector = new UsageVector (stype, Parent.CurrentUsageVector, null, loc);
 375                         }
 376
 377                         AddSibling (vector);
 378                 }
 379
 380                 public abstract UsageVector CurrentUsageVector {
 381                         get;
 382                 }
 383
 384                 // <summary>
 385                 //   Creates a sibling of the current usage vector.
 386                 // </summary>
 387                 public virtual void CreateSibling (Block block, SiblingType type)
 388                 {
 389                         UsageVector vector = new UsageVector (
 390                                 type, Parent.CurrentUsageVector, block, Location);
 391                         AddSibling (vector);
 392
 393                         Report.Debug (1, "  CREATED SIBLING", CurrentUsageVector);
 394                 }
 395
 396                 public void CreateSibling ()
 397                 {
 398                         CreateSibling (null, SiblingType.Conditional);
 399                 }
 400
 401                 protected abstract void AddSibling (UsageVector uv);
 402
 403                 protected abstract UsageVector Merge ();
 404
 405                 // <summary>
 406                 //   Merge a child branching.
 407                 // </summary>
 408                 public UsageVector MergeChild (FlowBranching child)
 409                 {
 410                         bool overwrite = false;
 411
 412                         switch (child.Type) {
 413                         case BranchingType.Labeled:
 414                                 overwrite = true;
 415                                 break;
 416                         case BranchingType.Block:
 417                                 if (child.Block != null && child.Block != child.Block.Explicit)
 418                                         overwrite = true;
 419                                 break;
 420                         }
 421
 422                         Report.Debug (2, "  MERGING CHILD", this, child);
 423                         UsageVector result = CurrentUsageVector.MergeChild (child.Merge (), overwrite);
 424                         Report.Debug (2, "  MERGING CHILD DONE", this, result);
 425                         return result;
 426                 }
 427
 428                 public virtual bool InTryWithCatch ()
 429                 {
 430                         return Parent.InTryWithCatch ();
 431                 }
 432
 433                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 434                 public virtual bool AddBreakOrigin (UsageVector vector, Location loc)
 435                 {
 436                         return Parent.AddBreakOrigin (vector, loc);
 437                 }
 438
 439                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 440                 public virtual bool AddContinueOrigin (UsageVector vector, Location loc)
 441                 {
 442                         return Parent.AddContinueOrigin (vector, loc);
 443                 }
 444
 445                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 446                 public virtual bool AddReturnOrigin (UsageVector vector, Location loc)
 447                 {
 448                         return Parent.AddReturnOrigin (vector, loc);
 449                 }
 450
 451                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 452                 public virtual bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 453                 {
 454                         return Parent.AddGotoOrigin (vector, goto_stmt);
 455                 }
 456
 457                 public virtual void StealFinallyClauses (ref ArrayList list)
 458                 {
 459                         Parent.StealFinallyClauses (ref list);
 460                 }
 461
 462                 public bool IsAssigned (VariableInfo vi)
 463                 {
 464                         return CurrentUsageVector.IsAssigned (vi, false);
 465                 }
 466
 467                 public bool IsFieldAssigned (VariableInfo vi, string field_name)
 468                 {
 469                         return CurrentUsageVector.IsAssigned (vi, false) || CurrentUsageVector.IsFieldAssigned (vi, field_name);
 470                 }
 471
 472                 public void SetAssigned (VariableInfo vi)
 473                 {
 474                         CurrentUsageVector.SetAssigned (vi);
 475                 }
 476
 477                 public void SetFieldAssigned (VariableInfo vi, string name)
 478                 {
 479                         CurrentUsageVector.SetFieldAssigned (vi, name);
 480                 }
 481
 482                 public override string ToString ()
 483                 {
 484                         StringBuilder sb = new StringBuilder ();
 485                         sb.Append (GetType ());
 486                         sb.Append (" (");
 487
 488                         sb.Append (id);
 489                         sb.Append (",");
 490                         sb.Append (Type);
 491                         if (Block != null) {
 492                                 sb.Append (" - ");
 493                                 sb.Append (Block.ID);
 494                                 sb.Append (" - ");
 495                                 sb.Append (Block.StartLocation);
 496                         }
 497                         sb.Append (" - ");
 498                         // sb.Append (Siblings.Length);
 499                         // sb.Append (" - ");
 500                         sb.Append (CurrentUsageVector);
 501                         sb.Append (")");
 502                         return sb.ToString ();
 503                 }
 504
 505                 public string Name {
 506                         get { return String.Format ("{0} ({1}:{2}:{3})", GetType (), id, Type, Location); }
 507                 }
 508         }
 509
 510         public class FlowBranchingBlock : FlowBranching
 511         {
 512                 UsageVector sibling_list = null;
 513
 514                 public FlowBranchingBlock (FlowBranching parent, BranchingType type,
 515                                            SiblingType stype, Block block, Location loc)
 516                         : base (parent, type, stype, block, loc)
 517                 { }
 518
 519                 public override UsageVector CurrentUsageVector {
 520                         get { return sibling_list; }
 521                 }
 522
 523                 protected override void AddSibling (UsageVector sibling)
 524                 {
 525                         sibling.Next = sibling_list;
 526                         sibling_list = sibling;
 527                 }
 528
 529                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 530                 {
 531                         LabeledStatement stmt = Block == null ? null : Block.LookupLabel (goto_stmt.Target);
 532                         if (stmt == null)
 533                                 return Parent.AddGotoOrigin (vector, goto_stmt);
 534
 535                         // forward jump
 536                         goto_stmt.SetResolvedTarget (stmt);
 537                         stmt.AddUsageVector (vector);
 538                         return false;
 539                 }
 540
 541                 public static void Error_UnknownLabel (Location loc, string label)
 542                 {
 543                         Report.Error(159, loc, "The label `{0}:' could not be found within the scope of the goto statement",
 544                                 label);
 545                 }
 546
 547                 protected override UsageVector Merge ()
 548                 {
 549                         Report.Debug (2, "  MERGING SIBLINGS", Name);
 550                         UsageVector vector = UsageVector.MergeSiblings (sibling_list, Location);
 551                         Report.Debug (2, "  MERGING SIBLINGS DONE", Name, vector);
 552                         return vector;
 553                 }
 554         }
 555
 556         public class FlowBranchingBreakable : FlowBranchingBlock
 557         {
 558                 UsageVector break_origins;
 559
 560                 public FlowBranchingBreakable (FlowBranching parent, BranchingType type, SiblingType stype, Block block, Location loc)
 561                         : base (parent, type, stype, block, loc)
 562                 { }
 563
 564                 public override bool AddBreakOrigin (UsageVector vector, Location loc)
 565                 {
 566                         vector = vector.Clone ();
 567                         vector.Next = break_origins;
 568                         break_origins = vector;
 569                         return false;
 570                 }
 571
 572                 protected override UsageVector Merge ()
 573                 {
 574                         UsageVector vector = base.Merge ();
 575                         vector.MergeOrigins (break_origins);
 576                         return vector;
 577                 }
 578         }
 579
 580         public class FlowBranchingContinuable : FlowBranchingBlock
 581         {
 582                 UsageVector continue_origins;
 583
 584                 public FlowBranchingContinuable (FlowBranching parent, BranchingType type, SiblingType stype, Block block, Location loc)
 585                         : base (parent, type, stype, block, loc)
 586                 { }
 587
 588                 public override bool AddContinueOrigin (UsageVector vector, Location loc)
 589                 {
 590                         vector = vector.Clone ();
 591                         vector.Next = continue_origins;
 592                         continue_origins = vector;
 593                         return false;
 594                 }
 595
 596                 protected override UsageVector Merge ()
 597                 {
 598                         UsageVector vector = base.Merge ();
 599                         vector.MergeOrigins (continue_origins);
 600                         return vector;
 601                 }
 602         }
 603
 604         public class FlowBranchingLabeled : FlowBranchingBlock
 605         {
 606                 LabeledStatement stmt;
 607                 UsageVector actual;
 608
 609                 public FlowBranchingLabeled (FlowBranching parent, LabeledStatement stmt)
 610                         : base (parent, BranchingType.Labeled, SiblingType.Conditional, null, stmt.loc)
 611                 {
 612                         this.stmt = stmt;
 613                         CurrentUsageVector.MergeOrigins (stmt.JumpOrigins);
 614                         actual = CurrentUsageVector.Clone ();
 615
 616                         // stand-in for backward jumps
 617                         CurrentUsageVector.ResetBarrier ();
 618                 }
 619
 620                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 621                 {
 622                         if (goto_stmt.Target != stmt.Name)
 623                                 return Parent.AddGotoOrigin (vector, goto_stmt);
 624
 625                         // backward jump
 626                         goto_stmt.SetResolvedTarget (stmt);
 627                         actual.MergeOrigins (vector.Clone ());
 628
 629                         return false;
 630                 }
 631
 632                 protected override UsageVector Merge ()
 633                 {
 634                         UsageVector vector = base.Merge ();
 635
 636                         if (actual.IsUnreachable)
 637                                 Report.Warning (162, 2, stmt.loc, "Unreachable code detected");
 638
 639                         actual.MergeChild (vector, false);
 640                         return actual;
 641                 }
 642         }
 643
 644         public class FlowBranchingToplevel : FlowBranchingBlock
 645         {
 646                 UsageVector return_origins;
 647
 648                 public FlowBranchingToplevel (FlowBranching parent, ToplevelBlock stmt)
 649                         : base (parent, BranchingType.Toplevel, SiblingType.Conditional, stmt, stmt.loc)
 650                 {
 651                 }
 652
 653                 public override bool InTryWithCatch ()
 654                 {
 655                         return false;
 656                 }
 657
 658                 public override bool AddBreakOrigin (UsageVector vector, Location loc)
 659                 {
 660                         Report.Error (139, loc, "No enclosing loop out of which to break or continue");
 661                         return false;
 662                 }
 663
 664                 public override bool AddContinueOrigin (UsageVector vector, Location loc)
 665                 {
 666                         Report.Error (139, loc, "No enclosing loop out of which to break or continue");
 667                         return false;
 668                 }
 669
 670                 public override bool AddReturnOrigin (UsageVector vector, Location loc)
 671                 {
 672                         vector = vector.Clone ();
 673                         vector.Location = loc;
 674                         vector.Next = return_origins;
 675                         return_origins = vector;
 676                         return false;
 677                 }
 678
 679                 public override void StealFinallyClauses (ref ArrayList list)
 680                 {
 681                         // nothing to do
 682                 }
 683
 684                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 685                 {
 686                         string name = goto_stmt.Target;
 687                         LabeledStatement s = Block.LookupLabel (name);
 688                         if (s != null)
 689                                 throw new InternalErrorException ("Shouldn't get here");
 690
 691                         if (Parent == null) {
 692                                 Error_UnknownLabel (goto_stmt.loc, name);
 693                                 return false;
 694                         }
 695
 696                         int errors = Report.Errors;
 697                         Parent.AddGotoOrigin (vector, goto_stmt);
 698                         if (errors == Report.Errors)
 699                                 Report.Error (1632, goto_stmt.loc, "Control cannot leave the body of an anonymous method");
 700                         return false;
 701                 }
 702
 703                 protected override UsageVector Merge ()
 704                 {
 705                         for (UsageVector origin = return_origins; origin != null; origin = origin.Next)
 706                                 Block.Toplevel.CheckOutParameters (origin, origin.Location);
 707
 708                         UsageVector vector = base.Merge ();
 709                         Block.Toplevel.CheckOutParameters (vector, Block.loc);
 710                         // Note: we _do_not_ merge in the return origins
 711                         return vector;
 712                 }
 713
 714                 public bool End ()
 715                 {
 716                         return Merge ().IsUnreachable;
 717                 }
 718         }
 719
 720         public class FlowBranchingException : FlowBranching
 721         {
 722                 ExceptionStatement stmt;
 723                 UsageVector current_vector;
 724                 UsageVector catch_vectors;
 725                 UsageVector finally_vector;
 726
 727                 UsageVector break_origins;
 728                 UsageVector continue_origins;
 729                 UsageVector return_origins;
 730                 GotoOrigin goto_origins;
 731
 732                 class GotoOrigin {
 733                         public GotoOrigin Next;
 734                         public Goto GotoStmt;
 735                         public UsageVector Vector;
 736
 737                         public GotoOrigin (UsageVector vector, Goto goto_stmt, GotoOrigin next)
 738                         {
 739                                 Vector = vector;
 740                                 GotoStmt = goto_stmt;
 741                                 Next = next;
 742                         }
 743                 }
 744
 745                 bool emit_finally;
 746
 747                 public FlowBranchingException (FlowBranching parent,
 748                                                ExceptionStatement stmt)
 749                         : base (parent, BranchingType.Exception, SiblingType.Try,
 750                                 null, stmt.loc)
 751                 {
 752                         this.stmt = stmt;
 753                         this.emit_finally = true;
 754                 }
 755
 756                 protected override void AddSibling (UsageVector sibling)
 757                 {
 758                         switch (sibling.Type) {
 759                         case SiblingType.Try:
 760                         case SiblingType.Catch:
 761                                 sibling.Next = catch_vectors;
 762                                 catch_vectors = sibling;
 763                                 break;
 764                         case SiblingType.Finally:
 765                                 finally_vector = sibling;
 766                                 break;
 767                         default:
 768                                 throw new InvalidOperationException ();
 769                         }
 770                         current_vector = sibling;
 771                 }
 772
 773                 public override UsageVector CurrentUsageVector {
 774                         get { return current_vector; }
 775                 }
 776
 777                 public override bool InTryWithCatch ()
 778                 {
 779                         if (finally_vector == null) {
 780                                 Try t = stmt as Try;
 781                                 if (t != null && t.HasCatch)
 782                                         return true;
 783                         }
 784
 785                         return base.InTryWithCatch ();
 786                 }
 787
 788                 public override bool AddBreakOrigin (UsageVector vector, Location loc)
 789                 {
 790                         vector = vector.Clone ();
 791                         if (finally_vector != null) {
 792                                 vector.MergeChild (finally_vector, false);
 793                                 int errors = Report.Errors;
 794                                 Parent.AddBreakOrigin (vector, loc);
 795                                 if (errors == Report.Errors)
 796                                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 797                         } else {
 798                                 vector.Location = loc;
 799                                 vector.Next = break_origins;
 800                                 break_origins = vector;
 801                         }
 802                         return true;
 803                 }
 804
 805                 public override bool AddContinueOrigin (UsageVector vector, Location loc)
 806                 {
 807                         vector = vector.Clone ();
 808                         if (finally_vector != null) {
 809                                 vector.MergeChild (finally_vector, false);
 810                                 int errors = Report.Errors;
 811                                 Parent.AddContinueOrigin (vector, loc);
 812                                 if (errors == Report.Errors)
 813                                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 814                         } else {
 815                                 vector.Location = loc;
 816                                 vector.Next = continue_origins;
 817                                 continue_origins = vector;
 818                         }
 819                         return true;
 820                 }
 821
 822                 public override bool AddReturnOrigin (UsageVector vector, Location loc)
 823                 {
 824                         vector = vector.Clone ();
 825                         if (finally_vector != null) {
 826                                 vector.MergeChild (finally_vector, false);
 827                                 int errors = Report.Errors;
 828                                 Parent.AddReturnOrigin (vector, loc);
 829                                 if (errors == Report.Errors)
 830                                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 831                         } else {
 832                                 vector.Location = loc;
 833                                 vector.Next = return_origins;
 834                                 return_origins = vector;
 835                         }
 836                         return true;
 837                 }
 838
 839                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 840                 {
 841                         LabeledStatement s = current_vector.Block == null ? null : current_vector.Block.LookupLabel (goto_stmt.Target);
 842                         if (s != null)
 843                                 throw new InternalErrorException ("Shouldn't get here");
 844
 845                         vector = vector.Clone ();
 846                         if (finally_vector != null) {
 847                                 vector.MergeChild (finally_vector, false);
 848                                 int errors = Report.Errors;
 849                                 Parent.AddGotoOrigin (vector, goto_stmt);
 850                                 if (errors == Report.Errors)
 851                                         Report.Error (157, goto_stmt.loc, "Control cannot leave the body of a finally clause");
 852                         } else {
 853                                 goto_origins = new GotoOrigin (vector, goto_stmt, goto_origins);
 854                         }
 855                         return true;
 856                 }
 857
 858                 public override void StealFinallyClauses (ref ArrayList list)
 859                 {
 860                         if (list == null)
 861                                 list = new ArrayList ();
 862                         list.Add (stmt);
 863                         emit_finally = false;
 864                         base.StealFinallyClauses (ref list);
 865                 }
 866
 867                 public bool EmitFinally {
 868                         get { return emit_finally; }
 869                 }
 870
 871                 protected override UsageVector Merge ()
 872                 {
 873                         Report.Debug (2, "  MERGING TRY/CATCH", Name);
 874                         UsageVector vector = UsageVector.MergeSiblings (catch_vectors, Location);
 875                         Report.Debug (2, "  MERGING TRY/CATCH DONE", vector);
 876
 877                         if (finally_vector != null)
 878                                 vector.MergeChild (finally_vector, false);
 879
 880                         for (UsageVector origin = break_origins; origin != null; origin = origin.Next) {
 881                                 if (finally_vector != null)
 882                                         origin.MergeChild (finally_vector, false);
 883                                 Parent.AddBreakOrigin (origin, origin.Location);
 884                         }
 885
 886                         for (UsageVector origin = continue_origins; origin != null; origin = origin.Next) {
 887                                 if (finally_vector != null)
 888                                         origin.MergeChild (finally_vector, false);
 889                                 Parent.AddContinueOrigin (origin, origin.Location);
 890                         }
 891
 892                         for (UsageVector origin = return_origins; origin != null; origin = origin.Next) {
 893                                 if (finally_vector != null)
 894                                         origin.MergeChild (finally_vector, false);
 895                                 Parent.AddReturnOrigin (origin, origin.Location);
 896                         }
 897
 898                         for (GotoOrigin origin = goto_origins; origin != null; origin = origin.Next) {
 899                                 if (finally_vector != null)
 900                                         origin.Vector.MergeChild (finally_vector, false);
 901                                 Parent.AddGotoOrigin (origin.Vector, origin.GotoStmt);
 902                         }
 903
 904                         return vector;
 905                 }
 906         }
 907
 908         // <summary>
 909         //   This is used by the flow analysis code to keep track of the type of local variables
 910         //   and variables.
 911         //
 912         //   The flow code uses a BitVector to keep track of whether a variable has been assigned
 913         //   or not.  This is easy for fundamental types (int, char etc.) or reference types since
 914         //   you can only assign the whole variable as such.
 915         //
 916         //   For structs, we also need to keep track of all its fields.  To do this, we allocate one
 917         //   bit for the struct itself (it's used if you assign/access the whole struct) followed by
 918         //   one bit for each of its fields.
 919         //
 920         //   This class computes this `layout' for each type.
 921         // </summary>
 922         public class TypeInfo
 923         {
 924                 public readonly Type Type;
 925
 926                 // <summary>
 927                 //   Total number of bits a variable of this type consumes in the flow vector.
 928                 // </summary>
 929                 public readonly int TotalLength;
 930
 931                 // <summary>
 932                 //   Number of bits the simple fields of a variable of this type consume
 933                 //   in the flow vector.
 934                 // </summary>
 935                 public readonly int Length;
 936
 937                 // <summary>
 938                 //   This is only used by sub-structs.
 939                 // </summary>
 940                 public readonly int Offset;
 941
 942                 // <summary>
 943                 //   If this is a struct.
 944                 // </summary>
 945                 public readonly bool IsStruct;
 946
 947                 // <summary>
 948                 //   If this is a struct, all fields which are structs theirselves.
 949                 // </summary>
 950                 public TypeInfo[] SubStructInfo;
 951
 952                 protected readonly StructInfo struct_info;
 953                 private static Hashtable type_hash = new Hashtable ();
 954
 955                 public static TypeInfo GetTypeInfo (Type type)
 956                 {
 957                         TypeInfo info = (TypeInfo) type_hash [type];
 958                         if (info != null)
 959                                 return info;
 960
 961                         info = new TypeInfo (type);
 962                         type_hash.Add (type, info);
 963                         return info;
 964                 }
 965
 966                 public static TypeInfo GetTypeInfo (TypeContainer tc)
 967                 {
 968                         TypeInfo info = (TypeInfo) type_hash [tc.TypeBuilder];
 969                         if (info != null)
 970                                 return info;
 971
 972                         info = new TypeInfo (tc);
 973                         type_hash.Add (tc.TypeBuilder, info);
 974                         return info;
 975                 }
 976
 977                 private TypeInfo (Type type)
 978                 {
 979                         this.Type = type;
 980
 981                         struct_info = StructInfo.GetStructInfo (type);
 982                         if (struct_info != null) {
 983                                 Length = struct_info.Length;
 984                                 TotalLength = struct_info.TotalLength;
 985                                 SubStructInfo = struct_info.StructFields;
 986                                 IsStruct = true;
 987                         } else {
 988                                 Length = 0;
 989                                 TotalLength = 1;
 990                                 IsStruct = false;
 991                         }
 992                 }
 993
 994                 private TypeInfo (TypeContainer tc)
 995                 {
 996                         this.Type = tc.TypeBuilder;
 997
 998                         struct_info = StructInfo.GetStructInfo (tc);
 999                         if (struct_info != null) {
1000                                 Length = struct_info.Length;
1001                                 TotalLength = struct_info.TotalLength;
1002                                 SubStructInfo = struct_info.StructFields;
1003                                 IsStruct = true;
1004                         } else {
1005                                 Length = 0;
1006                                 TotalLength = 1;
1007                                 IsStruct = false;
1008                         }
1009                 }
1010
1011                 protected TypeInfo (StructInfo struct_info, int offset)
1012                 {
1013                         this.struct_info = struct_info;
1014                         this.Offset = offset;
1015                         this.Length = struct_info.Length;
1016                         this.TotalLength = struct_info.TotalLength;
1017                         this.SubStructInfo = struct_info.StructFields;
1018                         this.Type = struct_info.Type;
1019                         this.IsStruct = true;
1020                 }
1021
1022                 public int GetFieldIndex (string name)
1023                 {
1024                         if (struct_info == null)
1025                                 return 0;
1026
1027                         return struct_info [name];
1028                 }
1029
1030                 public TypeInfo GetSubStruct (string name)
1031                 {
1032                         if (struct_info == null)
1033                                 return null;
1034
1035                         return struct_info.GetStructField (name);
1036                 }
1037
1038                 // <summary>
1039                 //   A struct's constructor must always assign all fields.
1040                 //   This method checks whether it actually does so.
1041                 // </summary>
1042                 public bool IsFullyInitialized (FlowBranching branching, VariableInfo vi, Location loc)
1043                 {
1044                         if (struct_info == null)
1045                                 return true;
1046
1047                         bool ok = true;
1048                         for (int i = 0; i < struct_info.Count; i++) {
1049                                 FieldInfo field = struct_info.Fields [i];
1050
1051                                 if (!branching.IsFieldAssigned (vi, field.Name)) {
1052                                         Report.Error (171, loc,
1053                                                 "Field `{0}' must be fully assigned before control leaves the constructor",
1054                                                 TypeManager.GetFullNameSignature (field));
1055                                         ok = false;
1056                                 }
1057                         }
1058
1059                         return ok;
1060                 }
1061
1062                 public override string ToString ()
1063                 {
1064                         return String.Format ("TypeInfo ({0}:{1}:{2}:{3})",
1065                                               Type, Offset, Length, TotalLength);
1066                 }
1067
1068                 protected class StructInfo {
1069                         public readonly Type Type;
1070                         public readonly FieldInfo[] Fields;
1071                         public readonly TypeInfo[] StructFields;
1072                         public readonly int Count;
1073                         public readonly int CountPublic;
1074                         public readonly int CountNonPublic;
1075                         public readonly int Length;
1076                         public readonly int TotalLength;
1077                         public readonly bool HasStructFields;
1078
1079                         private static Hashtable field_type_hash = new Hashtable ();
1080                         private Hashtable struct_field_hash;
1081                         private Hashtable field_hash;
1082
1083                         protected bool InTransit = false;
1084
1085                         // Private constructor.  To save memory usage, we only need to create one instance
1086                         // of this class per struct type.
1087                         private StructInfo (Type type)
1088                         {
1089                                 this.Type = type;
1090
1091                                 field_type_hash.Add (type, this);
1092
1093                                 if (type is TypeBuilder) {
1094                                         TypeContainer tc = TypeManager.LookupTypeContainer (type);
1095
1096                                         ArrayList fields = null;
1097                                         if (tc != null)
1098                                                 fields = tc.Fields;
1099
1100                                         ArrayList public_fields = new ArrayList ();
1101                                         ArrayList non_public_fields = new ArrayList ();
1102
1103                                         if (fields != null) {
1104                                                 foreach (FieldBase field in fields) {
1105                                                         if ((field.ModFlags & Modifiers.STATIC) != 0)
1106                                                                 continue;
1107                                                         if ((field.ModFlags & Modifiers.PUBLIC) != 0)
1108                                                                 public_fields.Add (field.FieldBuilder);
1109                                                         else
1110                                                                 non_public_fields.Add (field.FieldBuilder);
1111                                                 }
1112                                         }
1113
1114                                         CountPublic = public_fields.Count;
1115                                         CountNonPublic = non_public_fields.Count;
1116                                         Count = CountPublic + CountNonPublic;
1117
1118                                         Fields = new FieldInfo [Count];
1119                                         public_fields.CopyTo (Fields, 0);
1120                                         non_public_fields.CopyTo (Fields, CountPublic);
1121 #if GMCS_SOURCE
1122                                 } else if (type is GenericTypeParameterBuilder) {
1123                                         CountPublic = CountNonPublic = Count = 0;
1124
1125                                         Fields = new FieldInfo [0];
1126 #endif
1127                                 } else {
1128                                         FieldInfo[] public_fields = type.GetFields (
1129                                                 BindingFlags.Instance|BindingFlags.Public);
1130                                         FieldInfo[] non_public_fields = type.GetFields (
1131                                                 BindingFlags.Instance|BindingFlags.NonPublic);
1132
1133                                         CountPublic = public_fields.Length;
1134                                         CountNonPublic = non_public_fields.Length;
1135                                         Count = CountPublic + CountNonPublic;
1136
1137                                         Fields = new FieldInfo [Count];
1138                                         public_fields.CopyTo (Fields, 0);
1139                                         non_public_fields.CopyTo (Fields, CountPublic);
1140                                 }
1141
1142                                 struct_field_hash = new Hashtable ();
1143                                 field_hash = new Hashtable ();
1144
1145                                 Length = 0;
1146                                 StructFields = new TypeInfo [Count];
1147                                 StructInfo[] sinfo = new StructInfo [Count];
1148
1149                                 InTransit = true;
1150
1151                                 for (int i = 0; i < Count; i++) {
1152                                         FieldInfo field = (FieldInfo) Fields [i];
1153
1154                                         sinfo [i] = GetStructInfo (field.FieldType);
1155                                         if (sinfo [i] == null)
1156                                                 field_hash.Add (field.Name, ++Length);
1157                                         else if (sinfo [i].InTransit) {
1158                                                 Report.Error (523, String.Format (
1159                                                                       "Struct member `{0}.{1}' of type `{2}' causes " +
1160                                                                       "a cycle in the structure layout",
1161                                                                       type, field.Name, sinfo [i].Type));
1162                                                 sinfo [i] = null;
1163                                                 return;
1164                                         }
1165                                 }
1166
1167                                 InTransit = false;
1168
1169                                 TotalLength = Length + 1;
1170                                 for (int i = 0; i < Count; i++) {
1171                                         FieldInfo field = (FieldInfo) Fields [i];
1172
1173                                         if (sinfo [i] == null)
1174                                                 continue;
1175
1176                                         field_hash.Add (field.Name, TotalLength);
1177
1178                                         HasStructFields = true;
1179                                         StructFields [i] = new TypeInfo (sinfo [i], TotalLength);
1180                                         struct_field_hash.Add (field.Name, StructFields [i]);
1181                                         TotalLength += sinfo [i].TotalLength;
1182                                 }
1183                         }
1184
1185                         public int this [string name] {
1186                                 get {
1187                                         if (field_hash.Contains (name))
1188                                                 return (int) field_hash [name];
1189                                         else
1190                                                 return 0;
1191                                 }
1192                         }
1193
1194                         public TypeInfo GetStructField (string name)
1195                         {
1196                                 return (TypeInfo) struct_field_hash [name];
1197                         }
1198
1199                         public static StructInfo GetStructInfo (Type type)
1200                         {
1201                                 if (!TypeManager.IsValueType (type) || TypeManager.IsEnumType (type) ||
1202                                     TypeManager.IsBuiltinType (type))
1203                                         return null;
1204
1205                                 StructInfo info = (StructInfo) field_type_hash [type];
1206                                 if (info != null)
1207                                         return info;
1208
1209                                 return new StructInfo (type);
1210                         }
1211
1212                         public static StructInfo GetStructInfo (TypeContainer tc)
1213                         {
1214                                 StructInfo info = (StructInfo) field_type_hash [tc.TypeBuilder];
1215                                 if (info != null)
1216                                         return info;
1217
1218                                 return new StructInfo (tc.TypeBuilder);
1219                         }
1220                 }
1221         }
1222
1223         // <summary>
1224         //   This is used by the flow analysis code to store information about a single local variable
1225         //   or parameter.  Depending on the variable's type, we need to allocate one or more elements
1226         //   in the BitVector - if it's a fundamental or reference type, we just need to know whether
1227         //   it has been assigned or not, but for structs, we need this information for each of its fields.
1228         // </summary>
1229         public class VariableInfo {
1230                 public readonly string Name;
1231                 public readonly TypeInfo TypeInfo;
1232
1233                 // <summary>
1234                 //   The bit offset of this variable in the flow vector.
1235                 // </summary>
1236                 public readonly int Offset;
1237
1238                 // <summary>
1239                 //   The number of bits this variable needs in the flow vector.
1240                 //   The first bit always specifies whether the variable as such has been assigned while
1241                 //   the remaining bits contain this information for each of a struct's fields.
1242                 // </summary>
1243                 public readonly int Length;
1244
1245                 // <summary>
1246                 //   If this is a parameter of local variable.
1247                 // </summary>
1248                 public readonly bool IsParameter;
1249
1250                 public readonly LocalInfo LocalInfo;
1251
1252                 readonly VariableInfo Parent;
1253                 VariableInfo[] sub_info;
1254
1255                 protected VariableInfo (string name, Type type, int offset)
1256                 {
1257                         this.Name = name;
1258                         this.Offset = offset;
1259                         this.TypeInfo = TypeInfo.GetTypeInfo (type);
1260
1261                         Length = TypeInfo.TotalLength;
1262
1263                         Initialize ();
1264                 }
1265
1266                 protected VariableInfo (VariableInfo parent, TypeInfo type)
1267                 {
1268                         this.Name = parent.Name;
1269                         this.TypeInfo = type;
1270                         this.Offset = parent.Offset + type.Offset;
1271                         this.Parent = parent;
1272                         this.Length = type.TotalLength;
1273
1274                         this.IsParameter = parent.IsParameter;
1275                         this.LocalInfo = parent.LocalInfo;
1276
1277                         Initialize ();
1278                 }
1279
1280                 protected void Initialize ()
1281                 {
1282                         TypeInfo[] sub_fields = TypeInfo.SubStructInfo;
1283                         if (sub_fields != null) {
1284                                 sub_info = new VariableInfo [sub_fields.Length];
1285                                 for (int i = 0; i < sub_fields.Length; i++) {
1286                                         if (sub_fields [i] != null)
1287                                                 sub_info [i] = new VariableInfo (this, sub_fields [i]);
1288                                 }
1289                         } else
1290                                 sub_info = new VariableInfo [0];
1291                 }
1292
1293                 public VariableInfo (LocalInfo local_info, int offset)
1294                         : this (local_info.Name, local_info.VariableType, offset)
1295                 {
1296                         this.LocalInfo = local_info;
1297                         this.IsParameter = false;
1298                 }
1299
1300                 public VariableInfo (Parameters ip, int i, int offset)
1301                         : this (ip.ParameterName (i), TypeManager.GetElementType (ip.ParameterType (i)), offset)
1302                 {
1303                         this.IsParameter = true;
1304                 }
1305
1306                 public bool IsAssigned (EmitContext ec)
1307                 {
1308                         return !ec.DoFlowAnalysis ||
1309                                 ec.OmitStructFlowAnalysis && TypeInfo.IsStruct ||
1310                                 ec.CurrentBranching.IsAssigned (this);
1311                 }
1312
1313                 public bool IsAssigned (EmitContext ec, Location loc)
1314                 {
1315                         if (IsAssigned (ec))
1316                                 return true;
1317
1318                         Report.Error (165, loc,
1319                                       "Use of unassigned local variable `" + Name + "'");
1320                         ec.CurrentBranching.SetAssigned (this);
1321                         return false;
1322                 }
1323
1324                 public bool IsAssigned (MyBitVector vector)
1325                 {
1326                         if (vector == null)
1327                                 return true;
1328
1329                         if (vector [Offset])
1330                                 return true;
1331
1332                         // FIXME: Fix SetFieldAssigned to set the whole range like SetAssigned below. Then, get rid of this stanza
1333                         for (VariableInfo parent = Parent; parent != null; parent = parent.Parent) {
1334                                 if (vector [parent.Offset]) {
1335                                         // 'parent' is assigned, but someone forgot to note that all its components are assigned too
1336                                         parent.SetAssigned (vector);
1337                                         return true;
1338                                 }
1339                         }
1340
1341                         // Return unless this is a struct.
1342                         if (!TypeInfo.IsStruct)
1343                                 return false;
1344
1345                         // Ok, so each field must be assigned.
1346                         for (int i = 0; i < TypeInfo.Length; i++) {
1347                                 if (!vector [Offset + i + 1])
1348                                         return false;
1349                         }
1350
1351                         // Ok, now check all fields which are structs.
1352                         for (int i = 0; i < sub_info.Length; i++) {
1353                                 VariableInfo sinfo = sub_info [i];
1354                                 if (sinfo == null)
1355                                         continue;
1356
1357                                 if (!sinfo.IsAssigned (vector))
1358                                         return false;
1359                         }
1360
1361                         vector [Offset] = true;
1362                         return true;
1363                 }
1364
1365                 public void SetAssigned (EmitContext ec)
1366                 {
1367                         if (ec.DoFlowAnalysis)
1368                                 ec.CurrentBranching.SetAssigned (this);
1369                 }
1370
1371                 public void SetAssigned (MyBitVector vector)
1372                 {
1373                         if (Length == 1)
1374                                 vector [Offset] = true;
1375                         else
1376                                 vector.SetRange (Offset, Length);
1377                 }
1378
1379                 public bool IsFieldAssigned (EmitContext ec, string name, Location loc)
1380                 {
1381                         if (!ec.DoFlowAnalysis ||
1382                                 ec.OmitStructFlowAnalysis && TypeInfo.IsStruct ||
1383                                 ec.CurrentBranching.IsFieldAssigned (this, name))
1384                                 return true;
1385
1386                         Report.Error (170, loc,
1387                                       "Use of possibly unassigned field `" + name + "'");
1388                         ec.CurrentBranching.SetFieldAssigned (this, name);
1389                         return false;
1390                 }
1391
1392                 public bool IsFieldAssigned (MyBitVector vector, string field_name)
1393                 {
1394                         int field_idx = TypeInfo.GetFieldIndex (field_name);
1395
1396                         if (field_idx == 0)
1397                                 return true;
1398
1399                         return vector [Offset + field_idx];
1400                 }
1401
1402                 public void SetFieldAssigned (EmitContext ec, string name)
1403                 {
1404                         if (ec.DoFlowAnalysis)
1405                                 ec.CurrentBranching.SetFieldAssigned (this, name);
1406                 }
1407
1408                 public void SetFieldAssigned (MyBitVector vector, string field_name)
1409                 {
1410                         int field_idx = TypeInfo.GetFieldIndex (field_name);
1411
1412                         if (field_idx == 0)
1413                                 return;
1414
1415                         vector [Offset + field_idx] = true;
1416                 }
1417
1418                 public VariableInfo GetSubStruct (string name)
1419                 {
1420                         TypeInfo type = TypeInfo.GetSubStruct (name);
1421
1422                         if (type == null)
1423                                 return null;
1424
1425                         return new VariableInfo (this, type);
1426                 }
1427
1428                 public override string ToString ()
1429                 {
1430                         return String.Format ("VariableInfo ({0}:{1}:{2}:{3}:{4})",
1431                                               Name, TypeInfo, Offset, Length, IsParameter);
1432                 }
1433         }
1434
1435         // <summary>
1436         //   This is a special bit vector which can inherit from another bit vector doing a
1437         //   copy-on-write strategy.  The inherited vector may have a smaller size than the
1438         //   current one.
1439         // </summary>
1440         public class MyBitVector {
1441                 public readonly int Count;
1442                 public static readonly MyBitVector Empty = new MyBitVector ();
1443
1444                 // Invariant: vector != null => vector.Count == Count
1445                 // Invariant: vector == null || shared == null
1446                 //            i.e., at most one of 'vector' and 'shared' can be non-null.  They can both be null -- that means all-ones
1447                 // The object in 'shared' cannot be modified, while 'vector' can be freely modified
1448                 BitArray vector, shared;
1449
1450                 MyBitVector ()
1451                 {
1452                         shared = new BitArray (0, false);
1453                 }
1454
1455                 public MyBitVector (MyBitVector InheritsFrom, int Count)
1456                 {
1457                         if (InheritsFrom != null)
1458                                 shared = InheritsFrom.Shared;
1459
1460                         this.Count = Count;
1461                 }
1462
1463                 // Use this accessor to get a shareable copy of the underlying BitArray representation
1464                 BitArray Shared {
1465                         get {
1466                                 // Post-condition: vector == null
1467                                 if (shared == null) {
1468                                         shared = vector;
1469                                         vector = null;
1470                                 }
1471                                 return shared;
1472                         }
1473                 }
1474
1475                 // <summary>
1476                 //   Get/set bit `index' in the bit vector.
1477                 // </summary>
1478                 public bool this [int index] {
1479                         get {
1480                                 if (index >= Count)
1481                                         throw new ArgumentOutOfRangeException ();
1482
1483                                 if (vector != null)
1484                                         return vector [index];
1485                                 if (shared == null)
1486                                         return true;
1487                                 if (index < shared.Count)
1488                                         return shared [index];
1489                                 return false;
1490                         }
1491
1492                         set {
1493                                 // Only copy the vector if we're actually modifying it.
1494                                 if (this [index] != value) {
1495                                         if (vector == null)
1496                                                 initialize_vector ();
1497                                         vector [index] = value;
1498                                 }
1499                         }
1500                 }
1501
1502                 // <summary>
1503                 //   Performs an `or' operation on the bit vector.  The `new_vector' may have a
1504                 //   different size than the current one.
1505                 // </summary>
1506                 private MyBitVector Or (MyBitVector new_vector)
1507                 {
1508                         if (Count == 0 || new_vector.Count == 0)
1509                                 return this;
1510
1511                         BitArray o = new_vector.vector != null ? new_vector.vector : new_vector.shared;
1512
1513                         if (o == null) {
1514                                 int n = new_vector.Count;
1515                                 if (n < Count) {
1516                                         for (int i = 0; i < n; ++i)
1517                                                 this [i] = true;
1518                                 } else {
1519                                         SetAll (true);
1520                                 }
1521                                 return this;
1522                         }
1523
1524                         if (Count == o.Count) {
1525                                 if (vector == null) {
1526                                         if (shared == null)
1527                                                 return this;
1528                                         initialize_vector ();
1529                                 }
1530                                 vector.Or (o);
1531                                 return this;
1532                         }
1533
1534                         int min = o.Count;
1535                         if (Count < min)
1536                                 min = Count;
1537
1538                         for (int i = 0; i < min; i++) {
1539                                 if (o [i])
1540                                         this [i] = true;
1541                         }
1542
1543                         return this;
1544                 }
1545
1546                 // <summary>
1547                 //   Performs an `and' operation on the bit vector.  The `new_vector' may have
1548                 //   a different size than the current one.
1549                 // </summary>
1550                 private MyBitVector And (MyBitVector new_vector)
1551                 {
1552                         if (Count == 0)
1553                                 return this;
1554
1555                         BitArray o = new_vector.vector != null ? new_vector.vector : new_vector.shared;
1556
1557                         if (o == null) {
1558                                 for (int i = new_vector.Count; i < Count; ++i)
1559                                         this [i] = false;
1560                                 return this;
1561                         }
1562
1563                         if (o.Count == 0) {
1564                                 SetAll (false);
1565                                 return this;
1566                         }
1567
1568                         if (Count == o.Count) {
1569                                 if (vector == null) {
1570                                         if (shared == null) {
1571                                                 shared = new_vector.Shared;
1572                                                 return this;
1573                                         }
1574                                         initialize_vector ();
1575                                 }
1576                                 vector.And (o);
1577                                 return this;
1578                         }
1579
1580                         int min = o.Count;
1581                         if (Count < min)
1582                                 min = Count;
1583
1584                         for (int i = 0; i < min; i++) {
1585                                 if (! o [i])
1586                                         this [i] = false;
1587                         }
1588
1589                         for (int i = min; i < Count; i++)
1590                                 this [i] = false;
1591
1592                         return this;
1593                 }
1594
1595                 public static MyBitVector operator & (MyBitVector a, MyBitVector b)
1596                 {
1597                         if (a == b)
1598                                 return a;
1599                         if (a == null)
1600                                 return b.Clone ();
1601                         if (b == null)
1602                                 return a.Clone ();
1603                         if (a.Count > b.Count)
1604                                 return a.Clone ().And (b);
1605                         else
1606                                 return b.Clone ().And (a);
1607                 }
1608
1609                 public static MyBitVector operator | (MyBitVector a, MyBitVector b)
1610                 {
1611                         if (a == b)
1612                                 return a;
1613                         if (a == null)
1614                                 return new MyBitVector (null, b.Count);
1615                         if (b == null)
1616                                 return new MyBitVector (null, a.Count);
1617                         if (a.Count > b.Count)
1618                                 return a.Clone ().Or (b);
1619                         else
1620                                 return b.Clone ().Or (a);
1621                 }
1622
1623                 public MyBitVector Clone ()
1624                 {
1625                         return Count == 0 ? Empty : new MyBitVector (this, Count);
1626                 }
1627
1628                 public void SetRange (int offset, int length)
1629                 {
1630                         if (offset > Count || offset + length > Count)
1631                                 throw new ArgumentOutOfRangeException ();
1632
1633                         if (shared == null && vector == null)
1634                                 return;
1635
1636                         int i = 0;
1637                         if (shared != null) {
1638                                 if (offset + length <= shared.Count) {
1639                                         for (; i < length; ++i)
1640                                                 if (!shared [i+offset])
1641                                                     break;
1642                                         if (i == length)
1643                                                 return;
1644                                 }
1645                                 initialize_vector ();
1646                         }
1647                         for (; i < length; ++i)
1648                                 vector [i+offset] = true;
1649
1650                 }
1651
1652                 public void SetAll (bool value)
1653                 {
1654                         // Don't clobber Empty
1655                         if (Count == 0)
1656                                 return;
1657                         shared = value ? null : Empty.Shared;
1658                         vector = null;
1659                 }
1660
1661                 void initialize_vector ()
1662                 {
1663                         // Post-condition: vector != null
1664                         if (shared == null) {
1665                                 vector = new BitArray (Count, true);
1666                                 return;
1667                         }
1668
1669                         vector = new BitArray (shared);
1670                         if (Count != vector.Count)
1671                                 vector.Length = Count;
1672                         shared = null;
1673                 }
1674
1675                 StringBuilder Dump (StringBuilder sb)
1676                 {
1677                         BitArray dump = vector == null ? shared : vector;
1678                         if (dump == null)
1679                                 return sb.Append ("/");
1680                         if (dump == shared)
1681                                 sb.Append ("=");
1682                         for (int i = 0; i < dump.Count; i++)
1683                                 sb.Append (dump [i] ? "1" : "0");
1684                         return sb;
1685                 }
1686
1687                 public override string ToString ()
1688                 {
1689                         return Dump (new StringBuilder ("{")).Append ("}").ToString ();
1690                 }
1691         }
1692 }