mcs/class/System/System.Net/WebConnectionStream.cs

   1 //
   2 // System.Net.WebConnectionStream
   3 //
   4 // Authors:
   5 //      Gonzalo Paniagua Javier (gonzalo@ximian.com)
   6 //
   7 // (C) 2003 Ximian, Inc (http://www.ximian.com)
   8 // (C) 2004 Novell, Inc (http://www.novell.com)
   9 //
  10
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31
  32 using System.IO;
  33 using System.Text;
  34 using System.Threading;
  35
  36 namespace System.Net
  37 {
  38         class WebConnectionStream : Stream
  39         {
  40                 static byte [] crlf = new byte [] { 13, 10 };
  41                 bool isRead;
  42                 WebConnection cnc;
  43                 HttpWebRequest request;
  44                 byte [] readBuffer;
  45                 int readBufferOffset;
  46                 int readBufferSize;
  47                 int contentLength;
  48                 int totalRead;
  49                 bool nextReadCalled;
  50                 int pendingReads;
  51                 int pendingWrites;
  52                 ManualResetEvent pending;
  53                 bool allowBuffering;
  54                 bool sendChunked;
  55                 MemoryStream writeBuffer;
  56                 bool requestWritten;
  57                 byte [] headers;
  58                 bool disposed;
  59                 bool headersSent;
  60                 object locker = new object ();
  61                 bool initRead;
  62                 bool read_eof;
  63                 bool complete_request_written;
  64                 long max_buffer_size;
  65                 int read_timeout;
  66                 int write_timeout;
  67
  68                 public WebConnectionStream (WebConnection cnc)
  69                 {
  70                         isRead = true;
  71                         pending = new ManualResetEvent (true);
  72                         this.request = cnc.Data.request;
  73                         read_timeout = request.ReadWriteTimeout;
  74                         write_timeout = read_timeout;
  75                         this.cnc = cnc;
  76                         string contentType = cnc.Data.Headers ["Transfer-Encoding"];
  77                         bool chunkedRead = (contentType != null && contentType.ToLower ().IndexOf ("chunked") != -1);
  78                         string clength = cnc.Data.Headers ["Content-Length"];
  79                         if (!chunkedRead && clength != null && clength != "") {
  80
  81                                 try {
  82                                         contentLength = Int32.Parse (clength);
  83                                         if (contentLength == 0 && !IsNtlmAuth ()) {
  84                                                 ReadAll ();
  85                                         }
  86                                 } catch {
  87                                         contentLength = Int32.MaxValue;
  88                                 }
  89                         } else {
  90                                 contentLength = Int32.MaxValue;
  91                         }
  92                 }
  93
  94                 public WebConnectionStream (WebConnection cnc, HttpWebRequest request)
  95                 {
  96                         read_timeout = request.ReadWriteTimeout;
  97                         write_timeout = read_timeout;
  98                         isRead = false;
  99                         this.cnc = cnc;
 100                         this.request = request;
 101                         allowBuffering = request.InternalAllowBuffering;
 102                         sendChunked = request.SendChunked;
 103                         if (allowBuffering) {
 104                                 writeBuffer = new MemoryStream ();
 105                                 max_buffer_size = request.ContentLength;
 106                         } else {
 107                                 max_buffer_size = -1;
 108                         }
 109
 110                         if (sendChunked)
 111                                 pending = new ManualResetEvent (true);
 112                 }
 113
 114                 bool IsNtlmAuth ()
 115                 {
 116                         bool isProxy = (request.Proxy != null && !request.Proxy.IsBypassed (request.Address));
 117                         string header_name = (isProxy) ? "Proxy-Authenticate" : "WWW-Authenticate";
 118                         string authHeader = cnc.Data.Headers [header_name];
 119                         return (authHeader != null && authHeader.IndexOf ("NTLM") != -1);
 120                 }
 121
 122                 internal void CheckResponseInBuffer ()
 123                 {
 124                         if (contentLength > 0 && (readBufferSize - readBufferOffset) >= contentLength) {
 125                                 if (!IsNtlmAuth ())
 126                                         ReadAll ();
 127                         }
 128                 }
 129
 130                 internal WebConnection Connection {
 131                         get { return cnc; }
 132                 }
 133 #if NET_2_0
 134                 public override bool CanTimeout {
 135                         get { return true; }
 136                 }
 137 #endif
 138
 139 #if NET_2_0
 140                 public override
 141 #endif
 142                 int ReadTimeout {
 143                         get {
 144                                 return read_timeout;
 145                         }
 146
 147                         set {
 148                                 if (value < -1)
 149                                         throw new ArgumentOutOfRangeException ("value");
 150                                 read_timeout = value;
 151                         }
 152                 }
 153
 154 #if NET_2_0
 155                 public override
 156 #endif
 157                 int WriteTimeout {
 158                         get {
 159                                 return write_timeout;
 160                         }
 161
 162                         set {
 163                                 if (value < -1)
 164                                         throw new ArgumentOutOfRangeException ("value");
 165                                 write_timeout = value;
 166                         }
 167                 }
 168
 169                 internal bool CompleteRequestWritten {
 170                         get { return complete_request_written; }
 171                 }
 172
 173                 internal bool SendChunked {
 174                         set { sendChunked = value; }
 175                 }
 176
 177                 internal byte [] ReadBuffer {
 178                         set { readBuffer = value; }
 179                 }
 180
 181                 internal int ReadBufferOffset {
 182                         set { readBufferOffset = value;}
 183                 }
 184
 185                 internal int ReadBufferSize {
 186                         set { readBufferSize = value; }
 187                 }
 188
 189                 internal byte[] WriteBuffer {
 190                         get { return writeBuffer.GetBuffer (); }
 191                 }
 192
 193                 internal int WriteBufferLength {
 194                         get { return writeBuffer != null ? (int) writeBuffer.Length : (-1); }
 195                 }
 196
 197                 internal void ForceCompletion ()
 198                 {
 199                         if (!nextReadCalled) {
 200                                 if (contentLength == Int32.MaxValue)
 201                                         contentLength = 0;
 202                                 nextReadCalled = true;
 203                                 cnc.NextRead ();
 204                         }
 205                 }
 206
 207                 internal void CheckComplete ()
 208                 {
 209                         bool nrc = nextReadCalled;
 210                         if (!nrc && readBufferSize - readBufferOffset == contentLength) {
 211                                 nextReadCalled = true;
 212                                 cnc.NextRead ();
 213                         }
 214                 }
 215
 216                 internal void ReadAll ()
 217                 {
 218                         if (!isRead || read_eof || totalRead >= contentLength || nextReadCalled) {
 219                                 if (isRead && !nextReadCalled) {
 220                                         nextReadCalled = true;
 221                                         cnc.NextRead ();
 222                                 }
 223                                 return;
 224                         }
 225
 226                         pending.WaitOne ();
 227                         lock (locker) {
 228                                 if (totalRead >= contentLength)
 229                                         return;
 230
 231                                 byte [] b = null;
 232                                 int diff = readBufferSize - readBufferOffset;
 233                                 int new_size;
 234
 235                                 if (contentLength == Int32.MaxValue) {
 236                                         MemoryStream ms = new MemoryStream ();
 237                                         byte [] buffer = null;
 238                                         if (readBuffer != null && diff > 0) {
 239                                                 ms.Write (readBuffer, readBufferOffset, diff);
 240                                                 if (readBufferSize >= 8192)
 241                                                         buffer = readBuffer;
 242                                         }
 243
 244                                         if (buffer == null)
 245                                                 buffer = new byte [8192];
 246
 247                                         int read;
 248                                         while ((read = cnc.Read (buffer, 0, buffer.Length)) != 0)
 249                                                 ms.Write (buffer, 0, read);
 250
 251                                         b = ms.GetBuffer ();
 252                                         new_size = (int) ms.Length;
 253                                         contentLength = new_size;
 254                                 } else {
 255                                         new_size = contentLength - totalRead;
 256                                         b = new byte [new_size];
 257                                         if (readBuffer != null && diff > 0) {
 258                                                 if (diff > new_size)
 259                                                         diff = new_size;
 260
 261                                                 Buffer.BlockCopy (readBuffer, readBufferOffset, b, 0, diff);
 262                                         }
 263
 264                                         int remaining = new_size - diff;
 265                                         int r = -1;
 266                                         while (remaining > 0 && r != 0) {
 267                                                 r = cnc.Read (b, diff, remaining);
 268                                                 remaining -= r;
 269                                                 diff += r;
 270                                         }
 271                                 }
 272
 273                                 readBuffer = b;
 274                                 readBufferOffset = 0;
 275                                 readBufferSize = new_size;
 276                                 totalRead = 0;
 277                                 nextReadCalled = true;
 278                         }
 279
 280                         cnc.NextRead ();
 281                 }
 282
 283                 void WriteCallbackWrapper (IAsyncResult r)
 284                 {
 285                         WebAsyncResult result;
 286                         if (r.AsyncState != null) {
 287                                 result = (WebAsyncResult) r.AsyncState;
 288                                 result.InnerAsyncResult = r;
 289                                 result.DoCallback ();
 290                         } else {
 291                                 EndWrite (r);
 292                         }
 293                 }
 294
 295                 void ReadCallbackWrapper (IAsyncResult r)
 296                 {
 297                         WebAsyncResult result;
 298                         if (r.AsyncState != null) {
 299                                 result = (WebAsyncResult) r.AsyncState;
 300                                 result.InnerAsyncResult = r;
 301                                 result.DoCallback ();
 302                         } else {
 303                                 EndRead (r);
 304                         }
 305                 }
 306
 307                 public override int Read (byte [] buffer, int offset, int size)
 308                 {
 309                         if (!isRead)
 310                                 throw new NotSupportedException ("this stream does not allow reading");
 311
 312                         if (totalRead >= contentLength)
 313                                 return 0;
 314
 315                         AsyncCallback cb = new AsyncCallback (ReadCallbackWrapper);
 316                         WebAsyncResult res = (WebAsyncResult) BeginRead (buffer, offset, size, cb, null);
 317                         if (!res.IsCompleted && !res.WaitUntilComplete (ReadTimeout, false)) {
 318                                 nextReadCalled = true;
 319                                 cnc.Close (true);
 320                                 throw new WebException ("The operation has timed out.", WebExceptionStatus.Timeout);
 321                         }
 322
 323                         return EndRead (res);
 324                 }
 325
 326                 public override IAsyncResult BeginRead (byte [] buffer, int offset, int size,
 327                                                         AsyncCallback cb, object state)
 328                 {
 329                         if (!isRead)
 330                                 throw new NotSupportedException ("this stream does not allow reading");
 331
 332                         if (buffer == null)
 333                                 throw new ArgumentNullException ("buffer");
 334
 335                         int length = buffer.Length;
 336                         if (size < 0 || offset < 0 || length < offset || length - offset < size)
 337                                 throw new ArgumentOutOfRangeException ();
 338
 339                         lock (locker) {
 340                                 pendingReads++;
 341                                 pending.Reset ();
 342                         }
 343
 344                         WebAsyncResult result = new WebAsyncResult (cb, state, buffer, offset, size);
 345                         if (totalRead >= contentLength) {
 346                                 result.SetCompleted (true, -1);
 347                                 result.DoCallback ();
 348                                 return result;
 349                         }
 350
 351                         int remaining = readBufferSize - readBufferOffset;
 352                         if (remaining > 0) {
 353                                 int copy = (remaining > size) ? size : remaining;
 354                                 Buffer.BlockCopy (readBuffer, readBufferOffset, buffer, offset, copy);
 355                                 readBufferOffset += copy;
 356                                 offset += copy;
 357                                 size -= copy;
 358                                 totalRead += copy;
 359                                 if (size == 0 || totalRead >= contentLength) {
 360                                         result.SetCompleted (true, copy);
 361                                         result.DoCallback ();
 362                                         return result;
 363                                 }
 364                                 result.NBytes = copy;
 365                         }
 366
 367                         if (cb != null)
 368                                 cb = new AsyncCallback (ReadCallbackWrapper);
 369
 370                         if (contentLength != Int32.MaxValue && contentLength - totalRead < size)
 371                                 size = contentLength - totalRead;
 372
 373                         if (!read_eof) {
 374                                 result.InnerAsyncResult = cnc.BeginRead (buffer, offset, size, cb, result);
 375                         } else {
 376                                 result.SetCompleted (true, result.NBytes);
 377                                 result.DoCallback ();
 378                         }
 379                         return result;
 380                 }
 381
 382                 public override int EndRead (IAsyncResult r)
 383                 {
 384                         WebAsyncResult result = (WebAsyncResult) r;
 385                         if (result.EndCalled) {
 386                                 int xx = result.NBytes;
 387                                 return (xx >= 0) ? xx : 0;
 388                         }
 389
 390                         result.EndCalled = true;
 391
 392                         if (!result.IsCompleted) {
 393                                 int nbytes = -1;
 394                                 try {
 395                                         nbytes = cnc.EndRead (result);
 396                                 } catch (Exception exc) {
 397                                         lock (locker) {
 398                                                 pendingReads--;
 399                                                 if (pendingReads == 0)
 400                                                         pending.Set ();
 401                                         }
 402
 403                                         nextReadCalled = true;
 404                                         cnc.Close (true);
 405                                         result.SetCompleted (false, exc);
 406                                         throw;
 407                                 }
 408
 409                                 if (nbytes < 0) {
 410                                         nbytes = 0;
 411                                         read_eof = true;
 412                                 }
 413
 414                                 totalRead += nbytes;
 415                                 result.SetCompleted (false, nbytes + result.NBytes);
 416                                 result.DoCallback ();
 417                                 if (nbytes == 0)
 418                                         contentLength = totalRead;
 419                         }
 420
 421                         lock (locker) {
 422                                 pendingReads--;
 423                                 if (pendingReads == 0)
 424                                         pending.Set ();
 425                         }
 426
 427                         if (totalRead >= contentLength && !nextReadCalled)
 428                                 ReadAll ();
 429
 430                         int nb = result.NBytes;
 431                         return (nb >= 0) ? nb : 0;
 432                 }
 433
 434                 public override IAsyncResult BeginWrite (byte [] buffer, int offset, int size,
 435                                                         AsyncCallback cb, object state)
 436                 {
 437                         if (isRead)
 438                                 throw new NotSupportedException ("this stream does not allow writing");
 439
 440                         if (buffer == null)
 441                                 throw new ArgumentNullException ("buffer");
 442
 443                         int length = buffer.Length;
 444                         if (size < 0 || offset < 0 || length < offset || length - offset < size)
 445                                 throw new ArgumentOutOfRangeException ();
 446
 447                         if (sendChunked) {
 448                                 lock (locker) {
 449                                         pendingWrites++;
 450                                         pending.Reset ();
 451                                 }
 452                         }
 453
 454                         WebAsyncResult result = new WebAsyncResult (cb, state);
 455                         if (allowBuffering) {
 456                                 if (max_buffer_size >= 0) {
 457                                         long avail = max_buffer_size - writeBuffer.Length;
 458                                         if (size > avail) {
 459                                                 if (requestWritten)
 460                                                         throw new ProtocolViolationException (
 461                                                         "The number of bytes to be written is greater than " +
 462                                                         "the specified ContentLength.");
 463                                         }
 464                                 }
 465                                 writeBuffer.Write (buffer, offset, size);
 466                                 if (!sendChunked) {
 467                                         result.SetCompleted (true, 0);
 468                                         result.DoCallback ();
 469                                         return result;
 470                                 }
 471                         }
 472
 473                         AsyncCallback callback = null;
 474                         if (cb != null)
 475                                 callback = new AsyncCallback (WriteCallbackWrapper);
 476
 477                         if (sendChunked) {
 478                                 WriteRequest ();
 479
 480                                 string cSize = String.Format ("{0:X}\r\n", size);
 481                                 byte [] head = Encoding.ASCII.GetBytes (cSize);
 482                                 int chunkSize = 2 + size + head.Length;
 483                                 byte [] newBuffer = new byte [chunkSize];
 484                                 Buffer.BlockCopy (head, 0, newBuffer, 0, head.Length);
 485                                 Buffer.BlockCopy (buffer, offset, newBuffer, head.Length, size);
 486                                 Buffer.BlockCopy (crlf, 0, newBuffer, head.Length + size, crlf.Length);
 487
 488                                 buffer = newBuffer;
 489                                 offset = 0;
 490                                 size = chunkSize;
 491                         }
 492
 493                         result.InnerAsyncResult = cnc.BeginWrite (buffer, offset, size, callback, result);
 494                         return result;
 495                 }
 496
 497                 public override void EndWrite (IAsyncResult r)
 498                 {
 499                         if (r == null)
 500                                 throw new ArgumentNullException ("r");
 501
 502                         WebAsyncResult result = r as WebAsyncResult;
 503                         if (result == null)
 504                                 throw new ArgumentException ("Invalid IAsyncResult");
 505
 506                         if (result.EndCalled)
 507                                 return;
 508
 509                         result.EndCalled = true;
 510
 511                         if (allowBuffering && !sendChunked)
 512                                 return;
 513
 514                         if (result.GotException)
 515                                 throw result.Exception;
 516
 517                         try {
 518                                 cnc.EndWrite (result.InnerAsyncResult);
 519                                 result.SetCompleted (false, 0);
 520                         } catch (Exception e) {
 521                                 result.SetCompleted (false, e);
 522                         }
 523
 524                         if (sendChunked) {
 525                                 lock (locker) {
 526                                         pendingWrites--;
 527                                         if (pendingWrites == 0)
 528                                                 pending.Set ();
 529                                 }
 530                         }
 531                 }
 532
 533                 public override void Write (byte [] buffer, int offset, int size)
 534                 {
 535                         if (isRead)
 536                                 throw new NotSupportedException ("This stream does not allow writing");
 537
 538                         AsyncCallback cb = new AsyncCallback (WriteCallbackWrapper);
 539                         WebAsyncResult res = (WebAsyncResult) BeginWrite (buffer, offset, size, cb, null);
 540                         if (!res.IsCompleted && !res.WaitUntilComplete (WriteTimeout, false)) {
 541                                 nextReadCalled = true;
 542                                 cnc.Close (true);
 543                                 throw new IOException ("Write timed out.");
 544                         }
 545
 546                         EndWrite (res);
 547                 }
 548
 549                 public override void Flush ()
 550                 {
 551                 }
 552
 553                 internal void SetHeaders (byte [] buffer, int offset, int size)
 554                 {
 555                         if (headersSent)
 556                                 return;
 557
 558                         if (!allowBuffering || sendChunked) {
 559                                 headersSent = true;
 560                                 if (!cnc.Connected)
 561                                         throw new WebException ("Not connected", null, WebExceptionStatus.SendFailure, null);
 562
 563
 564                                 if (!cnc.Write (buffer, offset, size))
 565                                         throw new WebException ("Error writing request.", null, WebExceptionStatus.SendFailure, null);
 566
 567                                 if (!initRead) {
 568                                         initRead = true;
 569                                         WebConnection.InitRead (cnc);
 570                                 }
 571                         } else {
 572                                 headers = new byte [size];
 573                                 Buffer.BlockCopy (buffer, offset, headers, 0, size);
 574                         }
 575                 }
 576
 577                 internal bool RequestWritten {
 578                         get { return requestWritten; }
 579                 }
 580
 581                 internal void WriteRequest ()
 582                 {
 583                         if (requestWritten)
 584                                 return;
 585
 586                         if (sendChunked) {
 587                                 request.SendRequestHeaders ();
 588                                 requestWritten = true;
 589                                 return;
 590                         }
 591
 592                         if (!allowBuffering || writeBuffer == null)
 593                                 return;
 594
 595                         byte [] bytes = writeBuffer.GetBuffer ();
 596                         int length = (int) writeBuffer.Length;
 597                         if (request.ContentLength != -1 && request.ContentLength < length) {
 598                                 throw new WebException ("Specified Content-Length is less than the number of bytes to write", null,
 599                                                         WebExceptionStatus.ServerProtocolViolation, null);
 600                         }
 601
 602                         request.InternalContentLength = length;
 603                         request.SendRequestHeaders ();
 604                         requestWritten = true;
 605
 606                         //
 607                         // For small requests, make a copy, it will reduce the traffic, for large
 608                         // requests, the NoDelay bit on the socket should take effect (set in WebConnection).
 609                         //
 610                         if (headers.Length + length < 8192){
 611                                 byte[] b = new byte [headers.Length + length];
 612
 613                                 Buffer.BlockCopy (headers, 0, b, 0, headers.Length);
 614                                 Buffer.BlockCopy (bytes, 0, b, headers.Length, length);
 615
 616                                 if (!cnc.Write (b, 0, b.Length))
 617                                         throw new WebException ("Error writing request.", null, WebExceptionStatus.SendFailure, null);
 618
 619                                 headersSent = true;
 620                                 complete_request_written = true;
 621
 622                                 if (!initRead) {
 623                                         initRead = true;
 624                                         WebConnection.InitRead (cnc);
 625                                 }
 626                         } else {
 627                                 if (!cnc.Write (headers, 0, headers.Length))
 628                                         throw new WebException ("Error writing request.", null, WebExceptionStatus.SendFailure, null);
 629
 630                                 headersSent = true;
 631                                 if (cnc.Data.StatusCode != 0 && cnc.Data.StatusCode != 100)
 632                                         return;
 633
 634                                 IAsyncResult result = null;
 635                                 if (length > 0)
 636                                         result = cnc.BeginWrite (bytes, 0, length, null, null);
 637
 638                                 if (!initRead) {
 639                                         initRead = true;
 640                                         WebConnection.InitRead (cnc);
 641                                 }
 642
 643                                 if (length > 0)
 644                                         complete_request_written = cnc.EndWrite (result);
 645                                 else
 646                                         complete_request_written = true;
 647                         }
 648                 }
 649
 650                 internal void InternalClose ()
 651                 {
 652                         disposed = true;
 653                 }
 654
 655                 internal void ForceCloseConnection ()
 656                 {
 657                         if (!disposed) {
 658                                 disposed = true;
 659                                 cnc.Close (true);
 660                         }
 661                 }
 662
 663                 public override void Close ()
 664                 {
 665                         if (sendChunked) {
 666                                 pending.WaitOne ();
 667                                 byte [] chunk = Encoding.ASCII.GetBytes ("0\r\n\r\n");
 668                                 cnc.Write (chunk, 0, chunk.Length);
 669                                 return;
 670                         }
 671
 672                         if (isRead) {
 673                                 if (!nextReadCalled) {
 674                                         CheckComplete ();
 675                                         // If we have not read all the contents
 676                                         if (!nextReadCalled) {
 677                                                 nextReadCalled = true;
 678                                                 cnc.Close (true);
 679                                         }
 680                                 }
 681                                 return;
 682                         } else if (!allowBuffering) {
 683                                 complete_request_written = true;
 684                                 if (!initRead) {
 685                                         initRead = true;
 686                                         WebConnection.InitRead (cnc);
 687                                 }
 688                                 return;
 689                         }
 690
 691                         if (disposed)
 692                                 return;
 693
 694                         long length = request.ContentLength;
 695
 696                         // writeBuffer could be null if KillBuffer was already called.
 697                         if (writeBuffer != null && length != -1 && length > writeBuffer.Length)
 698                                 throw new WebException ("Cannot close the stream until all bytes are written", WebExceptionStatus.RequestCanceled);
 699
 700                         WriteRequest ();
 701                         disposed = true;
 702                 }
 703
 704                 internal void KillBuffer ()
 705                 {
 706                         writeBuffer = null;
 707                 }
 708
 709                 public override long Seek (long a, SeekOrigin b)
 710                 {
 711                         throw new NotSupportedException ();
 712                 }
 713
 714                 public override void SetLength (long a)
 715                 {
 716                         throw new NotSupportedException ();
 717                 }
 718
 719                 public override bool CanSeek {
 720                         get { return false; }
 721                 }
 722
 723                 public override bool CanRead {
 724                         get { return isRead; }
 725                 }
 726
 727                 public override bool CanWrite {
 728                         get { return !isRead; }
 729                 }
 730
 731                 public override long Length {
 732                         get { throw new NotSupportedException (); }
 733                 }
 734
 735                 public override long Position {
 736                         get { throw new NotSupportedException (); }
 737                         set { throw new NotSupportedException (); }
 738                 }
 739         }
 740 }
 741