context: //
  // System.IO.FileStream.cs
  //
  // Authors:
  // 	Dietmar Maurer (dietmar@ximian.com)
  // 	Dan Lewis (dihlewis@yahoo.co.uk)
  //	Gonzalo Paniagua Javier (gonzalo@ximian.com)
  //  Marek Safar (marek.safar@gmail.com)
  //
  // (C) 2001-2003 Ximian, Inc.  http://www.ximian.com
  // Copyright (C) 2004-2005, 2008, 2010 Novell, Inc (http://www.novell.com)
  // Copyright 2011 Xamarin Inc (http://www.xamarin.com).
  //
  // Permission is hereby granted, free of charge, to any person obtaining
  // a copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to
  // permit persons to whom the Software is furnished to do so, subject to
  // the following conditions:
  // 
  // The above copyright notice and this permission notice shall be
  // included in all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  
  using System.Collections;
  using System.Globalization;
  using System.Runtime.CompilerServices;
  using System.Runtime.InteropServices;
  using System.Runtime.Remoting.Messaging;
  using System.Security;
  using System.Security.Permissions;
  using System.Threading;
  using Microsoft.Win32.SafeHandles;
  
  #if NET_2_1
  using System.IO.IsolatedStorage;
  #else
  using System.Security.AccessControl;
  #endif
  
  using System.Threading.Tasks;
  
  namespace System.IO
  {
  	[ComVisible (true)]
  	public class FileStream : Stream
  	{
  		// construct from handle
  		
  		[Obsolete ("Use FileStream(SafeFileHandle handle, FileAccess access) instead")]
  		public FileStream (IntPtr handle, FileAccess access)
  			: this (handle, access, true, DefaultBufferSize, false, false) {}
  
  		[Obsolete ("Use FileStream(SafeFileHandle handle, FileAccess access) instead")]
  		public FileStream (IntPtr handle, FileAccess access, bool ownsHandle)
  			: this (handle, access, ownsHandle, DefaultBufferSize, false, false) {}
  		
  		[Obsolete ("Use FileStream(SafeFileHandle handle, FileAccess access, int bufferSize) instead")]
  		public FileStream (IntPtr handle, FileAccess access, bool ownsHandle, int bufferSize)
  			: this (handle, access, ownsHandle, bufferSize, false, false) {}
  
  		[Obsolete ("Use FileStream(SafeFileHandle handle, FileAccess access, int bufferSize, bool isAsync) instead")]
  		public FileStream (IntPtr handle, FileAccess access, bool ownsHandle, int bufferSize, bool isAsync)
  			: this (handle, access, ownsHandle, bufferSize, isAsync, false) {}
  
  		[SecurityPermission (SecurityAction.Demand, UnmanagedCode = true)]
  		internal FileStream (IntPtr handle, FileAccess access, bool ownsHandle, int bufferSize, bool isAsync, bool isZeroSize)
  		{
  			if (handle == MonoIO.InvalidHandle)
  				throw new ArgumentException ("handle", Locale.GetText ("Invalid."));
  
  			Init (new SafeFileHandle (handle, false), access, ownsHandle, bufferSize, isAsync, isZeroSize);
  		}
  
  		// construct from filename
  
  		public FileStream (string path, FileMode mode)
  			: this (path, mode, (mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite), FileShare.Read, DefaultBufferSize, false, FileOptions.None)
  		{
  		}
  
  		public FileStream (string path, FileMode mode, FileAccess access)
  			: this (path, mode, access, access == FileAccess.Write ? FileShare.None : FileShare.Read, DefaultBufferSize, false, false)
  		{
  		}
  
  		public FileStream (string path, FileMode mode, FileAccess access, FileShare share)
  			: this (path, mode, access, share, DefaultBufferSize, false, FileOptions.None)
  		{
  		}
  
  		public FileStream (string path, FileMode mode, FileAccess access, FileShare share, int bufferSize)
  			: this (path, mode, access, share, bufferSize, false, FileOptions.None)
  		{
  		}
  
  		public FileStream (string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, bool useAsync)
  			: this (path, mode, access, share, bufferSize, useAsync ? FileOptions.Asynchronous : FileOptions.None)
  		{
  		}
  
  		public FileStream (string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options)
  			: this (path, mode, access, share, bufferSize, false, options)
  		{
  		}
  
  #if !NET_2_1
  		public FileStream (SafeFileHandle handle, FileAccess access)
  			:this(handle, access, DefaultBufferSize, false)
  		{
  		}
  		
  		public FileStream (SafeFileHandle handle, FileAccess access,
  				   int bufferSize)
  			:this(handle, access, bufferSize, false)
  		{
  		}
  
  		public FileStream (SafeFileHandle handle, FileAccess access, int bufferSize, bool isAsync)
  		{
  			Init (handle, access, false, bufferSize, isAsync, false);
  		}
  
  		[MonoLimitation ("This ignores the rights parameter")]
  		public FileStream (string path, FileMode mode,
  				   FileSystemRights rights, FileShare share,
  				   int bufferSize, FileOptions options)
  			: this (path, mode, (mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite), share, bufferSize, false, options)
  		{
  		}
  		
  		[MonoLimitation ("This ignores the rights and fileSecurity parameters")]
  		public FileStream (string path, FileMode mode,
  				   FileSystemRights rights, FileShare share,
  				   int bufferSize, FileOptions options,
  				   FileSecurity fileSecurity)
  			: this (path, mode, (mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite), share, bufferSize, false, options)
  		{
  		}
  #endif
  
  		internal FileStream (string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options, string msgPath, bool bFromProxy, bool useLongPath = false, bool checkHost = false)
  			: this (path, mode, access, share, bufferSize, false, options)
  		{
  		}
  
  		internal FileStream (string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, bool isAsync, bool anonymous)
  			: this (path, mode, access, share, bufferSize, anonymous, isAsync ? FileOptions.Asynchronous : FileOptions.None)
  		{
  		}
  
  		internal FileStream (string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, bool anonymous, FileOptions options)
  		{
  			if (path == null) {
  				throw new ArgumentNullException ("path");
  			}
  
  			if (path.Length == 0) {
  				throw new ArgumentException ("Path is empty");
  			}
  
  			this.anonymous = anonymous;
  			// ignore the Inheritable flag
  			share &= ~FileShare.Inheritable;
  
  			if (bufferSize <= 0)
  				throw new ArgumentOutOfRangeException ("bufferSize", "Positive number required.");
  
  			if (mode < FileMode.CreateNew || mode > FileMode.Append) {
  #if NET_2_1
  				if (anonymous)
  					throw new ArgumentException ("mode", "Enum value was out of legal range.");
  				else
  #endif
  				throw new ArgumentOutOfRangeException ("mode", "Enum value was out of legal range.");
  			}
  
  			if (access < FileAccess.Read || access > FileAccess.ReadWrite) {
  				throw new ArgumentOutOfRangeException ("access", "Enum value was out of legal range.");
  			}
  
  			if (share < FileShare.None || share > (FileShare.ReadWrite | FileShare.Delete)) {
  				throw new ArgumentOutOfRangeException ("share", "Enum value was out of legal range.");
  			}
  
  			if (path.IndexOfAny (Path.InvalidPathChars) != -1) {
  				throw new ArgumentException ("Name has invalid chars");
  			}
  
  			if (Directory.Exists (path)) {
  				// don't leak the path information for isolated storage
  				string msg = Locale.GetText ("Access to the path '{0}' is denied.");
  				throw new UnauthorizedAccessException (String.Format (msg, GetSecureFileName (path, false)));
  			}
  
  			/* Append streams can't be read (see FileMode
  			 * docs)
  			 */
  			if (mode==FileMode.Append &&
  				(access&FileAccess.Read)==FileAccess.Read) {
  				throw new ArgumentException("Append access can be requested only in write-only mode.");
  			}
  
  			if ((access & FileAccess.Write) == 0 &&
  				(mode != FileMode.Open && mode != FileMode.OpenOrCreate)) {
  				string msg = Locale.GetText ("Combining FileMode: {0} with " +
  					"FileAccess: {1} is invalid.");
  				throw new ArgumentException (string.Format (msg, access, mode));
  			}
  
  			SecurityManager.EnsureElevatedPermissions (); // this is a no-op outside moonlight
  
  			string dname;
  			if (Path.DirectorySeparatorChar != '/' && path.IndexOf ('/') >= 0)
  				dname = Path.GetDirectoryName (Path.GetFullPath (path));
  			else
  				dname = Path.GetDirectoryName (path);
  			if (dname.Length > 0) {
  				string fp = Path.GetFullPath (dname);
  				if (!Directory.Exists (fp)) {
  					// don't leak the path information for isolated storage
  					string msg = Locale.GetText ("Could not find a part of the path \"{0}\".");
  					string fname = (anonymous) ? dname : Path.GetFullPath (path);
  					throw new DirectoryNotFoundException (String.Format (msg, fname));
  				}
  			}
  
  			if (access == FileAccess.Read && mode != FileMode.Create && mode != FileMode.OpenOrCreate &&
  					mode != FileMode.CreateNew && !File.Exists (path)) {
  				// don't leak the path information for isolated storage
  				string msg = Locale.GetText ("Could not find file \"{0}\".");
  				string fname = GetSecureFileName (path);
  				throw new FileNotFoundException (String.Format (msg, fname), fname);
  			}
  
  			// IsolatedStorage needs to keep the Name property to the default "[Unknown]"
  			if (!anonymous)
  				this.name = path;
  
  			// TODO: demand permissions
  
  			MonoIOError error;
  
  			var nativeHandle = MonoIO.Open (path, mode, access, share, options, out error);
  
  			if (nativeHandle == MonoIO.InvalidHandle) {
  				// don't leak the path information for isolated storage
  				throw MonoIO.GetException (GetSecureFileName (path), error);
  			}
  
  			this.safeHandle = new SafeFileHandle (nativeHandle, false);
  
  			this.access = access;
  			this.owner = true;
  
  			/* Can we open non-files by name? */
  
  			if (MonoIO.GetFileType (safeHandle, out error) == MonoFileType.Disk) {
  				this.canseek = true;
  				this.async = (options & FileOptions.Asynchronous) != 0;
  			} else {
  				this.canseek = false;
  				this.async = false;
  			}
  
  
  			if (access == FileAccess.Read && canseek && (bufferSize == DefaultBufferSize)) {
  				/* Avoid allocating a large buffer for small files */
  				long len = Length;
  				if (bufferSize > len) {
  					bufferSize = (int)(len < 1000 ? 1000 : len);
  				}
  			}
  
  			InitBuffer (bufferSize, false);
  
  			if (mode==FileMode.Append) {
  				this.Seek (0, SeekOrigin.End);
  				this.append_startpos=this.Position;
  			} else {
  				this.append_startpos=0;
  			}
  		}
  
  		private void Init (SafeFileHandle safeHandle, FileAccess access, bool ownsHandle, int bufferSize, bool isAsync, bool isZeroSize)
  		{
  			if (access < FileAccess.Read || access > FileAccess.ReadWrite)
  				throw new ArgumentOutOfRangeException ("access");
  
  			MonoIOError error;
  			MonoFileType ftype = MonoIO.GetFileType (safeHandle, out error);
  
  			if (error != MonoIOError.ERROR_SUCCESS) {
  				throw MonoIO.GetException (name, error);
  			}
  
  			if (ftype == MonoFileType.Unknown) {
  				throw new IOException ("Invalid handle.");
  			} else if (ftype == MonoFileType.Disk) {
  				this.canseek = true;
  			} else {
  				this.canseek = false;
  			}
  
  			this.safeHandle = safeHandle;
  			ExposeHandle ();
  			this.access = access;
  			this.owner = ownsHandle;
  			this.async = isAsync;
  			this.anonymous = false;
  
  			if (canseek) {
  				buf_start = MonoIO.Seek (safeHandle, 0, SeekOrigin.Current, out error);
  				if (error != MonoIOError.ERROR_SUCCESS) {
  					throw MonoIO.GetException (name, error);
  				}
  			}
  
  			/* Can't set append mode */
  			this.append_startpos=0;
  		}
  
  		// properties
  		
  		public override bool CanRead {
  			get {
  				return access == FileAccess.Read ||
  				       access == FileAccess.ReadWrite;
  			}
  		}
  
  		public override bool CanWrite {
  			get {
  				return access == FileAccess.Write ||
  					access == FileAccess.ReadWrite;
  			}
  		}
  		
  		public override bool CanSeek {
  			get {
  				return(canseek);
  			}
  		}
  
  		public virtual bool IsAsync {
  			get {
  				return (async);
  			}
  		}
  
  		public string Name {
  			get {
  				return name;
  			}
  		}
  
  		public override long Length {
  			get {
  				if (safeHandle.IsClosed)
  					throw new ObjectDisposedException ("Stream has been closed");
  
  				if (!CanSeek)
  					throw new NotSupportedException ("The stream does not support seeking");
  
  				// Buffered data might change the length of the stream
  				FlushBufferIfDirty ();
  
  				MonoIOError error;
  
  				long length = MonoIO.GetLength (safeHandle, out error);
  
  				if (error != MonoIOError.ERROR_SUCCESS) {
  					// don't leak the path information for isolated storage
  					throw MonoIO.GetException (GetSecureFileName (name), error);
  				}
  
  				return(length);
  			}
  		}
  
  		public override long Position {
  			get {
  				if (safeHandle.IsClosed)
  					throw new ObjectDisposedException ("Stream has been closed");
  
  				if (CanSeek == false)
  					throw new NotSupportedException("The stream does not support seeking");
  
  				if (!isExposed)
  					return(buf_start + buf_offset);
  
  				// If the handle was leaked outside we always ask the real handle
  				MonoIOError error;
  
  				long ret = MonoIO.Seek (safeHandle, 0, SeekOrigin.Current, out error);
  
  				if (error != MonoIOError.ERROR_SUCCESS) {
  					// don't leak the path information for isolated storage
  					throw MonoIO.GetException (GetSecureFileName (name), error);
  				}
  
  				return ret;
  			}
  			set {
  				if(value < 0) {
  					throw new ArgumentOutOfRangeException("Attempt to set the position to a negative value");
  				}
  				
  				Seek (value, SeekOrigin.Begin);
  			}
  		}
  
  		[Obsolete ("Use SafeFileHandle instead")]
  		public virtual IntPtr Handle {
  			[SecurityPermission (SecurityAction.LinkDemand, UnmanagedCode = true)]
  			[SecurityPermission (SecurityAction.InheritanceDemand, UnmanagedCode = true)]
  			get {
  				var handle = safeHandle.DangerousGetHandle ();
  				if (!isExposed)
  					ExposeHandle ();
  				return handle;
  			}
  		}
  
  		public virtual SafeFileHandle SafeFileHandle {
  			[SecurityPermission (SecurityAction.LinkDemand, UnmanagedCode = true)]
  			[SecurityPermission (SecurityAction.InheritanceDemand, UnmanagedCode = true)]
  			get {
  				if (!isExposed)
  					ExposeHandle ();
  				return safeHandle;
  			}
  		}
  
  		void ExposeHandle ()
  		{
  			isExposed = true;
  			FlushBuffer ();
  			InitBuffer (0, true);
  		}
  
  		// methods
  
  		public override int ReadByte ()
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			if (!CanRead)
  				throw new NotSupportedException ("Stream does not support reading");
  
  			if (buf_size == 0) {
  				int n = ReadData (safeHandle, buf, 0, 1);
  				if (n == 0) return -1;
  				else return buf[0];
  			}
  			else if (buf_offset >= buf_length) {
  				RefillBuffer ();
  
  				if (buf_length == 0)
  					return -1;
  			}
  			
  			return buf [buf_offset ++];
  		}
  
  		public override void WriteByte (byte value)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			if (!CanWrite)
  				throw new NotSupportedException ("Stream does not support writing");
  
  			if (buf_offset == buf_size)
  				FlushBuffer ();
  
  			if (buf_size == 0) { // No buffering
  				buf [0] = value;
  				buf_dirty = true;
  				buf_length = 1;
  				FlushBuffer ();
  				return;
  			}
  
  			buf [buf_offset ++] = value;
  			if (buf_offset > buf_length)
  				buf_length = buf_offset;
  
  			buf_dirty = true;
  		}
  
  		public override int Read ([In,Out] byte[] array, int offset, int count)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  			if (array == null)
  				throw new ArgumentNullException ("array");
  			if (!CanRead)
  				throw new NotSupportedException ("Stream does not support reading");
  			int len = array.Length;
  			if (offset < 0)
  				throw new ArgumentOutOfRangeException ("offset", "< 0");
  			if (count < 0)
  				throw new ArgumentOutOfRangeException ("count", "< 0");
  			if (offset > len)
  				throw new ArgumentException ("destination offset is beyond array size");
  			// reordered to avoid possible integer overflow
  			if (offset > len - count)
  				throw new ArgumentException ("Reading would overrun buffer");
  
  			if (async) {
  				IAsyncResult ares = BeginRead (array, offset, count, null, null);
  				return EndRead (ares);
  			}
  
  			return ReadInternal (array, offset, count);
  		}
  
  		int ReadInternal (byte [] dest, int offset, int count)
  		{
  			int n = ReadSegment (dest, offset, count);
  			if (n == count) {
  				return count;
  			}
  			
  			int copied = n;
  			count -= n;
  
  			if (count > buf_size) {
  				/* Read as much as we can, up
  				 * to count bytes
  				 */
  				FlushBuffer();
  				n = ReadData (safeHandle, dest, offset+n, count);
  
  				/* Make the next buffer read
  				 * start from the right place
  				 */
  				buf_start += n;
  			} else {
  				RefillBuffer ();
  				n = ReadSegment (dest, offset+copied, count);
  			}
  
  			return copied + n;
  		}
  
  		delegate int ReadDelegate (byte [] buffer, int offset, int count);
  
  		public override IAsyncResult BeginRead (byte [] array, int offset, int numBytes,
  							AsyncCallback userCallback, object stateObject)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			if (!CanRead)
  				throw new NotSupportedException ("This stream does not support reading");
  
  			if (array == null)
  				throw new ArgumentNullException ("array");
  
  			if (numBytes < 0)
  				throw new ArgumentOutOfRangeException ("numBytes", "Must be >= 0");
  
  			if (offset < 0)
  				throw new ArgumentOutOfRangeException ("offset", "Must be >= 0");
  
  			// reordered to avoid possible integer overflow
  			if (numBytes > array.Length - offset)
  				throw new ArgumentException ("Buffer too small. numBytes/offset wrong.");
  
  			if (!async)
  				return base.BeginRead (array, offset, numBytes, userCallback, stateObject);
  
  			ReadDelegate r = new ReadDelegate (ReadInternal);
  			return r.BeginInvoke (array, offset, numBytes, userCallback, stateObject);
  		}
  		
  		public override int EndRead (IAsyncResult asyncResult)
  		{
  			if (asyncResult == null)
  				throw new ArgumentNullException ("asyncResult");
  
  			if (!async)
  				return base.EndRead (asyncResult);
  
  			AsyncResult ares = asyncResult as AsyncResult;
  			if (ares == null)
  				throw new ArgumentException ("Invalid IAsyncResult", "asyncResult");
  
  			ReadDelegate r = ares.AsyncDelegate as ReadDelegate;
  			if (r == null)
  				throw new ArgumentException ("Invalid IAsyncResult", "asyncResult");
  
  			return r.EndInvoke (asyncResult);
  		}
  
  		public override void Write (byte[] array, int offset, int count)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  			if (array == null)
  				throw new ArgumentNullException ("array");
  			if (offset < 0)
  				throw new ArgumentOutOfRangeException ("offset", "< 0");
  			if (count < 0)
  				throw new ArgumentOutOfRangeException ("count", "< 0");
  			// ordered to avoid possible integer overflow
  			if (offset > array.Length - count)
  				throw new ArgumentException ("Reading would overrun buffer");
  			if (!CanWrite)
  				throw new NotSupportedException ("Stream does not support writing");
  
  			if (async) {
  				IAsyncResult ares = BeginWrite (array, offset, count, null, null);
  				EndWrite (ares);
  				return;
  			}
  
  			WriteInternal (array, offset, count);
  		}
  
  		void WriteInternal (byte [] src, int offset, int count)
  		{
  			if (count > buf_size) {
  				// shortcut for long writes
  				MonoIOError error;
  
  				FlushBuffer ();
  				int wcount = count;
  
  				while (wcount > 0){
  					int n = MonoIO.Write (safeHandle, src, offset, wcount, out error);
  					if (error != MonoIOError.ERROR_SUCCESS)
  						throw MonoIO.GetException (GetSecureFileName (name), error);
  
  					wcount -= n;
  					offset += n;
  				}
  				buf_start += count;
  			} else {
  
  				int copied = 0;
  				while (count > 0) {
  					
  					int n = WriteSegment (src, offset + copied, count);
  					copied += n;
  					count -= n;
  
  					if (count == 0) {
  						break;
  					}
  
  					FlushBuffer ();
  				}
  			}
  		}
  
  		delegate void WriteDelegate (byte [] buffer, int offset, int count);
  
  		public override IAsyncResult BeginWrite (byte [] array, int offset, int numBytes,
  							AsyncCallback userCallback, object stateObject)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			if (!CanWrite)
  				throw new NotSupportedException ("This stream does not support writing");
  
  			if (array == null)
  				throw new ArgumentNullException ("array");
  
  			if (numBytes < 0)
  				throw new ArgumentOutOfRangeException ("numBytes", "Must be >= 0");
  
  			if (offset < 0)
  				throw new ArgumentOutOfRangeException ("offset", "Must be >= 0");
  
  			// reordered to avoid possible integer overflow
  			if (numBytes > array.Length - offset)
  				throw new ArgumentException ("array too small. numBytes/offset wrong.");
  
  			if (!async)
  				return base.BeginWrite (array, offset, numBytes, userCallback, stateObject);
  
  			FileStreamAsyncResult result = new FileStreamAsyncResult (userCallback, stateObject);
  			result.BytesRead = -1;
  			result.Count = numBytes;
  			result.OriginalCount = numBytes;
  /*
  			if (buf_dirty) {
  				MemoryStream ms = new MemoryStream ();
  				FlushBuffer (ms);
  				ms.Write (array, offset, numBytes);
  
  				// Set arguments to new compounded buffer 
  				offset = 0;
  				array = ms.ToArray ();
  				numBytes = array.Length;
  			}
  */
  			WriteDelegate w = WriteInternal;
  			return w.BeginInvoke (array, offset, numBytes, userCallback, stateObject);	
  		}
  		
  		public override void EndWrite (IAsyncResult asyncResult)
  		{
  			if (asyncResult == null)
  				throw new ArgumentNullException ("asyncResult");
  
  			if (!async) {
  				base.EndWrite (asyncResult);
  				return;
  			}
  
  			AsyncResult ares = asyncResult as AsyncResult;
  			if (ares == null)
  				throw new ArgumentException ("Invalid IAsyncResult", "asyncResult");
  
  			WriteDelegate w = ares.AsyncDelegate as WriteDelegate;
  			if (w == null)
  				throw new ArgumentException ("Invalid IAsyncResult", "asyncResult");
  
  			w.EndInvoke (asyncResult);
  			return;
  		}
  
  		public override long Seek (long offset, SeekOrigin origin)
  		{
  			long pos;
  
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  			
  			// make absolute
  
  			if(CanSeek == false) {
  				throw new NotSupportedException("The stream does not support seeking");
  			}
  
  			switch (origin) {
  			case SeekOrigin.End:
  				pos = Length + offset;
  				break;
  
  			case SeekOrigin.Current:
  				pos = Position + offset;
  				break;
  
  			case SeekOrigin.Begin:
  				pos = offset;
  				break;
  
  			default:
  				throw new ArgumentException ("origin", "Invalid SeekOrigin");
  			}
  
  			if (pos < 0) {
  				/* LAMESPEC: shouldn't this be
  				 * ArgumentOutOfRangeException?
  				 */
  				throw new IOException("Attempted to Seek before the beginning of the stream");
  			}
  
  			if(pos < this.append_startpos) {
  				/* More undocumented crap */
  				throw new IOException("Can't seek back over pre-existing data in append mode");
  			}
  
  			FlushBuffer ();
  
  			MonoIOError error;
  
  			buf_start = MonoIO.Seek (safeHandle, pos, SeekOrigin.Begin, out error);
  
  			if (error != MonoIOError.ERROR_SUCCESS) {
  				// don't leak the path information for isolated storage
  				throw MonoIO.GetException (GetSecureFileName (name), error);
  			}
  			
  			return(buf_start);
  		}
  
  		public override void SetLength (long value)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			if(CanSeek == false)
  				throw new NotSupportedException("The stream does not support seeking");
  
  			if(CanWrite == false)
  				throw new NotSupportedException("The stream does not support writing");
  
  			if(value < 0)
  				throw new ArgumentOutOfRangeException("value is less than 0");
  			
  			FlushBuffer ();
  
  			MonoIOError error;
  
  			MonoIO.SetLength (safeHandle, value, out error);
  			if (error != MonoIOError.ERROR_SUCCESS) {
  				// don't leak the path information for isolated storage
  				throw MonoIO.GetException (GetSecureFileName (name), error);
  			}
  
  			if (Position > value)
  				Position = value;
  		}
  
  		public override void Flush ()
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			FlushBuffer ();
  		}
  
  		public virtual void Flush (bool flushToDisk)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  
  			FlushBuffer ();
  
  			// This does the fsync
  			if (flushToDisk){
  				MonoIOError error;
  				MonoIO.Flush (safeHandle, out error);
  			}
  		}
  
  		public virtual void Lock (long position, long length)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  			if (position < 0) {
  				throw new ArgumentOutOfRangeException ("position must not be negative");
  			}
  			if (length < 0) {
  				throw new ArgumentOutOfRangeException ("length must not be negative");
  			}
  
  			MonoIOError error;
  
  			MonoIO.Lock (safeHandle, position, length, out error);
  			if (error != MonoIOError.ERROR_SUCCESS) {
  				// don't leak the path information for isolated storage
  				throw MonoIO.GetException (GetSecureFileName (name), error);
  			}
  		}
  
  		public virtual void Unlock (long position, long length)
  		{
  			if (safeHandle.IsClosed)
  				throw new ObjectDisposedException ("Stream has been closed");
  			if (position < 0) {
  				throw new ArgumentOutOfRangeException ("position must not be negative");
  			}
  			if (length < 0) {
  				throw new ArgumentOutOfRangeException ("length must not be negative");
  			}
  
  			MonoIOError error;
  
  			MonoIO.Unlock (safeHandle, position, length, out error);
  			if (error != MonoIOError.ERROR_SUCCESS) {
  				// don't leak the path information for isolated storage
  				throw MonoIO.GetException (GetSecureFileName (name), error);
  			}
  		}
  
  		// protected
  
  		~FileStream ()
  		{
  			Dispose (false);
  		}
  
  		protected override void Dispose (bool disposing)
  		{
  			Exception exc = null;
  			if (safeHandle != null && !safeHandle.IsClosed) {
  				try {
  					// If the FileStream is in "exposed" status
  					// it means that we do not have a buffer(we write the data without buffering)
  					// therefor we don't and can't flush the buffer becouse we don't have one.
  					FlushBuffer ();
  				} catch (Exception e) {
  					exc = e;
  				}
  
  				if (owner) {
  					MonoIOError error;
  
  					MonoIO.Close (safeHandle.DangerousGetHandle (), out error);
  					if (error != MonoIOError.ERROR_SUCCESS) {
  						// don't leak the path information for isolated storage
  						throw MonoIO.GetException (GetSecureFileName (name), error);
  					}
  
  					safeHandle.DangerousRelease ();
  				}
  			}
  
  			canseek = false;
  			access = 0;
  			
  			if (disposing && buf != null) {
  
gt: 				if (buf.Length == DefaultBufferSize && buf_recycle == null) {