diff options
Diffstat (limited to 'src/mscorlib/corefx/System/IO/FileStream.Win32.cs')
-rw-r--r-- | src/mscorlib/corefx/System/IO/FileStream.Win32.cs | 1770 |
1 files changed, 0 insertions, 1770 deletions
diff --git a/src/mscorlib/corefx/System/IO/FileStream.Win32.cs b/src/mscorlib/corefx/System/IO/FileStream.Win32.cs deleted file mode 100644 index 683eef5e43..0000000000 --- a/src/mscorlib/corefx/System/IO/FileStream.Win32.cs +++ /dev/null @@ -1,1770 +0,0 @@ -// Licensed to the .NET Foundation under one or more agreements. -// The .NET Foundation licenses this file to you under the MIT license. -// See the LICENSE file in the project root for more information. - -using System.Buffers; -using System.Diagnostics; -using System.Runtime.InteropServices; -using System.Threading; -using System.Threading.Tasks; -using Microsoft.Win32.SafeHandles; -using System.Runtime.CompilerServices; - -/* - * Win32FileStream supports different modes of accessing the disk - async mode - * and sync mode. They are two completely different codepaths in the - * sync & async methods (i.e. Read/Write vs. ReadAsync/WriteAsync). File - * handles in NT can be opened in only sync or overlapped (async) mode, - * and we have to deal with this pain. Stream has implementations of - * the sync methods in terms of the async ones, so we'll - * call through to our base class to get those methods when necessary. - * - * Also buffering is added into Win32FileStream as well. Folded in the - * code from BufferedStream, so all the comments about it being mostly - * aggressive (and the possible perf improvement) apply to Win32FileStream as - * well. Also added some buffering to the async code paths. - * - * Class Invariants: - * The class has one buffer, shared for reading & writing. It can only be - * used for one or the other at any point in time - not both. The following - * should be true: - * 0 <= _readPos <= _readLen < _bufferSize - * 0 <= _writePos < _bufferSize - * _readPos == _readLen && _readPos > 0 implies the read buffer is valid, - * but we're at the end of the buffer. - * _readPos == _readLen == 0 means the read buffer contains garbage. - * Either _writePos can be greater than 0, or _readLen & _readPos can be - * greater than zero, but neither can be greater than zero at the same time. - * - */ - -namespace System.IO -{ - public partial class FileStream : Stream - { - private bool _canSeek; - private bool _isPipe; // Whether to disable async buffering code. - private long _appendStart; // When appending, prevent overwriting file. - - private static unsafe IOCompletionCallback s_ioCallback = FileStreamCompletionSource.IOCallback; - - private Task<int> _lastSynchronouslyCompletedTask = null; // cached task for read ops that complete synchronously - private Task _activeBufferOperation = null; // tracks in-progress async ops using the buffer - private PreAllocatedOverlapped _preallocatedOverlapped; // optimization for async ops to avoid per-op allocations - private FileStreamCompletionSource _currentOverlappedOwner; // async op currently using the preallocated overlapped - - private SafeFileHandle OpenHandle(FileMode mode, FileShare share, FileOptions options) - { - Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = GetSecAttrs(share); - - int fAccess = - ((_access & FileAccess.Read) == FileAccess.Read ? GENERIC_READ : 0) | - ((_access & FileAccess.Write) == FileAccess.Write ? GENERIC_WRITE : 0); - - // Our Inheritable bit was stolen from Windows, but should be set in - // the security attributes class. Don't leave this bit set. - share &= ~FileShare.Inheritable; - - // Must use a valid Win32 constant here... - if (mode == FileMode.Append) - mode = FileMode.OpenOrCreate; - - int flagsAndAttributes = (int)options; - - // For mitigating local elevation of privilege attack through named pipes - // make sure we always call CreateFile with SECURITY_ANONYMOUS so that the - // named pipe server can't impersonate a high privileged client security context - flagsAndAttributes |= (Interop.Kernel32.SecurityOptions.SECURITY_SQOS_PRESENT | Interop.Kernel32.SecurityOptions.SECURITY_ANONYMOUS); - - // Don't pop up a dialog for reading from an empty floppy drive - uint oldMode = Interop.Kernel32.SetErrorMode(Interop.Kernel32.SEM_FAILCRITICALERRORS); - try - { - SafeFileHandle fileHandle = Interop.Kernel32.SafeCreateFile(_path, fAccess, share, ref secAttrs, mode, flagsAndAttributes, IntPtr.Zero); - fileHandle.IsAsync = _useAsyncIO; - - if (fileHandle.IsInvalid) - { - // Return a meaningful exception with the full path. - - // NT5 oddity - when trying to open "C:\" as a Win32FileStream, - // we usually get ERROR_PATH_NOT_FOUND from the OS. We should - // probably be consistent w/ every other directory. - int errorCode = Marshal.GetLastWin32Error(); - - if (errorCode == Interop.Errors.ERROR_PATH_NOT_FOUND && _path.Equals(Directory.InternalGetDirectoryRoot(_path))) - errorCode = Interop.Errors.ERROR_ACCESS_DENIED; - - throw Win32Marshal.GetExceptionForWin32Error(errorCode, _path); - } - - return fileHandle; - } - finally - { - Interop.Kernel32.SetErrorMode(oldMode); - } - } - - private void Init(FileMode mode, FileShare share) - { - // Disallow access to all non-file devices from the Win32FileStream - // constructors that take a String. Everyone else can call - // CreateFile themselves then use the constructor that takes an - // IntPtr. Disallows "con:", "com1:", "lpt1:", etc. - int fileType = Interop.Kernel32.GetFileType(_fileHandle); - if (fileType != Interop.Kernel32.FileTypes.FILE_TYPE_DISK) - { - _fileHandle.Dispose(); - throw new NotSupportedException(SR.NotSupported_FileStreamOnNonFiles); - } - - // This is necessary for async IO using IO Completion ports via our - // managed Threadpool API's. This (theoretically) calls the OS's - // BindIoCompletionCallback method, and passes in a stub for the - // LPOVERLAPPED_COMPLETION_ROUTINE. This stub looks at the Overlapped - // struct for this request and gets a delegate to a managed callback - // from there, which it then calls on a threadpool thread. (We allocate - // our native OVERLAPPED structs 2 pointers too large and store EE state - // & GC handles there, one to an IAsyncResult, the other to a delegate.) - if (_useAsyncIO) - { - try - { - _fileHandle.ThreadPoolBinding = ThreadPoolBoundHandle.BindHandle(_fileHandle); - } - catch (ArgumentException ex) - { - throw new IOException(SR.IO_BindHandleFailed, ex); - } - finally - { - if (_fileHandle.ThreadPoolBinding == null) - { - // We should close the handle so that the handle is not open until SafeFileHandle GC - Debug.Assert(!_exposedHandle, "Are we closing handle that we exposed/not own, how?"); - _fileHandle.Dispose(); - } - } - } - - _canSeek = true; - - // For Append mode... - if (mode == FileMode.Append) - { - _appendStart = SeekCore(0, SeekOrigin.End); - } - else - { - _appendStart = -1; - } - } - - private void InitFromHandle(SafeFileHandle handle) - { - int handleType = Interop.Kernel32.GetFileType(_fileHandle); - Debug.Assert(handleType == Interop.Kernel32.FileTypes.FILE_TYPE_DISK || handleType == Interop.Kernel32.FileTypes.FILE_TYPE_PIPE || handleType == Interop.Kernel32.FileTypes.FILE_TYPE_CHAR, "FileStream was passed an unknown file type!"); - - _canSeek = handleType == Interop.Kernel32.FileTypes.FILE_TYPE_DISK; - _isPipe = handleType == Interop.Kernel32.FileTypes.FILE_TYPE_PIPE; - - // This is necessary for async IO using IO Completion ports via our - // managed Threadpool API's. This calls the OS's - // BindIoCompletionCallback method, and passes in a stub for the - // LPOVERLAPPED_COMPLETION_ROUTINE. This stub looks at the Overlapped - // struct for this request and gets a delegate to a managed callback - // from there, which it then calls on a threadpool thread. (We allocate - // our native OVERLAPPED structs 2 pointers too large and store EE - // state & a handle to a delegate there.) - // - // If, however, we've already bound this file handle to our completion port, - // don't try to bind it again because it will fail. A handle can only be - // bound to a single completion port at a time. - if (_useAsyncIO && !GetSuppressBindHandle(handle)) - { - try - { - _fileHandle.ThreadPoolBinding = ThreadPoolBoundHandle.BindHandle(_fileHandle); - } - catch (Exception ex) - { - // If you passed in a synchronous handle and told us to use - // it asynchronously, throw here. - throw new ArgumentException(SR.Arg_HandleNotAsync, nameof(handle), ex); - } - } - else if (!_useAsyncIO) - { - if (handleType != Interop.Kernel32.FileTypes.FILE_TYPE_PIPE) - VerifyHandleIsSync(); - } - - if (_canSeek) - SeekCore(0, SeekOrigin.Current); - else - _filePosition = 0; - } - - private static bool GetSuppressBindHandle(SafeFileHandle handle) - { - return handle.IsAsync.HasValue ? handle.IsAsync.Value : false; - } - - private unsafe static Interop.Kernel32.SECURITY_ATTRIBUTES GetSecAttrs(FileShare share) - { - Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = default(Interop.Kernel32.SECURITY_ATTRIBUTES); - if ((share & FileShare.Inheritable) != 0) - { - secAttrs = new Interop.Kernel32.SECURITY_ATTRIBUTES(); - secAttrs.nLength = (uint)sizeof(Interop.Kernel32.SECURITY_ATTRIBUTES); - - secAttrs.bInheritHandle = Interop.BOOL.TRUE; - } - return secAttrs; - } - - // Verifies that this handle supports synchronous IO operations (unless you - // didn't open it for either reading or writing). - private unsafe void VerifyHandleIsSync() - { - Debug.Assert(!_useAsyncIO); - - // Do NOT use this method on pipes. Reading or writing to a pipe may - // cause an app to block incorrectly, introducing a deadlock (depending - // on whether a write will wake up an already-blocked thread or this - // Win32FileStream's thread). - Debug.Assert(Interop.Kernel32.GetFileType(_fileHandle) != Interop.Kernel32.FileTypes.FILE_TYPE_PIPE); - - byte* bytes = stackalloc byte[1]; - int numBytesReadWritten; - int r = -1; - - // If the handle is a pipe, ReadFile will block until there - // has been a write on the other end. We'll just have to deal with it, - // For the read end of a pipe, you can mess up and - // accidentally read synchronously from an async pipe. - if ((_access & FileAccess.Read) != 0) // don't use the virtual CanRead or CanWrite, as this may be used in the ctor - { - r = Interop.Kernel32.ReadFile(_fileHandle, bytes, 0, out numBytesReadWritten, IntPtr.Zero); - } - else if ((_access & FileAccess.Write) != 0) // don't use the virtual CanRead or CanWrite, as this may be used in the ctor - { - r = Interop.Kernel32.WriteFile(_fileHandle, bytes, 0, out numBytesReadWritten, IntPtr.Zero); - } - - if (r == 0) - { - int errorCode = GetLastWin32ErrorAndDisposeHandleIfInvalid(throwIfInvalidHandle: true); - if (errorCode == ERROR_INVALID_PARAMETER) - throw new ArgumentException(SR.Arg_HandleNotSync, "handle"); - } - } - - private bool HasActiveBufferOperation - { - get { return _activeBufferOperation != null && !_activeBufferOperation.IsCompleted; } - } - - public override bool CanSeek - { - get { return _canSeek; } - } - - private long GetLengthInternal() - { - Interop.Kernel32.FILE_STANDARD_INFO info = new Interop.Kernel32.FILE_STANDARD_INFO(); - - if (!Interop.Kernel32.GetFileInformationByHandleEx(_fileHandle, Interop.Kernel32.FILE_INFO_BY_HANDLE_CLASS.FileStandardInfo, out info, (uint)Marshal.SizeOf<Interop.Kernel32.FILE_STANDARD_INFO>())) - throw Win32Marshal.GetExceptionForLastWin32Error(); - long len = info.EndOfFile; - // If we're writing near the end of the file, we must include our - // internal buffer in our Length calculation. Don't flush because - // we use the length of the file in our async write method. - if (_writePos > 0 && _filePosition + _writePos > len) - len = _writePos + _filePosition; - return len; - } - - protected override void Dispose(bool disposing) - { - // Nothing will be done differently based on whether we are - // disposing vs. finalizing. This is taking advantage of the - // weak ordering between normal finalizable objects & critical - // finalizable objects, which I included in the SafeHandle - // design for Win32FileStream, which would often "just work" when - // finalized. - try - { - if (_fileHandle != null && !_fileHandle.IsClosed) - { - // Flush data to disk iff we were writing. After - // thinking about this, we also don't need to flush - // our read position, regardless of whether the handle - // was exposed to the user. They probably would NOT - // want us to do this. - if (_writePos > 0) - { - FlushWriteBuffer(!disposing); - } - } - } - finally - { - if (_fileHandle != null && !_fileHandle.IsClosed) - { - if (_fileHandle.ThreadPoolBinding != null) - _fileHandle.ThreadPoolBinding.Dispose(); - - _fileHandle.Dispose(); - } - - if (_preallocatedOverlapped != null) - _preallocatedOverlapped.Dispose(); - - _canSeek = false; - - // Don't set the buffer to null, to avoid a NullReferenceException - // when users have a race condition in their code (i.e. they call - // Close when calling another method on Stream like Read). - //_buffer = null; - base.Dispose(disposing); - } - } - - private void FlushOSBuffer() - { - if (!Interop.Kernel32.FlushFileBuffers(_fileHandle)) - { - throw Win32Marshal.GetExceptionForLastWin32Error(); - } - } - - // Returns a task that flushes the internal write buffer - private Task FlushWriteAsync(CancellationToken cancellationToken) - { - Debug.Assert(_useAsyncIO); - Debug.Assert(_readPos == 0 && _readLength == 0, "FileStream: Read buffer must be empty in FlushWriteAsync!"); - - // If the buffer is already flushed, don't spin up the OS write - if (_writePos == 0) return Task.CompletedTask; - - Task flushTask = WriteInternalCoreAsync(GetBuffer(), 0, _writePos, cancellationToken); - _writePos = 0; - - // Update the active buffer operation - _activeBufferOperation = HasActiveBufferOperation ? - Task.WhenAll(_activeBufferOperation, flushTask) : - flushTask; - - return flushTask; - } - - // Writes are buffered. Anytime the buffer fills up - // (_writePos + delta > _bufferSize) or the buffer switches to reading - // and there is left over data (_writePos > 0), this function must be called. - private void FlushWriteBuffer(bool calledFromFinalizer = false) - { - if (_writePos == 0) return; - Debug.Assert(_readPos == 0 && _readLength == 0, "FileStream: Read buffer must be empty in FlushWrite!"); - - if (_useAsyncIO) - { - Task writeTask = FlushWriteAsync(CancellationToken.None); - // With our Whidbey async IO & overlapped support for AD unloads, - // we don't strictly need to block here to release resources - // since that support takes care of the pinning & freeing the - // overlapped struct. We need to do this when called from - // Close so that the handle is closed when Close returns, but - // we don't need to call EndWrite from the finalizer. - // Additionally, if we do call EndWrite, we block forever - // because AD unloads prevent us from running the managed - // callback from the IO completion port. Blocking here when - // called from the finalizer during AD unload is clearly wrong, - // but we can't use any sort of test for whether the AD is - // unloading because if we weren't unloading, an AD unload - // could happen on a separate thread before we call EndWrite. - if (!calledFromFinalizer) - { - writeTask.GetAwaiter().GetResult(); - } - } - else - { - WriteCore(GetBuffer(), 0, _writePos); - } - - _writePos = 0; - } - - private void SetLengthInternal(long value) - { - // Handle buffering updates. - if (_writePos > 0) - { - FlushWriteBuffer(); - } - else if (_readPos < _readLength) - { - FlushReadBuffer(); - } - _readPos = 0; - _readLength = 0; - - if (_appendStart != -1 && value < _appendStart) - throw new IOException(SR.IO_SetLengthAppendTruncate); - SetLengthCore(value); - } - - // We absolutely need this method broken out so that WriteInternalCoreAsync can call - // a method without having to go through buffering code that might call FlushWrite. - private void SetLengthCore(long value) - { - Debug.Assert(value >= 0, "value >= 0"); - long origPos = _filePosition; - - VerifyOSHandlePosition(); - if (_filePosition != value) - SeekCore(value, SeekOrigin.Begin); - if (!Interop.Kernel32.SetEndOfFile(_fileHandle)) - { - int errorCode = Marshal.GetLastWin32Error(); - if (errorCode == Interop.Errors.ERROR_INVALID_PARAMETER) - throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_FileLengthTooBig); - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - // Return file pointer to where it was before setting length - if (origPos != value) - { - if (origPos < value) - SeekCore(origPos, SeekOrigin.Begin); - else - SeekCore(0, SeekOrigin.End); - } - } - - // Instance method to help code external to this MarshalByRefObject avoid - // accessing its fields by ref. This avoids a compiler warning. - private FileStreamCompletionSource CompareExchangeCurrentOverlappedOwner(FileStreamCompletionSource newSource, FileStreamCompletionSource existingSource) => Interlocked.CompareExchange(ref _currentOverlappedOwner, newSource, existingSource); - - public override int Read(byte[] array, int offset, int count) - { - ValidateReadWriteArgs(array, offset, count); - return ReadCore(array, offset, count); - } - - private int ReadCore(byte[] array, int offset, int count) - { - Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), - "We're either reading or writing, but not both."); - - bool isBlocked = false; - int n = _readLength - _readPos; - // if the read buffer is empty, read into either user's array or our - // buffer, depending on number of bytes user asked for and buffer size. - if (n == 0) - { - if (!CanRead) throw Error.GetReadNotSupported(); - if (_writePos > 0) FlushWriteBuffer(); - if (!CanSeek || (count >= _bufferLength)) - { - n = ReadNative(array, offset, count); - // Throw away read buffer. - _readPos = 0; - _readLength = 0; - return n; - } - n = ReadNative(GetBuffer(), 0, _bufferLength); - if (n == 0) return 0; - isBlocked = n < _bufferLength; - _readPos = 0; - _readLength = n; - } - // Now copy min of count or numBytesAvailable (i.e. near EOF) to array. - if (n > count) n = count; - Buffer.BlockCopy(GetBuffer(), _readPos, array, offset, n); - _readPos += n; - - // We may have read less than the number of bytes the user asked - // for, but that is part of the Stream contract. Reading again for - // more data may cause us to block if we're using a device with - // no clear end of file, such as a serial port or pipe. If we - // blocked here & this code was used with redirected pipes for a - // process's standard output, this can lead to deadlocks involving - // two processes. But leave this here for files to avoid what would - // probably be a breaking change. -- - - // If we are reading from a device with no clear EOF like a - // serial port or a pipe, this will cause us to block incorrectly. - if (!_isPipe) - { - // If we hit the end of the buffer and didn't have enough bytes, we must - // read some more from the underlying stream. However, if we got - // fewer bytes from the underlying stream than we asked for (i.e. we're - // probably blocked), don't ask for more bytes. - if (n < count && !isBlocked) - { - Debug.Assert(_readPos == _readLength, "Read buffer should be empty!"); - int moreBytesRead = ReadNative(array, offset + n, count - n); - n += moreBytesRead; - // We've just made our buffer inconsistent with our position - // pointer. We must throw away the read buffer. - _readPos = 0; - _readLength = 0; - } - } - - return n; - } - - [Conditional("DEBUG")] - private void AssertCanRead(byte[] buffer, int offset, int count) - { - Debug.Assert(!_fileHandle.IsClosed, "!_fileHandle.IsClosed"); - Debug.Assert(CanRead, "CanRead"); - Debug.Assert(buffer != null, "buffer != null"); - Debug.Assert(_writePos == 0, "_writePos == 0"); - Debug.Assert(offset >= 0, "offset is negative"); - Debug.Assert(count >= 0, "count is negative"); - } - - private unsafe int ReadNative(byte[] buffer, int offset, int count) - { - AssertCanRead(buffer, offset, count); - - if (_useAsyncIO) - return ReadNativeAsync(buffer, offset, count, 0, CancellationToken.None).GetAwaiter().GetResult(); - - // Make sure we are reading from the right spot - VerifyOSHandlePosition(); - - int errorCode = 0; - int r = ReadFileNative(_fileHandle, buffer, offset, count, null, out errorCode); - - if (r == -1) - { - // For pipes, ERROR_BROKEN_PIPE is the normal end of the pipe. - if (errorCode == ERROR_BROKEN_PIPE) - { - r = 0; - } - else - { - if (errorCode == ERROR_INVALID_PARAMETER) - throw new ArgumentException(SR.Arg_HandleNotSync, "_fileHandle"); - - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - } - Debug.Assert(r >= 0, "FileStream's ReadNative is likely broken."); - _filePosition += r; - - return r; - } - - public override long Seek(long offset, SeekOrigin origin) - { - if (origin < SeekOrigin.Begin || origin > SeekOrigin.End) - throw new ArgumentException(SR.Argument_InvalidSeekOrigin, nameof(origin)); - if (_fileHandle.IsClosed) throw Error.GetFileNotOpen(); - if (!CanSeek) throw Error.GetSeekNotSupported(); - - Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both."); - - // If we've got bytes in our buffer to write, write them out. - // If we've read in and consumed some bytes, we'll have to adjust - // our seek positions ONLY IF we're seeking relative to the current - // position in the stream. This simulates doing a seek to the new - // position, then a read for the number of bytes we have in our buffer. - if (_writePos > 0) - { - FlushWriteBuffer(); - } - else if (origin == SeekOrigin.Current) - { - // Don't call FlushRead here, which would have caused an infinite - // loop. Simply adjust the seek origin. This isn't necessary - // if we're seeking relative to the beginning or end of the stream. - offset -= (_readLength - _readPos); - } - _readPos = _readLength = 0; - - // Verify that internal position is in sync with the handle - VerifyOSHandlePosition(); - - long oldPos = _filePosition + (_readPos - _readLength); - long pos = SeekCore(offset, origin); - - // Prevent users from overwriting data in a file that was opened in - // append mode. - if (_appendStart != -1 && pos < _appendStart) - { - SeekCore(oldPos, SeekOrigin.Begin); - throw new IOException(SR.IO_SeekAppendOverwrite); - } - - // We now must update the read buffer. We can in some cases simply - // update _readPos within the buffer, copy around the buffer so our - // Position property is still correct, and avoid having to do more - // reads from the disk. Otherwise, discard the buffer's contents. - if (_readLength > 0) - { - // We can optimize the following condition: - // oldPos - _readPos <= pos < oldPos + _readLen - _readPos - if (oldPos == pos) - { - if (_readPos > 0) - { - //Console.WriteLine("Seek: seeked for 0, adjusting buffer back by: "+_readPos+" _readLen: "+_readLen); - Buffer.BlockCopy(GetBuffer(), _readPos, GetBuffer(), 0, _readLength - _readPos); - _readLength -= _readPos; - _readPos = 0; - } - // If we still have buffered data, we must update the stream's - // position so our Position property is correct. - if (_readLength > 0) - SeekCore(_readLength, SeekOrigin.Current); - } - else if (oldPos - _readPos < pos && pos < oldPos + _readLength - _readPos) - { - int diff = (int)(pos - oldPos); - //Console.WriteLine("Seek: diff was "+diff+", readpos was "+_readPos+" adjusting buffer - shrinking by "+ (_readPos + diff)); - Buffer.BlockCopy(GetBuffer(), _readPos + diff, GetBuffer(), 0, _readLength - (_readPos + diff)); - _readLength -= (_readPos + diff); - _readPos = 0; - if (_readLength > 0) - SeekCore(_readLength, SeekOrigin.Current); - } - else - { - // Lose the read buffer. - _readPos = 0; - _readLength = 0; - } - Debug.Assert(_readLength >= 0 && _readPos <= _readLength, "_readLen should be nonnegative, and _readPos should be less than or equal _readLen"); - Debug.Assert(pos == Position, "Seek optimization: pos != Position! Buffer math was mangled."); - } - return pos; - } - - // This doesn't do argument checking. Necessary for SetLength, which must - // set the file pointer beyond the end of the file. This will update the - // internal position - // This is called during construction so it should avoid any virtual - // calls - private long SeekCore(long offset, SeekOrigin origin) - { - Debug.Assert(!_fileHandle.IsClosed && _canSeek, "!_handle.IsClosed && _parent.CanSeek"); - Debug.Assert(origin >= SeekOrigin.Begin && origin <= SeekOrigin.End, "origin>=SeekOrigin.Begin && origin<=SeekOrigin.End"); - long ret = 0; - - if (!Interop.Kernel32.SetFilePointerEx(_fileHandle, offset, out ret, (uint)origin)) - { - int errorCode = GetLastWin32ErrorAndDisposeHandleIfInvalid(); - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - - _filePosition = ret; - return ret; - } - - partial void OnBufferAllocated() - { - Debug.Assert(_buffer != null); - Debug.Assert(_preallocatedOverlapped == null); - - if (_useAsyncIO) - _preallocatedOverlapped = new PreAllocatedOverlapped(s_ioCallback, this, _buffer); - } - - public override void Write(byte[] array, int offset, int count) - { - ValidateReadWriteArgs(array, offset, count); - - if (_writePos == 0) - { - // Ensure we can write to the stream, and ready buffer for writing. - if (!CanWrite) throw Error.GetWriteNotSupported(); - if (_readPos < _readLength) FlushReadBuffer(); - _readPos = 0; - _readLength = 0; - } - - // If our buffer has data in it, copy data from the user's array into - // the buffer, and if we can fit it all there, return. Otherwise, write - // the buffer to disk and copy any remaining data into our buffer. - // The assumption here is memcpy is cheaper than disk (or net) IO. - // (10 milliseconds to disk vs. ~20-30 microseconds for a 4K memcpy) - // So the extra copying will reduce the total number of writes, in - // non-pathological cases (i.e. write 1 byte, then write for the buffer - // size repeatedly) - if (_writePos > 0) - { - int numBytes = _bufferLength - _writePos; // space left in buffer - if (numBytes > 0) - { - if (numBytes > count) - numBytes = count; - Buffer.BlockCopy(array, offset, GetBuffer(), _writePos, numBytes); - _writePos += numBytes; - if (count == numBytes) return; - offset += numBytes; - count -= numBytes; - } - // Reset our buffer. We essentially want to call FlushWrite - // without calling Flush on the underlying Stream. - - if (_useAsyncIO) - { - WriteInternalCoreAsync(GetBuffer(), 0, _writePos, CancellationToken.None).GetAwaiter().GetResult(); - } - else - { - WriteCore(GetBuffer(), 0, _writePos); - } - _writePos = 0; - } - // If the buffer would slow writes down, avoid buffer completely. - if (count >= _bufferLength) - { - Debug.Assert(_writePos == 0, "FileStream cannot have buffered data to write here! Your stream will be corrupted."); - WriteCore(array, offset, count); - return; - } - else if (count == 0) - { - return; // Don't allocate a buffer then call memcpy for 0 bytes. - } - - // Copy remaining bytes into buffer, to write at a later date. - Buffer.BlockCopy(array, offset, GetBuffer(), _writePos, count); - _writePos = count; - return; - } - - private unsafe void WriteCore(byte[] buffer, int offset, int count) - { - Debug.Assert(!_fileHandle.IsClosed, "!_handle.IsClosed"); - Debug.Assert(CanWrite, "_parent.CanWrite"); - - Debug.Assert(buffer != null, "buffer != null"); - Debug.Assert(_readPos == _readLength, "_readPos == _readLen"); - Debug.Assert(offset >= 0, "offset is negative"); - Debug.Assert(count >= 0, "count is negative"); - if (_useAsyncIO) - { - WriteInternalCoreAsync(buffer, offset, count, CancellationToken.None).GetAwaiter().GetResult(); - return; - } - - // Make sure we are writing to the position that we think we are - VerifyOSHandlePosition(); - - int errorCode = 0; - int r = WriteFileNative(_fileHandle, buffer, offset, count, null, out errorCode); - - if (r == -1) - { - // For pipes, ERROR_NO_DATA is not an error, but the pipe is closing. - if (errorCode == ERROR_NO_DATA) - { - r = 0; - } - else - { - // ERROR_INVALID_PARAMETER may be returned for writes - // where the position is too large (i.e. writing at Int64.MaxValue - // on Win9x) OR for synchronous writes to a handle opened - // asynchronously. - if (errorCode == ERROR_INVALID_PARAMETER) - throw new IOException(SR.IO_FileTooLongOrHandleNotSync); - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - } - Debug.Assert(r >= 0, "FileStream's WriteCore is likely broken."); - _filePosition += r; - return; - } - - private Task<int> ReadAsyncInternal(byte[] array, int offset, int numBytes, CancellationToken cancellationToken) - { - // If async IO is not supported on this platform or - // if this Win32FileStream was not opened with FileOptions.Asynchronous. - if (!_useAsyncIO) - { - return base.ReadAsync(array, offset, numBytes, cancellationToken); - } - - if (!CanRead) throw Error.GetReadNotSupported(); - - Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both."); - - if (_isPipe) - { - // Pipes are tricky, at least when you have 2 different pipes - // that you want to use simultaneously. When redirecting stdout - // & stderr with the Process class, it's easy to deadlock your - // parent & child processes when doing writes 4K at a time. The - // OS appears to use a 4K buffer internally. If you write to a - // pipe that is full, you will block until someone read from - // that pipe. If you try reading from an empty pipe and - // Win32FileStream's ReadAsync blocks waiting for data to fill it's - // internal buffer, you will be blocked. In a case where a child - // process writes to stdout & stderr while a parent process tries - // reading from both, you can easily get into a deadlock here. - // To avoid this deadlock, don't buffer when doing async IO on - // pipes. But don't completely ignore buffered data either. - if (_readPos < _readLength) - { - int n = _readLength - _readPos; - if (n > numBytes) n = numBytes; - Buffer.BlockCopy(GetBuffer(), _readPos, array, offset, n); - _readPos += n; - - // Return a completed task - return TaskFromResultOrCache(n); - } - else - { - Debug.Assert(_writePos == 0, "Win32FileStream must not have buffered write data here! Pipes should be unidirectional."); - return ReadNativeAsync(array, offset, numBytes, 0, cancellationToken); - } - } - - Debug.Assert(!_isPipe, "Should not be a pipe."); - - // Handle buffering. - if (_writePos > 0) FlushWriteBuffer(); - if (_readPos == _readLength) - { - // I can't see how to handle buffering of async requests when - // filling the buffer asynchronously, without a lot of complexity. - // The problems I see are issuing an async read, we do an async - // read to fill the buffer, then someone issues another read - // (either synchronously or asynchronously) before the first one - // returns. This would involve some sort of complex buffer locking - // that we probably don't want to get into, at least not in V1. - // If we did a sync read to fill the buffer, we could avoid the - // problem, and any async read less than 64K gets turned into a - // synchronous read by NT anyways... -- - - if (numBytes < _bufferLength) - { - Task<int> readTask = ReadNativeAsync(GetBuffer(), 0, _bufferLength, 0, cancellationToken); - _readLength = readTask.GetAwaiter().GetResult(); - int n = _readLength; - if (n > numBytes) n = numBytes; - Buffer.BlockCopy(GetBuffer(), 0, array, offset, n); - _readPos = n; - - // Return a completed task (recycling the one above if possible) - return (_readLength == n ? readTask : TaskFromResultOrCache(n)); - } - else - { - // Here we're making our position pointer inconsistent - // with our read buffer. Throw away the read buffer's contents. - _readPos = 0; - _readLength = 0; - return ReadNativeAsync(array, offset, numBytes, 0, cancellationToken); - } - } - else - { - int n = _readLength - _readPos; - if (n > numBytes) n = numBytes; - Buffer.BlockCopy(GetBuffer(), _readPos, array, offset, n); - _readPos += n; - - if (n >= numBytes) - { - // Return a completed task - return TaskFromResultOrCache(n); - } - else - { - // For streams with no clear EOF like serial ports or pipes - // we cannot read more data without causing an app to block - // incorrectly. Pipes don't go down this path - // though. This code needs to be fixed. - // Throw away read buffer. - _readPos = 0; - _readLength = 0; - return ReadNativeAsync(array, offset + n, numBytes - n, n, cancellationToken); - } - } - } - - unsafe private Task<int> ReadNativeAsync(byte[] bytes, int offset, int numBytes, int numBufferedBytesRead, CancellationToken cancellationToken) - { - AssertCanRead(bytes, offset, numBytes); - Debug.Assert(_useAsyncIO, "ReadNativeAsync doesn't work on synchronous file streams!"); - - // Create and store async stream class library specific data in the async result - - FileStreamCompletionSource completionSource = new FileStreamCompletionSource(this, numBufferedBytesRead, bytes, cancellationToken); - NativeOverlapped* intOverlapped = completionSource.Overlapped; - - // Calculate position in the file we should be at after the read is done - if (CanSeek) - { - long len = Length; - - // Make sure we are reading from the position that we think we are - VerifyOSHandlePosition(); - - if (_filePosition + numBytes > len) - { - if (_filePosition <= len) - numBytes = (int)(len - _filePosition); - else - numBytes = 0; - } - - // Now set the position to read from in the NativeOverlapped struct - // For pipes, we should leave the offset fields set to 0. - intOverlapped->OffsetLow = unchecked((int)_filePosition); - intOverlapped->OffsetHigh = (int)(_filePosition >> 32); - - // When using overlapped IO, the OS is not supposed to - // touch the file pointer location at all. We will adjust it - // ourselves. This isn't threadsafe. - - // WriteFile should not update the file pointer when writing - // in overlapped mode, according to MSDN. But it does update - // the file pointer when writing to a UNC path! - // So changed the code below to seek to an absolute - // location, not a relative one. ReadFile seems consistent though. - SeekCore(numBytes, SeekOrigin.Current); - } - - // queue an async ReadFile operation and pass in a packed overlapped - int errorCode = 0; - int r = ReadFileNative(_fileHandle, bytes, offset, numBytes, intOverlapped, out errorCode); - // ReadFile, the OS version, will return 0 on failure. But - // my ReadFileNative wrapper returns -1. My wrapper will return - // the following: - // On error, r==-1. - // On async requests that are still pending, r==-1 w/ errorCode==ERROR_IO_PENDING - // on async requests that completed sequentially, r==0 - // You will NEVER RELIABLY be able to get the number of bytes - // read back from this call when using overlapped structures! You must - // not pass in a non-null lpNumBytesRead to ReadFile when using - // overlapped structures! This is by design NT behavior. - if (r == -1 && numBytes != -1) - { - // For pipes, when they hit EOF, they will come here. - if (errorCode == ERROR_BROKEN_PIPE) - { - // Not an error, but EOF. AsyncFSCallback will NOT be - // called. Call the user callback here. - - // We clear the overlapped status bit for this special case. - // Failure to do so looks like we are freeing a pending overlapped later. - intOverlapped->InternalLow = IntPtr.Zero; - completionSource.SetCompletedSynchronously(0); - } - else if (errorCode != ERROR_IO_PENDING) - { - if (!_fileHandle.IsClosed && CanSeek) // Update Position - It could be anywhere. - { - SeekCore(0, SeekOrigin.Current); - } - - completionSource.ReleaseNativeResource(); - - if (errorCode == ERROR_HANDLE_EOF) - { - throw Error.GetEndOfFile(); - } - else - { - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - } - else - { - // Only once the IO is pending do we register for cancellation - completionSource.RegisterForCancellation(); - } - } - else - { - // Due to a workaround for a race condition in NT's ReadFile & - // WriteFile routines, we will always be returning 0 from ReadFileNative - // when we do async IO instead of the number of bytes read, - // irregardless of whether the operation completed - // synchronously or asynchronously. We absolutely must not - // set asyncResult._numBytes here, since will never have correct - // results. - //Console.WriteLine("ReadFile returned: "+r+" (0x"+Int32.Format(r, "x")+") The IO completed synchronously, but the user callback was called on a separate thread"); - } - - return completionSource.Task; - } - - // Reads a byte from the file stream. Returns the byte cast to an int - // or -1 if reading from the end of the stream. - public override int ReadByte() - { - return ReadByteCore(); - } - - private Task WriteAsyncInternal(byte[] array, int offset, int numBytes, CancellationToken cancellationToken) - { - // If async IO is not supported on this platform or - // if this Win32FileStream was not opened with FileOptions.Asynchronous. - if (!_useAsyncIO) - { - return base.WriteAsync(array, offset, numBytes, cancellationToken); - } - - if (!CanWrite) throw Error.GetWriteNotSupported(); - - Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both."); - Debug.Assert(!_isPipe || (_readPos == 0 && _readLength == 0), "Win32FileStream must not have buffered data here! Pipes should be unidirectional."); - - bool writeDataStoredInBuffer = false; - if (!_isPipe) // avoid async buffering with pipes, as doing so can lead to deadlocks (see comments in ReadInternalAsyncCore) - { - // Ensure the buffer is clear for writing - if (_writePos == 0) - { - if (_readPos < _readLength) - { - FlushReadBuffer(); - } - _readPos = 0; - _readLength = 0; - } - - // Determine how much space remains in the buffer - int remainingBuffer = _bufferLength - _writePos; - Debug.Assert(remainingBuffer >= 0); - - // Simple/common case: - // - The write is smaller than our buffer, such that it's worth considering buffering it. - // - There's no active flush operation, such that we don't have to worry about the existing buffer being in use. - // - And the data we're trying to write fits in the buffer, meaning it wasn't already filled by previous writes. - // In that case, just store it in the buffer. - if (numBytes < _bufferLength && !HasActiveBufferOperation && numBytes <= remainingBuffer) - { - Buffer.BlockCopy(array, offset, GetBuffer(), _writePos, numBytes); - _writePos += numBytes; - writeDataStoredInBuffer = true; - - // There is one special-but-common case, common because devs often use - // byte[] sizes that are powers of 2 and thus fit nicely into our buffer, which is - // also a power of 2. If after our write the buffer still has remaining space, - // then we're done and can return a completed task now. But if we filled the buffer - // completely, we want to do the asynchronous flush/write as part of this operation - // rather than waiting until the next write that fills the buffer. - if (numBytes != remainingBuffer) - return Task.CompletedTask; - - Debug.Assert(_writePos == _bufferLength); - } - } - - // At this point, at least one of the following is true: - // 1. There was an active flush operation (it could have completed by now, though). - // 2. The data doesn't fit in the remaining buffer (or it's a pipe and we chose not to try). - // 3. We wrote all of the data to the buffer, filling it. - // - // If there's an active operation, we can't touch the current buffer because it's in use. - // That gives us a choice: we can either allocate a new buffer, or we can skip the buffer - // entirely (even if the data would otherwise fit in it). For now, for simplicity, we do - // the latter; it could also have performance wins due to OS-level optimizations, and we could - // potentially add support for PreAllocatedOverlapped due to having a single buffer. (We can - // switch to allocating a new buffer, potentially experimenting with buffer pooling, should - // performance data suggest it's appropriate.) - // - // If the data doesn't fit in the remaining buffer, it could be because it's so large - // it's greater than the entire buffer size, in which case we'd always skip the buffer, - // or it could be because there's more data than just the space remaining. For the latter - // case, we need to issue an asynchronous write to flush that data, which then turns this into - // the first case above with an active operation. - // - // If we already stored the data, then we have nothing additional to write beyond what - // we need to flush. - // - // In any of these cases, we have the same outcome: - // - If there's data in the buffer, flush it by writing it out asynchronously. - // - Then, if there's any data to be written, issue a write for it concurrently. - // We return a Task that represents one or both. - - // Flush the buffer asynchronously if there's anything to flush - Task flushTask = null; - if (_writePos > 0) - { - flushTask = FlushWriteAsync(cancellationToken); - - // If we already copied all of the data into the buffer, - // simply return the flush task here. Same goes for if the task has - // already completed and was unsuccessful. - if (writeDataStoredInBuffer || - flushTask.IsFaulted || - flushTask.IsCanceled) - { - return flushTask; - } - } - - Debug.Assert(!writeDataStoredInBuffer); - Debug.Assert(_writePos == 0); - - // Finally, issue the write asynchronously, and return a Task that logically - // represents the write operation, including any flushing done. - Task writeTask = WriteInternalCoreAsync(array, offset, numBytes, cancellationToken); - return - (flushTask == null || flushTask.Status == TaskStatus.RanToCompletion) ? writeTask : - (writeTask.Status == TaskStatus.RanToCompletion) ? flushTask : - Task.WhenAll(flushTask, writeTask); - } - - private unsafe Task WriteInternalCoreAsync(byte[] bytes, int offset, int numBytes, CancellationToken cancellationToken) - { - Debug.Assert(!_fileHandle.IsClosed, "!_handle.IsClosed"); - Debug.Assert(CanWrite, "_parent.CanWrite"); - Debug.Assert(bytes != null, "bytes != null"); - Debug.Assert(_readPos == _readLength, "_readPos == _readLen"); - Debug.Assert(_useAsyncIO, "WriteInternalCoreAsync doesn't work on synchronous file streams!"); - Debug.Assert(offset >= 0, "offset is negative"); - Debug.Assert(numBytes >= 0, "numBytes is negative"); - - // Create and store async stream class library specific data in the async result - FileStreamCompletionSource completionSource = new FileStreamCompletionSource(this, 0, bytes, cancellationToken); - NativeOverlapped* intOverlapped = completionSource.Overlapped; - - if (CanSeek) - { - // Make sure we set the length of the file appropriately. - long len = Length; - //Console.WriteLine("WriteInternalCoreAsync - Calculating end pos. pos: "+pos+" len: "+len+" numBytes: "+numBytes); - - // Make sure we are writing to the position that we think we are - VerifyOSHandlePosition(); - - if (_filePosition + numBytes > len) - { - //Console.WriteLine("WriteInternalCoreAsync - Setting length to: "+(pos + numBytes)); - SetLengthCore(_filePosition + numBytes); - } - - // Now set the position to read from in the NativeOverlapped struct - // For pipes, we should leave the offset fields set to 0. - intOverlapped->OffsetLow = (int)_filePosition; - intOverlapped->OffsetHigh = (int)(_filePosition >> 32); - - // When using overlapped IO, the OS is not supposed to - // touch the file pointer location at all. We will adjust it - // ourselves. This isn't threadsafe. - SeekCore(numBytes, SeekOrigin.Current); - } - - //Console.WriteLine("WriteInternalCoreAsync finishing. pos: "+pos+" numBytes: "+numBytes+" _pos: "+_pos+" Position: "+Position); - - int errorCode = 0; - // queue an async WriteFile operation and pass in a packed overlapped - int r = WriteFileNative(_fileHandle, bytes, offset, numBytes, intOverlapped, out errorCode); - - // WriteFile, the OS version, will return 0 on failure. But - // my WriteFileNative wrapper returns -1. My wrapper will return - // the following: - // On error, r==-1. - // On async requests that are still pending, r==-1 w/ errorCode==ERROR_IO_PENDING - // On async requests that completed sequentially, r==0 - // You will NEVER RELIABLY be able to get the number of bytes - // written back from this call when using overlapped IO! You must - // not pass in a non-null lpNumBytesWritten to WriteFile when using - // overlapped structures! This is ByDesign NT behavior. - if (r == -1 && numBytes != -1) - { - //Console.WriteLine("WriteFile returned 0; Write will complete asynchronously (if errorCode==3e5) errorCode: 0x{0:x}", errorCode); - - // For pipes, when they are closed on the other side, they will come here. - if (errorCode == ERROR_NO_DATA) - { - // Not an error, but EOF. AsyncFSCallback will NOT be called. - // Completing TCS and return cached task allowing the GC to collect TCS. - completionSource.SetCompletedSynchronously(0); - return Task.CompletedTask; - } - else if (errorCode != ERROR_IO_PENDING) - { - if (!_fileHandle.IsClosed && CanSeek) // Update Position - It could be anywhere. - { - SeekCore(0, SeekOrigin.Current); - } - - completionSource.ReleaseNativeResource(); - - if (errorCode == ERROR_HANDLE_EOF) - { - throw Error.GetEndOfFile(); - } - else - { - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - } - else // ERROR_IO_PENDING - { - // Only once the IO is pending do we register for cancellation - completionSource.RegisterForCancellation(); - } - } - else - { - // Due to a workaround for a race condition in NT's ReadFile & - // WriteFile routines, we will always be returning 0 from WriteFileNative - // when we do async IO instead of the number of bytes written, - // irregardless of whether the operation completed - // synchronously or asynchronously. We absolutely must not - // set asyncResult._numBytes here, since will never have correct - // results. - //Console.WriteLine("WriteFile returned: "+r+" (0x"+Int32.Format(r, "x")+") The IO completed synchronously, but the user callback was called on another thread."); - } - - return completionSource.Task; - } - - public override void WriteByte(byte value) - { - WriteByteCore(value); - } - - // Windows API definitions, from winbase.h and others - - private const int FILE_ATTRIBUTE_NORMAL = 0x00000080; - private const int FILE_ATTRIBUTE_ENCRYPTED = 0x00004000; - private const int FILE_FLAG_OVERLAPPED = 0x40000000; - internal const int GENERIC_READ = unchecked((int)0x80000000); - private const int GENERIC_WRITE = 0x40000000; - - private const int FILE_BEGIN = 0; - private const int FILE_CURRENT = 1; - private const int FILE_END = 2; - - // Error codes (not HRESULTS), from winerror.h - internal const int ERROR_BROKEN_PIPE = 109; - internal const int ERROR_NO_DATA = 232; - private const int ERROR_HANDLE_EOF = 38; - private const int ERROR_INVALID_PARAMETER = 87; - private const int ERROR_IO_PENDING = 997; - - // __ConsoleStream also uses this code. - private unsafe int ReadFileNative(SafeFileHandle handle, byte[] bytes, int offset, int count, NativeOverlapped* overlapped, out int errorCode) - { - Debug.Assert(handle != null, "handle != null"); - Debug.Assert(offset >= 0, "offset >= 0"); - Debug.Assert(count >= 0, "count >= 0"); - Debug.Assert(bytes != null, "bytes != null"); - // Don't corrupt memory when multiple threads are erroneously writing - // to this stream simultaneously. - if (bytes.Length - offset < count) - throw new IndexOutOfRangeException(SR.IndexOutOfRange_IORaceCondition); - - Debug.Assert((_useAsyncIO && overlapped != null) || (!_useAsyncIO && overlapped == null), "Async IO and overlapped parameters inconsistent in call to ReadFileNative."); - - // You can't use the fixed statement on an array of length 0. - if (bytes.Length == 0) - { - errorCode = 0; - return 0; - } - - int r = 0; - int numBytesRead = 0; - - fixed (byte* p = &bytes[0]) - { - if (_useAsyncIO) - r = Interop.Kernel32.ReadFile(handle, p + offset, count, IntPtr.Zero, overlapped); - else - r = Interop.Kernel32.ReadFile(handle, p + offset, count, out numBytesRead, IntPtr.Zero); - } - - if (r == 0) - { - errorCode = GetLastWin32ErrorAndDisposeHandleIfInvalid(); - return -1; - } - else - { - errorCode = 0; - return numBytesRead; - } - } - - private unsafe int WriteFileNative(SafeFileHandle handle, byte[] bytes, int offset, int count, NativeOverlapped* overlapped, out int errorCode) - { - Debug.Assert(handle != null, "handle != null"); - Debug.Assert(offset >= 0, "offset >= 0"); - Debug.Assert(count >= 0, "count >= 0"); - Debug.Assert(bytes != null, "bytes != null"); - // Don't corrupt memory when multiple threads are erroneously writing - // to this stream simultaneously. (the OS is reading from - // the array we pass to WriteFile, but if we read beyond the end and - // that memory isn't allocated, we could get an AV.) - if (bytes.Length - offset < count) - throw new IndexOutOfRangeException(SR.IndexOutOfRange_IORaceCondition); - - Debug.Assert((_useAsyncIO && overlapped != null) || (!_useAsyncIO && overlapped == null), "Async IO and overlapped parameters inconsistent in call to WriteFileNative."); - - // You can't use the fixed statement on an array of length 0. - if (bytes.Length == 0) - { - errorCode = 0; - return 0; - } - - int numBytesWritten = 0; - int r = 0; - - fixed (byte* p = &bytes[0]) - { - if (_useAsyncIO) - r = Interop.Kernel32.WriteFile(handle, p + offset, count, IntPtr.Zero, overlapped); - else - r = Interop.Kernel32.WriteFile(handle, p + offset, count, out numBytesWritten, IntPtr.Zero); - } - - if (r == 0) - { - errorCode = GetLastWin32ErrorAndDisposeHandleIfInvalid(); - return -1; - } - else - { - errorCode = 0; - return numBytesWritten; - } - } - - private int GetLastWin32ErrorAndDisposeHandleIfInvalid(bool throwIfInvalidHandle = false) - { - int errorCode = Marshal.GetLastWin32Error(); - - // If ERROR_INVALID_HANDLE is returned, it doesn't suffice to set - // the handle as invalid; the handle must also be closed. - // - // Marking the handle as invalid but not closing the handle - // resulted in exceptions during finalization and locked column - // values (due to invalid but unclosed handle) in SQL Win32FileStream - // scenarios. - // - // A more mainstream scenario involves accessing a file on a - // network share. ERROR_INVALID_HANDLE may occur because the network - // connection was dropped and the server closed the handle. However, - // the client side handle is still open and even valid for certain - // operations. - // - // Note that _parent.Dispose doesn't throw so we don't need to special case. - // SetHandleAsInvalid only sets _closed field to true (without - // actually closing handle) so we don't need to call that as well. - if (errorCode == Interop.Errors.ERROR_INVALID_HANDLE) - { - _fileHandle.Dispose(); - - if (throwIfInvalidHandle) - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - - return errorCode; - } - - public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken) - { - // If we're in sync mode, just use the shared CopyToAsync implementation that does - // typical read/write looping. We also need to take this path if this is a derived - // instance from FileStream, as a derived type could have overridden ReadAsync, in which - // case our custom CopyToAsync implementation isn't necessarily correct. - if (!_useAsyncIO || GetType() != typeof(FileStream)) - { - return base.CopyToAsync(destination, bufferSize, cancellationToken); - } - - StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize); - - // Bail early for cancellation if cancellation has been requested - if (cancellationToken.IsCancellationRequested) - { - return Task.FromCanceled<int>(cancellationToken); - } - - // Fail if the file was closed - if (_fileHandle.IsClosed) - { - throw Error.GetFileNotOpen(); - } - - // Do the async copy, with differing implementations based on whether the FileStream was opened as async or sync - Debug.Assert((_readPos == 0 && _readLength == 0 && _writePos >= 0) || (_writePos == 0 && _readPos <= _readLength), "We're either reading or writing, but not both."); - return AsyncModeCopyToAsync(destination, bufferSize, cancellationToken); - } - - private async Task AsyncModeCopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken) - { - Debug.Assert(_useAsyncIO, "This implementation is for async mode only"); - Debug.Assert(!_fileHandle.IsClosed, "!_handle.IsClosed"); - Debug.Assert(CanRead, "_parent.CanRead"); - - // Make sure any pending writes have been flushed before we do a read. - if (_writePos > 0) - { - await FlushWriteAsync(cancellationToken).ConfigureAwait(false); - } - - // Typically CopyToAsync would be invoked as the only "read" on the stream, but it's possible some reading is - // done and then the CopyToAsync is issued. For that case, see if we have any data available in the buffer. - if (GetBuffer() != null) - { - int bufferedBytes = _readLength - _readPos; - if (bufferedBytes > 0) - { - await destination.WriteAsync(GetBuffer(), _readPos, bufferedBytes, cancellationToken).ConfigureAwait(false); - _readPos = _readLength = 0; - } - } - - // For efficiency, we avoid creating a new task and associated state for each asynchronous read. - // Instead, we create a single reusable awaitable object that will be triggered when an await completes - // and reset before going again. - var readAwaitable = new AsyncCopyToAwaitable(this); - - // Make sure we are reading from the position that we think we are. - // Only set the position in the awaitable if we can seek (e.g. not for pipes). - bool canSeek = CanSeek; - if (canSeek) - { - VerifyOSHandlePosition(); - readAwaitable._position = _filePosition; - } - - // Get the buffer to use for the copy operation, as the base CopyToAsync does. We don't try to use - // _buffer here, even if it's not null, as concurrent operations are allowed, and another operation may - // actually be using the buffer already. Plus, it'll be rare for _buffer to be non-null, as typically - // CopyToAsync is used as the only operation performed on the stream, and the buffer is lazily initialized. - // Further, typically the CopyToAsync buffer size will be larger than that used by the FileStream, such that - // we'd likely be unable to use it anyway. Instead, we rent the buffer from a pool. - byte[] copyBuffer = ArrayPool<byte>.Shared.Rent(bufferSize); - bufferSize = 0; // repurpose bufferSize to be the high water mark for the buffer, to avoid an extra field in the state machine - - // Allocate an Overlapped we can use repeatedly for all operations - var awaitableOverlapped = new PreAllocatedOverlapped(AsyncCopyToAwaitable.s_callback, readAwaitable, copyBuffer); - var cancellationReg = default(CancellationTokenRegistration); - try - { - // Register for cancellation. We do this once for the whole copy operation, and just try to cancel - // whatever read operation may currently be in progress, if there is one. It's possible the cancellation - // request could come in between operations, in which case we flag that with explicit calls to ThrowIfCancellationRequested - // in the read/write copy loop. - if (cancellationToken.CanBeCanceled) - { - cancellationReg = cancellationToken.Register(s => - { - var innerAwaitable = (AsyncCopyToAwaitable)s; - unsafe - { - lock (innerAwaitable.CancellationLock) // synchronize with cleanup of the overlapped - { - if (innerAwaitable._nativeOverlapped != null) - { - // Try to cancel the I/O. We ignore the return value, as cancellation is opportunistic and we - // don't want to fail the operation because we couldn't cancel it. - Interop.Kernel32.CancelIoEx(innerAwaitable._fileStream._fileHandle, innerAwaitable._nativeOverlapped); - } - } - } - }, readAwaitable); - } - - // Repeatedly read from this FileStream and write the results to the destination stream. - while (true) - { - cancellationToken.ThrowIfCancellationRequested(); - readAwaitable.ResetForNextOperation(); - - try - { - bool synchronousSuccess; - int errorCode; - unsafe - { - // Allocate a native overlapped for our reusable overlapped, and set position to read based on the next - // desired address stored in the awaitable. (This position may be 0, if either we're at the beginning or - // if the stream isn't seekable.) - readAwaitable._nativeOverlapped = _fileHandle.ThreadPoolBinding.AllocateNativeOverlapped(awaitableOverlapped); - if (canSeek) - { - readAwaitable._nativeOverlapped->OffsetLow = unchecked((int)readAwaitable._position); - readAwaitable._nativeOverlapped->OffsetHigh = (int)(readAwaitable._position >> 32); - } - - // Kick off the read. - synchronousSuccess = ReadFileNative(_fileHandle, copyBuffer, 0, copyBuffer.Length, readAwaitable._nativeOverlapped, out errorCode) >= 0; - } - - // If the operation did not synchronously succeed, it either failed or initiated the asynchronous operation. - if (!synchronousSuccess) - { - switch (errorCode) - { - case ERROR_IO_PENDING: - // Async operation in progress. - break; - case ERROR_BROKEN_PIPE: - case ERROR_HANDLE_EOF: - // We're at or past the end of the file, and the overlapped callback - // won't be raised in these cases. Mark it as completed so that the await - // below will see it as such. - readAwaitable.MarkCompleted(); - break; - default: - // Everything else is an error (and there won't be a callback). - throw Win32Marshal.GetExceptionForWin32Error(errorCode); - } - } - - // Wait for the async operation (which may or may not have already completed), then throw if it failed. - await readAwaitable; - switch (readAwaitable._errorCode) - { - case 0: // success - Debug.Assert(readAwaitable._numBytes >= 0, $"Expected non-negative numBytes, got {readAwaitable._numBytes}"); - break; - case ERROR_BROKEN_PIPE: // logically success with 0 bytes read (write end of pipe closed) - case ERROR_HANDLE_EOF: // logically success with 0 bytes read (read at end of file) - Debug.Assert(readAwaitable._numBytes == 0, $"Expected 0 bytes read, got {readAwaitable._numBytes}"); - break; - case Interop.Errors.ERROR_OPERATION_ABORTED: // canceled - throw new OperationCanceledException(cancellationToken.IsCancellationRequested ? cancellationToken : new CancellationToken(true)); - default: // error - throw Win32Marshal.GetExceptionForWin32Error((int)readAwaitable._errorCode); - } - - // Successful operation. If we got zero bytes, we're done: exit the read/write loop. - int numBytesRead = (int)readAwaitable._numBytes; - if (numBytesRead == 0) - { - break; - } - - // Otherwise, update the read position for next time accordingly. - if (canSeek) - { - readAwaitable._position += numBytesRead; - } - - // (and keep track of the maximum number of bytes in the buffer we used, to avoid excessive and unnecessary - // clearing of the buffer before we return it to the pool) - if (numBytesRead > bufferSize) - { - bufferSize = numBytesRead; - } - } - finally - { - // Free the resources for this read operation - unsafe - { - NativeOverlapped* overlapped; - lock (readAwaitable.CancellationLock) // just an Exchange, but we need this to be synchronized with cancellation, so using the same lock - { - overlapped = readAwaitable._nativeOverlapped; - readAwaitable._nativeOverlapped = null; - } - if (overlapped != null) - { - _fileHandle.ThreadPoolBinding.FreeNativeOverlapped(overlapped); - } - } - } - - // Write out the read data. - await destination.WriteAsync(copyBuffer, 0, (int)readAwaitable._numBytes, cancellationToken).ConfigureAwait(false); - } - } - finally - { - // Cleanup from the whole copy operation - cancellationReg.Dispose(); - awaitableOverlapped.Dispose(); - - Array.Clear(copyBuffer, 0, bufferSize); - ArrayPool<byte>.Shared.Return(copyBuffer, clearArray: false); - - // Make sure the stream's current position reflects where we ended up - if (!_fileHandle.IsClosed && CanSeek) - { - SeekCore(0, SeekOrigin.End); - } - } - } - - /// <summary>Used by CopyToAsync to enable awaiting the result of an overlapped I/O operation with minimal overhead.</summary> - private sealed unsafe class AsyncCopyToAwaitable : ICriticalNotifyCompletion - { - /// <summary>Sentinel object used to indicate that the I/O operation has completed before being awaited.</summary> - private readonly static Action s_sentinel = () => { }; - /// <summary>Cached delegate to IOCallback.</summary> - internal static readonly IOCompletionCallback s_callback = IOCallback; - - /// <summary>The FileStream that owns this instance.</summary> - internal readonly FileStream _fileStream; - - /// <summary>Tracked position representing the next location from which to read.</summary> - internal long _position; - /// <summary>The current native overlapped pointer. This changes for each operation.</summary> - internal NativeOverlapped* _nativeOverlapped; - /// <summary> - /// null if the operation is still in progress, - /// s_sentinel if the I/O operation completed before the await, - /// s_callback if it completed after the await yielded. - /// </summary> - internal Action _continuation; - /// <summary>Last error code from completed operation.</summary> - internal uint _errorCode; - /// <summary>Last number of read bytes from completed operation.</summary> - internal uint _numBytes; - - /// <summary>Lock object used to protect cancellation-related access to _nativeOverlapped.</summary> - internal object CancellationLock => this; - - /// <summary>Initialize the awaitable.</summary> - internal unsafe AsyncCopyToAwaitable(FileStream fileStream) - { - _fileStream = fileStream; - } - - /// <summary>Reset state to prepare for the next read operation.</summary> - internal void ResetForNextOperation() - { - Debug.Assert(_position >= 0, $"Expected non-negative position, got {_position}"); - _continuation = null; - _errorCode = 0; - _numBytes = 0; - } - - /// <summary>Overlapped callback: store the results, then invoke the continuation delegate.</summary> - internal unsafe static void IOCallback(uint errorCode, uint numBytes, NativeOverlapped* pOVERLAP) - { - var awaitable = (AsyncCopyToAwaitable)ThreadPoolBoundHandle.GetNativeOverlappedState(pOVERLAP); - - Debug.Assert(awaitable._continuation != s_sentinel, "Sentinel must not have already been set as the continuation"); - awaitable._errorCode = errorCode; - awaitable._numBytes = numBytes; - - (awaitable._continuation ?? Interlocked.CompareExchange(ref awaitable._continuation, s_sentinel, null))?.Invoke(); - } - - /// <summary> - /// Called when it's known that the I/O callback for an operation will not be invoked but we'll - /// still be awaiting the awaitable. - /// </summary> - internal void MarkCompleted() - { - Debug.Assert(_continuation == null, "Expected null continuation"); - _continuation = s_sentinel; - } - - public AsyncCopyToAwaitable GetAwaiter() => this; - public bool IsCompleted => _continuation == s_sentinel; - public void GetResult() { } - public void OnCompleted(Action continuation) => UnsafeOnCompleted(continuation); - public void UnsafeOnCompleted(Action continuation) - { - if (_continuation == s_sentinel || - Interlocked.CompareExchange(ref _continuation, continuation, null) != null) - { - Debug.Assert(_continuation == s_sentinel, $"Expected continuation set to s_sentinel, got ${_continuation}"); - Task.Run(continuation); - } - } - } - - // Unlike Flush(), FlushAsync() always flushes to disk. This is intentional. - // Legend is that we chose not to flush the OS file buffers in Flush() in fear of - // perf problems with frequent, long running FlushFileBuffers() calls. But we don't - // have that problem with FlushAsync() because we will call FlushFileBuffers() in the background. - private Task FlushAsyncInternal(CancellationToken cancellationToken) - { - if (cancellationToken.IsCancellationRequested) - return Task.FromCanceled(cancellationToken); - - if (_fileHandle.IsClosed) - throw Error.GetFileNotOpen(); - - // The always synchronous data transfer between the OS and the internal buffer is intentional - // because this is needed to allow concurrent async IO requests. Concurrent data transfer - // between the OS and the internal buffer will result in race conditions. Since FlushWrite and - // FlushRead modify internal state of the stream and transfer data between the OS and the - // internal buffer, they cannot be truly async. We will, however, flush the OS file buffers - // asynchronously because it doesn't modify any internal state of the stream and is potentially - // a long running process. - try - { - FlushInternalBuffer(); - } - catch (Exception e) - { - return Task.FromException(e); - } - - if (CanWrite) - { - return Task.Factory.StartNew( - state => ((FileStream)state).FlushOSBuffer(), - this, - cancellationToken, - TaskCreationOptions.DenyChildAttach, - TaskScheduler.Default); - } - else - { - return Task.CompletedTask; - } - } - - private Task<int> TaskFromResultOrCache(int result) - { - Task<int> completedTask = _lastSynchronouslyCompletedTask; - Debug.Assert(completedTask == null || completedTask.Status == TaskStatus.RanToCompletion, "Cached task should have completed successfully"); - - if ((completedTask == null) || (completedTask.Result != result)) - { - completedTask = Task.FromResult(result); - _lastSynchronouslyCompletedTask = completedTask; - } - - return completedTask; - } - - private void LockInternal(long position, long length) - { - int positionLow = unchecked((int)(position)); - int positionHigh = unchecked((int)(position >> 32)); - int lengthLow = unchecked((int)(length)); - int lengthHigh = unchecked((int)(length >> 32)); - - if (!Interop.Kernel32.LockFile(_fileHandle, positionLow, positionHigh, lengthLow, lengthHigh)) - { - throw Win32Marshal.GetExceptionForLastWin32Error(); - } - } - - private void UnlockInternal(long position, long length) - { - int positionLow = unchecked((int)(position)); - int positionHigh = unchecked((int)(position >> 32)); - int lengthLow = unchecked((int)(length)); - int lengthHigh = unchecked((int)(length >> 32)); - - if (!Interop.Kernel32.UnlockFile(_fileHandle, positionLow, positionHigh, lengthLow, lengthHigh)) - { - throw Win32Marshal.GetExceptionForLastWin32Error(); - } - } - } -} |