From a56e30c8d33048216567753d9d3fefc2152af8ac Mon Sep 17 00:00:00 2001 From: Jiyoung Yun Date: Thu, 13 Apr 2017 14:17:19 +0900 Subject: Imported Upstream version 2.0.0.11353 --- .../shared/System/IO/FileStream.Windows.cs | 1717 ++++++++++++++++++++ 1 file changed, 1717 insertions(+) create mode 100644 src/mscorlib/shared/System/IO/FileStream.Windows.cs (limited to 'src/mscorlib/shared/System/IO/FileStream.Windows.cs') diff --git a/src/mscorlib/shared/System/IO/FileStream.Windows.cs b/src/mscorlib/shared/System/IO/FileStream.Windows.cs new file mode 100644 index 0000000000..7c09ae1a1c --- /dev/null +++ b/src/mscorlib/shared/System/IO/FileStream.Windows.cs @@ -0,0 +1,1717 @@ +// 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 _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 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 unsafe 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)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 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 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 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(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.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.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); + } + } + } + + /// Used by CopyToAsync to enable awaiting the result of an overlapped I/O operation with minimal overhead. + private sealed unsafe class AsyncCopyToAwaitable : ICriticalNotifyCompletion + { + /// Sentinel object used to indicate that the I/O operation has completed before being awaited. + private readonly static Action s_sentinel = () => { }; + /// Cached delegate to IOCallback. + internal static readonly IOCompletionCallback s_callback = IOCallback; + + /// The FileStream that owns this instance. + internal readonly FileStream _fileStream; + + /// Tracked position representing the next location from which to read. + internal long _position; + /// The current native overlapped pointer. This changes for each operation. + internal NativeOverlapped* _nativeOverlapped; + /// + /// 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. + /// + internal Action _continuation; + /// Last error code from completed operation. + internal uint _errorCode; + /// Last number of read bytes from completed operation. + internal uint _numBytes; + + /// Lock object used to protect cancellation-related access to _nativeOverlapped. + internal object CancellationLock => this; + + /// Initialize the awaitable. + internal unsafe AsyncCopyToAwaitable(FileStream fileStream) + { + _fileStream = fileStream; + } + + /// Reset state to prepare for the next read operation. + internal void ResetForNextOperation() + { + Debug.Assert(_position >= 0, $"Expected non-negative position, got {_position}"); + _continuation = null; + _errorCode = 0; + _numBytes = 0; + } + + /// Overlapped callback: store the results, then invoke the continuation delegate. + 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(); + } + + /// + /// 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. + /// + 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 TaskFromResultOrCache(int result) + { + Task 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(); + } + } + } +} -- cgit v1.2.3