public override IAsyncResult BeginWrite(byte[] array, int offset, int numBytes, AsyncCallback userCallback, Object stateObject)
{
if (array==null)
throw new ArgumentNullException("array");
if (offset < 0)
throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (numBytes < 0)
throw new ArgumentOutOfRangeException("numBytes", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (array.Length - offset < numBytes)
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
Contract.EndContractBlock();
if (_handle.IsClosed) __Error.FileNotOpen();
#if !FEATURE_PAL && FEATURE_ASYNC_IO
if (!_isAsync)
return base.BeginWrite(array, offset, numBytes, userCallback, stateObject);
if (!CanWrite) __Error.WriteNotSupported();
Contract.Assert((_readPos==0 && _readLen==0 && _writePos >= 0) || (_writePos==0 && _readPos <= _readLen), "We're either reading or writing, but not both.");
if (_isPipe) {
// Pipes are ----ed up, 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
// FileStream's BeginRead 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.
Contract.Assert(_readPos == 0 && _readLen == 0, "FileStream must not have buffered data here! Pipes should be unidirectional.");
if (_writePos > 0)
FlushWrite(false);
return BeginWriteCore(array, offset, numBytes, userCallback, stateObject);
}
// Handle buffering.
FileStreamAsyncResult asyncResult;
if (_writePos==0) {
if (_readPos < _readLen) FlushRead();
_readPos = 0;
_readLen = 0;
}
int n = _bufferSize - _writePos;
if (numBytes <= n) {
if (_writePos==0) _buffer = new byte[_bufferSize];
Buffer.InternalBlockCopy(array, offset, _buffer, _writePos, numBytes);
_writePos += numBytes;
asyncResult = new FileStreamAsyncResult();
asyncResult._userCallback = userCallback;
asyncResult._userStateObject = stateObject;
asyncResult._waitHandle = null;
asyncResult._isWrite = true;
asyncResult._numBufferedBytes = numBytes;
asyncResult.CallUserCallback();
return asyncResult;
}
if (_writePos > 0) FlushWrite(false);
return BeginWriteCore(array, offset, numBytes, userCallback, stateObject);
#else
return base.BeginWrite(array, offset, numBytes, userCallback, stateObject);
#endif // !FEATURE_PAL && FEATURE_ASYNC_IO
}
unsafe private FileStreamAsyncResult BeginWriteCore(byte[] bytes, int offset, int numBytes, AsyncCallback userCallback, Object stateObject)
{
Contract.Assert(!_handle.IsClosed, "!_handle.IsClosed");
Contract.Assert(CanWrite, "CanWrite");
Contract.Assert(bytes != null, "bytes != null");
Contract.Assert(_readPos == _readLen, "_readPos == _readLen");
Contract.Assert(_isAsync, "BeginWriteCore doesn't work on synchronous file streams!");
Contract.Assert(offset >= 0, "offset is negative");
Contract.Assert(numBytes >= 0, "numBytes is negative");
// Create and store async stream class library specific data in the
// async result
FileStreamAsyncResult asyncResult = new FileStreamAsyncResult();
asyncResult._handle = _handle;
asyncResult._userCallback = userCallback;
asyncResult._userStateObject = stateObject;
asyncResult._isWrite = true;
// For Synchronous IO, I could go with either a callback and using
// the managed Monitor class, or I could create a handle and wait on it.
ManualResetEvent waitHandle = new ManualResetEvent(false);
asyncResult._waitHandle = waitHandle;
// Create a managed overlapped class
// We will set the file offsets later
Overlapped overlapped = new Overlapped(0, 0, IntPtr.Zero, asyncResult);
// Pack the Overlapped class, and store it in the async result
NativeOverlapped* intOverlapped;
if (userCallback != null)
intOverlapped = overlapped.Pack(IOCallback, bytes);
else
intOverlapped = overlapped.UnsafePack(null, bytes);
asyncResult._overlapped = intOverlapped;
if (CanSeek) {
// Make sure we set the length of the file appropriately.
long len = Length;
//Console.WriteLine("BeginWrite - Calculating end pos. pos: "+pos+" len: "+len+" numBytes: "+numBytes);
// Make sure we are writing to the position that we think we are
if (_exposedHandle)
VerifyOSHandlePosition();
if (_pos + numBytes > len) {
//Console.WriteLine("BeginWrite - Setting length to: "+(pos + numBytes));
SetLengthCore(_pos + 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)_pos;
intOverlapped->OffsetHigh = (int)(_pos>>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("BeginWrite finishing. pos: "+pos+" numBytes: "+numBytes+" _pos: "+_pos+" Position: "+Position);
int hr = 0;
// queue an async WriteFile operation and pass in a packed overlapped
int r = WriteFileNative(_handle, bytes, offset, numBytes, intOverlapped, out hr);
// 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/ hr==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 hr==3e5) hr: 0x{0:x}", hr);
// For pipes, when they are closed on the other side, they will come here.
if (hr == ERROR_NO_DATA) {
// Not an error, but EOF. AsyncFSCallback will NOT be
// called. Call the user callback here.
asyncResult.CallUserCallback();
// EndWrite will free the Overlapped struct correctly.
}
else if (hr != ERROR_IO_PENDING) {
if (!_handle.IsClosed && CanSeek) // Update Position - It could be anywhere.
SeekCore(0, SeekOrigin.Current);
if (hr == ERROR_HANDLE_EOF)
__Error.EndOfFile();
else
__Error.WinIOError(hr, String.Empty);
}
}
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 asyncResult;
}
unsafe private FileStreamAsyncResult BeginReadCore(byte[] bytes, int offset, int numBytes, AsyncCallback userCallback, Object stateObject, int numBufferedBytesRead)
{
Contract.Assert(!_handle.IsClosed, "!_handle.IsClosed");
Contract.Assert(CanRead, "CanRead");
Contract.Assert(bytes != null, "bytes != null");
Contract.Assert(_writePos == 0, "_writePos == 0");
Contract.Assert(_isAsync, "BeginReadCore doesn't work on synchronous file streams!");
Contract.Assert(offset >= 0, "offset is negative");
Contract.Assert(numBytes >= 0, "numBytes is negative");
// Create and store async stream class library specific data in the
// async result
FileStreamAsyncResult asyncResult = new FileStreamAsyncResult();
asyncResult._handle = _handle;
asyncResult._userCallback = userCallback;
asyncResult._userStateObject = stateObject;
asyncResult._isWrite = false;
// Must set this here to ensure all the state on the IAsyncResult
// object is set before we call ReadFile, which gives the OS an
// opportunity to run our callback (including the user callback &
// the call to EndRead) before ReadFile has returned.
asyncResult._numBufferedBytes = numBufferedBytesRead;
// For Synchronous IO, I could go with either a callback and using
// the managed Monitor class, or I could create a handle and wait on it.
ManualResetEvent waitHandle = new ManualResetEvent(false);
asyncResult._waitHandle = waitHandle;
// Create a managed overlapped class
// We will set the file offsets later
Overlapped overlapped = new Overlapped(0, 0, IntPtr.Zero, asyncResult);
// Pack the Overlapped class, and store it in the async result
NativeOverlapped* intOverlapped;
if (userCallback != null)
intOverlapped = overlapped.Pack(IOCallback, bytes);
else
intOverlapped = overlapped.UnsafePack(null, bytes);
asyncResult._overlapped = intOverlapped;
// 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
if (_exposedHandle)
VerifyOSHandlePosition();
if (_pos + numBytes > len) {
if (_pos <= len)
numBytes = (int) (len - _pos);
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)_pos);
intOverlapped->OffsetHigh = (int)(_pos>>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 hr = 0;
int r = ReadFileNative(_handle, bytes, offset, numBytes, intOverlapped, out hr);
// 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/ hr==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 (hr == 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;
asyncResult.CallUserCallback();
// EndRead will free the Overlapped struct correctly.
}
else if (hr != ERROR_IO_PENDING) {
if (!_handle.IsClosed && CanSeek) // Update Position - It could be anywhere.
SeekCore(0, SeekOrigin.Current);
if (hr == ERROR_HANDLE_EOF)
__Error.EndOfFile();
else
__Error.WinIOError(hr, String.Empty);
}
}
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 asyncResult;
}
