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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
/*============================================================
**
** Class: StreamWriter
**
** <OWNER>gpaperin</OWNER>
**
**
** Purpose: For writing text to streams in a particular
** encoding.
**
**
===========================================================*/
using System;
using System.Text;
using System.Threading;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.Versioning;
using System.Security.Permissions;
using System.Runtime.Serialization;
using System.Diagnostics.Contracts;
using System.Runtime.InteropServices;
#if FEATURE_ASYNC_IO
using System.Threading.Tasks;
#endif
namespace System.IO
{
// This class implements a TextWriter for writing characters to a Stream.
// This is designed for character output in a particular Encoding,
// whereas the Stream class is designed for byte input and output.
//
[Serializable]
[ComVisible(true)]
public class StreamWriter : TextWriter
{
// For UTF-8, the values of 1K for the default buffer size and 4K for the
// file stream buffer size are reasonable & give very reasonable
// performance for in terms of construction time for the StreamWriter and
// write perf. Note that for UTF-8, we end up allocating a 4K byte buffer,
// which means we take advantage of adaptive buffering code.
// The performance using UnicodeEncoding is acceptable.
internal const int DefaultBufferSize = 1024; // char[]
private const int DefaultFileStreamBufferSize = 4096;
private const int MinBufferSize = 128;
#if FEATURE_ASYNC_IO
private const Int32 DontCopyOnWriteLineThreshold = 512;
#endif
// Bit bucket - Null has no backing store. Non closable.
public new static readonly StreamWriter Null = new StreamWriter(Stream.Null, new UTF8Encoding(false, true), MinBufferSize, true);
private Stream stream;
private Encoding encoding;
private Encoder encoder;
private byte[] byteBuffer;
private char[] charBuffer;
private int charPos;
private int charLen;
private bool autoFlush;
private bool haveWrittenPreamble;
private bool closable;
#if MDA_SUPPORTED
[NonSerialized]
// For StreamWriterBufferedDataLost MDA
private MdaHelper mdaHelper;
#endif
#if FEATURE_ASYNC_IO
// We don't guarantee thread safety on StreamWriter, but we should at
// least prevent users from trying to write anything while an Async
// write from the same thread is in progress.
[NonSerialized]
private volatile Task _asyncWriteTask;
private void CheckAsyncTaskInProgress()
{
// We are not locking the access to _asyncWriteTask because this is not meant to guarantee thread safety.
// We are simply trying to deter calling any Write APIs while an async Write from the same thread is in progress.
Task t = _asyncWriteTask;
if (t != null && !t.IsCompleted)
throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_AsyncIOInProgress"));
}
#endif
// The high level goal is to be tolerant of encoding errors when we read and very strict
// when we write. Hence, default StreamWriter encoding will throw on encoding error.
// Note: when StreamWriter throws on invalid encoding chars (for ex, high surrogate character
// D800-DBFF without a following low surrogate character DC00-DFFF), it will cause the
// internal StreamWriter's state to be irrecoverable as it would have buffered the
// illegal chars and any subsequent call to Flush() would hit the encoding error again.
// Even Close() will hit the exception as it would try to flush the unwritten data.
// Maybe we can add a DiscardBufferedData() method to get out of such situation (like
// StreamReader though for different reason). Either way, the buffered data will be lost!
private static volatile Encoding _UTF8NoBOM;
internal static Encoding UTF8NoBOM {
[FriendAccessAllowed]
get {
if (_UTF8NoBOM == null) {
// No need for double lock - we just want to avoid extra
// allocations in the common case.
UTF8Encoding noBOM = new UTF8Encoding(false, true);
Thread.MemoryBarrier();
_UTF8NoBOM = noBOM;
}
return _UTF8NoBOM;
}
}
internal StreamWriter(): base(null) { // Ask for CurrentCulture all the time
}
public StreamWriter(Stream stream)
: this(stream, UTF8NoBOM, DefaultBufferSize, false) {
}
public StreamWriter(Stream stream, Encoding encoding)
: this(stream, encoding, DefaultBufferSize, false) {
}
// Creates a new StreamWriter for the given stream. The
// character encoding is set by encoding and the buffer size,
// in number of 16-bit characters, is set by bufferSize.
//
public StreamWriter(Stream stream, Encoding encoding, int bufferSize)
: this(stream, encoding, bufferSize, false) {
}
public StreamWriter(Stream stream, Encoding encoding, int bufferSize, bool leaveOpen)
: base(null) // Ask for CurrentCulture all the time
{
if (stream == null || encoding == null)
throw new ArgumentNullException((stream == null ? "stream" : "encoding"));
if (!stream.CanWrite)
throw new ArgumentException(Environment.GetResourceString("Argument_StreamNotWritable"));
if (bufferSize <= 0) throw new ArgumentOutOfRangeException("bufferSize", Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum"));
Contract.EndContractBlock();
Init(stream, encoding, bufferSize, leaveOpen);
}
[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
public StreamWriter(String path)
: this(path, false, UTF8NoBOM, DefaultBufferSize) {
}
[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
public StreamWriter(String path, bool append)
: this(path, append, UTF8NoBOM, DefaultBufferSize) {
}
[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
public StreamWriter(String path, bool append, Encoding encoding)
: this(path, append, encoding, DefaultBufferSize) {
}
[System.Security.SecuritySafeCritical]
[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
public StreamWriter(String path, bool append, Encoding encoding, int bufferSize): this(path, append, encoding, bufferSize, true) {
}
[System.Security.SecurityCritical]
[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
internal StreamWriter(String path, bool append, Encoding encoding, int bufferSize, bool checkHost)
: base(null)
{ // Ask for CurrentCulture all the time
if (path == null)
throw new ArgumentNullException("path");
if (encoding == null)
throw new ArgumentNullException("encoding");
if (path.Length == 0)
throw new ArgumentException(Environment.GetResourceString("Argument_EmptyPath"));
if (bufferSize <= 0) throw new ArgumentOutOfRangeException("bufferSize", Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum"));
Contract.EndContractBlock();
Stream stream = CreateFile(path, append, checkHost);
Init(stream, encoding, bufferSize, false);
}
[System.Security.SecuritySafeCritical]
private void Init(Stream streamArg, Encoding encodingArg, int bufferSize, bool shouldLeaveOpen)
{
this.stream = streamArg;
this.encoding = encodingArg;
this.encoder = encoding.GetEncoder();
if (bufferSize < MinBufferSize) bufferSize = MinBufferSize;
charBuffer = new char[bufferSize];
byteBuffer = new byte[encoding.GetMaxByteCount(bufferSize)];
charLen = bufferSize;
// If we're appending to a Stream that already has data, don't write
// the preamble.
if (stream.CanSeek && stream.Position > 0)
haveWrittenPreamble = true;
closable = !shouldLeaveOpen;
#if MDA_SUPPORTED
if (Mda.StreamWriterBufferedDataLost.Enabled) {
String callstack = null;
if (Mda.StreamWriterBufferedDataLost.CaptureAllocatedCallStack)
callstack = Environment.GetStackTrace(null, false);
mdaHelper = new MdaHelper(this, callstack);
}
#endif
}
[System.Security.SecurityCritical]
[ResourceExposure(ResourceScope.Machine)]
[ResourceConsumption(ResourceScope.Machine)]
private static Stream CreateFile(String path, bool append, bool checkHost) {
FileMode mode = append? FileMode.Append: FileMode.Create;
FileStream f = new FileStream(path, mode, FileAccess.Write, FileShare.Read,
DefaultFileStreamBufferSize, FileOptions.SequentialScan, Path.GetFileName(path), false, false, checkHost);
return f;
}
public override void Close() {
Dispose(true);
GC.SuppressFinalize(this);
}
protected override void Dispose(bool disposing) {
try {
// We need to flush any buffered data if we are being closed/disposed.
// Also, we never close the handles for stdout & friends. So we can safely
// write any buffered data to those streams even during finalization, which
// is generally the right thing to do.
if (stream != null) {
// Note: flush on the underlying stream can throw (ex., low disk space)
if (disposing || (LeaveOpen && stream is __ConsoleStream))
{
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
Flush(true, true);
#if MDA_SUPPORTED
// Disable buffered data loss mda
if (mdaHelper != null)
GC.SuppressFinalize(mdaHelper);
#endif
}
}
}
finally {
// Dispose of our resources if this StreamWriter is closable.
// Note: Console.Out and other such non closable streamwriters should be left alone
if (!LeaveOpen && stream != null) {
try {
// Attempt to close the stream even if there was an IO error from Flushing.
// Note that Stream.Close() can potentially throw here (may or may not be
// due to the same Flush error). In this case, we still need to ensure
// cleaning up internal resources, hence the finally block.
if (disposing)
stream.Close();
}
finally {
stream = null;
byteBuffer = null;
charBuffer = null;
encoding = null;
encoder = null;
charLen = 0;
base.Dispose(disposing);
}
}
}
}
public override void Flush()
{
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
Flush(true, true);
}
private void Flush(bool flushStream, bool flushEncoder)
{
// flushEncoder should be true at the end of the file and if
// the user explicitly calls Flush (though not if AutoFlush is true).
// This is required to flush any dangling characters from our UTF-7
// and UTF-8 encoders.
if (stream == null)
__Error.WriterClosed();
// Perf boost for Flush on non-dirty writers.
if (charPos==0 && ((!flushStream && !flushEncoder) || CompatibilitySwitches.IsAppEarlierThanWindowsPhone8))
return;
if (!haveWrittenPreamble) {
haveWrittenPreamble = true;
byte[] preamble = encoding.GetPreamble();
if (preamble.Length > 0)
stream.Write(preamble, 0, preamble.Length);
}
int count = encoder.GetBytes(charBuffer, 0, charPos, byteBuffer, 0, flushEncoder);
charPos = 0;
if (count > 0)
stream.Write(byteBuffer, 0, count);
// By definition, calling Flush should flush the stream, but this is
// only necessary if we passed in true for flushStream. The Web
// Services guys have some perf tests where flushing needlessly hurts.
if (flushStream)
stream.Flush();
}
public virtual bool AutoFlush {
get { return autoFlush; }
set
{
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
autoFlush = value;
if (value) Flush(true, false);
}
}
public virtual Stream BaseStream {
get { return stream; }
}
internal bool LeaveOpen {
get { return !closable; }
}
internal bool HaveWrittenPreamble {
set { haveWrittenPreamble= value; }
}
public override Encoding Encoding {
get { return encoding; }
}
public override void Write(char value)
{
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
if (charPos == charLen) Flush(false, false);
charBuffer[charPos] = value;
charPos++;
if (autoFlush) Flush(true, false);
}
public override void Write(char[] buffer)
{
// This may be faster than the one with the index & count since it
// has to do less argument checking.
if (buffer==null)
return;
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
int index = 0;
int count = buffer.Length;
while (count > 0) {
if (charPos == charLen) Flush(false, false);
int n = charLen - charPos;
if (n > count) n = count;
Contract.Assert(n > 0, "StreamWriter::Write(char[]) isn't making progress! This is most likely a ---- in user code.");
Buffer.InternalBlockCopy(buffer, index * sizeof(char), charBuffer, charPos * sizeof(char), n * sizeof(char));
charPos += n;
index += n;
count -= n;
}
if (autoFlush) Flush(true, false);
}
public override void Write(char[] buffer, int index, int count) {
if (buffer==null)
throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));
if (index < 0)
throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (count < 0)
throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (buffer.Length - index < count)
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
Contract.EndContractBlock();
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
while (count > 0) {
if (charPos == charLen) Flush(false, false);
int n = charLen - charPos;
if (n > count) n = count;
Contract.Assert(n > 0, "StreamWriter::Write(char[], int, int) isn't making progress! This is most likely a race condition in user code.");
Buffer.InternalBlockCopy(buffer, index * sizeof(char), charBuffer, charPos * sizeof(char), n * sizeof(char));
charPos += n;
index += n;
count -= n;
}
if (autoFlush) Flush(true, false);
}
public override void Write(String value)
{
if (value != null)
{
#if FEATURE_ASYNC_IO
CheckAsyncTaskInProgress();
#endif
int count = value.Length;
int index = 0;
while (count > 0) {
if (charPos == charLen) Flush(false, false);
int n = charLen - charPos;
if (n > count) n = count;
Contract.Assert(n > 0, "StreamWriter::Write(String) isn't making progress! This is most likely a race condition in user code.");
value.CopyTo(index, charBuffer, charPos, n);
charPos += n;
index += n;
count -= n;
}
if (autoFlush) Flush(true, false);
}
}
#if FEATURE_ASYNC_IO
#region Task based Async APIs
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteAsync(char value)
{
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteAsync(value);
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, value, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: false);
_asyncWriteTask = task;
return task;
}
// We pass in private instance fields of this MarshalByRefObject-derived type as local params
// to ensure performant access inside the state machine that corresponds this async method.
// Fields that are written to must be assigned at the end of the method *and* before instance invocations.
private static async Task WriteAsyncInternal(StreamWriter _this, Char value,
Char[] charBuffer, Int32 charPos, Int32 charLen, Char[] coreNewLine,
bool autoFlush, bool appendNewLine)
{
if (charPos == charLen) {
await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
charBuffer[charPos] = value;
charPos++;
if (appendNewLine)
{
for (Int32 i = 0; i < coreNewLine.Length; i++) // Expect 2 iterations, no point calling BlockCopy
{
if (charPos == charLen) {
await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
charBuffer[charPos] = coreNewLine[i];
charPos++;
}
}
if (autoFlush) {
await _this.FlushAsyncInternal(true, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
_this.CharPos_Prop = charPos;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteAsync(String value)
{
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteAsync(value);
if (value != null)
{
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, value, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: false);
_asyncWriteTask = task;
return task;
}
else
{
return Task.CompletedTask;
}
}
// We pass in private instance fields of this MarshalByRefObject-derived type as local params
// to ensure performant access inside the state machine that corresponds this async method.
// Fields that are written to must be assigned at the end of the method *and* before instance invocations.
private static async Task WriteAsyncInternal(StreamWriter _this, String value,
Char[] charBuffer, Int32 charPos, Int32 charLen, Char[] coreNewLine,
bool autoFlush, bool appendNewLine)
{
Contract.Requires(value != null);
int count = value.Length;
int index = 0;
while (count > 0)
{
if (charPos == charLen) {
await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
int n = charLen - charPos;
if (n > count)
n = count;
Contract.Assert(n > 0, "StreamWriter::Write(String) isn't making progress! This is most likely a race condition in user code.");
value.CopyTo(index, charBuffer, charPos, n);
charPos += n;
index += n;
count -= n;
}
if (appendNewLine)
{
for (Int32 i = 0; i < coreNewLine.Length; i++) // Expect 2 iterations, no point calling BlockCopy
{
if (charPos == charLen) {
await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
charBuffer[charPos] = coreNewLine[i];
charPos++;
}
}
if (autoFlush) {
await _this.FlushAsyncInternal(true, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
_this.CharPos_Prop = charPos;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteAsync(char[] buffer, int index, int count)
{
if (buffer==null)
throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));
if (index < 0)
throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (count < 0)
throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (buffer.Length - index < count)
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
Contract.EndContractBlock();
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteAsync(buffer, index, count);
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, buffer, index, count, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: false);
_asyncWriteTask = task;
return task;
}
// We pass in private instance fields of this MarshalByRefObject-derived type as local params
// to ensure performant access inside the state machine that corresponds this async method.
// Fields that are written to must be assigned at the end of the method *and* before instance invocations.
private static async Task WriteAsyncInternal(StreamWriter _this, Char[] buffer, Int32 index, Int32 count,
Char[] charBuffer, Int32 charPos, Int32 charLen, Char[] coreNewLine,
bool autoFlush, bool appendNewLine)
{
Contract.Requires(count == 0 || (count > 0 && buffer != null));
Contract.Requires(index >= 0);
Contract.Requires(count >= 0);
Contract.Requires(buffer == null || (buffer != null && buffer.Length - index >= count));
while (count > 0)
{
if (charPos == charLen) {
await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
int n = charLen - charPos;
if (n > count) n = count;
Contract.Assert(n > 0, "StreamWriter::Write(char[], int, int) isn't making progress! This is most likely a race condition in user code.");
Buffer.InternalBlockCopy(buffer, index * sizeof(char), charBuffer, charPos * sizeof(char), n * sizeof(char));
charPos += n;
index += n;
count -= n;
}
if (appendNewLine)
{
for (Int32 i = 0; i < coreNewLine.Length; i++) // Expect 2 iterations, no point calling BlockCopy
{
if (charPos == charLen) {
await _this.FlushAsyncInternal(false, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
charBuffer[charPos] = coreNewLine[i];
charPos++;
}
}
if (autoFlush) {
await _this.FlushAsyncInternal(true, false, charBuffer, charPos).ConfigureAwait(false);
Contract.Assert(_this.charPos == 0);
charPos = 0;
}
_this.CharPos_Prop = charPos;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteLineAsync()
{
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteLineAsync();
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, null, 0, 0, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: true);
_asyncWriteTask = task;
return task;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteLineAsync(char value)
{
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteLineAsync(value);
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, value, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: true);
_asyncWriteTask = task;
return task;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteLineAsync(String value)
{
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteLineAsync(value);
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, value, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: true);
_asyncWriteTask = task;
return task;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task WriteLineAsync(char[] buffer, int index, int count)
{
if (buffer==null)
throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer"));
if (index < 0)
throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (count < 0)
throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (buffer.Length - index < count)
throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
Contract.EndContractBlock();
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Write() which a subclass might have overriden.
// To be safe we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Write) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.WriteLineAsync(buffer, index, count);
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = WriteAsyncInternal(this, buffer, index, count, charBuffer, charPos, charLen, CoreNewLine, autoFlush, appendNewLine: true);
_asyncWriteTask = task;
return task;
}
[HostProtection(ExternalThreading = true)]
[ComVisible(false)]
public override Task FlushAsync()
{
// If we have been inherited into a subclass, the following implementation could be incorrect
// since it does not call through to Flush() which a subclass might have overriden. To be safe
// we will only use this implementation in cases where we know it is safe to do so,
// and delegate to our base class (which will call into Flush) when we are not sure.
if (this.GetType() != typeof(StreamWriter))
return base.FlushAsync();
// flushEncoder should be true at the end of the file and if
// the user explicitly calls Flush (though not if AutoFlush is true).
// This is required to flush any dangling characters from our UTF-7
// and UTF-8 encoders.
if (stream == null)
__Error.WriterClosed();
CheckAsyncTaskInProgress();
Task task = FlushAsyncInternal(true, true, charBuffer, charPos);
_asyncWriteTask = task;
return task;
}
private Int32 CharPos_Prop {
set { this.charPos = value; }
}
private bool HaveWrittenPreamble_Prop {
set { this.haveWrittenPreamble = value; }
}
private Task FlushAsyncInternal(bool flushStream, bool flushEncoder,
Char[] sCharBuffer, Int32 sCharPos) {
// Perf boost for Flush on non-dirty writers.
if (sCharPos == 0 && !flushStream && !flushEncoder)
return Task.CompletedTask;
Task flushTask = FlushAsyncInternal(this, flushStream, flushEncoder, sCharBuffer, sCharPos, this.haveWrittenPreamble,
this.encoding, this.encoder, this.byteBuffer, this.stream);
this.charPos = 0;
return flushTask;
}
// We pass in private instance fields of this MarshalByRefObject-derived type as local params
// to ensure performant access inside the state machine that corresponds this async method.
private static async Task FlushAsyncInternal(StreamWriter _this, bool flushStream, bool flushEncoder,
Char[] charBuffer, Int32 charPos, bool haveWrittenPreamble,
Encoding encoding, Encoder encoder, Byte[] byteBuffer, Stream stream)
{
if (!haveWrittenPreamble)
{
_this.HaveWrittenPreamble_Prop = true;
byte[] preamble = encoding.GetPreamble();
if (preamble.Length > 0)
await stream.WriteAsync(preamble, 0, preamble.Length).ConfigureAwait(false);
}
int count = encoder.GetBytes(charBuffer, 0, charPos, byteBuffer, 0, flushEncoder);
if (count > 0)
await stream.WriteAsync(byteBuffer, 0, count).ConfigureAwait(false);
// By definition, calling Flush should flush the stream, but this is
// only necessary if we passed in true for flushStream. The Web
// Services guys have some perf tests where flushing needlessly hurts.
if (flushStream)
await stream.FlushAsync().ConfigureAwait(false);
}
#endregion
#endif //FEATURE_ASYNC_IO
#if MDA_SUPPORTED
// StreamWriterBufferedDataLost MDA
// Instead of adding a finalizer to StreamWriter for detecting buffered data loss
// (ie, when the user forgets to call Close/Flush on the StreamWriter), we will
// have a separate object with normal finalization semantics that maintains a
// back pointer to this StreamWriter and alerts about any data loss
private sealed class MdaHelper
{
private StreamWriter streamWriter;
private String allocatedCallstack; // captures the callstack when this streamwriter was allocated
internal MdaHelper(StreamWriter sw, String cs)
{
streamWriter = sw;
allocatedCallstack = cs;
}
// Finalizer
~MdaHelper()
{
// Make sure people closed this StreamWriter, exclude StreamWriter::Null.
if (streamWriter.charPos != 0 && streamWriter.stream != null && streamWriter.stream != Stream.Null) {
String fileName = (streamWriter.stream is FileStream) ? ((FileStream)streamWriter.stream).NameInternal : "<unknown>";
String callStack = allocatedCallstack;
if (callStack == null)
callStack = Environment.GetResourceString("IO_StreamWriterBufferedDataLostCaptureAllocatedFromCallstackNotEnabled");
String message = Environment.GetResourceString("IO_StreamWriterBufferedDataLost", streamWriter.stream.GetType().FullName, fileName, callStack);
Mda.StreamWriterBufferedDataLost.ReportError(message);
}
}
} // class MdaHelper
#endif // MDA_SUPPORTED
} // class StreamWriter
} // namespace