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HttpResponseStreamWriter.cs
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/
HttpResponseStreamWriter.cs
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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Buffers;
using System.Diagnostics;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
namespace Microsoft.AspNetCore.WebUtilities
{
/// <summary>
/// Writes to the <see cref="Stream"/> using the supplied <see cref="Encoding"/>.
/// It does not write the BOM and also does not close the stream.
/// </summary>
public class HttpResponseStreamWriter : TextWriter
{
private const int MinBufferSize = 128;
internal const int DefaultBufferSize = 16 * 1024;
private Stream _stream;
private readonly Encoder _encoder;
private readonly ArrayPool<byte> _bytePool;
private readonly ArrayPool<char> _charPool;
private readonly int _charBufferSize;
private byte[] _byteBuffer;
private char[] _charBuffer;
private int _charBufferCount;
private bool _disposed;
public HttpResponseStreamWriter(Stream stream, Encoding encoding)
: this(stream, encoding, DefaultBufferSize, ArrayPool<byte>.Shared, ArrayPool<char>.Shared)
{
}
public HttpResponseStreamWriter(Stream stream, Encoding encoding, int bufferSize)
: this(stream, encoding, bufferSize, ArrayPool<byte>.Shared, ArrayPool<char>.Shared)
{
}
public HttpResponseStreamWriter(
Stream stream,
Encoding encoding,
int bufferSize,
ArrayPool<byte> bytePool,
ArrayPool<char> charPool)
{
_stream = stream ?? throw new ArgumentNullException(nameof(stream));
Encoding = encoding ?? throw new ArgumentNullException(nameof(encoding));
_bytePool = bytePool ?? throw new ArgumentNullException(nameof(bytePool));
_charPool = charPool ?? throw new ArgumentNullException(nameof(charPool));
if (bufferSize <= 0)
{
throw new ArgumentOutOfRangeException(nameof(bufferSize));
}
if (!_stream.CanWrite)
{
throw new ArgumentException(Resources.HttpResponseStreamWriter_StreamNotWritable, nameof(stream));
}
_charBufferSize = bufferSize;
_encoder = encoding.GetEncoder();
_charBuffer = charPool.Rent(bufferSize);
try
{
var requiredLength = encoding.GetMaxByteCount(bufferSize);
_byteBuffer = bytePool.Rent(requiredLength);
}
catch
{
charPool.Return(_charBuffer);
if (_byteBuffer != null)
{
bytePool.Return(_byteBuffer);
}
throw;
}
}
public override Encoding Encoding { get; }
public override void Write(char value)
{
if (_disposed)
{
throw new ObjectDisposedException(nameof(HttpResponseStreamWriter));
}
if (_charBufferCount == _charBufferSize)
{
FlushInternal(flushEncoder: false);
}
_charBuffer[_charBufferCount] = value;
_charBufferCount++;
}
public override void Write(char[] values, int index, int count)
{
if (_disposed)
{
throw new ObjectDisposedException(nameof(HttpResponseStreamWriter));
}
if (values == null)
{
return;
}
while (count > 0)
{
if (_charBufferCount == _charBufferSize)
{
FlushInternal(flushEncoder: false);
}
CopyToCharBuffer(values, ref index, ref count);
}
}
public override void Write(string value)
{
if (_disposed)
{
throw new ObjectDisposedException(nameof(HttpResponseStreamWriter));
}
if (value == null)
{
return;
}
var count = value.Length;
var index = 0;
while (count > 0)
{
if (_charBufferCount == _charBufferSize)
{
FlushInternal(flushEncoder: false);
}
CopyToCharBuffer(value, ref index, ref count);
}
}
public override Task WriteAsync(char value)
{
if (_disposed)
{
return GetObjectDisposedTask();
}
if (_charBufferCount == _charBufferSize)
{
return WriteAsyncAwaited(value);
}
else
{
// Enough room in buffer, no need to go async
_charBuffer[_charBufferCount] = value;
_charBufferCount++;
return Task.CompletedTask;
}
}
private async Task WriteAsyncAwaited(char value)
{
Debug.Assert(_charBufferCount == _charBufferSize);
await FlushInternalAsync(flushEncoder: false);
_charBuffer[_charBufferCount] = value;
_charBufferCount++;
}
public override Task WriteAsync(char[] values, int index, int count)
{
if (_disposed)
{
return GetObjectDisposedTask();
}
if (values == null || count == 0)
{
return Task.CompletedTask;
}
var remaining = _charBufferSize - _charBufferCount;
if (remaining >= count)
{
// Enough room in buffer, no need to go async
CopyToCharBuffer(values, ref index, ref count);
return Task.CompletedTask;
}
else
{
return WriteAsyncAwaited(values, index, count);
}
}
private async Task WriteAsyncAwaited(char[] values, int index, int count)
{
Debug.Assert(count > 0);
Debug.Assert(_charBufferSize - _charBufferCount > count);
while (count > 0)
{
if (_charBufferCount == _charBufferSize)
{
await FlushInternalAsync(flushEncoder: false);
}
CopyToCharBuffer(values, ref index, ref count);
Debug.Assert(count == 0);
}
}
public override Task WriteAsync(string value)
{
if (_disposed)
{
return GetObjectDisposedTask();
}
var count = value?.Length ?? 0;
if (count == 0)
{
return Task.CompletedTask;
}
var remaining = _charBufferSize - _charBufferCount;
if (remaining >= count)
{
// Enough room in buffer, no need to go async
CopyToCharBuffer(value);
return Task.CompletedTask;
}
else
{
return WriteAsyncAwaited(value);
}
}
private async Task WriteAsyncAwaited(string value)
{
var count = value.Length;
Debug.Assert(count > 0);
Debug.Assert(_charBufferSize - _charBufferCount < count);
var index = 0;
while (count > 0)
{
if (_charBufferCount == _charBufferSize)
{
await FlushInternalAsync(flushEncoder: false);
}
CopyToCharBuffer(value, ref index, ref count);
}
}
// We want to flush the stream when Flush/FlushAsync is explicitly
// called by the user (example: from a Razor view).
public override void Flush()
{
if (_disposed)
{
throw new ObjectDisposedException(nameof(HttpResponseStreamWriter));
}
FlushInternal(flushEncoder: true);
}
public override Task FlushAsync()
{
if (_disposed)
{
return GetObjectDisposedTask();
}
return FlushInternalAsync(flushEncoder: true);
}
protected override void Dispose(bool disposing)
{
if (disposing && !_disposed)
{
_disposed = true;
try
{
FlushInternal(flushEncoder: true);
}
finally
{
_bytePool.Return(_byteBuffer);
_charPool.Return(_charBuffer);
}
}
base.Dispose(disposing);
}
// Note: our FlushInternal method does NOT flush the underlying stream. This would result in
// chunking.
private void FlushInternal(bool flushEncoder)
{
if (_charBufferCount == 0)
{
return;
}
var count = _encoder.GetBytes(
_charBuffer,
0,
_charBufferCount,
_byteBuffer,
0,
flush: flushEncoder);
_charBufferCount = 0;
if (count > 0)
{
_stream.Write(_byteBuffer, 0, count);
}
}
// Note: our FlushInternalAsync method does NOT flush the underlying stream. This would result in
// chunking.
private async Task FlushInternalAsync(bool flushEncoder)
{
if (_charBufferCount == 0)
{
return;
}
var count = _encoder.GetBytes(
_charBuffer,
0,
_charBufferCount,
_byteBuffer,
0,
flush: flushEncoder);
_charBufferCount = 0;
if (count > 0)
{
await _stream.WriteAsync(_byteBuffer, 0, count);
}
}
private void CopyToCharBuffer(string value)
{
Debug.Assert(_charBufferSize - _charBufferCount >= value.Length);
value.CopyTo(
sourceIndex: 0,
destination: _charBuffer,
destinationIndex: _charBufferCount,
count: value.Length);
_charBufferCount += value.Length;
}
private void CopyToCharBuffer(string value, ref int index, ref int count)
{
var remaining = Math.Min(_charBufferSize - _charBufferCount, count);
value.CopyTo(
sourceIndex: index,
destination: _charBuffer,
destinationIndex: _charBufferCount,
count: remaining);
_charBufferCount += remaining;
index += remaining;
count -= remaining;
}
private void CopyToCharBuffer(char[] values, ref int index, ref int count)
{
var remaining = Math.Min(_charBufferSize - _charBufferCount, count);
Buffer.BlockCopy(
src: values,
srcOffset: index * sizeof(char),
dst: _charBuffer,
dstOffset: _charBufferCount * sizeof(char),
count: remaining * sizeof(char));
_charBufferCount += remaining;
index += remaining;
count -= remaining;
}
[MethodImpl(MethodImplOptions.NoInlining)]
private static Task GetObjectDisposedTask()
{
return Task.FromException(new ObjectDisposedException(nameof(HttpResponseStreamWriter)));
}
}
}