C# 内存中是否有像文件流一样阻塞的流
我使用的库要求我提供一个实现此接口的对象:C# 内存中是否有像文件流一样阻塞的流,c#,stream,memorystream,C#,Stream,Memorystream,我使用的库要求我提供一个实现此接口的对象: public interface IConsole { TextWriter StandardInput { get; } TextReader StandardOutput { get; } TextReader StandardError { get; } } 然后,该对象的读取器将被库使用: IConsole console = new MyConsole(); int readBytes = console.Stand
public interface IConsole {
TextWriter StandardInput { get; }
TextReader StandardOutput { get; }
TextReader StandardError { get; }
}
然后,该对象的读取器将被库使用:
IConsole console = new MyConsole();
int readBytes = console.StandardOutput.Read(buffer, 0, buffer.Length);
通常,实现IConsole的类具有来自外部进程的标准输出流。在这种情况下,console.StandardOutput.Read调用通过阻塞工作,直到有一些数据写入StandardOutput流
我要做的是创建一个测试IConsole实现,它使用MemoryStream和echo的任何出现在StandardInput上的内容返回到StandardInput。我试过:
MemoryStream echoOutStream = new MemoryStream();
StandardOutput = new StreamReader(echoOutStream);
但问题是console.StandardOutput.Read将返回0而不是阻塞,直到有一些数据。如果没有可用的数据,我是否可以让MemoryStream阻塞?或者我是否可以使用不同的内存流?最后,我找到了一种简单的方法,从MemoryStream继承并接管读写方法
public class EchoStream : MemoryStream {
private ManualResetEvent m_dataReady = new ManualResetEvent(false);
private byte[] m_buffer;
private int m_offset;
private int m_count;
public override void Write(byte[] buffer, int offset, int count) {
m_buffer = buffer;
m_offset = offset;
m_count = count;
m_dataReady.Set();
}
public override int Read(byte[] buffer, int offset, int count) {
if (m_buffer == null) {
// Block until the stream has some more data.
m_dataReady.Reset();
m_dataReady.WaitOne();
}
Buffer.BlockCopy(m_buffer, m_offset, buffer, offset, (count < m_count) ? count : m_count);
m_buffer = null;
return (count < m_count) ? count : m_count;
}
}
公共类EchoStream:MemoryStream{
private ManualResetEvent m_dataReady=新的ManualResetEvent(错误);
专用字节[]m_缓冲区;
私人国际货币单位偏移量;
私人国际货币单位计数;
公共重写无效写入(字节[]缓冲区、整数偏移量、整数计数){
m_buffer=缓冲区;
m_offset=偏移量;
m_计数=计数;
m_dataReady.Set();
}
公共重写整型读取(字节[]缓冲区、整型偏移量、整型计数){
if(m_buffer==null){
//阻塞,直到流具有更多数据。
m_dataReady.Reset();
m_dataReady.WaitOne();
}
Buffer.BlockCopy(m_Buffer,m_offset,Buffer,offset,(计数
受您答案的启发,以下是我的多线程、多写版本:
public class EchoStream : MemoryStream
{
private readonly ManualResetEvent _DataReady = new ManualResetEvent(false);
private readonly ConcurrentQueue<byte[]> _Buffers = new ConcurrentQueue<byte[]>();
public bool DataAvailable{get { return !_Buffers.IsEmpty; }}
public override void Write(byte[] buffer, int offset, int count)
{
_Buffers.Enqueue(buffer);
_DataReady.Set();
}
public override int Read(byte[] buffer, int offset, int count)
{
_DataReady.WaitOne();
byte[] lBuffer;
if (!_Buffers.TryDequeue(out lBuffer))
{
_DataReady.Reset();
return -1;
}
if (!DataAvailable)
_DataReady.Reset();
Array.Copy(lBuffer, buffer, lBuffer.Length);
return lBuffer.Length;
}
}
公共类EchoStream:MemoryStream
{
私有只读ManualResetEvent _DataReady=新的ManualResetEvent(错误);
私有只读ConcurrentQueue _Buffers=新ConcurrentQueue();
public bool DataAvailable{get{return!\u Buffers.IsEmpty;}
公共重写无效写入(字节[]缓冲区、整数偏移量、整数计数)
{
_Buffers.排队(buffer);
_DataReady.Set();
}
公共重写整型读取(字节[]缓冲区、整型偏移量、整型计数)
{
_DataReady.WaitOne();
字节[]lBuffer;
if(!\u Buffers.TryDequeue(out lBuffer))
{
_DataReady.Reset();
返回-1;
}
如果(!数据可用)
_DataReady.Reset();
复制(lBuffer,buffer,lBuffer.Length);
返回lBuffer.Length;
}
}
对于您的版本,您应该在写入时读取流,而不允许任何连续写入。我的版本在ConcurrentQueue中缓冲任何写入的缓冲区(将其更改为简单队列并锁定非常简单)我将添加一个更完善的EchoStream版本。这是其他两个版本的组合,加上评论中的一些建议 更新-我已经连续几天用超过50 TB的数据测试了这个EchoStream。测试让它位于网络流和ZStandard压缩流之间。异步也已经过测试,这给表面带来了一种罕见的挂起状态。内置System.IO.Stream似乎不希望在同一个流上同时调用ReadAsync和WriteAsync,如果没有任何可用数据,这可能会导致挂起,因为两个调用使用相同的内部变量。因此,我必须重写这些函数,这解决了悬而未决的问题 此版本具有以下增强功能: 1) 这是使用System.IO.Stream基类而不是MemoryStream从头开始编写的 2) 构造函数可以设置最大队列深度,如果达到此级别,则流写入将阻塞,直到执行读取,从而将队列深度降至最大级别以下(无限制=0,默认值=10) 3) 在读取/写入数据时,缓冲区偏移量和计数现在已生效。此外,您可以使用比Write更小的缓冲区调用Read,而不会引发异常或丢失数据。在循环中使用BlockCopy填充字节,直到满足计数 4) 有一个名为AlwaysCopyBuffer的公共属性,它在Write函数中创建缓冲区的副本。将此设置为true将安全地允许在调用Write后重用字节缓冲区 5) 有一个名为ReadTimeout/WriteTimeout的公共属性,它控制读/写函数在返回0(默认值为无穷,-1)之前阻塞的时间 6) 使用BlockingCollection类,它将ConcurrentQueue和AutoResteEvent类组合在一起。最初我使用的是这两个类,但存在一种罕见的情况,即在数据进入队列()后,当AutoResteEvent允许线程在Read()中通过时,它无法立即使用。这种情况大约每500GB的数据通过它就会发生一次。治疗方法是睡觉并再次检查数据。有时,睡眠(0)起作用,但在CPU使用率很高的极端情况下,在数据显示之前,它可能高达睡眠(1000)。在我切换到BlockingCollection之后,它有很多额外的代码要优雅地处理,而且没有问题 7) 这已被测试为同步异步读写的线程安全
using System;
using System.IO;
using System.Threading.Tasks;
using System.Threading;
using System.Collections.Concurrent;
public class EchoStream : Stream
{
public override bool CanTimeout { get; } = true;
public override int ReadTimeout { get; set; } = Timeout.Infinite;
public override int WriteTimeout { get; set; } = Timeout.Infinite;
public override bool CanRead { get; } = true;
public override bool CanSeek { get; } = false;
public override bool CanWrite { get; } = true;
public bool CopyBufferOnWrite { get; set; } = false;
private readonly object _lock = new object();
// Default underlying mechanism for BlockingCollection is ConcurrentQueue<T>, which is what we want
private readonly BlockingCollection<byte[]> _Buffers;
private int _maxQueueDepth = 10;
private byte[] m_buffer = null;
private int m_offset = 0;
private int m_count = 0;
private bool m_Closed = false;
public override void Close()
{
m_Closed = true;
// release any waiting writes
_Buffers.CompleteAdding();
}
public bool DataAvailable
{
get
{
return _Buffers.Count > 0;
}
}
private long _Length = 0L;
public override long Length
{
get
{
return _Length;
}
}
private long _Position = 0L;
public override long Position
{
get
{
return _Position;
}
set
{
throw new NotImplementedException();
}
}
public EchoStream() : this(10)
{
}
public EchoStream(int maxQueueDepth)
{
_maxQueueDepth = maxQueueDepth;
_Buffers = new BlockingCollection<byte[]>(_maxQueueDepth);
}
// we override the xxxxAsync functions because the default base class shares state between ReadAsync and WriteAsync, which causes a hang if both are called at once
public new Task WriteAsync(byte[] buffer, int offset, int count)
{
return Task.Run(() => Write(buffer, offset, count));
}
// we override the xxxxAsync functions because the default base class shares state between ReadAsync and WriteAsync, which causes a hang if both are called at once
public new Task<int> ReadAsync(byte[] buffer, int offset, int count)
{
return Task.Run(() =>
{
return Read(buffer, offset, count);
});
}
public override void Write(byte[] buffer, int offset, int count)
{
if (m_Closed || buffer.Length - offset < count || count <= 0)
return;
byte[] newBuffer;
if (!CopyBufferOnWrite && offset == 0 && count == buffer.Length)
newBuffer = buffer;
else
{
newBuffer = new byte[count];
System.Buffer.BlockCopy(buffer, offset, newBuffer, 0, count);
}
if (!_Buffers.TryAdd(newBuffer, WriteTimeout))
throw new TimeoutException("EchoStream Write() Timeout");
_Length += count;
}
public override int Read(byte[] buffer, int offset, int count)
{
if (count == 0)
return 0;
lock (_lock)
{
if (m_count == 0 && _Buffers.Count == 0)
{
if (m_Closed)
return -1;
if (_Buffers.TryTake(out m_buffer, ReadTimeout))
{
m_offset = 0;
m_count = m_buffer.Length;
}
else
return m_Closed ? -1 : 0;
}
int returnBytes = 0;
while (count > 0)
{
if (m_count == 0)
{
if (_Buffers.TryTake(out m_buffer, 0))
{
m_offset = 0;
m_count = m_buffer.Length;
}
else
break;
}
var bytesToCopy = (count < m_count) ? count : m_count;
System.Buffer.BlockCopy(m_buffer, m_offset, buffer, offset, bytesToCopy);
m_offset += bytesToCopy;
m_count -= bytesToCopy;
offset += bytesToCopy;
count -= bytesToCopy;
returnBytes += bytesToCopy;
}
_Position += returnBytes;
return returnBytes;
}
}
public override int ReadByte()
{
byte[] returnValue = new byte[1];
return (Read(returnValue, 0, 1) <= 0 ? -1 : (int)returnValue[0]);
}
public override void Flush()
{
}
public override long Seek(long offset, SeekOrigin origin)
{
throw new NotImplementedException();
}
public override void SetLength(long value)
{
throw new NotImplementedException();
}
}
使用系统;
使用System.IO;
使用System.Threading.Tasks;
使用系统线程;
使用System.Collections.Concurrent;
公共类EchoStream:Stream
{
公共覆盖boolcantimeout{get;}=true;
public override int ReadTimeout{get;set;}=Timeout.Infinite;
public override int WriteTimeout{get;set;}=Timeout.Infinite;
public override bool CanRead{get;}=true;
公共图书馆
public class EchoStream : MemoryStream
{
private readonly ManualResetEvent _DataReady = new ManualResetEvent(false);
private readonly ConcurrentQueue<byte[]> _Buffers = new ConcurrentQueue<byte[]>();
public bool DataAvailable { get { return !_Buffers.IsEmpty; } }
public override void Write(byte[] buffer, int offset, int count)
{
_Buffers.Enqueue(buffer.Skip(offset).Take(count).ToArray());
_DataReady.Set();
}
public override int Read(byte[] buffer, int offset, int count)
{
_DataReady.WaitOne();
byte[] lBuffer;
if (!_Buffers.TryDequeue(out lBuffer))
{
_DataReady.Reset();
return -1;
}
if (!DataAvailable)
_DataReady.Reset();
Array.Copy(lBuffer, 0, buffer, offset, Math.Min(lBuffer.Length, count));
return lBuffer.Length;
}
}