"Chunked" MemoryStream

Question

Estoy buscando la implementación de MemoryStream que no asigna la memoria como un bloque grande, sino más bien como una colección de fragmentos. Quiero almacenar algunos GB de datos en la memoria (64 bits) y evitar la limitación de la fragmentación de la memoria.

Answer 1

Primero debe determinar si la fragmentación de la dirección virtual es el problema.

Si está en una máquina de 64 bits (que parece indicar que es) lo dudo seriamente. Cada proceso de 64 bits tiene casi todo el espacio de memoria virtual de 64 bits disponible y su única preocupación es la fragmentación del espacio de direcciones virtuales, no la fragmentación de la memoria física (que es lo que el sistema operativo debe preocuparse). El administrador de memoria del sistema operativo ya almacena la memoria debajo de las cubiertas. Para el futuro previsible, no se quedará sin espacio de direcciones virtuales antes de que se quede sin memoria física. Es poco probable que cambie antes de que ambos nos retiremos.

Si tiene un espacio de direcciones de 32 bits y luego asigna grandes bloques contiguos de memoria en GB ramge, encontrará un problema de fragmentación bastante rápido. No hay un stock stock que asigne la secuencia de memoria en el CLR. Hay uno debajo de las coberturas en ASP.NET (por otras razones) pero no es accesible. Si debe recorrer este camino, probablemente sea mejor que se escriba usted mismo porque el patrón de uso de su aplicación es poco probable que sea similar a muchos otros y tratar de ajustar sus datos en un espacio de direcciones de 32 bits probablemente sea su cuello de botella.

Recomiendo que se requiera un proceso de 64 bits si está manipulando GB de datos. Hará un trabajo mucho mejor que las soluciones laminadas a mano para la fragmentación del espacio de direcciones de 32 bits, independientemente de cuán inteligente sea.

Answer 2

Algo como esto:

class ChunkedMemoryStream : Stream 
{ 
    private readonly List<byte[]> _chunks = new List<byte[]>(); 
    private int _positionChunk; 
    private int _positionOffset; 
    private long _position; 

    public override bool CanRead 
    { 
     get { return true; } 
    } 

    public override bool CanSeek 
    { 
     get { return true; } 
    } 

    public override bool CanWrite 
    { 
     get { return true; } 
    } 

    public override void Flush() { } 

    public override long Length 
    { 
     get { return _chunks.Sum(c => c.Length); } 
    } 

    public override long Position 
    { 
     get 
     { 
      return _position; 
     } 
     set 
     { 
      _position = value; 

      _positionChunk = 0; 

      while (_positionOffset != 0) 
      { 
       if (_positionChunk >= _chunks.Count) 
        throw new OverflowException(); 

       if (_positionOffset < _chunks[_positionChunk].Length) 
        return; 

       _positionOffset -= _chunks[_positionChunk].Length; 
       _positionChunk++; 
      } 
     } 
    } 

    public override int Read(byte[] buffer, int offset, int count) 
    { 
     int result = 0; 
     while ((count != 0) && (_positionChunk != _chunks.Count)) 
     { 
      int fromChunk = Math.Min(count, _chunks[_positionChunk].Length - _positionOffset); 
      if (fromChunk != 0) 
      { 
       Array.Copy(_chunks[_positionChunk], _positionOffset, buffer, offset, fromChunk); 
       offset += fromChunk; 
       count -= fromChunk; 
       result += fromChunk; 
       _position += fromChunk; 
      } 

      _positionOffset = 0; 
      _positionChunk++; 
     } 
     return result; 
    } 

    public override long Seek(long offset, SeekOrigin origin) 
    { 
     long newPos = 0; 

     switch (origin) 
     { 
      case SeekOrigin.Begin: 
       newPos = offset; 
       break; 
      case SeekOrigin.Current: 
       newPos = Position + offset; 
       break; 
      case SeekOrigin.End: 
       newPos = Length - offset; 
       break; 
     } 

     Position = Math.Max(0, Math.Min(newPos, Length)); 
     return newPos; 
    } 

    public override void SetLength(long value) 
    { 
     throw new NotImplementedException(); 
    } 

    public override void Write(byte[] buffer, int offset, int count) 
    { 
     while ((count != 0) && (_positionChunk != _chunks.Count)) 
     { 
      int toChunk = Math.Min(count, _chunks[_positionChunk].Length - _positionOffset); 
      if (toChunk != 0) 
      { 
       Array.Copy(buffer, offset, _chunks[_positionChunk], _positionOffset, toChunk); 
       offset += toChunk; 
       count -= toChunk; 
       _position += toChunk; 
      } 

      _positionOffset = 0; 
      _positionChunk++; 
     } 

     if (count != 0) 
     { 
      byte[] chunk = new byte[count]; 
      Array.Copy(buffer, offset, chunk, 0, count); 
      _chunks.Add(chunk); 
      _positionChunk = _chunks.Count; 
      _position += count; 
     } 
    } 
} 

class Program 
{ 
    static void Main(string[] args) 
    { 
     ChunkedMemoryStream cms = new ChunkedMemoryStream(); 

     Debug.Assert(cms.Length == 0); 
     Debug.Assert(cms.Position == 0); 

     cms.Position = 0; 

     byte[] helloworld = Encoding.UTF8.GetBytes("hello world"); 

     cms.Write(helloworld, 0, 3); 
     cms.Write(helloworld, 3, 3); 
     cms.Write(helloworld, 6, 5); 

     Debug.Assert(cms.Length == 11); 
     Debug.Assert(cms.Position == 11); 

     cms.Position = 0; 

     byte[] b = new byte[20]; 
     cms.Read(b, 3, (int)cms.Length); 
     Debug.Assert(b.Skip(3).Take(11).SequenceEqual(helloworld)); 

     cms.Position = 0; 
     cms.Write(Encoding.UTF8.GetBytes("seeya"), 0, 5); 

     Debug.Assert(cms.Length == 11); 
     Debug.Assert(cms.Position == 5); 

     cms.Position = 0; 
     cms.Read(b, 0, (byte) cms.Length); 
     Debug.Assert(b.Take(11).SequenceEqual(Encoding.UTF8.GetBytes("seeya world"))); 

     Debug.Assert(cms.Length == 11); 
     Debug.Assert(cms.Position == 11); 

     cms.Write(Encoding.UTF8.GetBytes(" again"), 0, 6); 

     Debug.Assert(cms.Length == 17); 
     Debug.Assert(cms.Position == 17); 

     cms.Position = 0; 
     cms.Read(b, 0, (byte)cms.Length); 
     Debug.Assert(b.Take(17).SequenceEqual(Encoding.UTF8.GetBytes("seeya world again"))); 

    } 
} 

Answer 3

puede utilizar este problema similar

http://www.123aspx.com/Rotor/src/chunkedmemorystream.cs.txt

Answer 4

que he encontrado en mi solicitud. He leído gran cantidad de datos comprimidos y sufrí OutOfMemoryException usando MemoryStream. Escribí mi propia implementación de secuencia de memoria "fragmentada" basada en la colección de matrices de bytes. Si tiene alguna idea de cómo hacer que esta secuencia de memoria sea más efectiva, escríbame al respecto.

public sealed class ChunkedMemoryStream : Stream 
{ 
    #region Constants 

    private const int BUFFER_LENGTH = 65536; 
    private const byte ONE = 1; 
    private const byte ZERO = 0; 

    #endregion 

    #region Readonly & Static Fields 

    private readonly Collection<byte[]> _chunks; 

    #endregion 

    #region Fields 

    private long _length; 

    private long _position; 
    private const byte TWO = 2; 

    #endregion 

    #region C'tors 

    public ChunkedMemoryStream() 
    { 
     _chunks = new Collection<byte[]> { new byte[BUFFER_LENGTH], new byte[BUFFER_LENGTH] }; 
     _position = ZERO; 
     _length = ZERO; 
    } 

    #endregion 

    #region Instance Properties 

    public override bool CanRead 
    { 
     get { return true; } 
    } 

    public override bool CanSeek 
    { 
     get { return true; } 
    } 

    public override bool CanWrite 
    { 
     get { return true; } 
    } 

    public override long Length 
    { 
     get { return _length; } 
    } 

    public override long Position 
    { 
     get { return _position; } 
     set 
     { 
      if (!CanSeek) 
       throw new NotSupportedException(); 

      _position = value; 

      if (_position > _length) 
       _position = _length - ONE; 
     } 
    } 


    private byte[] CurrentChunk 
    { 
     get 
     { 
      long positionDividedByBufferLength = _position/BUFFER_LENGTH; 
      var chunkIndex = Convert.ToInt32(positionDividedByBufferLength); 
      byte[] chunk = _chunks[chunkIndex]; 
      return chunk; 
     } 
    } 

    private int PositionInChunk 
    { 
     get 
     { 
      int positionInChunk = Convert.ToInt32(_position % BUFFER_LENGTH); 
      return positionInChunk; 
     } 
    } 

    private int RemainingBytesInCurrentChunk 
    { 
     get 
     { 
      Contract.Ensures(Contract.Result<int>() > ZERO); 
      int remainingBytesInCurrentChunk = CurrentChunk.Length - PositionInChunk; 
      return remainingBytesInCurrentChunk; 
     } 
    } 

    #endregion 

    #region Instance Methods 

    public override void Flush() 
    { 
    } 

    public override int Read(byte[] buffer, int offset, int count) 
    { 
     if (offset + count > buffer.Length) 
      throw new ArgumentException(); 

     if (buffer == null) 
      throw new ArgumentNullException(); 

     if (offset < ZERO || count < ZERO) 
      throw new ArgumentOutOfRangeException(); 

     if (!CanRead) 
      throw new NotSupportedException(); 

     int bytesToRead = count; 
     if (_length - _position < bytesToRead) 
      bytesToRead = Convert.ToInt32(_length - _position); 

     int bytesreaded = 0; 
     while (bytesToRead > ZERO) 
     { 
      // get remaining bytes in current chunk 
      // read bytes in current chunk 
      // advance to next position 
      int remainingBytesInCurrentChunk = RemainingBytesInCurrentChunk; 
      if (remainingBytesInCurrentChunk > bytesToRead) 
       remainingBytesInCurrentChunk = bytesToRead; 
      Array.Copy(CurrentChunk, PositionInChunk, buffer, offset, remainingBytesInCurrentChunk); 
      //move position in source 
      _position += remainingBytesInCurrentChunk; 
      //move position in target 
      offset += remainingBytesInCurrentChunk; 
      //bytesToRead is smaller 
      bytesToRead -= remainingBytesInCurrentChunk; 
      //count readed bytes; 
      bytesreaded += remainingBytesInCurrentChunk; 
     } 
     return bytesreaded; 
    } 

    public override long Seek(long offset, SeekOrigin origin) 
    { 
     switch (origin) 
     { 
      case SeekOrigin.Begin: 
       Position = offset; 
       break; 
      case SeekOrigin.Current: 
       Position += offset; 
       break; 
      case SeekOrigin.End: 
       Position = Length + offset; 
       break; 
     } 
     return Position; 
    } 

    private long Capacity 
    { 
     get 
     { 
      int numberOfChunks = _chunks.Count; 


      long capacity = numberOfChunks * BUFFER_LENGTH; 
      return capacity; 
     } 
    } 

    public override void SetLength(long value) 
    { 
     if (value > _length) 
     { 
      while (value > Capacity) 
      { 
       var item = new byte[BUFFER_LENGTH]; 
       _chunks.Add(item); 
      } 
     } 
     else if (value < _length) 
     { 
      var decimalValue = Convert.ToDecimal(value); 
      var valueToBeCompared = decimalValue % BUFFER_LENGTH == ZERO ? Capacity : Capacity - BUFFER_LENGTH; 
      //remove data chunks, but leave at least two chunks 
      while (value < valueToBeCompared && _chunks.Count > TWO) 
      { 
       byte[] lastChunk = _chunks.Last(); 
       _chunks.Remove(lastChunk); 
      } 
     } 
     _length = value; 
     if (_position > _length - ONE) 
      _position = _length == 0 ? ZERO : _length - ONE; 
    } 

    public override void Write(byte[] buffer, int offset, int count) 
    { 
     if (!CanWrite) 
      throw new NotSupportedException(); 

     int bytesToWrite = count; 

     while (bytesToWrite > ZERO) 
     { 
      //get remaining space in current chunk 
      int remainingBytesInCurrentChunk = RemainingBytesInCurrentChunk; 

      //if count of bytes to be written is fewer than remaining 
      if (remainingBytesInCurrentChunk > bytesToWrite) 
       remainingBytesInCurrentChunk = bytesToWrite; 

      //if remaining bytes is still greater than zero 
      if (remainingBytesInCurrentChunk > ZERO) 
      { 
       //write remaining bytes to current Chunk 

       Array.Copy(buffer, offset, CurrentChunk, PositionInChunk, remainingBytesInCurrentChunk); 

       //change offset of source array 
       offset += remainingBytesInCurrentChunk; 
       //change bytes to write 
       bytesToWrite -= remainingBytesInCurrentChunk; 
       //change length and position 
       _length += remainingBytesInCurrentChunk; 
       _position += remainingBytesInCurrentChunk; 
      } 

      if (Capacity == _position) 
       _chunks.Add(new byte[BUFFER_LENGTH]); 
     } 
    } 

    /// <summary> 
    ///  Gets entire content of stream regardless of Position value and return output as byte array 
    /// </summary> 
    /// <returns>byte array</returns> 
    public byte[] ToArray() 
    { 
     var outputArray = new byte[Length]; 
     if (outputArray.Length != ZERO) 
     { 
      long outputPosition = ZERO; 
      foreach (byte[] chunk in _chunks) 
      { 
       var remainingLength = (Length - outputPosition) > chunk.Length 
              ? chunk.Length 
              : Length - outputPosition; 
       Array.Copy(chunk, ZERO, outputArray, outputPosition, remainingLength); 
       outputPosition = outputPosition + remainingLength; 
      } 
     } 
     return outputArray; 
    } 

    /// <summary> 
    ///  Method set Position to first element and write entire stream to another 
    /// </summary> 
    /// <param name="stream">Target stream</param> 
    public void WriteTo(Stream stream) 
    { 
     Contract.Requires(stream != null); 

     Position = ZERO; 
     var buffer = new byte[BUFFER_LENGTH]; 
     int bytesReaded; 
     do 
     { 
      bytesReaded = Read(buffer, ZERO, BUFFER_LENGTH); 
      stream.Write(buffer, ZERO, bytesReaded); 
     } while (bytesReaded > ZERO); 
    } 

    #endregion 
} 

Answer 5

Se debe utilizar la UnmanagedMemoryStream cuando se trata de trozos más de 2 GB de memoria, como MemoryStream está limitado a 2 GB, y el UnmanagedMemoryStream se hizo para hacer frente a este problema.

Answer 6

SparseMemoryStream hace en .NET está en enterrada en el fondo de una biblioteca de clases interna, aunque - el código fuente está disponible, por supuesto, ya que Microsoft puso todo hacia fuera allí como código abierto.

Puede agarrar el código para ello aquí: http://www.dotnetframework.org/default.aspx/4@0/4@0/DEVDIV_TFS/Dev10/Releases/RTMRel/wpf/src/Base/MS/Internal/IO/Packaging/SparseMemoryStream@cs/1305600/SparseMemoryStream@cs

Dicho esto, yo altamente no recomienda el uso de él como es - Por lo menos eliminar todas las llamadas a IsolatedStorage para empezar, ya que esto parece ser la causa de un sin fin de errores * en la API de empaquetado del framework.

(*: además de propagar los datos en las transmisiones, si se vuelve demasiado grande, básicamente reinventa los archivos de intercambio por algún motivo, en el almacenamiento aislado del usuario no menos, y casualmente, la mayoría de los productos de MS que permiten para los complementos basados ​​en .NET no tienen configurados sus dominios de aplicación de modo que pueda acceder a Almacenamiento aislado: los complementos VSTO son notorios por sufrir este problema, por ejemplo.)

Answer 7

Aquí es una implementación completa:

/// <summary> 
/// Defines a MemoryStream that does not sit on the Large Object Heap, thus avoiding memory fragmentation. 
/// </summary> 
public sealed class ChunkedMemoryStream : Stream 
{ 
    /// <summary> 
    /// Defines the default chunk size. Currently defined as 0x10000. 
    /// </summary> 
    public const int DefaultChunkSize = 0x10000; // needs to be < 85000 

    private List<byte[]> _chunks = new List<byte[]>(); 
    private long _position; 
    private int _chunkSize; 
    private int _lastChunkPos; 
    private int _lastChunkPosIndex; 

    /// <summary> 
    /// Initializes a new instance of the <see cref="ChunkedMemoryStream"/> class. 
    /// </summary> 
    public ChunkedMemoryStream() 
     : this(DefaultChunkSize) 
    { 
    } 

    /// <summary> 
    /// Initializes a new instance of the <see cref="ChunkedMemoryStream"/> class. 
    /// </summary> 
    /// <param name="chunkSize">Size of the underlying chunks.</param> 
    public ChunkedMemoryStream(int chunkSize) 
     : this(null) 
    { 
    } 

    /// <summary> 
    /// Initializes a new instance of the <see cref="ChunkedMemoryStream"/> class based on the specified byte array. 
    /// </summary> 
    /// <param name="buffer">The array of unsigned bytes from which to create the current stream.</param> 
    public ChunkedMemoryStream(byte[] buffer) 
     : this(DefaultChunkSize, buffer) 
    { 
    } 

    /// <summary> 
    /// Initializes a new instance of the <see cref="ChunkedMemoryStream"/> class based on the specified byte array. 
    /// </summary> 
    /// <param name="chunkSize">Size of the underlying chunks.</param> 
    /// <param name="buffer">The array of unsigned bytes from which to create the current stream.</param> 
    public ChunkedMemoryStream(int chunkSize, byte[] buffer) 
    { 
     FreeOnDispose = true; 
     ChunkSize = chunkSize; 
     _chunks.Add(new byte[chunkSize]); 
     if (buffer != null) 
     { 
      Write(buffer, 0, buffer.Length); 
      Position = 0; 
     } 
    } 

    /// <summary> 
    /// Gets or sets a value indicating whether to free the underlying chunks on dispose. 
    /// </summary> 
    /// <value><c>true</c> if [free on dispose]; otherwise, <c>false</c>.</value> 
    public bool FreeOnDispose { get; set; } 

    /// <summary> 
    /// Releases the unmanaged resources used by the <see cref="T:System.IO.Stream"/> and optionally releases the managed resources. 
    /// </summary> 
    /// <param name="disposing">true to release both managed and unmanaged resources; false to release only unmanaged resources.</param> 
    protected override void Dispose(bool disposing) 
    { 
     if (FreeOnDispose) 
     { 
      if (_chunks != null) 
      { 
       _chunks = null; 
       _chunkSize = 0; 
       _position = 0; 
      } 
     } 
     base.Dispose(disposing); 
    } 

    /// <summary> 
    /// When overridden in a derived class, clears all buffers for this stream and causes any buffered data to be written to the underlying device. 
    /// This implementation does nothing. 
    /// </summary> 
    public override void Flush() 
    { 
     // do nothing 
    } 

    /// <summary> 
    /// When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. 
    /// </summary> 
    /// <param name="buffer">An array of bytes. When this method returns, the buffer contains the specified byte array with the values between <paramref name="offset"/> and (<paramref name="offset"/> + <paramref name="count"/> - 1) replaced by the bytes read from the current source.</param> 
    /// <param name="offset">The zero-based byte offset in <paramref name="buffer"/> at which to begin storing the data read from the current stream.</param> 
    /// <param name="count">The maximum number of bytes to be read from the current stream.</param> 
    /// <returns> 
    /// The total number of bytes read into the buffer. This can be less than the number of bytes requested if that many bytes are not currently available, or zero (0) if the end of the stream has been reached. 
    /// </returns> 
    /// <exception cref="T:System.ArgumentException"> 
    /// The sum of <paramref name="offset"/> and <paramref name="count"/> is larger than the buffer length. 
    /// </exception> 
    /// <exception cref="T:System.ArgumentNullException"> 
    ///  <paramref name="buffer"/> is null. 
    /// </exception> 
    /// <exception cref="T:System.ArgumentOutOfRangeException"> 
    ///  <paramref name="offset"/> or <paramref name="count"/> is negative. 
    /// </exception> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override int Read(byte[] buffer, int offset, int count) 
    { 
     if (buffer == null) 
      throw new ArgumentNullException("buffer"); 

     if (offset < 0) 
      throw new ArgumentOutOfRangeException("offset"); 

     if (count < 0) 
      throw new ArgumentOutOfRangeException("count"); 

     if ((buffer.Length - offset) < count) 
      throw new ArgumentException(null, "count"); 

     CheckDisposed(); 

     int chunkIndex = (int)(_position/ChunkSize); 
     if (chunkIndex == _chunks.Count) 
      return 0; 

     int chunkPos = (int)(_position % ChunkSize); 
     count = (int)Math.Min(count, Length - _position); 
     if (count == 0) 
      return 0; 

     int left = count; 
     int inOffset = offset; 
     int total = 0; 
     do 
     { 
      int toCopy = Math.Min(left, ChunkSize - chunkPos); 
      Buffer.BlockCopy(_chunks[chunkIndex], chunkPos, buffer, inOffset, toCopy); 
      inOffset += toCopy; 
      left -= toCopy; 
      total += toCopy; 
      if ((chunkPos + toCopy) == ChunkSize) 
      { 
       if (chunkIndex == (_chunks.Count - 1)) 
       { 
        // last chunk 
        break; 
       } 
       chunkPos = 0; 
       chunkIndex++; 
      } 
      else 
      { 
       chunkPos += toCopy; 
      } 
     } 
     while (left > 0); 
     _position += total; 
     return total; 
    } 

    /// <summary> 
    /// Reads a byte from the stream and advances the position within the stream by one byte, or returns -1 if at the end of the stream. 
    /// </summary> 
    /// <returns> 
    /// The unsigned byte cast to an Int32, or -1 if at the end of the stream. 
    /// </returns> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override int ReadByte() 
    { 
     CheckDisposed(); 
     if (_position >= Length) 
      return -1; 

     byte b = _chunks[(int)(_position/ChunkSize)][_position % ChunkSize]; 
     _position++; 
     return b; 
    } 

    /// <summary> 
    /// When overridden in a derived class, sets the position within the current stream. 
    /// </summary> 
    /// <param name="offset">A byte offset relative to the <paramref name="origin"/> parameter.</param> 
    /// <param name="origin">A value of type <see cref="T:System.IO.SeekOrigin"/> indicating the reference point used to obtain the new position.</param> 
    /// <returns> 
    /// The new position within the current stream. 
    /// </returns> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override long Seek(long offset, SeekOrigin origin) 
    { 
     CheckDisposed(); 
     switch (origin) 
     { 
      case SeekOrigin.Begin: 
       Position = offset; 
       break; 

      case SeekOrigin.Current: 
       Position += offset; 
       break; 

      case SeekOrigin.End: 
       Position = Length + offset; 
       break; 
     } 
     return Position; 
    } 

    private void CheckDisposed() 
    { 
     if (_chunks == null) 
      throw new ObjectDisposedException(null, "Cannot access a disposed stream"); 
    } 

    /// <summary> 
    /// When overridden in a derived class, sets the length of the current stream. 
    /// </summary> 
    /// <param name="value">The desired length of the current stream in bytes.</param> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override void SetLength(long value) 
    { 
     CheckDisposed(); 
     if (value < 0) 
      throw new ArgumentOutOfRangeException("value"); 

     if (value > Length) 
      throw new ArgumentOutOfRangeException("value"); 

     long needed = value/ChunkSize; 
     if ((value % ChunkSize) != 0) 
     { 
      needed++; 
     } 

     if (needed > int.MaxValue) 
      throw new ArgumentOutOfRangeException("value"); 

     if (needed < _chunks.Count) 
     { 
      int remove = (int)(_chunks.Count - needed); 
      for (int i = 0; i < remove; i++) 
      { 
       _chunks.RemoveAt(_chunks.Count - 1); 
      } 
     } 
     _lastChunkPos = (int)(value % ChunkSize); 
    } 

    /// <summary> 
    /// Converts the current stream to a byte array. 
    /// </summary> 
    /// <returns>An array of bytes</returns> 
    public byte[] ToArray() 
    { 
     CheckDisposed(); 
     byte[] bytes = new byte[Length]; 
     int offset = 0; 
     for (int i = 0; i < _chunks.Count; i++) 
     { 
      int count = (i == (_chunks.Count - 1)) ? _lastChunkPos : _chunks[i].Length; 
      if (count > 0) 
      { 
       Buffer.BlockCopy(_chunks[i], 0, bytes, offset, count); 
       offset += count; 
      } 
     } 
     return bytes; 
    } 

    /// <summary> 
    /// When overridden in a derived class, writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. 
    /// </summary> 
    /// <param name="buffer">An array of bytes. This method copies <paramref name="count"/> bytes from <paramref name="buffer"/> to the current stream.</param> 
    /// <param name="offset">The zero-based byte offset in <paramref name="buffer"/> at which to begin copying bytes to the current stream.</param> 
    /// <param name="count">The number of bytes to be written to the current stream.</param> 
    /// <exception cref="T:System.ArgumentException"> 
    /// The sum of <paramref name="offset"/> and <paramref name="count"/> is greater than the buffer length. 
    /// </exception> 
    /// <exception cref="T:System.ArgumentNullException"> 
    ///  <paramref name="buffer"/> is null. 
    /// </exception> 
    /// <exception cref="T:System.ArgumentOutOfRangeException"> 
    ///  <paramref name="offset"/> or <paramref name="count"/> is negative. 
    /// </exception> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override void Write(byte[] buffer, int offset, int count) 
    { 
     if (buffer == null) 
      throw new ArgumentNullException("buffer"); 

     if (offset < 0) 
      throw new ArgumentOutOfRangeException("offset"); 

     if (count < 0) 
      throw new ArgumentOutOfRangeException("count"); 

     if ((buffer.Length - offset) < count) 
      throw new ArgumentException(null, "count"); 

     CheckDisposed(); 

     int chunkPos = (int)(_position % ChunkSize); 
     int chunkIndex = (int)(_position/ChunkSize); 
     if (chunkIndex == _chunks.Count) 
     { 
      _chunks.Add(new byte[ChunkSize]); 
     } 

     int left = count; 
     int inOffset = offset; 
     do 
     { 
      int copied = Math.Min(left, ChunkSize - chunkPos); 
      Buffer.BlockCopy(buffer, inOffset, _chunks[chunkIndex], chunkPos, copied); 
      inOffset += copied; 
      left -= copied; 
      if ((chunkPos + copied) == ChunkSize) 
      { 
       chunkIndex++; 
       chunkPos = 0; 
       if (chunkIndex == _chunks.Count) 
       { 
        _chunks.Add(new byte[ChunkSize]); 
       } 
      } 
      else 
      { 
       chunkPos += copied; 
      } 
     } 
     while (left > 0); 
     _position += count; 
     if (chunkIndex == (_chunks.Count - 1)) 
     { 
      if ((chunkIndex > _lastChunkPosIndex) || 
       ((chunkIndex == _lastChunkPosIndex) && (chunkPos > _lastChunkPos))) 
      { 
       _lastChunkPos = chunkPos; 
       _lastChunkPosIndex = chunkIndex; 
      } 
     } 
    } 

    /// <summary> 
    /// Writes a byte to the current position in the stream and advances the position within the stream by one byte. 
    /// </summary> 
    /// <param name="value">The byte to write to the stream.</param> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override void WriteByte(byte value) 
    { 
     CheckDisposed(); 
     int chunkIndex = (int)(_position/ChunkSize); 
     int chunkPos = (int)(_position % ChunkSize); 

     if (chunkPos > (ChunkSize - 1)) //changed from (chunkPos >= (ChunkSize - 1)) 
     { 
      chunkIndex++; 
      chunkPos = 0; 
      if (chunkIndex == _chunks.Count) 
      { 
       _chunks.Add(new byte[ChunkSize]); 
      } 
     } 
     _chunks[chunkIndex][chunkPos++] = value; 
     _position++; 
     if (chunkIndex == (_chunks.Count - 1)) 
     { 
      if ((chunkIndex > _lastChunkPosIndex) || 
       ((chunkIndex == _lastChunkPosIndex) && (chunkPos > _lastChunkPos))) 
      { 
       _lastChunkPos = chunkPos; 
       _lastChunkPosIndex = chunkIndex; 
      } 
     } 
    } 

    /// <summary> 
    /// Writes to the specified stream. 
    /// </summary> 
    /// <param name="stream">The stream.</param> 
    public void WriteTo(Stream stream) 
    { 
     if (stream == null) 
      throw new ArgumentNullException("stream"); 

     CheckDisposed(); 
     for (int i = 0; i < _chunks.Count; i++) 
     { 
      int count = (i == (_chunks.Count - 1)) ? _lastChunkPos : _chunks[i].Length; 
      stream.Write(_chunks[i], 0, count); 
     } 
    } 

    /// <summary> 
    /// When overridden in a derived class, gets a value indicating whether the current stream supports reading. 
    /// </summary> 
    /// <value></value> 
    /// <returns>true if the stream supports reading; otherwise, false. 
    /// </returns> 
    public override bool CanRead 
    { 
     get 
     { 
      return true; 
     } 
    } 

    /// <summary> 
    /// When overridden in a derived class, gets a value indicating whether the current stream supports seeking. 
    /// </summary> 
    /// <value></value> 
    /// <returns>true if the stream supports seeking; otherwise, false. 
    /// </returns> 
    public override bool CanSeek 
    { 
     get 
     { 
      return true; 
     } 
    } 

    /// <summary> 
    /// When overridden in a derived class, gets a value indicating whether the current stream supports writing. 
    /// </summary> 
    /// <value></value> 
    /// <returns>true if the stream supports writing; otherwise, false. 
    /// </returns> 
    public override bool CanWrite 
    { 
     get 
     { 
      return true; 
     } 
    } 

    /// <summary> 
    /// When overridden in a derived class, gets the length in bytes of the stream. 
    /// </summary> 
    /// <value></value> 
    /// <returns> 
    /// A long value representing the length of the stream in bytes. 
    /// </returns> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override long Length 
    { 
     get 
     { 
      CheckDisposed(); 
      if (_chunks.Count == 0) 
       return 0; 

      return (_chunks.Count - 1) * ChunkSize + _lastChunkPos; 
     } 
    } 

    /// <summary> 
    /// Gets or sets the size of the underlying chunks. Cannot be greater than or equal to 85000. 
    /// </summary> 
    /// <value>The chunks size.</value> 
    public int ChunkSize 
    { 
     get 
     { 
      return _chunkSize; 
     } 
     set 
     { 
      if ((value <= 0) || (value >= 85000)) 
       throw new ArgumentOutOfRangeException("value"); 

      _chunkSize = value; 
     } 
    } 

    /// <summary> 
    /// When overridden in a derived class, gets or sets the position within the current stream. 
    /// </summary> 
    /// <value></value> 
    /// <returns> 
    /// The current position within the stream. 
    /// </returns> 
    /// <exception cref="T:System.ObjectDisposedException"> 
    /// Methods were called after the stream was closed. 
    /// </exception> 
    public override long Position 
    { 
     get 
     { 
      CheckDisposed(); 
      return _position; 
     } 
     set 
     { 
      CheckDisposed(); 
      if (value < 0) 
       throw new ArgumentOutOfRangeException("value"); 

      if (value > Length) 
       throw new ArgumentOutOfRangeException("value"); 

      _position = value; 
     } 
    } 
} 

Answer 8

El equipo de Bing ha lanzado RecyclableMemoryStream y escribió sobre ello here. Los beneficios que se citan son:

1. Eliminar las grandes asignaciones del montón de objetos mediante el uso de tampones agrupados
2. incurrir muchos menos Gen 2 GC, y pasan mucho menos tiempo en pausa debido a la GC
3. pérdidas de memoria Evitar por tener una acotada tamaño de la piscina
4. Evitar la fragmentación de memoria
5. proporcionan una excelente debuggability
6. proporcionar mediciones de seguimiento del rendimiento

Answer 9

Otra implementación de la transmisión fragmentada se podría considerar como una sustitución de existencias de MemoryStream. Adicionalmente permite asignar una única matriz de bytes grande en LOH que se utiliza como una piscina "trozo", compartida entre todas las instancias ChunkedStream ...

https://github.com/ImmortalGAD/ChunkedStream