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UnmanagedMemoryStream Class

Provides access to unmanaged blocks of memory from managed code.

Namespace:  System.IO
Assembly:  mscorlib (in mscorlib.dll)

public class UnmanagedMemoryStream : Stream

The UnmanagedMemoryStream type exposes the following members.

  NameDescription
Protected methodUnmanagedMemoryStream()Initializes a new instance of the UnmanagedMemoryStream class.
Public methodUnmanagedMemoryStream(Byte*, Int64)Initializes a new instance of the UnmanagedMemoryStream class using the specified location and memory length.
Public methodUnmanagedMemoryStream(SafeBuffer, Int64, Int64)Initializes a new instance of the UnmanagedMemoryStream class in a safe buffer with a specified offset and length.
Public methodUnmanagedMemoryStream(Byte*, Int64, Int64, FileAccess)Initializes a new instance of the UnmanagedMemoryStream class using the specified location, memory length, total amount of memory, and file access values.
Public methodUnmanagedMemoryStream(SafeBuffer, Int64, Int64, FileAccess)Initializes a new instance of the UnmanagedMemoryStream class in a safe buffer with a specified offset, length, and file access.
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  NameDescription
Public propertyCanReadGets a value indicating whether a stream supports reading. (Overrides Stream.CanRead.)
Public propertyCanSeekGets a value indicating whether a stream supports seeking. (Overrides Stream.CanSeek.)
Public propertyCanTimeoutGets a value that determines whether the current stream can time out. (Inherited from Stream.)
Public propertyCanWriteGets a value indicating whether a stream supports writing. (Overrides Stream.CanWrite.)
Public propertyCapacityGets the stream length (size) or the total amount of memory assigned to a stream (capacity).
Public propertyLengthGets the length of the data in a stream. (Overrides Stream.Length.)
Public propertyPositionGets or sets the current position in a stream. (Overrides Stream.Position.)
Public propertyPositionPointerGets or sets a byte pointer to a stream based on the current position in the stream.
Public propertyReadTimeoutGets or sets a value, in miliseconds, that determines how long the stream will attempt to read before timing out. (Inherited from Stream.)
Public propertyWriteTimeoutGets or sets a value, in miliseconds, that determines how long the stream will attempt to write before timing out. (Inherited from Stream.)
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  NameDescription
Public methodBeginReadBegins an asynchronous read operation. (Consider using ReadAsync instead; see the Remarks section.) (Inherited from Stream.)
Public methodBeginWriteBegins an asynchronous write operation. (Consider using WriteAsync instead; see the Remarks section.) (Inherited from Stream.)
Public methodCloseCloses the current stream and releases any resources (such as sockets and file handles) associated with the current stream. Instead of calling this method, ensure that the stream is properly disposed. (Inherited from Stream.)
Public methodCopyTo(Stream)Reads the bytes from the current stream and writes them to another stream. (Inherited from Stream.)
Public methodCopyTo(Stream, Int32)Reads the bytes from the current stream and writes them to another stream, using a specified buffer size. (Inherited from Stream.)
Public methodCopyToAsync(Stream)Asynchronously reads the bytes from the current stream and writes them to another stream. (Inherited from Stream.)
Public methodCopyToAsync(Stream, Int32)Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size. (Inherited from Stream.)
Public methodCopyToAsync(Stream, Int32, CancellationToken)Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size and cancellation token. (Inherited from Stream.)
Public methodCreateObjRefCreates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject.)
Protected methodCreateWaitHandle Obsolete. Allocates a WaitHandle object. (Inherited from Stream.)
Public methodDispose()Releases all resources used by the Stream. (Inherited from Stream.)
Protected methodDispose(Boolean)Releases the unmanaged resources used by the UnmanagedMemoryStream and optionally releases the managed resources. (Overrides Stream.Dispose(Boolean).)
Public methodEndReadWaits for the pending asynchronous read to complete. (Consider using ReadAsync instead; see the Remarks section.) (Inherited from Stream.)
Public methodEndWriteEnds an asynchronous write operation. (Consider using WriteAsync instead; see the Remarks section.) (Inherited from Stream.)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodFlushOverrides the Flush method so that no action is performed. (Overrides Stream.Flush().)
Public methodFlushAsync()Asynchronously clears all buffers for this stream and causes any buffered data to be written to the underlying device. (Inherited from Stream.)
Public methodFlushAsync(CancellationToken) (Overrides Stream.FlushAsync(CancellationToken).)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetLifetimeServiceRetrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodInitialize(Byte*, Int64, Int64, FileAccess)Initializes a new instance of the UnmanagedMemoryStream class by using a pointer to an unmanaged memory location.
Protected methodInitialize(SafeBuffer, Int64, Int64, FileAccess)Initializes a new instance of the UnmanagedMemoryStream class in a safe buffer with a specified offset, length, and file access.
Public methodInitializeLifetimeServiceObtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject.)
Protected methodMemberwiseClone()Creates a shallow copy of the current Object. (Inherited from Object.)
Protected methodMemberwiseClone(Boolean)Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject.)
Protected methodObjectInvariantInfrastructure. Obsolete. Provides support for a Contract. (Inherited from Stream.)
Public methodReadReads the specified number of bytes into the specified array. (Overrides Stream.Read(Byte[], Int32, Int32).)
Public methodReadAsync(Byte[], Int32, Int32)Asynchronously reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. (Inherited from Stream.)
Public methodReadAsync(Byte[], Int32, Int32, CancellationToken) (Overrides Stream.ReadAsync(Byte[], Int32, Int32, CancellationToken).)
Public methodReadByteReads a byte from a stream and advances the position within the stream by one byte, or returns -1 if at the end of the stream. (Overrides Stream.ReadByte().)
Public methodSeekSets the current position of the current stream to the given value. (Overrides Stream.Seek(Int64, SeekOrigin).)
Public methodSetLengthSets the length of a stream to a specified value. (Overrides Stream.SetLength(Int64).)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodWriteWrites a block of bytes to the current stream using data from a buffer. (Overrides Stream.Write(Byte[], Int32, Int32).)
Public methodWriteAsync(Byte[], Int32, Int32)Asynchronously writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. (Inherited from Stream.)
Public methodWriteAsync(Byte[], Int32, Int32, CancellationToken) (Overrides Stream.WriteAsync(Byte[], Int32, Int32, CancellationToken).)
Public methodWriteByteWrites a byte to the current position in the file stream. (Overrides Stream.WriteByte(Byte).)
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This class supports access to unmanaged memory using the existing stream-based model and does not require that the contents in the unmanaged memory be copied to the heap.

Important noteImportant

This type implements the IDisposable interface. When you have finished using the type, you should dispose of it either directly or indirectly. To dispose of the type directly, call its Dispose method in a try/catch block. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). For more information, see the “Using an Object that Implements IDisposable” section in the IDisposable interface topic.

The following code example demonstrates how to read from and write to unmanaged memory using the UnmanagedMemoryStream class. A block of unmanaged memory is allocated and de-allocated using the Marshal class.


// Note: you must compile this sample using the unsafe flag. 
// From the command line, type the following: csc sample.cs /unsafe 

using System;
using System.IO;
using System.Text;
using System.Runtime.InteropServices;

unsafe class TestWriter
{

    static void Main()
	{
		
            // Create some data to read and write. 
            byte[] message = UnicodeEncoding.Unicode.GetBytes("Here is some data.");

	    // Allocate a block of unmanaged memory and return an IntPtr object.	
            IntPtr memIntPtr = Marshal.AllocHGlobal(message.Length);

            // Get a byte pointer from the IntPtr object. 
            byte* memBytePtr = (byte*) memIntPtr.ToPointer();

            // Create an UnmanagedMemoryStream object using a pointer to unmanaged memory.
            UnmanagedMemoryStream writeStream = new UnmanagedMemoryStream(memBytePtr, message.Length, message.Length, FileAccess.Write);

            // Write the data.
            writeStream.Write(message, 0, message.Length);

            // Close the stream.
            writeStream.Close();

            // Create another UnmanagedMemoryStream object using a pointer to unmanaged memory.
            UnmanagedMemoryStream readStream = new UnmanagedMemoryStream(memBytePtr, message.Length, message.Length, FileAccess.Read);

	    // Create a byte array to hold data from unmanaged memory. 
            byte[] outMessage = new byte[message.Length];

            // Read from unmanaged memory to the byte array.
            readStream.Read(outMessage, 0, message.Length);

            // Close the stream.
            readStream.Close();

            // Display the data to the console.
            Console.WriteLine(UnicodeEncoding.Unicode.GetString(outMessage));

            // Free the block of unmanaged memory.
            Marshal.FreeHGlobal(memIntPtr);

            Console.ReadLine();
    }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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