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UnmanagedMemoryStream Constructor (Byte*, Int64)

Initializes a new instance of the UnmanagedMemoryStream class using the specified location and memory length.

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

public UnmanagedMemoryStream(
	byte* pointer,
	long length
)

Parameters

pointer
Type: System.Byte*

A pointer to an unmanaged memory location.

length
Type: System.Int64

The length of the memory to use.

ExceptionCondition
SecurityException

The user does not have the required permission.

ArgumentNullException

The pointer value is null.

ArgumentOutOfRangeException

The length value is less than zero.

- or -

The length is large enough to cause an overflow.

This constructor creates a new instance of the UnmanagedMemoryStream class, and by default sets the CanWrite property to false and the CanRead property to true. The Length property is set to the value of the length parameter and cannot be changed.

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.Runtime.InteropServices;
using System.Text;

unsafe class Program
{
    static void Main()
    {
        // Create some data to write.
        byte[] text = UnicodeEncoding.Unicode.GetBytes("Data to write.");

        // Allocate a block of unmanaged memory.
        IntPtr memIntPtr = Marshal.AllocHGlobal(text.Length);

        // Get a byte pointer from the unmanaged memory block.
        byte* memBytePtr = (byte*)memIntPtr.ToPointer();

        UnmanagedMemoryStream writeStream =
            new UnmanagedMemoryStream(
            memBytePtr, text.Length, text.Length, FileAccess.Write);

        // Write the data.
        WriteToStream(writeStream, text);

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

        // Create another UnmanagedMemoryStream for reading.
        UnmanagedMemoryStream readStream =
            new UnmanagedMemoryStream(memBytePtr, text.Length);

        // Display the contents of the stream to the console.
        PrintStream(readStream);

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

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

    }

    public static void WriteToStream(UnmanagedMemoryStream writeStream, byte[] text)
    {
        // Verify that the stream is writable: 
        // By default, UnmanagedMemoryStream objects do not have write access, 
        // write access must be set explicitly. 
        if (writeStream.CanWrite)
        {
            // Write the data, byte by byte 
            for (int i = 0; i < writeStream.Length; i++)
            {
                writeStream.WriteByte(text[i]);
            }
        }
    }

    public static void PrintStream(UnmanagedMemoryStream readStream)
    {
        byte[] text = new byte[readStream.Length];
        // Verify that the stream is writable: 
        // By default, UnmanagedMemoryStream objects do not have write access, 
        // write access must be set explicitly. 
        if (readStream.CanRead)
        {
            // Write the data, byte by byte 
            for (int i = 0; i < readStream.Length; i++)
            {
                text[i] = (byte)readStream.ReadByte();
            }
        }

        Console.WriteLine(UnicodeEncoding.Unicode.GetString(text));
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

Supported in: 3.5, 3.0, 2.0
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