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SocketAsyncEventArgs.SetBuffer Method (Byte[], Int32, Int32)

Sets the data buffer to use with an asynchronous socket method.

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)

public void SetBuffer(
	byte[] buffer,
	int offset,
	int count
)

Parameters

buffer
Type: System.Byte[]

The data buffer to use with an asynchronous socket method.

offset
Type: System.Int32

The offset, in bytes, in the data buffer where the operation starts.

count
Type: System.Int32

The maximum amount of data, in bytes, to send or receive in the buffer.

ExceptionCondition
ArgumentException

There are ambiguous buffers specified. This exception occurs if the Buffer property is also not null and the BufferList property is also not null.

ArgumentOutOfRangeException

An argument was out of range. This exception occurs if the offset parameter is less than zero or greater than the length of the array in the Buffer property. This exception also occurs if the count parameter is less than zero or greater than the length of the array in the Buffer property minus the offset parameter.

The offset and count parameters can't be negative numbers. The combination of the offset and count parameters must be in bounds of the data array in the buffer parameter.

This method sets the Buffer property to the buffer parameter, the Count property to the count parameter, and the Offset property to the offset parameter.

The following code example creates a single large buffer which can be divided up and assigned to SocketAsyncEventArgs objects for use with each socket I/O operation. This enables buffers to be easily reused and guards against fragmenting heap memory.

// This class creates a single large buffer which can be divided up  
// and assigned to SocketAsyncEventArgs objects for use with each  
// socket I/O operation.   
// This enables bufffers to be easily reused and guards against  
// fragmenting heap memory. 
//  
// The operations exposed on the BufferManager class are not thread safe. 
class BufferManager
{
    int m_numBytes;                 // the total number of bytes controlled by the buffer pool 
    byte[] m_buffer;                // the underlying byte array maintained by the Buffer Manager
    Stack<int> m_freeIndexPool;     //  
    int m_currentIndex;
    int m_bufferSize;

    public BufferManager(int totalBytes, int bufferSize)
    {
        m_numBytes = totalBytes;
        m_currentIndex = 0;
        m_bufferSize = bufferSize;
        m_freeIndexPool = new Stack<int>();
    }

    // Allocates buffer space used by the buffer pool 
    public void InitBuffer()
    {
        // create one big large buffer and divide that  
        // out to each SocketAsyncEventArg object
        m_buffer = new byte[m_numBytes];
    }

    // Assigns a buffer from the buffer pool to the  
    // specified SocketAsyncEventArgs object 
    // 
    // <returns>true if the buffer was successfully set, else false</returns> 
    public bool SetBuffer(SocketAsyncEventArgs args)
    {

        if (m_freeIndexPool.Count > 0)
        {
            args.SetBuffer(m_buffer, m_freeIndexPool.Pop(), m_bufferSize);
        }
        else
        {
            if ((m_numBytes - m_bufferSize) < m_currentIndex)
            {
                return false;
            }
            args.SetBuffer(m_buffer, m_currentIndex, m_bufferSize);
            m_currentIndex += m_bufferSize;
        }
        return true;
    }

    // Removes the buffer from a SocketAsyncEventArg object.   
    // This frees the buffer back to the buffer pool 
    public void FreeBuffer(SocketAsyncEventArgs args)
    {
        m_freeIndexPool.Push(args.Offset);
        args.SetBuffer(null, 0, 0);
    }

}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5 SP1, 3.0 SP1, 2.0 SP1

.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.

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