BufferManager.cs

using System.Net.Sockets;

namespace SocketHelper;

// modified from: https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.socketasynceventargs.setbuffer?view=net-8.0#system-net-sockets-socketasynceventargs-setbuffer(system-byte()-system-int32-system-int32)
// 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);
  }
}