누워서 코딩하는 개발자

학기초에 MFC를 공부하기 위해서 구입한 도서 인데
책 두께로 보거나 프리텍에 명성의 걸맞은 걸주간 책이 나왔다고 생각하고 그당시 학생신분에서는 꽤 큰돈으로 구입했었다.
학기초에는 시간도 나고 해서 공부를 첨에만 조금 했다가 최근들어 소켓통신 공부좀 해볼려고 책을 펼쳐서
뒷장으로 넘어가서 보는데 이건모 어다르고 아 다르다고, 원래 책을 보면서 코딩을 하면 쭈~~욱 쳐 내려가면서 이해하고 칠수 있을정도로 책을 지필해야 하는데 이건모 완전 순서도 엉켜져 있고, 초보들이 따라치다가는 날샐꺼 같다. 비록 본인은 MFC를 조금 해봐서 이리저리 앞뒤로 책을 넘겨보면서 쳐서 완성은 했지만 그래도 이건 아니다 쉽다.
책의 순서가 이렇게 엉켜 있음 어떻게 독자가 보란 말인가?
반성해 하자.

문제의 발단은 위에서 굵게 선언된 맴버함수를 사용하기 위해서 부터다. 책을 쭈욱 치고 갔지만 위에서와 같이 인텔리전스가 나오질 않아서 당황했다. 뒷장을 계속 찾아보아서 아래와 같은 코드를 찾을수 있었다. CClientSocket 클래스에서 맴버함수를 만들어 넣지도 않고 위에 코드가 먼저 설명이 나온것이다.

아 정말 어이없다. 이것때문에 시간 낭비하는 사람들을 위해서 구글링했을때 쉽게 찾을수 있도록 기록으로 남겨 둔다.

/***************************************************************************************
****************************************************************************************

 class cSocket

 Description:
 A universal asynchronous bidirectional TCP Winsock Socket class for client and server.
 The server supports up to 62 connections at the same time.
 This class may run within one single thread.

 All functions in this class return an API error code or 0 on success.

 Author:
 Elm?(www.netcult.ch/elmue)

****************************************************************************************
****************************************************************************************/

#include "stdafx.h"
#include "Socket.h"

/*
----------------------------------------------------------------------------------
Using these conventions results in better readable code and less coding errors !
----------------------------------------------------------------------------------

     cName  for generic class definitions
     CName  for MFC     class definitions
     tName  for type    definitions
     eName  for enum    definitions
     kName  for struct  definitions

    e_Name  for enum variables
    E_Name  for enum constant values

    i_Name  for instances of classes
    h_Name  for handles

    M_Name  for macros
    T_Name  for Templates
    t_Name  for TCHAR or LPTSTR

    s_Name  for strings
   sa_Name  for Ascii strings
   sw_Name  for Wide (Unicode) strings
   bs_Name  for BSTR
    f_Name  for function pointers
    k_Name  for contructs (struct)

    b_Name  bool,BOOL 1 Bit

   s8_Name    signed  8 Bit (char)
  s16_Name    signed 16 Bit (SHORT)
  s32_Name    signed 32 Bit (LONG, int)
  s64_Name    signed 64 Bit (LONGLONG)

   u8_Name  unsigned  8 Bit (BYTE)
  u16_Name  unsigned 16 bit (WORD, WCHAR)
  u32_Name  unsigned 32 Bit (DWORD, UINT)
  u64_Name  unsigned 64 Bit (ULONGLONG)

    d_Name  for double

  ----------------

    m_Name  for member variables of a class (e.g. ms32_Name for int member variable)
    g_Name  for global (static) variables   (e.g. gu16_Name for global WORD)
    p_Name  for pointer                     (e.g.   ps_Name  *pointer to string)
   pp_Name  for pointer to pointer          (e.g.  ppd_Name **pointer to double)
*/

TCP::cSocket::cSocket()
{
 mb_Initialized    = FALSE;
 mu32_WaitIndex    = 0;
 ms8_ReadBuffer    = 0;
 mu32_Tick64Lo     = 0;
 mu32_Tick64Hi     = 0;
 ms64_MaxIdleTime  = 0;
 mu32_EventTimeout = 0;
}

TCP::cSocket::~cSocket()
{
 if (mb_Initialized)
 {
  Close();
  WSACleanup();
 }

 if (ms8_ReadBuffer) delete ms8_ReadBuffer;
}

// protected
// Load ws2_32.dll and initialize Windsock 2.0
DWORD TCP::cSocket::Initialize()
{
 if (mb_Initialized)
  return 0;

 // Winsock version 2.0 is available on ALL Windows operating systems
 // except Windows 95 which comes with Winsock 1.1
 WSADATA k_Data;
 DWORD u32_Error = WSAStartup(MAKEWORD(2,0), &k_Data);
 if (u32_Error)
  return u32_Error;

 ms8_ReadBuffer = new char[READ_BUFFER_SIZE];
 mb_Initialized = TRUE;
 return 0;
}

// Closes all open sockets
DWORD TCP::cSocket::Close()
{
 if (!mi_List.mu32_Count)
  return WSAENOTCONN; // no socket open

 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("Close()");
 #endif
  
 // Request thread safe access to mi_List
 cLock i_Lock;
 DWORD u32_Error = i_Lock.Request(&mk_Lock);
 if (u32_Error)
  return u32_Error;

 mi_List.RemoveAll();
 return 0;
}

// returns the current state of the socket
TCP::cSocket::eState TCP::cSocket::GetState()
{
 return mi_List.me_State;
}

// Get the count of open sockets
DWORD TCP::cSocket::GetSocketCount()
{
 return mi_List.mu32_Count;
}

// returns all open sockets: Key = socket handle, Value = peer IP
DWORD TCP::cSocket::GetAllConnectedSockets(cHash<SOCKET,DWORD>* pi_SockList)
{
 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("GetAllConnectedSockets()");
 #endif

 pi_SockList->Clear();

 // Request thread safe access to mi_List
 cLock i_Lock;
 DWORD u32_Error = i_Lock.Request(&mk_Lock);
 if (u32_Error)
  return u32_Error;

 for (DWORD i=0; i<mi_List.mu32_Count; i++)
 {
  // On a server do not return socket[0] which is never connected
  if (!mi_List.mk_Data[i].u32_IP)
   continue;

  if (mi_List.mk_Data[i].b_Shutdown || mi_List.mk_Data[i].b_Closed)
   continue;

  pi_SockList->Append(mi_List.mk_Data[i].h_Socket, mi_List.mk_Data[i].u32_IP);
 }

 #if TRACE_EVENTS
  TraceA("Returning list with %d connected Sockets", pi_SockList->GetCount());
 #endif
 return 0;
}

// protected
// Create a new unbound socket and add it to mi_List at index 0
DWORD TCP::cSocket::CreateSocket()
{
 DWORD u32_Error = Initialize();
 if (u32_Error)
  return u32_Error;

 if (mi_List.mu32_Count)
  return WSAEISCONN; // Socket already created

 SOCKET h_Socket = socket(AF_INET, SOCK_STREAM, 0);
 if (h_Socket == INVALID_SOCKET)
  return WSAGetLastError();

 HANDLE h_Event = WSACreateEvent();
 if (h_Event == WSA_INVALID_EVENT)
 {
  u32_Error = WSAGetLastError();
  closesocket(h_Socket);
  return u32_Error;
 }

 // Monitor all events on the socket
 if (WSAEventSelect(h_Socket, h_Event, FD_ALL_EVENTS) == SOCKET_ERROR)
 {
  u32_Error = WSAGetLastError();
  closesocket  (h_Socket);
  WSACloseEvent(h_Event);
  return u32_Error;
 }

 mi_List.Add(h_Socket, h_Event);
 return 0;
}

// Creates a Server socket
// You must wait for FD_ACCEPT events before sending data
// u32_BindIP = 0          --> listen on all network adapters
// u32_BindIP = 10.1.0.143 --> listen only on the network adapter with local IP 10.1.0.143
// u32_BindIP = 10.1.2.208 --> listen only on the network adapter with local IP 10.1.2.208
// u32_EventTimeout = the timeout after which ProcessEvents() will abort waiting for an event
// If u32_MaxIdleTime > 0  --> automatically disconnect clients which are idle for a longer time (in seconds)
DWORD TCP::cSocket::Listen(DWORD u32_BindIP, USHORT u16_Port, DWORD u32_EventTimeout, DWORD u32_MaxIdleTime)
{
 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("Listen()");
 #endif

 // Create a server socket which waits for Accept events
 // This socket itself will never be connected to any client!
 DWORD u32_Error = CreateSocket();
 if (u32_Error)
  return u32_Error;

 // get the new socket's data structure which has been filled in CreateSocket()
 kData* pk_Data = &mi_List.mk_Data[0];

 SOCKADDR_IN k_Addr;
 k_Addr.sin_family      = AF_INET;
 k_Addr.sin_addr.s_addr = u32_BindIP;
 k_Addr.sin_port        = htons(u16_Port);

 // Bind the socket to the given port
 if (bind(pk_Data->h_Socket, (LPSOCKADDR)&k_Addr, sizeof(SOCKADDR_IN)) == SOCKET_ERROR)
 {
  u32_Error = WSAGetLastError();
  mi_List.RemoveAll();
  return u32_Error;
 }

 // Start listening for connection requests
 if (listen(pk_Data->h_Socket, WSA_MAXIMUM_WAIT_EVENTS) == SOCKET_ERROR)
 {
  u32_Error = WSAGetLastError();
  mi_List.RemoveAll();
  return u32_Error;
 }

 // The server is not yet connected (wait for FD_ACCEPT!)
 mi_List.me_State  = E_Server;
 ms64_MaxIdleTime  = u32_MaxIdleTime * 1000; // seconds -> ms
 mu32_EventTimeout = u32_EventTimeout; // ms
 return 0;
}

// Creates a Client socket
// u32_ServIP = 0x6401a8c0 -> 192.168.1.100
// If u32_MaxIdleTime > 0  -> automatically disconnect from server if idle for a longer time (in seconds)
// u32_EventTimeout = the timeout after which ProcessEvents() will abort waiting for an event
// *************************** ATTENTION ************************************
// When this funcion returns without error the socket is NOT YET connected!
// You must wait for the FD_CONNECT event before sending data to this socket!
// *************************** ATTENTION ************************************
DWORD TCP::cSocket::ConnectTo(DWORD u32_ServIP, USHORT u16_Port, DWORD u32_EventTimeout, DWORD u32_MaxIdleTime)
{
 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("ConnectTo()");
 #endif

 // Create a client socket which will connect to the server
 DWORD u32_Error = CreateSocket();
 if (u32_Error)
  return u32_Error;

 // get the new socket's data structure which has been filled in CreateSocket()
 kData* pk_Data = &mi_List.mk_Data[0];

 SOCKADDR_IN k_Addr;
 k_Addr.sin_family      = AF_INET;
 k_Addr.sin_addr.s_addr = u32_ServIP;
 k_Addr.sin_port        = htons(u16_Port);

 // Connect the socket to the given IP and port
 if (connect(pk_Data->h_Socket, (LPSOCKADDR)&k_Addr, sizeof(SOCKADDR_IN)) == SOCKET_ERROR)
 {
  u32_Error = WSAGetLastError();
  if (u32_Error != WSAEWOULDBLOCK)
  {
   mi_List.RemoveAll();
   return u32_Error;
  }
 }

 // The client is not yet connected (wait for FD_CONNECT!)
 mi_List.me_State  = E_Client;
 ms64_MaxIdleTime  = u32_MaxIdleTime * 1000; // seconds -> ms
 mu32_EventTimeout = u32_EventTimeout; // ms

 // s64_IdleSince MUST be set HERE otherwise the socket will be closed before FD_CONNECT is received
 pk_Data->s64_IdleSince = GetTickCount64();
 pk_Data->u32_IP = u32_ServIP;
 return 0;
}

// This function is for use on a server only
// It can be called to force a disconnect of a specific client from the server
DWORD TCP::cSocket::DisconnectClient(SOCKET h_Socket)
{
 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("DisconnectClient(%X)", h_Socket);
 #endif

 // Request thread safe access to mi_List
 cLock i_Lock;
 DWORD u32_Error = i_Lock.Request(&mk_Lock);
 if (u32_Error)
  return u32_Error;
 
 // On a server Socket 0 is not connected
 int s32_Index = mi_List.FindSocket(h_Socket);
 if (s32_Index < 1)
  return ERROR_INVALID_PARAMETER;

 // Ignore all events on this socket except FD_CLOSE
 mi_List.mk_Data[s32_Index].b_Shutdown = TRUE;

 // DO NOT call closesocket() here !!!
 // shutdown() --> FD_CLOSE --> b_Shutdown=TRUE --> cList::Remove() --> closesocket()
 shutdown(h_Socket, SD_BOTH);
 return 0;
}

// Waits for incoming events on the port and processes them (used on Server + Client)
// returns the event(s) that occurred and the socket and it's IP-address which has caused the event.
// If the event is FD_READ the data will be returned in ppi_RecvMem which MUST be cleared with DeleteLeft() by the caller.
// If the event is FD_WRITE the remaining data in the send buffer will be sent and pu32_Sent receives the bytes sent.
// If there is more data to be read or sent, the next call to ProcessEvents() will process the next block of data.
// returns ERROR_TIMEOUT if during the given timeout no event occurres
// pu32_IP = 0x6401a8c0 -> 192.168.1.100
DWORD TCP::cSocket::ProcessEvents(DWORD*   pu32_Events,  // OUT
                                  DWORD*   pu32_IP,      // OUT
          SOCKET*    ph_Socket,  // OUT
                                  cMemory** ppi_RecvMem, // OUT
                                  DWORD*   pu32_Read,    // OUT
          DWORD*   pu32_Sent)    // OUT
{
 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("Entering ProcessEvents()");
 #endif

 DWORD u32_Error;
 kData* pk_Data;
 WSANETWORKEVENTS k_Events;

 *ph_Socket   = 0;
 *pu32_Events = 0;
 *pu32_IP     = 0;
 *pu32_Read   = 0;
 *pu32_Sent   = 0;
 *ppi_RecvMem = 0;

 // Block here if SendTo() or Close() have requested thread safe access to manipulate mi_List.
 cLock i_Lock;
 u32_Error = i_Lock.Loop(&mk_Lock);
 if (u32_Error)
  return u32_Error;

 // Remove all sockets which had a FD_CLOSE event in the last round
 mi_List.RemoveClosed();

 if (!mi_List.mu32_Count)
  return WSAENOTCONN; // No socket open

 // This timer is set to escape from WaitForMultiplEventsEx
 mi_List.mh_Events[0] = mk_Lock.h_ExitTimer;

 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("!!!!! ProcessEvents WAIT");
 #endif

 // Wait until an event occurred or the timeout has elapsed
 // u32_Index is the index in the eventlist mh_Events of the event that has occurred
 DWORD u32_Index = WSAWaitForMultipleEventsEx(mi_List.mu32_Count+1, &mu32_WaitIndex, mi_List.mh_Events, mu32_EventTimeout);
 if (u32_Index == WSA_WAIT_FAILED)
  return WSAGetLastError();

 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("");
  TraceA(">>>>> ProcessEvents CONTINUE");
 #endif

 // -------------------------------------------

 if (u32_Index == WSA_WAIT_TIMEOUT)
 {
  #if TRACE_EVENTS
   TraceA("# WSA_WAIT_TIMEOUT");
  #endif
  u32_Error = ERROR_TIMEOUT;
  goto _Exit;
 }

 // -------------------------------------------

 u32_Index -= WSA_WAIT_EVENT_0;

 // mi_List.mh_Events[0] is used for the Timer. It is not associated with a socket.
 if (u32_Index == 0)
 {
  #if TRACE_EVENTS
   TraceA("# Idle/Request Timer elapsed");
  #endif
  u32_Error = 0; // no error
  goto _Exit;
 }

 // Convert the 1-based event index into the zero-based socket index
 u32_Index--;

 // Get the data associated with the socket that has signaled the event
 pk_Data = &mi_List.mk_Data[u32_Index];

 // -------------------------------------------

 // Get the event(s) that occurred and their associated error array
 if (WSAEnumNetworkEvents(pk_Data->h_Socket, mi_List.mh_Events[u32_Index+1], &k_Events) == SOCKET_ERROR)
 {
  u32_Error = WSAGetLastError();
  mi_List.Remove(u32_Index); // remove socket with problem
  goto _Exit;
 }

 // After shutdown(pk_Data->h_Socket) has been called remove all events except FD_CLOSE
 if (pk_Data->b_Shutdown) k_Events.lNetworkEvents &= FD_CLOSE;

 // Signal the FD_TIMEOUT flag always together with FD_CLOSE
 if (pk_Data->b_Timeout && k_Events.lNetworkEvents & FD_CLOSE)
  k_Events.lNetworkEvents |= FD_TIMEOUT;

 #if TRACE_EVENTS
  char s8_Buf[200];
  FormatEvents(k_Events.lNetworkEvents, s8_Buf);
  TraceA("# Socket %X: Events: %s", pk_Data->h_Socket, s8_Buf);
 #endif

 *pu32_Events = k_Events.lNetworkEvents;

 // -------------------------------------------

 if (k_Events.lNetworkEvents & FD_ACCEPT)
 {
  if (k_Events.iErrorCode[FD_ACCEPT_BIT])
  {
   u32_Error = k_Events.iErrorCode[FD_ACCEPT_BIT];
   goto _Exit;
  }

  SOCKADDR_IN k_Addr;
  int s32_Len = sizeof(k_Addr);
  // Accept the connect request from a client (k_Addr receives peer IP of connecting client)
  // The callback AcceptCondition() checks if the maximum count of connected clients was exceeded
  // If there are already 63 sockets open, the connect request is rejected.
  SOCKET h_Socket = WSAAccept(pk_Data->h_Socket, (LPSOCKADDR)&k_Addr, &s32_Len, AcceptCondition, (DWORD_PTR)this);
  if (h_Socket == INVALID_SOCKET)
  {
   u32_Error = WSAGetLastError();
   goto _Exit;
  }

  HANDLE h_Event = WSACreateEvent();
  if (h_Event == WSA_INVALID_EVENT)
  {
   u32_Error = WSAGetLastError();
   closesocket(h_Socket);
   goto _Exit;
  }
  
  // Monitor events on the newly connected client socket
  if (WSAEventSelect(h_Socket, h_Event, FD_ALL_EVENTS) == SOCKET_ERROR)
  {
   u32_Error = WSAGetLastError();
   closesocket  (h_Socket);
   WSACloseEvent(h_Event);
   goto _Exit;
  }

  // Append the new socket to the socket list
  pk_Data = mi_List.Add(h_Socket, h_Event);
  // Store the client's IP in the socket list
  pk_Data->u32_IP = k_Addr.sin_addr.s_addr;
  // Store the time when the last action was executed on the socket
  pk_Data->s64_IdleSince = GetTickCount64();

  // successfully connected
  if (mi_List.me_State & E_Server)
   mi_List.me_State = (eState)(E_Server | E_Connected);

  // This is a workaround for Windows CE:
  // Without the following code Socket[0] would be dead (deaf) after the first connection.
  // So no further connection could be made after the first connection.
  // This may be a bug but if it is, this bug has never been confirmed by Microsoft.
  // On the other hand Microsoft did not document that this behaviour is normal for Windows CE.
  // So it is an enigma. At least this is a workaround which solves the problem.
  #ifdef _WIN32_WCE
   if (WSAEventSelect(mi_List.mk_Data[0].h_Socket, mi_List.mh_Events[1], FD_ALL_EVENTS) == SOCKET_ERROR)
   {
    u32_Error = WSAGetLastError();
    mi_List.RemoveAll();
    return u32_Error;
   }
  #endif
  
  // Multiple events may be set!
 }

 *ph_Socket = pk_Data->h_Socket;
 *pu32_IP   = pk_Data->u32_IP;
 
 // -------------------------------------------

 if (k_Events.lNetworkEvents & FD_CONNECT)
 {
  if (k_Events.iErrorCode[FD_CONNECT_BIT])
  {
   u32_Error = k_Events.iErrorCode[FD_CONNECT_BIT];
   // The connection has failed -> remove faulty socket from the socket list
   mi_List.Remove(u32_Index);
   goto _Exit;
  }

  // Store the time when the last action was executed on the socket
  pk_Data->s64_IdleSince = GetTickCount64();

  // successfully connected
  // NOTE: on Windows CE a server signals FD_ACCEPT and FD_CONNECT at the same time! (Bug?)
  // So ignore this FD_CONNECT on a Server.
  if (mi_List.me_State & E_Client)
   mi_List.me_State = (eState)(E_Client | E_Connected);
  
  // Multiple events may be set!
 }

 // -------------------------------------------

 if (k_Events.lNetworkEvents & FD_READ)
 {
  if (k_Events.iErrorCode[FD_READ_BIT])
  {
   u32_Error = k_Events.iErrorCode[FD_READ_BIT];
   mi_List.Remove(u32_Index); // remove socket with Read error
   goto _Exit;
  }

  // Read the data into the read buffer
  DWORD u32_Flags = 0;
  WSABUF  k_Buf;
  k_Buf.buf = ms8_ReadBuffer;
  k_Buf.len = READ_BUFFER_SIZE;
  if (WSARecv(pk_Data->h_Socket, &k_Buf, 1, pu32_Read, &u32_Flags, 0, 0) == SOCKET_ERROR)
  {
   u32_Error = WSAGetLastError();

   if (u32_Error == WSAEWOULDBLOCK) u32_Error = 0;
   if (u32_Error)
   { 
    mi_List.Remove(u32_Index); // remove socket with Read error
    goto _Exit;
   }
  }

  #if TRACE_EVENTS
   TraceA("Received %d Bytes", *pu32_Read);
  #endif

  if (!pk_Data->pi_RecvMem)
    pk_Data->pi_RecvMem = new cMemory(MEMORY_INITIAL_SIZE);
  
  pk_Data->pi_RecvMem->Append(ms8_ReadBuffer, *pu32_Read);

  // Store the time when the last action was executed on the socket
  pk_Data->s64_IdleSince = GetTickCount64();

  *ppi_RecvMem = pk_Data->pi_RecvMem;
  
  // Multiple events may be set!
 }

 // -------------------------------------------

 if (k_Events.lNetworkEvents & FD_WRITE)
 {
  if (k_Events.iErrorCode[FD_WRITE_BIT])
  {
   u32_Error = k_Events.iErrorCode[FD_WRITE_BIT];
   mi_List.Remove(u32_Index); // remove socket with Write error
   goto _Exit;
  }

  // Is there pending data in the send buffer waiting to be sent ?
  if (pk_Data->s8_SendBuf)
  {
   // Send as much as possible data from the send buffer
   DWORD u32_Before = pk_Data->u32_SendPos;
   u32_Error = SendDataBlock(pk_Data->h_Socket, pk_Data->s8_SendBuf, &pk_Data->u32_SendPos, pk_Data->u32_SendLen);
   *pu32_Sent = pk_Data->u32_SendPos - u32_Before;

   if (pk_Data->u32_SendPos == pk_Data->u32_SendLen)
   {
    // All data has been sent successfully -> delete the buffer
    delete pk_Data->s8_SendBuf;
    pk_Data->s8_SendBuf = 0;
   }

   if (u32_Error == WSAEWOULDBLOCK) u32_Error = 0;
   if (u32_Error)
   {
    mi_List.Remove(u32_Index); // remove socket with Write error
    goto _Exit;
   }
  }

  // Store the time when the last action was executed on the socket
  pk_Data->s64_IdleSince = GetTickCount64();
  
  // Multiple events may be set!
 }

 // -------------------------------------------

 if (k_Events.lNetworkEvents & FD_CLOSE)
 {
  // ATTENTION: The socket must NOT yet be removed from mi_List!
  // Sometimes a FD_READ comes at the same time as a FD_CLOSE.
  // In this case the read data would be lost.
  // The socket will be removed in mi_List.RemoveClosed() in the next round
  pk_Data->b_Closed = TRUE;

  if (k_Events.iErrorCode[FD_CLOSE_BIT]) // e.g. WSAECONNABORTED
  {
   u32_Error = k_Events.iErrorCode[FD_CLOSE_BIT];
   goto _Exit;
  }
  
  // Multiple events may be set!
 }

 u32_Error = 0; // Success

 // -------------------------------------------

 _Exit:
 // 1.) Shutdown all connected sockets that are idle for longer than mi_List.ms64_MaxIdleTime
 // 2.) Set the timer mk_Lock.h_ExitTimer to fire when the socket with the longest idle time will be due
 // When cLock::Request() is called, WsaWaitForMultipleEventsEx() must stop blocking.
 // Therefore ProcessIdleSockets() must not be called between cLock::Loop() and WsaWaitForMultipleEventsEx()
 // because it sets the same timer!
 DWORD u32_IdleErr = ProcessIdleSockets("ProcessEvents()");
 if (u32_IdleErr)
  return u32_IdleErr;

 return u32_Error;
}

// This is a special Wait function which eliminates a problem of WSAWaitForMultipleEvents:
// WSAWaitForMultipleEvents scans the events in the event array ph_Events from zero on.
// When it finds one that is signaled it stops and retruns it's index.
// This may cause a problem on a server with high load near 100% CPU power:
// When multiple events are signaled always the ones at the begin of the event array will be preferred
// and the events at the end of the array will be in disadvantage.
// To avoid this, this function uses a pointer pu32_Index from which on a signaled event is searched.
// This pointer is incremented until the last event and then starts from the first again.
// So every client on a server has the same priority in being served.
// ph_Events  = array of event handles
// u32_Count  = count of events in array
// pu32_Index = rotating index
DWORD TCP::cSocket::WSAWaitForMultipleEventsEx(DWORD u32_Count, DWORD* pu32_Index, WSAEVENT* ph_Events, DWORD u32_Timeout)
{
 // Here *pu32_Index is at the position where the last time an event has been signaled
 // Search for a signaled event from *pu32_Index +1 upwards
 for (DWORD C=0; C<u32_Count; C++)
 {
  (*pu32_Index)++;

  if (*pu32_Index >= u32_Count)
   *pu32_Index = 0;

  // Check if the event is set (Timeout = 0)
  DWORD u32_Res = WaitForSingleObject(ph_Events[*pu32_Index], 0);
  if (u32_Res == WAIT_OBJECT_0)
   return WSA_WAIT_EVENT_0 + *pu32_Index;
 }

 // There is no event signaled -> this means that the server is not under stress
 // There is no reason to check the events one by one anymore.
 DWORD u32_Res = WSAWaitForMultipleEvents(u32_Count, ph_Events, FALSE, u32_Timeout, FALSE);
 if (u32_Res != WSA_WAIT_FAILED && u32_Res != WSA_WAIT_TIMEOUT)
 {
  *pu32_Index = u32_Res - WSA_WAIT_EVENT_0;
 }
 return u32_Res;
}

// static
// Decides if a connection request from a client is accepted. (Max 63 open sockets possible)
// WSAAccept() will return WSAECONNREFUSED if AcceptCondition() returns CF_REJECT
int WINAPI TCP::cSocket::AcceptCondition(WSABUF* pk_CallerId, WSABUF* pk_CallerData, QOS* pk_SQOS, QOS* pk_GQOS,
           WSABUF* pk_CalleeId, WSABUF* pk_CalleeData, UINT* pu32_Group, DWORD_PTR p_Param)
{
 cSocket* p_This = (cSocket*)p_Param;

 if (p_This->mi_List.mu32_Count >= WSA_MAXIMUM_WAIT_EVENTS-1)
  return CF_REJECT;
 else
  return CF_ACCEPT;
}

// Shutdown all sockets that are idle for longer than ms64_MaxIdleTime milliseconds
// Set timer mk_Lock.h_ExitTimer to fire when the socket with the longest idle time will become due
// s8_Caller = the calling function, only used for debugging (Trace)
DWORD TCP::cSocket::ProcessIdleSockets(char* s8_Caller)
{
 if (!ms64_MaxIdleTime)
  return 0;

 LONGLONG s64_Now    = GetTickCount64(); // current tick count in ms
 LONGLONG s64_Oldest = s64_Now +1;

 for (DWORD i=0; i<mi_List.mu32_Count; i++)
 {
  kData* pk_Data = &mi_List.mk_Data[i];

  if (!pk_Data->u32_IP || pk_Data->b_Shutdown)
   continue; // Ignore socket 0 on a server (IP = 0.0.0.0)

  // Add 100 ms to assure that the max idle time surely has elapsed because
  // GetTickCount() increments in 17 ms steps (clock interrupt) and is not as exact as SetWaitableTimer()
  if (s64_Now - pk_Data->s64_IdleSince + 100 >= ms64_MaxIdleTime)
  {
   #if TRACE_EVENTS
    TraceA("+ Shutting down idle Socket %X", pk_Data->h_Socket);
   #endif

   // Set FD_TIMEOUT flag when FD_CLOSE will be fired
   pk_Data->b_Timeout = TRUE;
   // Ignore all events on this socket except FD_CLOSE
   pk_Data->b_Shutdown = TRUE;

   // DO NOT call closesocket() here !!!
   // shutdown() --> FD_CLOSE --> b_Shutdown=TRUE --> cList::Remove() --> closesocket()
   shutdown(pk_Data->h_Socket, SD_BOTH);
  }
  else if (s64_Oldest > pk_Data->s64_IdleSince)
  {
   // Get the oldest "last activity"
   s64_Oldest = pk_Data->s64_IdleSince;
  }
 }

 // Do not set the timer if there is no socket connected (s64_Oldest == s64_Now +1)
 if (s64_Oldest <= s64_Now)
 {
  DWORD u32_Interval = (DWORD)max(0, ms64_MaxIdleTime - (s64_Now - s64_Oldest));

  // If the event timeout is short there is no need to set the timer
  if (u32_Interval > mu32_EventTimeout)
   return 0;
  
  #if TRACE_EVENTS
   TraceA("+ %s Setting Timer: Idle Interval= %d ms", s8_Caller, u32_Interval);
  #endif

  // k_Interval must be negative value with 100 nano seconds resolution to set a relative time
  LARGE_INTEGER k_Interval;
  k_Interval.QuadPart = (LONGLONG)u32_Interval * -10000;
  
  // mh_Events[0] == mk_Lock.h_ExitTimer
  if (!SetWaitableTimer(mi_List.mh_Events[0], &k_Interval, 0, 0, 0, FALSE))
   return GetLastError();
 }
 return 0;
}

// protected
// Send the remaining data and adjust the pu32_Pos pointer.
// If the data was sent only partially (WSAEWOULDBLOCK) this function must be called again
DWORD TCP::cSocket::SendDataBlock(SOCKET h_Socket, char* s8_Buf, DWORD* pu32_Pos, DWORD u32_Len)
{
 while (*pu32_Pos < u32_Len)
 {
  WSABUF k_Buf;
  k_Buf.buf =  s8_Buf + *pu32_Pos;
  k_Buf.len = u32_Len - *pu32_Pos;
  
  DWORD u32_Sent = 0;
  if (WSASend(h_Socket, &k_Buf, 1, &u32_Sent, 0, 0, 0) == SOCKET_ERROR)
   return WSAGetLastError();

  #if TRACE_EVENTS
   TraceA("SendDataBlock has sent %d Bytes", u32_Sent);
  #endif

  *pu32_Pos += u32_Sent;
 };
 return 0;
}

// Send the data in s8_Buf to the given socket (Server + Client)
// This function will not block.
// If the data cannot be sent immediately, the function returns WSAEWOULDBLOCK and the data is buffered until the next
// FD_WRITE event which will be signaled when the correct time has come to send more data to that socket.
// It is possible that a part of the data is sent immediately and the rest is buffered to be sent after next FD_WRITE.
// If you call this function while a previous Send operation is still pending, the function returns WSA_IO_PENDING.
// In this case try again later!
// ATTENTION:
// When this function returns without error, this does not mean that all data has already arrived at the recipient!
// WinSock uses a transport buffer and the real transmision of the data may take a long time after this function has returned.
DWORD TCP::cSocket::SendTo(SOCKET h_Socket, char* s8_Buf, DWORD u32_Len)
{
 #if TRACE_EVENTS || TRACE_LOCK
  TraceA("SendTo(Socket %X, %d Bytes)", h_Socket, u32_Len);
 #endif

 // Request thread safe access to mi_List
 cLock i_Lock;
 DWORD u32_Error = i_Lock.Request(&mk_Lock);
 if (u32_Error)
  return u32_Error;

 if (!(mi_List.me_State & E_Connected))
  return WSAENOTCONN; // Socket is not connected

 int s32_Index = mi_List.FindSocket(h_Socket);
 if (s32_Index < 0)
  return ERROR_INVALID_PARAMETER; // Invalid Socket handle passed

 kData* pk_Data = &mi_List.mk_Data[s32_Index];
 if (pk_Data->b_Shutdown || pk_Data->b_Closed)
  return WSAESHUTDOWN; // The socket has already been shut down, but mi_List.Remove() has not yet been called

 pk_Data->s64_IdleSince = GetTickCount64();

 // Set Idle Timer
 if (u32_Error = ProcessIdleSockets("SendTo()       "))
  return u32_Error;

 if (pk_Data->s8_SendBuf)
  return WSA_IO_PENDING; // a Send operation is still in progress on this socket

 // Sends as much data as possible at this moment, increases u32_Pos
 DWORD u32_Pos = 0;
 u32_Error = SendDataBlock(h_Socket, s8_Buf, &u32_Pos, u32_Len);

 // Not all the data could be sent right now:
 // The remaining data is copied into a buffer and will be sent when FD_WRITE becomes signaled.
 if (u32_Error == WSAEWOULDBLOCK)
 {
  u32_Len -= u32_Pos;
  s8_Buf  += u32_Pos;

  pk_Data-> s8_SendBuf = new char[u32_Len];
  pk_Data->u32_SendLen = u32_Len;
  pk_Data->u32_SendPos = 0;
  memcpy(pk_Data->s8_SendBuf, s8_Buf, u32_Len);
  return u32_Error;
 }

 if (u32_Error && u32_Error != WSA_IO_PENDING)
  mi_List.Remove(s32_Index); // remove socket with Write error
 
 return u32_Error;
}

// LocalIp = 0x6401a8c0 -> 192.168.1.100
// returns a list of all local IP's on this computer (multiple IP's if multiple network adapters)
// cHash is used as an array with Key= 0, Value= local IP
DWORD TCP::cSocket::GetLocalIPs(cHash<DWORD,DWORD>* pi_IpList)
{
 pi_IpList->Clear();

 DWORD u32_Error = Initialize();
 if (u32_Error)
  return u32_Error;

 char s8_Host[500];
 if (gethostname(s8_Host, sizeof(s8_Host)) == SOCKET_ERROR)
  return WSAGetLastError();
 
 struct hostent* pk_Host = gethostbyname(s8_Host);
 if (!pk_Host)
  return WSAGetLastError();

 for (DWORD i=0; TRUE; i++)
 {
  if (!pk_Host->h_addr_list[i])
   break; // The IP list is zero terminated
 
  pi_IpList->Append(0, *((DWORD*)pk_Host->h_addr_list[i]));
 }

 if (!pi_IpList->GetCount())
  return WSAENETDOWN; // no local IP means no network available

 return 0;
}

// GetTickCount() flows over to zero after 49 days.
// GetTickCount64() runs eternally.
// Why not use GetSystemTimeAsFileTime() ?
// Because the Systemtime jumps if someone adjusts the Windows clock.
// And when daylight saving time becomes winter time it will always jump by one hour.
// The tick counter runs continously and is not affected by any external influence.
LONGLONG TCP::cSocket::GetTickCount64()
{
 DWORD u32_Tick = GetTickCount(); // UNSIGNED!!

 if (u32_Tick < mu32_Tick64Lo)
  mu32_Tick64Hi ++; // Increment once every 49 days 

 mu32_Tick64Lo = u32_Tick;

 return 0x100000000 * mu32_Tick64Hi + u32_Tick;
}

// Pass a buffer of 200 characters!
// Can be used for debugging: TraceA("Events: %s", s8_Buf);
void TCP::cSocket::FormatEvents(DWORD u32_Events, char* s8_Buf)
{
 s8_Buf[0] = 0;
  if (u32_Events & FD_ACCEPT)                   strcat(s8_Buf, "FD_ACCEPT ");
 if (u32_Events & FD_CONNECT)                  strcat(s8_Buf, "FD_CONNECT ");
 if (u32_Events & FD_CLOSE)                    strcat(s8_Buf, "FD_CLOSE ");
 if (u32_Events & FD_TIMEOUT)                  strcat(s8_Buf, "FD_TIMEOUT ");
 if (u32_Events & FD_READ)                     strcat(s8_Buf, "FD_READ ");
 if (u32_Events & FD_WRITE)                    strcat(s8_Buf, "FD_WRITE ");
 if (u32_Events & FD_OOB)                      strcat(s8_Buf, "FD_OOB ");
 if (u32_Events & FD_QOS)                      strcat(s8_Buf, "FD_QOS ");
 if (u32_Events & FD_GROUP_QOS)                strcat(s8_Buf, "FD_GROUP_QOS ");
 if (u32_Events & FD_ROUTING_INTERFACE_CHANGE) strcat(s8_Buf, "FD_ROUTING_INTERFACE_CHANGE ");
 if (u32_Events & FD_ADDRESS_LIST_CHANGE)      strcat(s8_Buf, "FD_ADDRESS_LIST_CHANGE ");

 if (!u32_Events) strcpy(s8_Buf, "----");
}

// static
// Use this to write Debug output to DebugView from www.sysinternals.com
// TraceA("Closing Socket %X", h_Socket);
void TCP::cSocket::TraceA(const char* s8_Format, ...)
{
#if _DEBUG && (TRACE_EVENTS || TRACE_LOCK)

 static DWORD u32_LastTick   = 0;
 static DWORD u32_LastThread = 0;

 DWORD u32_Tick   = GetTickCount();
 DWORD u32_Thread = GetCurrentThreadId();

 char* s8_Delim = "";
 if (u32_LastThread != u32_Thread)
 {
  s8_Delim = "+++++++++++++++++++++++++++++++++++++\r\n";
 }
 else if (u32_Tick - u32_LastTick > 100)
 {
  s8_Delim = "- - - - - - - - - - - - - - - - - - -\r\n";
 }

 u32_LastTick   = u32_Tick;
 u32_LastThread = u32_Thread;

 const int BUF_SIZE = 5000;
 char s8_Buf[BUF_SIZE+1];
 
 sprintf(s8_Buf, "%s{%04d} ", s8_Delim, u32_Thread);
 DWORD u32_Len = strlen(s8_Buf);
 
 va_list  args;
 va_start(args, s8_Format);
 _vsnprintf(s8_Buf+u32_Len, BUF_SIZE-u32_Len, s8_Format, args);
 
 OutputDebugStringA(s8_Buf);
#endif
}

/***************************************************************************************
****************************************************************************************

 embedded class cList

 Description:
 Stores for all open sockets: their Handle, Wait Event, IP address, Write buffer for pending data

 CLIENT:
 - uses only Index=0 which holds the socket that is connect to the server.

 SERVER:
 - uses a socket at Index=0 which only waits for incomming connection requests. (always: mk_Data[0].u32_IP==0)
 - The socket at Index=0 is never connected to any client.
 - Each of the following sockets Index=1,2,3... may be connected to one client.

 Author:
 Elm?(www.netcult.ch/elmue)

****************************************************************************************
****************************************************************************************/

TCP::cSocket::cList::cList()
{
 mu32_Count = 0;
 me_State   = E_Disconnected;
}

TCP::cSocket::cList::~cList()
{
 RemoveAll();
}

TCP::cSocket::kData* TCP::cSocket::cList::Add(SOCKET h_Socket, HANDLE h_Event)
{
 // Store max 63 sockets
 if (mu32_Count >= WSA_MAXIMUM_WAIT_EVENTS-1)
  return 0;

 memset(&mk_Data[mu32_Count], 0, sizeof(kData));

 mk_Data  [mu32_Count].h_Socket = h_Socket;
 // mh_Events[0] is used for the lock. It is not associated with a socket.
 mh_Events[mu32_Count+1] = h_Event;

 return &mk_Data[mu32_Count++];
}

void TCP::cSocket::cList::RemoveAll()
{
 while (mu32_Count)
 {
  Remove(mu32_Count-1);
 }
}

// Remove sockets that have already received a FD_CLOSE
void TCP::cSocket::cList::RemoveClosed()
{
 for (int i=(int)mu32_Count-1; i>=0; i--)
 {
  if (mk_Data[i].b_Closed) Remove(i);
 }
}

BOOL TCP::cSocket::cList::Remove(DWORD u32_Index)
{
 if (u32_Index >= mu32_Count)
  return FALSE;

 shutdown   (mk_Data[u32_Index].h_Socket, SD_BOTH);
 closesocket(mk_Data[u32_Index].h_Socket);

 // mh_Events[0] is used for the lock. It is not associated with a socket.
 WSACloseEvent(mh_Events[u32_Index+1]);

 if (mk_Data[u32_Index].s8_SendBuf) delete mk_Data[u32_Index].s8_SendBuf;
 if (mk_Data[u32_Index].pi_RecvMem) delete mk_Data[u32_Index].pi_RecvMem;

 // Close the gap by copying the last socket to the deleted location
 mu32_Count--;
 mk_Data  [u32_Index]   = mk_Data  [mu32_Count];
 mh_Events[u32_Index+1] = mh_Events[mu32_Count+1];
 
 if (mu32_Count==0)
  me_State = E_Disconnected;

 // remove E_Connected flag from the server (Socket[0] is never connected)
 if (mu32_Count==1 && (me_State & E_Server))
  me_State = E_Server;

 return TRUE;
}

// returns the index of the given socket in the socket list
// returns -1 if not found
int TCP::cSocket::cList::FindSocket(SOCKET h_Socket)
{
 for (DWORD i=0; i<mu32_Count; i++)
 {
  if (mk_Data[i].h_Socket == h_Socket)
   return i;
 }
 return -1;
}

/***************************************************************************************
****************************************************************************************

 embedded struct kLock and class cLock
 
 Description:
 This class is used to mutually lock the access to mi_List if cSocket is running multithreaded.
 cLock must be created on the stack in a function requesting write access to mi_List:
 The function Loop()    locks when entering into the endless loop ProcessEvents()
 The function Request() locks when entering into Close() or SendTo(),
 The destructor of cLock releases the lock when these functions have exited.
 
 ATTENTION:
 A Mutex alone will not work here because ProcessEvents() is an endless loop,
 which re-enters before the thread context has been switched to the other thread!
 
 If multithreading is not in use this class does not block in neither function.
 
 Author:
 Elm?(www.netcult.ch/elmue)

****************************************************************************************
****************************************************************************************/

TCP::cSocket::kLock::kLock()
{
 h_LoopEvent = 0;
 h_ExitTimer = 0;
 h_Mutex     = 0;
}

TCP::cSocket::kLock::~kLock()
{
 CloseHandle(h_LoopEvent);
 CloseHandle(h_ExitTimer);
 CloseHandle(h_Mutex);
}

DWORD TCP::cSocket::kLock::Init()
{
 if (!h_LoopEvent) h_LoopEvent = CreateEvent(0, TRUE,  TRUE,  0); // manual-reset, default= run
 if (!h_LoopEvent) return GetLastError();
 
 if (!h_ExitTimer) h_ExitTimer = CreateWaitableTimer(0, FALSE, 0); // auto-reset,  default= block
 if (!h_ExitTimer) return GetLastError();

 if (!h_Mutex)     h_Mutex     = CreateMutex(0, FALSE, 0);
 if (!h_Mutex)     return GetLastError();

 return 0;
}

// -------------------------------------------------------------------------------------

TCP::cSocket::cLock::cLock()
{
 mh_Mutex = 0;
}

// Blocks a Request in SendTo() and Close()
// If cSocket is used single-threaded, Request() will never block
DWORD TCP::cSocket::cLock::Request(kLock* pk_Lock)
{
 DWORD u32_Error = pk_Lock->Init();
 if (u32_Error)
  return u32_Error;

 // FIRST: Block ProcessEvents() the next time BEFORE WaitForMultipleEvents() is reached
 if (!ResetEvent(pk_Lock->h_LoopEvent))
  return GetLastError();

 // SECOND: Escape from a blocking WaitForMultipleEvents()
 LARGE_INTEGER k_Interval;
 k_Interval.QuadPart = -1; // negative due time = set a relative time => fire timer in 100 nanoseconds

 #if TRACE_EVENTS || TRACE_LOCK
  cSocket::TraceA("Setting Timer: Lock Request Interval= 1 ns");
 #endif

 if (!SetWaitableTimer(pk_Lock->h_ExitTimer, &k_Interval, 0, 0, 0, FALSE))
  return GetLastError();

 #if TRACE_LOCK
  cSocket::TraceA("!!! cLock::Request WAIT");
 #endif
 
 // THIRD: Wait until ProcessEvents() has exited (only if multithreading)
 if (WaitForSingleObject(pk_Lock->h_Mutex, INFINITE) == WAIT_FAILED)
  return GetLastError();

 #if TRACE_LOCK
  cSocket::TraceA(">>> cLock::Request CONTINUE");
 #endif
 
 // Now we grabbed the Mutex -> allow ProcessEvents to continue
 if (!SetEvent(pk_Lock->h_LoopEvent))
  return GetLastError();

 // Store the mutex to be released in the destructor
 mh_Mutex = pk_Lock->h_Mutex;
 return 0;
}

// Blocks the endless loop ProcessEvents() after a Request() was made.
// If cSocket is used single-threaded, Loop() will never block
DWORD TCP::cSocket::cLock::Loop(kLock* pk_Lock)
{
 DWORD u32_Error = pk_Lock->Init();
 if (u32_Error)
  return u32_Error;

 #if TRACE_LOCK
  cSocket::TraceA("!!! cLock::Loop WAIT");
 #endif

 // The following line normally does not block (Event always set). Only after a Request() it
 // will block to give Request() a chance to grab the Mutex before the endless loop re-enters
 if (WaitForSingleObject(pk_Lock->h_LoopEvent, INFINITE) == WAIT_FAILED)
  return GetLastError();

 // Wait until SendTo() or Close() have exited
 if (WaitForSingleObject(pk_Lock->h_Mutex, INFINITE) == WAIT_FAILED)
  return GetLastError();

 #if TRACE_LOCK
  cSocket::TraceA(">>> cLock::Loop CONTINUE");
 #endif

 mh_Mutex = pk_Lock->h_Mutex;
 return 0;
}

// Destructor is executed, when the calling function (SendTo(), Close(), ProcessEvents()) has exited
TCP::cSocket::cLock::~cLock()
{
 #if TRACE_LOCK
  cSocket::TraceA("--- Release Mutex");
 #endif

 // Allow the other thread to continue its work
 ReleaseMutex(mh_Mutex);
}

/***************************************************************************************
****************************************************************************************

 embedded class cMemory
 
 Description:
 This tiny class allocates memory dynamically.
 The caller does not have to care about buffer sizes.
 This class is used to realize a FIFO memory for dynamic length datablocks.
 
 ATTENTION:
 With intention I do NOT use any functionalty of the STL library here.
 This would create a dependency to MSVCP70.DLL or MSVCP71.DLL or MSVCP80.DLL depending on the compiler.
 These DLLs are NOT available on every computer and must be installed with your application!
 
 Author:
 Elm?(www.netcult.ch/elmue)

****************************************************************************************
****************************************************************************************/

TCP::cSocket::cMemory::cMemory(DWORD u32_InitialSize)
{
  ms8_Mem  = new char[u32_InitialSize];
 mu32_Size = u32_InitialSize;
 mu32_Len  = 0;
}
TCP::cSocket::cMemory::~cMemory()
{
 delete ms8_Mem;
}
char* TCP::cSocket::cMemory::GetBuffer()
{
 return ms8_Mem;
}
DWORD TCP::cSocket::cMemory::GetLength()
{
 return mu32_Len;
}

// Append data to the end. If more memory is required, the current size is doubled.
void TCP::cSocket::cMemory::Append(char* s8_Data, DWORD u32_Count)
{
 DWORD u32_NewLen = mu32_Len + u32_Count;
 if (u32_NewLen > mu32_Size)
 {
  mu32_Size = max(u32_NewLen, mu32_Size *2);

  char*  s8_NewMem = new char[mu32_Size];
  memcpy(s8_NewMem, ms8_Mem, mu32_Len);
  
  delete ms8_Mem;
  ms8_Mem = s8_NewMem;
 }
 memcpy(ms8_Mem+mu32_Len, s8_Data, u32_Count);
 mu32_Len += u32_Count;
}

// Deletes the first u32_Count Bytes from the buffer by shifting down the Bytes that follow
void TCP::cSocket::cMemory::DeleteLeft(DWORD u32_Count)
{
 u32_Count = min(u32_Count, mu32_Len);
 memmove(ms8_Mem, ms8_Mem+u32_Count, mu32_Len-u32_Count);
 mu32_Len -= u32_Count;
}

/***************************************************************************************
****************************************************************************************

 embedded template class cHash
 
 Description:
 This tiny class allows to pass a list of unlimited size from a function to it's caller.
 The caller does not have to care to free the memory after using the data.
 This avoids memory leaks if the programmer forgets to call delete.
 
 ATTENTION:
 With intention I do NOT use any functionalty of the STL library here.
 This would create a dependency to MSVCP70.DLL or MSVCP71.DLL or MSVCP80.DLL depending on the compiler.
 These DLLs are NOT available on every computer and must be installed with your application!
 
 Author:
 Elm?(www.netcult.ch/elmue)

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//  Due to the way the C++ compiler works the template class must be defined in the header file

두서없이 붙여 넣기만 하고 설명은 안한다. 시간날때 하려고 한다. 그럼.

1. 배열

   배열은 동일한 형식의 데이터 메모리 상의 연속된 공간에 저장하는 구조를 말합니다.

   장점 : 데이터를 처음부터 끝까지 차례로 처리하는 등의 일을 매우 빠른 속도로 수행할 수 있다는 장점이 있습니다.

   단점 : 배열은 저장 공간이 한정되기 때문에 크기를 늘리거나 중간에 데이터를 삽입하기가 어렵습니다.

   예를들어 100개의 배열을 잡아놓고 사용하다가 101번째 데이터를 저장하려면 101개의 데이터가 들어갈만한 영역에 배열을 새로 잡아야 한다.

    

2. 리스트

   리스트는 하나하나가 따로 저장됩니다. 데이터들의 저장위치가 포인터로 줄줄이 연결됩니다.

   노드 : 데이터가 저장되는 공간

   링크 : 노드를 연결하는 포인터

   모든 노드가 포인터로 연결되어 있기 때문에 첫번째 노드의 포인터만 기억하고 있으면, 리스트에 저장된 모든 노드를 찾아갈 수 있다.

   데이터의 추가, 삭제가 빈번한 응용에는 배열보다 리스트를 사용하는 것이 좋습니다.

    

3. 맵

   맵은 디셔너리라고도 하고, 해시 테이블 이라고도 합니다. 데이터가 키 값과 함께 저장될 때 맵 구조를 사용하면 좋습니다.

   예를들어 사전처럼 어떤 단어와 그 단어의 뜻을 함께 저장한다고 할 때, 단어는 키가 되고, 그 단어의 뜻은 데이터가 됩니다.

   맵과 일반배열의 차이점

   100대의 차를 주차할 수 있는 주차장에 차를 넣고 넣고 빼는 예를 들어보겠습니다.

   여기서 주차장은 데이터를 저장할 배열이고, 자동차는 데이터, 자동차의 번호가 키 값이라고 생각하시면 됩니다.

   일반 배열 같으면

   1. 들어오는 순서대로 주차장에 넣을 겁니다.
   2. 나중에 차 주인이 차를 빼러 오면 몇 번째 칸에 주차를 했는지 인덱스를 기억하던가
   3. 자신의 차를 발견할때까지 첫번째 칸부터 차례로 찾아보야 합니다.

   맵을 이용하면

   1. 차를 주차할 때부터 키 값을 이용합니다.
   2. 주차장에 100대의 차를 주차할 수 있으니까 자동차 번호의 뒷자리 두 개를 가지고 저장될 위치를 결정하면 되겠네요.

1. MFC 배열 클래스

1. MFC 배열 클래스들의 주요 맴버 함수

InsetAt, RemoveAt, Add 등의 함수는 배열의 속성상 하기 힘든 일을 억지로 시키는 함수들입니다. 이 함수를 호출하는 것은 쉽지만, 그 대가는 생각보다 큽니다. 예를 들어, InsertAt 함수를 호출하여 배열의 6번째 항목에 새로운 값을 추가하도록 하면, 6번째 항목 이후의 모든 값이 뒤로 한 칸씩 밀려야 하기 때문에 배열의 크기가 큰 경우에는 메모리에서 많은 양의 데이터가 이동해야 합니다. 우리는 배열의 속성을 잘 이해하고 있으므로 InsertAt, RemoveAt, Add 함수와 같이 비용이 큰 함수는 불 필요하게 남발하지 말아야 겠습니다.

COM(Component Object Model)은 Visual C++를 비롯한 다양한 언어로 만들어서 배포할 수 있으며,

DLL이나 EXE 파일처럼 이진코드(binary)에서의 표준을 말한다. COM을 만드는 것은 어떤 언어든 관계가 없으며

단지 COM 표준을 잘 지켜서 만들면 된다. COM은 다음과 같이 발전해 왔다.

메인프레임 -> 클라이언트/서버 -> 3 tier 클라이언트/서버(분산 컴퓨팅 환경)

분산 컴퓨팅 환경에서 응용 프로그램을 어떻게 구성하고 묶어나가는가는 중요한 문제로 떠올랐으며,

이를 해결하기 위해 컴포넌트에 기반한 객체 기술이 생겨났다. 컴포넌트 기반 기술은 각 회사별로 다음과 같다.

윈도우:

마이크로소프트 - COM/DCOM, COM+

유닉스:

OMG(object management group) - CORBA

선마이크로시스템즈 - EJB(enterprise java beans)

다음은 COM의 발전사이다.

OLE(object linking and embedding) - 객체(엑셀,워드,비트맵)를 서로 연결하고 포함하는 기술로써

      DDE(dynamic data exchange)를 사용하여 구현.

OLE2 - DDE의 문제점을 개선. 이때부터 COM이라 부름.

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COM 용어

COM 인터페이스 - C++에서 볼 수 있는 가상 함수 테이블. 우리는 이 가상함수 테이블의 포인터를 얻는

                           것을 QueryInterface() 함수를 통해 구현할 수 있다.

메서드 - COM 인터페이스가 제공하는 함수를 메서드(method)라 부른다.

IUnknown 인터페이스 - 모든 COM 프로그램이 반드시 상속 받아야 하는 인터페이스로, QueryInterface(),

                                 AddRef(), Release() 메서드(함수)를 갖고 있다.

CoClass - 하나 이상의 인터페이스와 실제 구현 코드. CoClass는 하나 이상이 모여서 DLL 또는 EXE 파일로

               컴파일되어 저장된다.

COM 오브젝트 - CoClass가 메모리에 로드되어 객체화된 상태

COM 서버 - 기능을 제공하는 프로그램(DLL 또는 EXE)

COM 클라이언트 - DLL 또는 EXE를 사용하는 프로그램

GUID - Globally Unique IDentifier. 전세계적으로 유일한 값(ID)으로 16바이트(128bits)로 구성, GUID는

          네트워크 카드의 물리적인 주소(48비트), 1582년 이후의 10억분의 1초(60비트), 기타(20비트)로 구성.

CLSID - COM객체마다 유일한 GUID.

IID - CoClass의 인터페이스마다 유일한 GUID.

HRESULT - COM에서 사용되는 함수가 리턴하는 값. S_OK, E_NOTIMPL, E_NOINTERFACE 등.

COM 라이브러리 - COM을 지원하기 위한 운영체제의 함수들. 보통 CoXXX()처럼 호출됨.

ProgID - GUID를 대신해서 사용할 수 있는 문자열로 구성된 ID. (예-Excel.Application.12)

COM 응용 기술

자동화(Automation) - IDispatch 인터페이스를 통해 COM을 제어하는 기술.

OLE 문서 - IOleContainer, IOleObject 등의 인터페이스를 통해 서로 데이터를 공유하는 기술.

클립 보드 - IDataObject 인터페이스를 통해 데이터를 주고 받는 기술.

드래그 앤 드롭 - IDropTarget, IDropSource 등의 인터페이스를 사용하며, 마우스로 데이터를 끌어다

                       놓고 전송하는 기술.

ActiveX 컨트롤 - 일반적인 컨트롤처럼 사용될 수 있으며, 비주얼 베이직, 웹페이지에 삽입될 수 있음.

                        다른 말로 OLE 컨트롤이라고도 부름. 확장자가 OCX 임.