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Shared Memory with IPC with threads

, 4 Oct 2004
Shared memory as used along with threads to communicate between processes.
oneatatimesrc.zip
OneAtaTime
OneAtaTime.clw
OneAtaTime.dsw
OneAtaTime.dsp
res
OneAtaTime.ico
oneatatime_demo.zip
Debug
OneAtaTime.exe
// OneAtaTimeDlg.cpp : implementation file
//

#include "stdafx.h"
#include "OneAtaTime.h"
#include "OneAtaTimeDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App About
HANDLE kSendCommand;
HANDLE kReceiveCommand;

HANDLE kSendMessage;
HANDLE kReceiveMessage;

HANDLE kChildAck; // Acknowledgement By The Child

CWinThread* thread;

class CAboutDlg : public CDialog
{
public:
	CAboutDlg();

// Dialog Data
	//{{AFX_DATA(CAboutDlg)
	enum { IDD = IDD_ABOUTBOX };
	//}}AFX_DATA

	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CAboutDlg)
	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	//}}AFX_VIRTUAL

// Implementation
protected:
	//{{AFX_MSG(CAboutDlg)
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
	//{{AFX_DATA_INIT(CAboutDlg)
	//}}AFX_DATA_INIT
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CAboutDlg)
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
	//{{AFX_MSG_MAP(CAboutDlg)
		// No message handlers
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// COneAtaTimeDlg dialog

COneAtaTimeDlg::COneAtaTimeDlg(CWnd* pParent /*=NULL*/)
	: CDialog(COneAtaTimeDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(COneAtaTimeDlg)
	m_status = _T("");
	m_message = _T("");
	//}}AFX_DATA_INIT
	// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
	m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void COneAtaTimeDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(COneAtaTimeDlg)
	DDX_Control(pDX, IDC_LIST_RECVMESSAGE, m_recvlist);
	DDX_Text(pDX, IDC_STATIC_STATUS, m_status);
	DDX_Text(pDX, IDC_EDIT_MESSAGE, m_message);
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(COneAtaTimeDlg, CDialog)
ON_MESSAGE(KILL_APP,OnKillApp)
ON_MESSAGE(RECV_MESSAGE,OnRecvMessage)
ON_MESSAGE(CHILD_START,OnChildStart)
	//{{AFX_MSG_MAP(COneAtaTimeDlg)
	ON_WM_SYSCOMMAND()
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	ON_WM_CREATE()
	ON_BN_CLICKED(IDC_BUTTON_KILL, OnButtonKill)
	ON_BN_CLICKED(IDC_BUTTON_SEND, OnButtonSend)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// COneAtaTimeDlg message handlers

BOOL COneAtaTimeDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	// Add "About..." menu item to system menu.

	// IDM_ABOUTBOX must be in the system command range.
	ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
	ASSERT(IDM_ABOUTBOX < 0xF000);

	CMenu* pSysMenu = GetSystemMenu(FALSE);
	if (pSysMenu != NULL)
	{
		CString strAboutMenu;
		strAboutMenu.LoadString(IDS_ABOUTBOX);
		if (!strAboutMenu.IsEmpty())
		{
			pSysMenu->AppendMenu(MF_SEPARATOR);
			pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
		}
	}

	// Set the icon for this dialog.  The framework does this automatically
	//  when the application's main window is not a dialog
	SetIcon(m_hIcon, TRUE);			// Set big icon
	SetIcon(m_hIcon, FALSE);		// Set small icon
	
	// TODO: Add extra initialization here
	if(kParentOrChild) // This is the parent. Receive the message from child.
	{
		this->SetWindowText("Parent: Receiving Command");
		GetDlgItem(IDC_BUTTON_KILL)->DestroyWindow();
		GetDlgItem(IDC_EDIT_MESSAGE)->EnableWindow(false);
		GetDlgItem(IDC_BUTTON_SEND)->EnableWindow(false);
		thread = AfxBeginThread(StartProbing,GetSafeHwnd(),THREAD_PRIORITY_NORMAL); // Start Checking for Commands from Child
		if(thread != NULL)
		{
			UpdateData(true);
			m_status = "Parent waiting for messages ...";
			UpdateData(false);

		}
		else
		{
			UpdateData(true);
			m_status = "Thread not started ...";
			UpdateData(false);

		}
		

	}
	else
	{
		GetDlgItem(IDC_BUTTON_KILL)->EnableWindow(true);
		kShMem->childAck = TRUE;
		::SetEvent(kChildAck);
		this->SetWindowText("Child: Send Command / Message to Parent");

	}

	
	return TRUE;  // return TRUE  unless you set the focus to a control
}

void COneAtaTimeDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
	if ((nID & 0xFFF0) == IDM_ABOUTBOX)
	{
		CAboutDlg dlgAbout;
		dlgAbout.DoModal();
	}
	else
	{
		CDialog::OnSysCommand(nID, lParam);
	}
}

// If you add a minimize button to your dialog, you will need the code below
//  to draw the icon.  For MFC applications using the document/view model,
//  this is automatically done for you by the framework.

void COneAtaTimeDlg::OnPaint() 
{
	if (IsIconic())
	{
		CPaintDC dc(this); // device context for painting

		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{
		CDialog::OnPaint();
	}
}

// The system calls this to obtain the cursor to display while the user drags
//  the minimized window.
HCURSOR COneAtaTimeDlg::OnQueryDragIcon()
{
	return (HCURSOR) m_hIcon;
}

int COneAtaTimeDlg::OnCreate(LPCREATESTRUCT lpCreateStruct) 
{
	CString title;
//	UpdateData(true);
	if (CDialog::OnCreate(lpCreateStruct) == -1)
		return -1;
	
	
	kProcessId = ::GetCurrentProcessId();
	title.Format("Process: %d",kProcessId);
	this->SetWindowText(title);
	
	/* Create a file map for sharing the memory. This is for sharing the memory between same processes. */
	kMap = CreateFileMapping((HANDLE)0xFFFFFFFF,NULL,PAGE_READWRITE,0,sizeof(KSharedMemory),"KBuildDevelop");
	if(GetLastError() == ERROR_ALREADY_EXISTS)
	{
		// COMMENTED SECTION BELOW [TEST]: This was great. Identifies if the process has been created earlier or not. 
		/*MessageBox("One at a time please !!","One At A Time", MB_OK);
		::PostQuitMessage(0);*/
		kMap = ::OpenFileMapping(FILE_MAP_WRITE,FALSE,"KBuildDevelop");
		kMutex = ::CreateMutex(NULL,FALSE,"KBuildDevelop");
		kParentOrChild = FALSE;
		
	}
	else
	{
		kParentOrChild = TRUE;
	}

	kShMem = (KSharedMemory*)::MapViewOfFile(kMap,FILE_MAP_WRITE,0,0,sizeof(KSharedMemory));

	kSendCommand = ::CreateEvent(NULL,FALSE,FALSE,"SendCommand");
	kSendMessage = ::CreateEvent(NULL,FALSE,FALSE,"SendMessage");
	kReceiveMessage = ::CreateEvent(NULL,FALSE,FALSE,"ReceiveMessage");
	kReceiveCommand = ::CreateEvent(NULL,FALSE,FALSE,"ReceiveCommand");
	kChildAck = ::CreateEvent(NULL,FALSE,FALSE,"ChildAcknowledge");




	return 0;
}


UINT StartProbing(LPVOID lParam)
{
	while(1)
	{
		if(::WaitForSingleObject(kChildAck,10)== WAIT_OBJECT_0) /* Wait for acknowledgement from the child */
			PostMessage((HWND) lParam,CHILD_START,0,0);
		if(::WaitForSingleObject(kSendCommand, 10) == WAIT_OBJECT_0)
		{
			PostMessage((HWND) lParam, KILL_APP,0,0);
			::SetEvent(kReceiveCommand);
			break;

		}	
		else
		{
			// Add code here to wait for another event. 
			if(::WaitForSingleObject(kSendMessage, 10) == WAIT_OBJECT_0)
			{
				PostMessage((HWND) lParam, RECV_MESSAGE,0,0);
				::SetEvent(kReceiveMessage);
			}
		}
	
	}
	return 0;

}


void COneAtaTimeDlg::OnKillApp()
{
	
		PostQuitMessage(0);

}

void COneAtaTimeDlg::OnButtonKill() 
{

		::SetEvent(kSendCommand);
		::ReleaseMutex(kMutex);

}

void COneAtaTimeDlg::OnButtonSend() 
{
	UpdateData(true);
	char buffer[100];
	sprintf(buffer,"%s",m_message);
	strcpy(kShMem->data,buffer);
	m_message=_T("");
	UpdateData(false);
	::SetEvent(kSendMessage);// Set send message event

}

void COneAtaTimeDlg::OnRecvMessage()
{
	UpdateData(true);
	if(strcmp(kShMem->data,"bye")==0)
		PostQuitMessage(0);
	m_recvlist.AddString(kShMem->data);
	UpdateData(false);


}

void COneAtaTimeDlg::OnChildStart()
{
	UpdateData(true);
	m_status = "Child Started...";
	UpdateData(false);

}

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About the Author

Sreekanth Muralidharan
Technical Lead
India India
I am a personality from Trivandrum , a green peaceful place in Kerala, South India.
I have been an enthusiast of Windows programming when I started creating simple windows when I learnt VC++ in LCC in Trivandrum. From then on its all about Windows in my flesh and blood.
My career graph moves like this:
1. I started working as a C/C++ programmer in a company in Trivandrum where I learnt the ABCs of Software Industry. I worked with them for about 1 year. I could not contine since I was in contract for 1 year.
2. Then I joined another organization in Trivandrum who gave me challenges to love. They made me mad about VC++ and Windows.
I was mad about Embedded Systems which made me, Myself = Embedded Systems + VC++.
3. Software Engineer in a telecom company in Hyderabad, Andhra Pradesh, S.India.
4. Currently working with a telecom company in Bangalore.
I totally, so, have experience of about 4.5 years.

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