Windows NT Systems Programming

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Remote Procedure Calls (continued).

Mandelbrot Sets

• Draws the Set - uses MFC for drawing in the client
• Server is a console application
• The RPC  is executed for each PIXEL

MIDL File

[
  uuid (87654321-4321-1234-4321-987654321CBA),
  version(1.0),
  endpoint ("ncacn_np:[\\pipe\\ccrpc]")
]
interface calcclr
{
  typedef struct
  {
    double real;
    double imag;
  } complex;

  short CalcColor([in] complex k);
}

// And the ACF file

[
  implicit_handle(handle_t calcclrHandle)
]
interface calcclr
{
}

Server

// mandels.cpp

#include <windows.h>
#include <iostream.h>
#include <rpc.h>
#include "ccrpc.h"
#include "memstub"

INT main(VOID)
{
  // use the protocols specified in 
  // the IDL file for this interface
  if (RpcServerUseAllProtseqsIf(1, 
    calcclr_v1_0_s_ifspec,
    NULL))
  // register the interface
  if (RpcServerRegisterIf(calcclr_v1_0_s_ifspec,
    NULL, NULL))

  // listen for and service RPC requests
  if (RpcServerListen(1, 5, FALSE))

  return(0);
}

Client

// mandelc.cpp

const double left = -1.0;
const double right = 1.0;
const double top = -1.0;
const double bottom = 1.0;

DWORD colors[64];

typedef struct
{
	WORD height;
	WORD width;
} mandelParams;

// Define the application object class
class CManApp : public CWinApp
{
public:
	virtual BOOL InitInstance();
};

// Define the edit window class
class CManWindow : public CFrameWnd
{
private:
	HANDLE threadHandle;
	BOOL running;
	BOOL initialized;
	mandelParams params;
public:
	CManWindow();
	void RunMandel();
	void SetPix(int x, int y, WORD iter);
	afx_msg void OnPaint();
	afx_msg void OnStartStop();
	afx_msg void OnExit();
	DECLARE_MESSAGE_MAP()
};

// Create an instance of the application object
CManApp manApp;

// member function used to set pixel colors
// in the window
void CManWindow::SetPix(int x, int y, WORD iter)
{
	CClientDC dc(this);
	dc.SetPixel(x, y, colors[iter]);
}

// the thread function which does the drawing // WHY in a thread?
DWORD MandelThread(mandelParams *params)
{
	double xstep, ystep;
	double x, y;
	int i,j;
	WORD iter;
	complex k;

	ystep = (double) (bottom - top) / 
		params->height;
	xstep = (double) (right - left) / 
		params->width;
	
	for (y=top, j=0; y <= bottom; y += ystep, j++)
	{
		for (x=left, i=0; x<=right; x += xstep, i++)
		{
			k.real = x;
			k.imag = y;
			RpcTryExcept
			{
				iter=CalcColor(k); // RPC
			}
			RpcExcept(1)
			{
				MessageBox(NULL,
					"Unable to call CalcColor( ).\n\Click OK and then Exit.",
					"ERROR", MB_SETFOREGROUND | 
						MB_OK | MB_ICONSTOP);
				ExitThread(1);
			}
			RpcEndExcept;

			((CManWindow *)manApp.m_pMainWnd)->
				SetPix(i, j, iter);
		}
	}
	return(0);
}

// member function used to instigate the
// drawing thread
void CManWindow::RunMandel()
{
	DWORD threadID;
	CRect r;

	GetClientRect(&r);
	params.height=r.Height();
	params.width=r.Width();

	threadHandle=CreateThread(NULL, 0,
		(LPTHREAD_START_ROUTINE) MandelThread,
		&params, 0, &threadID);

	running=TRUE;
}

// The message map
BEGIN_MESSAGE_MAP(CManWindow, CFrameWnd)
	ON_WM_PAINT()
	ON_COMMAND(IDM_STARTSTOP, OnStartStop)
	ON_COMMAND(IDM_EXIT, OnExit)
END_MESSAGE_MAP()

// Handler for the Start/Stop menu option
void CManWindow::OnStartStop()
{
	if(running)
		SuspendThread(threadHandle);
	else
		ResumeThread(threadHandle);

	running=!running;
}

// Handler for WM_PAINT messages
void CManWindow::OnPaint()
{
	ValidateRect(NULL);
	if (!initialized)
	{
		initialized=TRUE;
		RunMandel();
	}
	else
	if (running)
	{
		// stop the existing thread
		TerminateThread(threadHandle, 0);
		CloseHandle(threadHandle);
		// clear the window
		CClientDC dc(this);
		CRect r;
		GetClientRect(&r);
		dc.PatBlt(0, 0, r.Width(), r.Height(),
		WHITENESS);
		// start over again
		RunMandel();
	}
}

// Handler for the Exit menu option
void CManWindow::OnExit()
{
	SuspendThread(threadHandle);
	CloseHandle(threadHandle);
	RpcBindingFree(&calcclrHandle);
	DestroyWindow();
}

// CManWindow constructor
CManWindow::CManWindow()
{
	WORD x;
	BYTE red=0, green=0, blue=0;
	UCHAR *stringBinding;
	CHAR serverName[MAX_PATH];

	BOOL test = Create( NULL, "RPC Mandel Example",
		WS_OVERLAPPEDWINDOW,
		CRect(0,0,150,150), NULL, "MainMenu" );
	// Set up a set of colors
	for (x=0; x<64; x++)
	{
		colors[x] = RGB(red, green, blue);
		if (!(red += 64)) 
			if (!(green += 64)) 
		blue += 64;
	}
	colors[63] = RGB(255,255,255);

	if (strlen(manApp.m_lpCmdLine))
		strcpy(serverName, manApp.m_lpCmdLine);
	else
		strcpy(serverName, "\\\\.");

	RpcStringBindingCompose(NULL,
		(UCHAR *) "ncacn_np", (UCHAR *) serverName,
		(UCHAR *) "\\pipe\\ccrpc", NULL,
		&stringBinding);

	RpcBindingFromStringBinding(stringBinding,
		&calcclrHandle);

	RpcStringFree(&stringBinding);

	initialized=FALSE;
}

// Initialize the CManApp m_pMainWnd data member
BOOL CManApp::InitInstance()
{
	m_pMainWnd = new CManWindow();
	m_pMainWnd -> ShowWindow( m_nCmdShow );
	m_pMainWnd -> UpdateWindow();

	return TRUE;
}

• F1: Begins block of guarded statements. If an exception occurs, then the exception condition decribed below is tested
• F2: if an exception occurs, transfer is made here and the condition is evaluted. Here it is always true (1). but in general you can specify the exception conditions which are handled by the following exception block
• F3: Paints a rectangle with a pattern
• F4:

Memstub

void __RPC_FAR * __RPC_API
	midl_user_allocate(size_t len)
{
	return(new(unsigned char [len]));
}

void __RPC_API midl_user_free(void __RPC_FAR * ptr)
{
	delete(ptr);
}

Improved Version

• RPC call for each PIXEL has a lot of overhead
• Could do RPC for the entire frame
  • frame too big, would be divided into many packets
  • User would not see any intermediate drawing
  • Could have seperate thread for drawing
  • can't send out in parallel.
• Or could do a line at a time.
• Of interest is passing the array representing a line in the picture

[
  uuid (87654329-4321-1234-4321-987654321CBA),
  version(1.0),
  endpoint ("ncacn_np:[\\pipe\\ccrpc2]")
]
interface calcline
{
  typedef struct
  {
    double real;
    double imag;
  } complex;

  void CalcLine([in] double left, 
	[in] double right,
	[in] double y, [in] long width,
	[out, size_is(width)] short line[]);
}

Running Second Version

(code is here)

• Run midl on ccrpc.idl to generate
  • Either use console window and type command "midl ccrpc.idl"
  • Or import into project (created below) and in Project/Settings, custom build with the command
    midl $(InputPath)
• Create server project as console application
• Import ccrpc2.idl, mandels2.cpp,ccrpc2.h, ccrpc2_s.c (last two generated by midl)
• Change project settings to add to the Link tab the libraries "rpcrt4.lib" and "rpcns4.lib"
• Build project
• Create client project (could open another VC++) as a win32 application
• Add files ccprc2.h, ccrpc2_c.c mandelc2.cpp mandelc2.rc, menus.h
• Add two libraries above
• Change general settings to use MFC in shared DLL
• added "#include "memstub" to mandelc2.cpp
• build project

Copyright chris wild 1997.
For problems or questions regarding this web contact [Dr. Wild].
Last updated: November 03, 1997.