C / C++ / MFC

Re: CStdioFile file size limit

19-Aug-09 6:41

Bill Heitler wrote:
and I need to do quite a bit of skipping around with small reads and writes.

Traditional buffered I/O is terrible for this. It means you will keep filling and flushing the buffer. You are better off writing an algorithm tailored to your needs.

Bill Heitler20-Aug-09 4:17

Bill Heitler

20-Aug-09 4:17

Good point - I'm sure you're right in principal about the buffering. Although I suppose it must depend on how close together the data locations are.

Just for interest I ran a very quick-and-dirty measure of the time to write then read 100,000 consecutive single floats. With CStdioFile it took 0.343 s, with CFile it took 3.348 s, and constructing a CArchive from the CFile and flushing and closing between the write and read, it just took 0.152 s. So I guess the buffering of CArchive makes a difference, at least for consecutive operations. But I don't know whether CArchive also has the 2^32 file size limit of CStdioFile. Does anyone else?

for loop pause resume

RaymondM18-Aug-09 10:56

18-Aug-09 10:56

I have in a C++ module a for loop that can take some minutes to complete. I would like to add a pause/resume feature, and would also like to be able to stop it. However while the loop is running the program is totally unresponsive. Is there anything to be done ?

Raymond Mercier

Nemanja Trifunovic18-Aug-09 11:06

Nemanja Trifunovic

18-Aug-09 11:06

Move the loop into a background thread and on each iteration (or every nth one) check for a "pause" flag that can be set by the UI thread; just be sure it is done in a thread-safe manner.

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utf8-cpp

RaymondM18-Aug-09 11:22

18-Aug-09 11:22

Thanks, but I have so little experience with threads, I will have to bone up on it.
Raymond

Joe Woodbury18-Aug-09 11:13

18-Aug-09 11:13

For dialog boxes, you can add and periodically call the following. Adjust to get best responsiveness:

BOOL CMyDialog::Pump()
{
	MSG msg;
	while (::PeekMessage (&msg, NULL, 0, 0, PM_NOREMOVE))
	{
		if (!AfxGetApp()->PumpMessage())
		{
			::PostQuitMessage(0);
			return FALSE;
        }
	}

	//
	// Simulate the framework's idle processing mechanism.
	//
	LONG idle = 0;
	while (AfxGetApp()->OnIdle(idle++));
	return TRUE;
}

RaymondM18-Aug-09 11:24

18-Aug-09 11:24

Thanks, but I don't see how that can be made to deal with a loop.

Raymond

Joe Woodbury18-Aug-09 11:26

18-Aug-09 11:26

In the loop you periodically call the function; this keeps the message pump going and allows messages to be processed. This is the traditional way to make a progress/cancelable dialog box.

The alternative, and preferable for anything lengthy, is to run the operation in a thread.

RaymondM23-Aug-09 7:27

23-Aug-09 7:27

In the end it was easy enough to run the function with its loop in a thread.
"ThreadProcTCP" is a rather involved module, with a loop, but it all works fine.

if (hChild)
               GetExitCodeThread( hChild, &dwExitCodeThread );
            if (dwExitCodeThread!=STILL_ACTIVE)
                hChild = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadProcTCP, hWnd, 0, &dwChild );

RaymondM

Joe Woodbury23-Aug-09 8:34

Preventing a child window to change its z-order?

23-Aug-09 8:34

Note two things; a thread handle is non-signaled when it's running and signaled when it's not. Thus you can do a WaitForSingleObject() on a thread handle. Second: if you do any CRT calls in your thread, you should use __beginthreadex() (not all CRT calls need thread local storage (TLS), but figuring out which ones need it is tedious and, to my knowledge, not documented.)

Don Rolando18-Aug-09 10:39

Don Rolando

18-Aug-09 10:39

Hallo,

is there any possibility to prevent an embedded child window to change its z-order?

My current problem is, I have an control embedded that brings itself into the front sporadically. Since it's embedded in one of my dialogs, the corresponding dialog is popping into the foreground, too. Frown | :(

Within the application this causes an affected dialog to pop in front of another dialog the user could be working in at the same moment.

For testing purposes I made a ::SetParent(controlHwnd, NULL). Once being a child of the desktop, it pops in front of any application now, not only on top of the application it was embedded in.

Anyhow, since I have no chance to modify the control itself (no sources!), I am searching for a way to prevent the control of changing its z-order. Is there any chance to "pin" it?
I have tried nearly all windows styles, but since the control seems to push itself into the front, I cannot do a lot against it this way. Perhaps subclassing the control's window and filtering some specific events? Any help appreciated!

Thanks a lot in advance,
Roland

Re: Preventing a child window to change its z-order?

Baltoro18-Aug-09 14:37

Baltoro

18-Aug-09 14:37

This Article by Raymond Chen[^], might suggest a solution.
Then again it might make things worse by confusing the issue.
What you want to determine is why your control "brings itself into the front sporadically".
It's being triggered by something, obviously.
Here's another Interesting bit of z-order lore[^].

boost bind expression not doing what I expect

Stone Free18-Aug-09 8:17

Stone Free

18-Aug-09 8:17

I obviously don't get this bind stuff as I cannot seem to get it right

#include <map>
#include <set>
#include <vector>
#include <algorithm>
#include <boost/bind.hpp>

using namespace boost::bind;

typedef int DWORD;
typedef std::pair<std::string, bool> user_info;
typedef std::map<DWORD, user_info> USER_MAP;
typedef std::vector<DWORD> VEC_STAFF;



int _tmain(int argc, _TCHAR* argv[])
{
	USER_MAP m_Users;
	VEC_STAFF Staff;

	VEC_STAFF::iterator it = std::partition(Staff.begin(), Staff.end(),(bind(&USER_MAP::find, m_Users, _1) != m_Users.end()));

What I wanted to code to do is that for every entry in the Staff vector it should check to see whether that user id was present in the map, and if so move those items to the front.

I have an example using a functor that works as I hoped the above code would, but the bind version is obviously not doing what I think its doing.

struct InUsersMap : public std::unary_function<USER_MAP::key_type,bool>
{
	InUsersMap(USER_MAP & theMap, USER_MAP::const_iterator end)
		: m_theMap(theMap)
	{
	}
	inline bool operator()(CSecurePatients::USER_MAP::key_type& id) const
	{
		return m_theMap.find(id) != m_theMap.end();
	}
private:
	const USER_MAP &m_theMap;
}

Finally does anyone know how to avoid getting the socket bind function from windows being included

.Net and unmanaged C++ (executing thread & exception handling)

Ahmed Charfeddine18-Aug-09 6:48

Ahmed Charfeddine

18-Aug-09 6:48

When a .Net code calls an unmanaged C++ code, do we have the same thread executing the code.

And what about code exception ? Is .Net code capable of catching exception
originating from the unmanaged C++ code.

Thank you in advance.

(I don't program in .Net I just would like to know).

Easy Profiler : a compile-time profiler for C++
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Re: .Net and unmanaged C++ (executing thread & exception handling)

Joe Woodbury18-Aug-09 11:14

How to enumerate remote socket ports

18-Aug-09 11:14

Yes
No (except possibly for a structured exception [generated by the OS])

MarkLTX18-Aug-09 6:26

MarkLTX

18-Aug-09 6:26

Is there a way in C or C# to enumerate the port numbers in listening state on a remote Windows computer? I know you can use GetTcpTable() to enumerate the ports on the local computer, but I want remote.

Ahmed Charfeddine18-Aug-09 6:51

Ahmed Charfeddine

18-Aug-09 6:51

I do'nt think this is possible.

Some applications called port scanners (like SATAN) give result by looping on a all port numbers within a specified range, initiate a connection i,n each time then decide using the reply result.

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www.potatosoftware.com

Rajesh R Subramanian18-Aug-09 7:05

Rajesh R Subramanian

18-Aug-09 7:05

Like the other poster said, you could do a port scan, or run your client on the other end and that should send you a snapshot of the ports that the computer is listening on.

It is a crappy thing, but it's life -^ Carlo Pallini

MarkLTX18-Aug-09 8:16

MarkLTX

18-Aug-09 8:16

OP here.

There can be multiple instances of my app running on computer A, each listening on a different port. On computer B, I want to run a monitor app that can connect to any of the app instances running on computer A. It would be nice if I could enumerate those instances rather than having to just "know" what port(s) are listening.

What I might do is code my application to use a limited range or list of ports (say 100 fixed port numbers) and then code the monitor app to simply scan that list.