C / C++ / MFC

30-Jul-07 1:54

Hi Here is the Problem:

To access a Datafile which contains 26 Million addresses and find a given address. The Datafile is an ascii text file and is fixed

What I have come up with:
1. Sort the 26 Million addresses into Postcode order. (I have application for this)
2. Using FSEEK look at the MIDDLE of the file and compare using STRNCMP the POSTCODE for searching, against the POSTCODE within the Datafile.
3. Using the result move the file pointer backwards from the middle (half it) or forwards and keep checking until a match is found.
This will loop for roughly 24-25 times and not 26 Million.

Is there a better way?

Randor 30-Jul-07 1:58

Randor

30-Jul-07 1:58

I would recommend converting the text file and using a binary tree for faster searching.

I can think of two libraries you could possibly use to accomplish this:

QDBM
http://qdbm.sourceforge.net/[^]

SQLITE
http://www.sqlite.org/[^]

Best Wishes,
-David Delaune

Bryster30-Jul-07 2:25

30-Jul-07 2:25

Thank you, I will have a look at these. Big Grin | :-D

Hans Dietrich30-Jul-07 3:17

Hans Dietrich

30-Jul-07 3:17

Probably the easiest way to speed searching is to divide the big file into N smaller files, maybe organized by a partial postcode. Then, after you have selected the correct (smaller) file, the search will be that much faster. This involves a minimum or presort setup.

Best wishes,
Hans

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Bryster30-Jul-07 4:12

re: Problems with Progress Bar

30-Jul-07 4:12

Thank you, that sounds like a good idea.

Bryster30-Jul-07 1:25

30-Jul-07 1:25

Hi I have recently upgraded from Windows 2000 to Windows XP Professional and have noticed that when I run my applications the progress bar stops and the application looks as if it has crashed, but after a while finishes.
I have Mcafee Virus protection running in the background, is this causing the problem?

The code is a simple "UpdateData(FALSE)" instruction after setting the ProgressBar.SetPos() which is looping until an EOF instruction.

Any Ideas?

Thank you in advance

Brian. D'Oh! | :doh:

Hans Dietrich30-Jul-07 3:21

Hans Dietrich

30-Jul-07 3:21

1. Disable McAfee and observe the result.

2. Put a ProgressBar.RedrawWindow(); after the UpdateData(FALSE); and observe the result.

Best wishes,
Hans

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Bryster30-Jul-07 4:24

30-Jul-07 4:24

Unfortunately this has not solved the problem.

Thanks for trying.

krmed30-Jul-07 4:53

krmed

30-Jul-07 4:53

After your UpdateData(FALSE) add a

ProgressBar.UpdateWindow()

I believe that will solve your problem.

Hope that helps.

Karl - WK5M
PP-ASEL-IA (N43CS)
PGP Key: 0xDB02E193
PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

Mark Salsbery30-Jul-07 6:20

Mark Salsbery

30-Jul-07 6:20

Why do you need to call UpdateData? Are other controls changing or just the progress control?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

can not delete a file

George_George30-Jul-07 0:13

30-Jul-07 0:13

Hello everyone,

I am using the following program to delete all files in a specified directory. But when running, no files could be deleted, and the related error information is,

failed with error 5 -- access denied. Anything wrong with the program?

<br />
remove_non_empty_directory ("c:\\temp\\non_empty_dir\\*");<br />
<br />
// ErrorExit implementation from MSDN<br />
// http://msdn2.microsoft.com/en-us/library/ms680582.aspx<br />
<br />
int remove_non_empty_directory (const char* path)<br />
{<br />
<br />
  WIN32_FIND_DATA FindFileData;<br />
  HANDLE hFind;<br />
  int rtn;<br />
<br />
  hFind = FindFirstFile(path, &FindFileData);<br />
  if (hFind == INVALID_HANDLE_VALUE) <br />
  {<br />
        FindClose(hFind);<br />
        return -1;<br />
  } <br />
  else <br />
  {<br />
      // delete 1st file<br />
      rtn = DeleteFile(&(FindFileData.cFileName));<br />
<br />
      if (0 == rtn)<br />
      {<br />
         ErrorExit (NULL);<br />
      }<br />
<br />
      // List all the other files in the directory and delete all files<br />
      while (FindNextFile(hFind, &FindFileData) != 0) <br />
      {<br />
            rtn = DeleteFile(&(FindFileData.cFileName));<br />
      }<br />
<br />
      FindClose(hFind);<br />
  }<br />
<br />
  return 0;<br />
        <br />
}<br />

thanks in advance,
George

Jonathan [Darka]30-Jul-07 0:18

30-Jul-07 0:18

Do you have permissions to delete from that folder, have you tried deleting a file manually through explorer ?

Jonathan Wilkes
Darka[Xanya.net]

George_George30-Jul-07 0:23

Re: can not delete a file [modified]

30-Jul-07 0:23

Sure Jonathan, I have the privilege. I am admin and I can manually delete such files. I think there should be something wrong with my program, but through debugging for almost an hour, I still can not find the reason. Any ideas?

regards,
George

Jonathan [Darka]30-Jul-07 0:57

30-Jul-07 0:57

I think the problem is that the first file you will 'find' is the current folder '.', you will get an access denied if you try to delete this, so you need to exclude both '.' and '..' from your wildcard search, something like this (obviously could be optimised, this is just to show an example):

Also, you could make it recursive if you wanted to delete sub folders too.

int remove_non_empty_directory(const char* path)
{
	WIN32_FIND_DATA FindFileData;
	int rtn;

	HANDLE hFind = FindFirstFile(path, &FindFileData);
	if (hFind == INVALID_HANDLE_VALUE)
	{
		FindClose(hFind);
		return -1;
	}
	else
	{
            bool bDelete = true;
            if((_tcsicmp(FindFileData.cFileName, "..") == 0) || (_tcsicmp(FindFileData.cFileName, ".") == 0))
                bDelete = false;

            if(bDelete) // delete 1st file
            {
		rtn = DeleteFile((LPCSTR)FindFileData.cFileName);
                // .... original error handling code
            }

   	        // List all the other files in the directory and delete all files
	    while (FindNextFile(hFind, &FindFileData) != 0)
            {
                bDelete = true;
                if((_tcsicmp(FindFileData.cFileName, "..") == 0) || (_tcsicmp(FindFileData.cFileName, ".") == 0))
                    bDelete = false;

                if(bDelete)
		    rtn = DeleteFile((LPCSTR)FindFileData.cFileName);

		FindClose(hFind);
	}

	return 0;
}

And change this code:

DeleteFile(&(FindFileData.cFileName));

to this:

DeleteFile((LPCSTR)FindFileData.cFileName);

regards,

-- modified at 7:09 Monday 30th July, 2007

Jonathan Wilkes
Darka[Xanya.net]

George_George30-Jul-07 1:23

30-Jul-07 1:23

Thanks Jonathan,

I have tried and slightly modified your program to make it compile. Smile | :)

Now the error condition is, error number 2 -- system can not find specified file. I am confused since the file actually exists.

I need to using absolute path other than relative path to delete the file?

<br />
int remove_non_empty_directory(const char* path)<br />
{<br />
    WIN32_FIND_DATA FindFileData;<br />
    int rtn;<br />
    HANDLE hFind = FindFirstFile(path, &FindFileData);<br />
    int bDelete = 0;<br />
<br />
    if (hFind == INVALID_HANDLE_VALUE)<br />
    {		<br />
        FindClose(hFind);<br />
        return -1;<br />
    }<br />
    else<br />
    {<br />
        if((_tcscmp((LPCSTR)FindFileData.cFileName, "..") == 0) || (_tcscmp((LPCSTR)FindFileData.cFileName, ".") == 0))<br />
        {<br />
            bDelete = 0;<br />
        }<br />
        if(bDelete) // delete 1st file<br />
        {<br />
            rtn = DeleteFile((LPCSTR)FindFileData.cFileName); // .... original error handling code<br />
        }<br />
        // List all the other files in the directory and delete all file<br />
        while (FindNextFile(hFind, &FindFileData) != 0)<br />
        {<br />
             bDelete = 1;<br />
             if((_tcscmp((LPCSTR)FindFileData.cFileName, "..") == 0) || (_tcscmp((LPCSTR)FindFileData.cFileName, ".") == 0))<br />
             {<br />
                 bDelete = 0;<br />
             }<br />
             if(bDelete)<br />
             {<br />
                 rtn = DeleteFile((LPCSTR)FindFileData.cFileName);<br />
                 if (0 == rtn)<br />
                 {<br />
                        ErrorExit (NULL);<br />
                 }<br />
             }<br />
        }<br />
        FindClose(hFind);<br />
    }<br />
<br />
    return 0;<br />
}<br />

regards,
George

Jonathan [Darka]30-Jul-07 2:06

30-Jul-07 2:06

which line is producing error 2, and what is the value of FindFileData.cFileName at that point ?

Jonathan Wilkes
Darka[Xanya.net]

George_George30-Jul-07 2:37

30-Jul-07 2:37

Relative file name.

regards,
George

Jonathan [Darka]30-Jul-07 2:25

30-Jul-07 2:25

George_George wrote:
I have tried and slightly modified your program to make it compile.

George_George wrote:
I need to using absolute path other than relative path to delete the file?

Yes, in this case you should.

regards,

Jonathan Wilkes
Darka[Xanya.net]

George_George30-Jul-07 2:37

30-Jul-07 2:37

Thanks Jonathan,

I have tried that if I am using absolute path, it works!

regards,
George