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Thanks for your reply. It's just like you said. Judging by the Windows Task Manager, the system is cacheing the file data. As long as the file is smaller than the memory available for the system cache, the execution can keep up. For large files, though, it's getting killed by the swapping.
I switched to FILE_FLAG_NO_BUFFERING. Now I no longer see the system cache filling up, but the transfers have actually slowed down! Does that make any sense?
1. I wrote a loop in which I repeatedly read from the file until the end of the file. It executed fastest when the file was declared as "SEQUENTIAL_SCAN", slowest with "NO_BUFFERING", somewhere in between when "SEQ_SCAN | NO_BUF". I would have expected the last one to be the fastest.
2. I wrote a loop in which I read 1MB into a buffer, then wrote it to a new file. The results weren't conclusive here. I wouldn't be surprised if "NO_BUF" was slower, though. There could be an advantage to cacheing the 1MB of data if you're going to immediately write it back out again.
Please let me know if you have any suggestions.
Best regards,
Jason
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Try overriding CFile:Open and add the FILE_FLAG_NO_BUFFERING (and possibly FILE_FLAG_OVERLAPPED) flag to ::CreateFile().
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Thanks to everyone for your help. Here's an update:
I saw a lot of improvement using "FILE_FLAG_SEQUENTIAL_SCAN".
To use FILE_FLAG_NO_BUFFERING I need to make sure that the buffer is sector aligned. I had been using malloc, but I've switched to VirtualAlloc to control the buffer address alignment. It looks like VirtualAlloc will give me a page-aligned buffer, but is that necessarily sector-aligned? How do I report the sector size? GetDiskFreeSpace will give me that, but only for volumes of less than 2GB.
Regards,
Jason
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Hi ...
i am writing this code to test if there is internet connection :
**********************************************************
void CServerInternetDlg::OnOn()
{
HINTERNET hInternet= ::InternetOpen("BSAtomicEdu", INTERNET_OPEN_TYPE_PRECONFIG , NULL, NULL, 0);
if(!hInternet)
{
AfxMessageBox( "Internet open error! Test your system and try again.", MB_OK | MB_ICONERROR );
return;
}
else
{
AfxMessageBox( "Internet open Success", MB_OK | MB_ICONERROR );
return;
}
}
**********************************************************
but i am getting the following error:
Server InternetDlg.obj : error LNK2001: unresolved external symbol __imp__InternetOpenA@20
Debug/Server Internet.exe : fatal error LNK1120: 1 unresolved externals
**********************************************************
i think i have missing library i am using
#include <afxdb.h>
#include <afxinet.h>
#include <afx.h>
#include <wininet.h>
#include <stdio.h>
#include <tchar.h>
#include <wincrypt.h>
any idea about the error ??!!???
Best Regards
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In order to get rid of your error, simply link the Wininet.lib library to your project. That oughta clean it up.
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Thank you very much its working now...
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I want to make project like Tweak Manager .. any one can help me with open source code or any information about it....
Thanks
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Hi.
I have a thread that adds values to a vector variable in a class. also main program reads same thread an to display data in it. I havn't used critical section or other sync methods but program works ok, is it necessary to use critical section ?
thanks.
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main program reads same vector variable not thread.
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Hi,
Because u r using multi-threading application you SHOULD sync ur work using critical sections, events, semaphores,...
your program runs well now, but when the thread writes to the variable at the same time as the main thread reads it, the value read by the main thread will be out-of-date, it is not the current value of the variable.
Furthermore, if you don't use the keyword volatitle in declaring shared variables, the compiler may perform wrong optimizations to speed the code up, and you may get wrong results.
-Always take the safest way
Regards,
Mohammad Gdeisat
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Another concern is a possible program crash. When vectors are changed, all iterators are invalidated. So if the main function has an interator and is in the process of reading the data, the thread could interrupt and add something to the vector. Now the main function has an invalid iterator. The problem with not using synch methods is that the errors may not be noticed for months. You could think all is well and then one day, your program crashes while doing the same thing it's been doing all along.
Shawn
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i need to be able to delete the browser history. also it would be a big help to be able to delete temporary internet files. thanks
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deleteurlcacheentry is a function, use it.
however you need to know the exact url that you want to delete
hope this helps you
peace
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I declared a variable through ClassView>Add Member Variable in my Cview.
I included header in my MainFrm.cpp.
How to use the variable because it doesnt recognise my variable. Do I need to make an object inside my MainFrm.cpp?
I tried to use
CProgView cview;
cview.myvariable;
but it says cannot access protected member declared in class.
Thanks
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Add Member Variable with 'public',not 'protect', than you can access it.
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It is public variable from CView. I use it in CDoc, how to declare it? THanks
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Thx Astham
There are 3 kinds of member variables/functions:
public:
Can be used/called by objects of any class
private:
Can be used by objects of this class only
protected:
Can be used by objects of this class and derived classes only.
So if you want to use the variable from somewhere else than a CProgView member
function, you need to make the variable public. If you use Add Member Variable
there's three radio buttons at the bottom of the dialog. Or you could just write
public: at the line before the variable declaration.
THis is my header code,
public:
float pointX[100];
float pointY[100];
virtual ~CMyProgView();
#ifdef _DEBUG
virtual void AssertValid() const;
virtual void Dump(CDumpContext& dc) const;
#endif ]
This is my public variable declaration. Why cant I use it?
How to use it from my CMyProgDoc? I have #include CMyProgView.h and use it such as below:
CMyProgView obView;
obView.pointX[i] = something;
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When you right click a RichEdit Control.
<italic>Work hard and a bit of luck is the key to success. You don`t need to be genius, to be rich.
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Does anyone know how to find a local group's permissions? I am enumerating through the local groups on my machine using the NetLocalGroupEnum API, but when I check the group using the NetLocalGroupGetInfo API, I only get two pieces of information that I don't need:
1 The group's name - already have, don't need again
2 The group's description - doesn't serve my purpose
Are there any APIs or methods that I can use to find if a local group is an admin group? I've spent many many hours working on this problem and I am getting a little frustrated.
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Hi, in my VC7 app, I would like to record calls to a dll that I have made using my GUI part and be able to play them back if I need the same sequence again. Any suggestions on how to start, where to look?
Paul
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hello
how do I send a key combination to a window like for example ctrl+c. I have tryed with keybd_event and SendInput but I could not send more than one key. Is there a way to send a key combination to a window?
thank you
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Hello!
I had such a problem a year ago,
I didn't find a good answer so I decided
to 'Put a hidden BUTTON on the dialog' and use '&' to give it a shortcut to a On... Message.
It solved my problem temporarily! but it's not a good way I think.
But I'm a begginer yet.(I started VC++ about a year ago).
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Hi, in the code of dll, I need to extract the full path of a file at runtime. Any suggestions?
paul
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