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CreateFile returns INVALID_HANDLE_VALUE. Probably file doesn't exist. Check GetLastError for more info.
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Right.I had problem in my file path.Thank you.
Mazy
"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down
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Hello
I have a txt file I need to insert a string into at the start of. If the file does not exist I need to create it, and insert the line of txt.
What is the most elegant way of doing this using C++? An ugly ways seems to be to check if the file exists. If it doesn't, create, write and go home. If it does then I must make a copy of it, overwrite the original with my new line of txt, and then append the contents of my copy into this. This seems a real hack, and I am looking for a nicer way? Perhaps there is some nice strstream method?
Looking forward to replies...
solosnake
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I can think of another hack - You can map it to memory, memmove the content, then write the text on the beginning.
The benefit will be, that the rewriting will be done by the OS.
Sonork 100.15206;PavelK
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How do you change the length of memory-mapped file?
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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I think You can't change the length of the memory mapped file, after it's mapped, but You can specify the new (bigger) length while creating the file mapping object using CreateFileMapping in dwMaximumSizeHigh and dwMaximumSizeLow parameters. You need to know the needed size in advance because the file will be truncated or filled with zeros otherwise.
Sonork 100.15206;PavelK
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Thanks Pavel, but this cannot be done in pure C++ (can it?) and I prefer to write only using the stl. Can this be done using the stl?
- solosnake
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Pavel Klocek wrote:
You can map it to memory, memmove the content
A memory-mapped file is fixed in length so you can't do what you proposed.
bibamus, edamus, cras moriemur [eat, drink, for tomorrow we die]
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Is there any chance of loading file into memory? Or it may be multi-megabyte one?
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Its going to be a small file, but I am really looking for a C++ solution. File mapping is not part of the standard, as far as I know?
Thanks
- solosnake
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If file is small, load the contents, add stuff at the beginning and write back. You can use stdio or iostreams - whatever you like.
OTOH, if there's even slight chance for large file, you shouldn't try to load all contents. Instead of copying original file, just change its name and delete it after completing the operation.
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Personalyy I'd just do something simple like this:
#include <fstream>
using std::ofstream;
.
.
.
ofstream outFile("filename_here", ios::app);
outFile.seekp(0, ios::beg);
and then use outFile << "hello" << endl; to write to the file.
Maybe thats what your after. [edit] But I've been informed tat thats not what your after[/edit]
Regards,
Brian Dela 
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But this will overwrite first bytes. OP wants to shift existing content to make space for inserted data.
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Tomasz Sowinski wrote:
But this will overwrite first bytes. OP wants to shift existing content to make space for inserted data.
U sure... Doesn't the ios:app cause the bytes to be shifted??? Oh wait. Your right. It doesn'ts.. ok.. just read the file to memory and the put it back.
Regards,
Brian Dela
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In my MMC snapin are string resources in 3 languages. The thread locale is exactly what I've set in the 'Regional settings', yet still I get the English (U.S.) resource string. I have no more clues what is going on here.
Using plain win32 API (LoadString) from the dll. No MFC involved, no messing with locale settings or resource handles.
Even the sublang of the resource is correct.
Clues, hints and even solutions are welcome.
int x=1, y=5;
x^=y^=x^=y;
<a href="http://www.codeproject.com/tips/StupidXORTrick.asp" target="_blank">ClickHereForHelp();</a>
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The MSDN docs for SetThreadLocale says that it affects LoadString API. However, according to KB article Q200893, you may have problems on Win9x. The article offers a workaround using FindResourceEx API.
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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No way. Am using W2k/XP only. No Win9x support anymore. And I really would appreciate to avoid loading resources manually as this gets complicated with dialogs.
int x=1, y=5;
x^=y^=x^=y;
<a href="http://www.codeproject.com/tips/StupidXORTrick.asp" target="_blank">ClickHereForHelp();</a>
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So you're calling SetThreadLocale, then LoadString and you're getting unexpected results?
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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No, I am not messing with the threads locale. But a call to GetThreadLocale verifies that I really have the correct language/sublanguage set.
I use just the LoadString call and it doesnt behave as expected/documented. Seems that it is related to the MMC/snap-in mechanism. Other apps run fine with similar configurations.
int x=1, y=5;
x^=y^=x^=y;
<a href="http://www.codeproject.com/tips/StupidXORTrick.asp" target="_blank">ClickHereForHelp();</a>
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Andreas Saurwein wrote:
Other apps run fine with similar configurations.
So it seems you'll ultimately have to call FindResourceEx...
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Tomasz Sowinski wrote:
you'll ultimately have to call FindResourceEx
Thanks for turning my day into hell 
There must be something else... (is there?)
int x=1, y=5;
x^=y^=x^=y;
<a href="http://www.codeproject.com/tips/StupidXORTrick.asp" target="_blank">ClickHereForHelp();</a>
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Andreas Saurwein wrote:
Thanks for turning my day into hell
No problem. The bill will appear on your monthly CC statement 
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Hello Everybody ok, here is my code:
HKEY keyHandle;
char *rgValue = NULL;
PLONG buffLen = NULL;
if(RegOpenKey( HKEY_LOCAL_MACHINE,
"Software\\Microsoft\\Windows\\CurrentVersion",
&keyHandle) == ERROR_SUCCESS)
{
//MessageBox(_T("Key was opened"));
RegQueryValue(keyHandle, "MediaPath", rgValue, buffLen );
MessageBox(rgValue);
}
What I want to do is to query the registry value of MediaPath and store it in the rgValue variable. I looked at it in MSDN and I did exactly that it says. I tryed a couple of times and nothing is being saved in rgValue. Have you guys had this problem before. What should I do? Am I missing something? Any anwer is more than welcome.
Have a good day,
Luis E. Cuadrado
 )
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You need to initialize buffLen with an address of variable containing max size of buffer before calling RegQueryValue.
Tomasz Sowinski -- http://www.shooltz.com
Free your mind and your ass will follow.
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Hi Tomasz:
Thank you for your quick reply. This is what I did to my code after reading your reply:
HKEY keyHandle;
char rgValue[MAX_PATH];
DWORD buffLen = MAX_PATH;
if(RegOpenKey( HKEY_LOCAL_MACHINE,
"Software\\Microsoft\\Windows\\CurrentVersion",
&keyHandle) == ERROR_SUCCESS)
{
//MessageBox(_T("Key was opened"));
RegQueryValue(keyHandle, "MediaPath", rgValue, (PLONG) buffLen );
MessageBox(rgValue);
}
Is that what you meant by initializing buffLen? I'm new in MFC specially reading registry stuff, so I apologize for my ignorance.
Luis E. Cuadrado
)
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