'CreateFileW' : cannot convert parameter 1 from 'const char [13]' to 'LPCWSTR'

[asenthil]

Hai this is senthil...

I had tried to write a string which fetched from a database. into a file...

when i tried to compile the solution the following error occurs like this

error C2664: 'CreateFileW' : cannot convert parameter 1 from 'const char [13]' to 'LPCWSTR'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

My codings are below...
----------------------------------------------------------------------
void main()
{

  MYSQL *conn; 
  conn = mysql_init(NULL);
  mysql_real_connect(conn,host,username,password,database,0,NULL,0);     
  MYSQL_RES *res_set; 
  MYSQL_ROW row;
  mysql_query(conn,"SELECT * FROM imagedb2");
  res_set = mysql_store_result(conn);
  unsigned int numrows = mysql_num_rows(res_set);
	
   //For Creating a file....
  HANDLE hFile; 
  DWORD wmWritten;   
  hFile =CreateFile"d:\\text3.doc",GENERIC_READ|GENERIC_WRITE,             
  FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL); 
  
   while (( row = mysql_fetch_row(res_set)) != NULL)
{		

       char str[255];
       char *tmp = str;
       strcpy(str, row[2]); 

				       
       WriteFile(hFile,str,(DWORD)(sizeof(str)),&wmWritten,NULL); 
       CloseHandle(hFile); 
     
			        	                   
		}
           mysql_close(conn);
getch();
	
   }

In Project->Properties->General->Character Set::Use Multi-Byte Character Set

This configuration proterties i'm using....

What shall i do for the above error...

Can any one plzz help me??

[deadbeatclub]

Hi Senthil,
Although I can't take the time to research a full solution, you're clearly dealing with a conflict between single byte and multi byte strings. I run into this all the time with CE. The compiler is using the wide char version of CreateFile (CreateFileW) which needs wide char parameters (wchar_t), yet str is a single byte string (char). You'll need to switch one or the other - either get rid of the multi byte compiler option, or make str a multi byte string.

[CornedBee]

The latter is the better option.

[wiccaan]

Not sure if this will fix your error but I did notice you're missing a parenthese in your CreateFile line:

  hFile =CreateFile("d:\\text3.doc",GENERIC_READ|GENERIC_WRITE,             
  FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);

[asenthil]

Hi to all,

thanks for ur response

i already found the solution...

sorry for saying it in forum...

i just put 'L' in the CreateFile method...

hFile = CreateFile(L"C:\\tab.doc",GENERIC_READ|GENERIC_WRITE,
// FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);

thanks...
senthil..

[CornedBee]

No! Wrong!
You have three valid options. All others are invalid. The third of these options is the best.

Option 1: Force ANSI (slower on NT, doesn't work on CE, possible problems with internationalization)

hFile = CreateFileA("C:\\tab.doc",GENERIC_READ|GENERIC_WRITE,
 FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);

Option 2: Force Unicode (doesn't work on 9x)

hFile = CreateFileW(L"C:\\tab.doc",GENERIC_READ|GENERIC_WRITE,
 FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);

Option 3: Make it easily switchable in the project settings (easy to get working and ideal versions for everywhere)

hFile = CreateFile(TEXT("C:\\tab.doc"),GENERIC_READ|GENERIC_WRITE,
 FILE_SHARE_READ,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);

If you include <tchar.h>, you can use _TEXT() or _T() instead of TEXT(), but that is the only permitted variation. Everything else is invalid.

[asenthil]

Ya okay,

But in my program that L method works well...

there is no problem....

It easily creates any type of file....

thanks for ur reply...
senthil.

[CornedBee]

Yeah, sure. Now go into the project settings and change using Unicode to multi-byte character set and see if it still compiles.

Or take your current compiled executable to a Win98 computer and start it there.

[wey97]

This is off the subject a little but most functions manipulating characters have a _w_ version such as wprintf for printf but what can you use in place of atof to make your code portable?

EDIT: sorry, I found it. _wtof for anyone interested. Not sure of why the underscore is used though.

[wey97]

What's the best way to handle strings and wstrings besides changing between both on a recompile?

[CornedBee]

The underscore is because it's a compiler extension, not part of the standard.

What exactly do you mean by handle?

[wey97]

The underscore is because it's a compiler extension, not part of the standard.

What exactly do you mean by handle?

1) I decided to use ostringstream and istringstream for conversion back and forth between numeric and text.

2) Lets say you are compiling in Unicode and declare some std::wstrings. There is no portable or generic way (that I know of) to switch right to Multi-Byte without changing all of your std::wstring references to std::string.

Unless you declare something like this:

#ifdef UNICODE
typedef std::wstring _string;
#else
typedef std::string _string;
#endif

Then declare only _strings so you don't have to rename your strings to wstrings and vice versa.

[CornedBee]

Nothing simpler. std::string and std::wstring are both just typedefs in the first place. The real stuff is a template called std::basic_string, which gets instantiated (among other things) with the character type. Like this:

namespace std {
typedef basic_string<char> string;
typedef basic_string<wchar_t> wstring;
}

Getting a switching string therefore is as simply as

typedef std::basic_string<TCHAR> tstring;

Then just use tstring everywhere and you're all set.

The same applies to many more things: std::istream is a typedef for std::basic_istream<char>, std::istringstream for std::basic_istringstream<char>. They all have wchar_t versions, and you can instantiate them all with TCHAR.

I dug up some old threads of mine on the topic.
http://www.vbforums.com/showthread.p...hlight=tstring
http://www.vbforums.com/showthread.p...hlight=tstring
http://www.vbforums.com/showthread.p...hlight=tstring (My goodness, this one's old. Parksie replied in it.)

Ah, the walk down memory lane. To think that I, too, once wanted to derive from std::string.

I attached my tcpp.h. Note that the file is a few years old. It violates the C++ standard by introducing new names into the std namespace, so you should change that, but otherwise it's still fine.