LPCTSTR typecast for use with GetFileAttributes

Question

I´m trying to build a method to see if a file exists. the method in it´s current isn´t complete form. i´m trying to figur out whyy it doesn´t behave as code.

    BOOL FileExists(LPCTSTR szPath)
        {
            //MessageBox(NULL,szPath,L"File Error",MB_OK);
          DWORD dwAttrib = GetFileAttributes(szPath);

            switch(dwAttrib)
            {

                case FILE_ATTRIBUTE_DIRECTORY:
                    MessageBox(NULL,L"FILE_ATTRIBUTE_DIRECTORY",L"File Error",MB_OK);
                    break;
                case FILE_ATTRIBUTE_ARCHIVE:
                    MessageBox(NULL,L"FILE_ATTRIBUTE_ARCHIVE",L"File Error",MB_OK);
                    break;
                case FILE_READ_ONLY_VOLUME:
                    MessageBox(NULL,L"FILE_READ_ONLY_VOLUME",L"File Error",MB_OK);
                    break;
                case FILE_INVALID_FILE_ID:
                    MessageBox(NULL,L"FILE_INVALID_FILE_ID",L"File Error",MB_OK);
                    break;
                default:
                    MessageBox(NULL,(LPCWSTR)dwAttrib,L"File Error",MB_OK);
                    break;
            }
return true;
        }

this is how i call the method:

FileExists((LPCWSTR)path.c_str());

this is where my file resides:

std::string path = "C:\\smiley.bmp"

i always end up here, no mather in what order the switched is coded:

FILE_INVALID_FILE_ID

i'm wondering if i'm typecastings correct to "LPCTSTR".

Because i tried using a MessageBox to display the contents of "szPath" and it showed up as human unreadeble format.

the path i provide is correct, properly escaped. how can i check if "szPath" contains the proper information?

`MessageBox(NULL,(LPCWSTR)dwAttrib,L"File Error",MB_OK);` What the?!?! What on earth are you doing? This is a recipe for disaster. Please remove it. — Nik Bougalis, May 29 '14 at 02:18
wel, it´s commented out ... but i do tend to use a messagebox to figure out what is happening! — NaturalDemon, May 29 '14 at 02:26
Casting a `DWORD` to a `LPCWSTR` and printing it out won't help you figure anything out. Best case scenario: it will print out garbage. — Nik Bougalis, May 29 '14 at 02:34
You have to understand what these casts do. They do not do what you think they do. — David Heffernan, May 29 '14 at 11:00

score 4 · Accepted Answer · edited May 23 '17 at 12:27

4

std::string is based on char, so when you call .c_str(), you can a char *.

But LPCWSTR is a pointer to a wide character string.

I believe, if you're compiling with UNICODE enabled (so LPCTSTR == LPCWSTR), you'll need to use std::wstring.

Relevant:

Converting string to tchar in VC++

edited May 23 '17 at 12:27

Community

1
1

answered May 29 '14 at 01:50

Jonathon Reinhart

132,704
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thank you for your answer. but i´m a bit lost now! http://en.cppreference.com/w/cpp/string/basic_string/to_wstring what do i need to change? – NaturalDemon May 29 '14 at 02:27

score 1 · Answer 2 · answered May 29 '14 at 03:28

1

Casting does not convert a string into a wide string. It just tells the compiler to shut up, and the error will move. You need the L prefix on literal strings to make them wide strings. And you need to use wstring instead of string.

std::wstring path = L"C:\\smiley.bmp";
FileExists(path.c_str());

answered May 29 '14 at 03:28

ScottMcP-MVP

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Ok, i did it wrong and forgot to add the 'L' in the path variable. the software compiles fine, but still i hit the same point 'FILE_INVALID_FILE_ID'. i added #include , it should work, because the file is on that spot – NaturalDemon May 29 '14 at 15:20

LPCTSTR typecast for use with GetFileAttributes

2 Answers2

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