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  4. Converting CString to char*

Converting CString to char*

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  • D DSPCottage

    Dear All In visual C++ 2005 I want to change a CString file to char* I used following code But fopen needs a char* for its first parameter Please let me know what to do Regards char buffer[MAX_PATH]; GetModuleFileName(NULL,(LPWCH)buffer,MAX_PATH); CString path = buffer; path = path.Left(path.ReverseFind('\\')+1); path += "result.mp3"; f = fopen( path , "wb");

    L Offline
    L Offline
    led mike
    wrote on last edited by
    #5

    Gut Mikh Tappe wrote:

    Please let me know what to do

    Ok I will try. What you need to do is read the documentation.[^] Also reading this might help as well.[^] In my experience not all authors match every reader. So if you find reading those sources don't supply your need 100% keep looking for more. The bottom line is what you need to do is read and study rather than type code and forum messages.

    led mike

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    • Z zafersavas

      Hi super_ttd, What's the problem with CString::GetBuffer()? Why dont you like it? :)

      M Offline
      M Offline
      Mark Salsbery
      wrote on last edited by
      #6

      GetBuffer() is completely unnecessary when you're only reading the string (i.e. when you only need a const pointer to the string's internal buffer). The LPCSTR operator is safe and more efficient. GetBuffer() is for when you need a non-const pointer.

      Mark Salsbery Microsoft MVP - Visual C++ :java:

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      • M Mark Salsbery

        GetBuffer() is completely unnecessary when you're only reading the string (i.e. when you only need a const pointer to the string's internal buffer). The LPCSTR operator is safe and more efficient. GetBuffer() is for when you need a non-const pointer.

        Mark Salsbery Microsoft MVP - Visual C++ :java:

        L Offline
        L Offline
        led mike
        wrote on last edited by
        #7

        Same ocean, different fish, same bait. You have lunch yet? ;P

        led mike

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        • D DSPCottage

          Dear All In visual C++ 2005 I want to change a CString file to char* I used following code But fopen needs a char* for its first parameter Please let me know what to do Regards char buffer[MAX_PATH]; GetModuleFileName(NULL,(LPWCH)buffer,MAX_PATH); CString path = buffer; path = path.Left(path.ReverseFind('\\')+1); path += "result.mp3"; f = fopen( path , "wb");

          M Offline
          M Offline
          Mark Salsbery
          wrote on last edited by
          #8

          In addition to super_ttd's reply... If you must use fopen(), then you should probably use a CStringA. CString has a generic internal character type, depending on whether UNICODE or _UNICODE is defined. If you want to use the generic text CString, then it will pair nicely with the generic text version of fopen(), which is _tfopen().

          Gut Mikh Tappe wrote:

          char buffer[MAX_PATH]; GetModuleFileName(NULL,(LPWCH)buffer,MAX_PATH);

          Bad cast!! GetModuleFileName takes a LPTSTR as its second parameter. Your buffer, therefore, should be a TCHAR type, not char. Mind your types.....if you need a cast to get something to compile, look at WHY. Mark

          Mark Salsbery Microsoft MVP - Visual C++ :java:

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          • L led mike

            Same ocean, different fish, same bait. You have lunch yet? ;P

            led mike

            M Offline
            M Offline
            Mark Salsbery
            wrote on last edited by
            #9

            led mike wrote:

            You have lunch yet?

            Heh. I'm going to HAVE to now ;P

            Mark Salsbery Microsoft MVP - Visual C++ :java:

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            • M Mark Salsbery

              led mike wrote:

              You have lunch yet?

              Heh. I'm going to HAVE to now ;P

              Mark Salsbery Microsoft MVP - Visual C++ :java:

              D Offline
              D Offline
              DSPCottage
              wrote on last edited by
              #10

              Thanks It was great

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              • Z zafersavas

                Hi super_ttd, What's the problem with CString::GetBuffer()? Why dont you like it? :)

                C Offline
                C Offline
                Cedric Moonen
                wrote on last edited by
                #11

                Read the documentation about CString::GetBuffer and you will see why you have to absolutely avoids it if you don't know exactly what you are doing.

                Cédric Moonen Software developer
                Charting control [v1.5] OpenGL game tutorial in C++

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                • S super_ttd

                  It should do. So, what's wrong ? Do you get an error ? CString has an inner cast Operator (LPCTSTR) which converts the CString object to a const char* (if compiling ANSI) of const wchar_t* (if building unicode), so you should not have to do any much stuff. And please (if you get this advice from anywhere), don't use the CString::GetBuffer()) method at all for such a thing !!! So, to come back to you problem, what is your problem ?


                  D Offline
                  D Offline
                  DSPCottage
                  wrote on last edited by
                  #12

                  Visual C++ 2005 doesn't support (LPCTSTR) cast operator. thus I need an interface to change a CString object to a char* exactly now I am porting an project from VC6 to VC2005 and it is my problem Regards Mahdi

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                  • M Mark Salsbery

                    GetBuffer() is completely unnecessary when you're only reading the string (i.e. when you only need a const pointer to the string's internal buffer). The LPCSTR operator is safe and more efficient. GetBuffer() is for when you need a non-const pointer.

                    Mark Salsbery Microsoft MVP - Visual C++ :java:

                    D Offline
                    D Offline
                    DSPCottage
                    wrote on last edited by
                    #13

                    But it appears that VC2005 doesn't support (LPSTR) or (LPCTSTR) operator. isn't it? Regards

                    C M 2 Replies Last reply
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                    • M Mark Salsbery

                      In addition to super_ttd's reply... If you must use fopen(), then you should probably use a CStringA. CString has a generic internal character type, depending on whether UNICODE or _UNICODE is defined. If you want to use the generic text CString, then it will pair nicely with the generic text version of fopen(), which is _tfopen().

                      Gut Mikh Tappe wrote:

                      char buffer[MAX_PATH]; GetModuleFileName(NULL,(LPWCH)buffer,MAX_PATH);

                      Bad cast!! GetModuleFileName takes a LPTSTR as its second parameter. Your buffer, therefore, should be a TCHAR type, not char. Mind your types.....if you need a cast to get something to compile, look at WHY. Mark

                      Mark Salsbery Microsoft MVP - Visual C++ :java:

                      D Offline
                      D Offline
                      DSPCottage
                      wrote on last edited by
                      #14

                      May you please give me an article about UNICODE ? Regards Mahdi

                      R 1 Reply Last reply
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                      • L led mike

                        Gut Mikh Tappe wrote:

                        Please let me know what to do

                        Ok I will try. What you need to do is read the documentation.[^] Also reading this might help as well.[^] In my experience not all authors match every reader. So if you find reading those sources don't supply your need 100% keep looking for more. The bottom line is what you need to do is read and study rather than type code and forum messages.

                        led mike

                        C Offline
                        C Offline
                        Cedric Moonen
                        wrote on last edited by
                        #15

                        led mike wrote:

                        Also reading this might help as well.[^]

                        I think that is the best choice to start with :)

                        Cédric Moonen Software developer
                        Charting control [v1.5] OpenGL game tutorial in C++

                        1 Reply Last reply
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                        • D DSPCottage

                          But it appears that VC2005 doesn't support (LPSTR) or (LPCTSTR) operator. isn't it? Regards

                          C Offline
                          C Offline
                          Cedric Moonen
                          wrote on last edited by
                          #16

                          Yes, it is simply because UNICODE is defined by default (which was not the case with VC6). I strongly suggest that you read the article given by Led Mike, things will be much more clear afterwards.

                          Cédric Moonen Software developer
                          Charting control [v1.5] OpenGL game tutorial in C++

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                          • D DSPCottage

                            But it appears that VC2005 doesn't support (LPSTR) or (LPCTSTR) operator. isn't it? Regards

                            M Offline
                            M Offline
                            Mark Salsbery
                            wrote on last edited by
                            #17

                            The operator is a member of the CSimpleStringT class, which is the base class of CStringT. The actual operator is PCXSTR (the ATL type), which is the equivalent of LPCTSTR (a Win32 type). Here's your code using generic text types:

                            TCHAR buffer[MAX_PATH];
                            GetModuleFileName(NULL,buffer,MAX_PATH);
                            CString path = buffer;
                            path = path.Left(path.ReverseFind(_T('\\'))+1);
                            path += _T("result.mp3");
                            f = _tfopen( path , _T("wb")); // <-- implicitly uses CString's PCXSTR operator!

                            See Generic-Text Mappings in Tchar.h[^] and for Unicode info: International Programming[^] Mark

                            Mark Salsbery Microsoft MVP - Visual C++ :java:

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                            • L led mike

                              Gut Mikh Tappe wrote:

                              Please let me know what to do

                              Ok I will try. What you need to do is read the documentation.[^] Also reading this might help as well.[^] In my experience not all authors match every reader. So if you find reading those sources don't supply your need 100% keep looking for more. The bottom line is what you need to do is read and study rather than type code and forum messages.

                              led mike

                              M Offline
                              M Offline
                              Mark Salsbery
                              wrote on last edited by
                              #18

                              led mike wrote:

                              Also reading this might help as well.[^]

                              That IS a good link. I bookmarked that to post in the future, Thanks! :beer:

                              Mark Salsbery Microsoft MVP - Visual C++ :java:

                              1 Reply Last reply
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                              • D DSPCottage

                                May you please give me an article about UNICODE ? Regards Mahdi

                                R Offline
                                R Offline
                                Rick York
                                wrote on last edited by
                                #19

                                Here are a few : http://www.google.com/search?hl=en&q=UNICODE&btnG=Google+Search[^]

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                                • Z zafersavas

                                  There a various ways: 1)

                                  CString str = "filename";

                                  char charPtr[100];
                                  sprintf(charPtr, "%s", str);

                                  CString str = "filename";
                                  char* charPtr = str.GetBuffer(str.GetLength());

                                  S Offline
                                  S Offline
                                  super_ttd
                                  wrote on last edited by
                                  #20

                                  zafersavas wrote:

                                  str.GetBuffer(str.GetLength());

                                  Memory Leak here ! Why the hell do people use that dangerous GetBuffer() function when it's absolutely useless ? :doh:


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