BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  char to string conversion          BorlandTalk.com Forum Index -> C++ Builder (Students) View previous topic :: View next topic   Author Message Roger Guest Posted: Mon Apr 09, 2007 9:40 pm    Post subject: char to string conversion I am having trouble with a char to string conversion, e.g. char *pStr; pStr = (char *)lpDevCaps + lpDevCaps->dwLineNameOffset; // points to "Some Text"; string sText = pStr; // sText = { } How can I set sText to equal "Some Text" ??? Roger Back to top Thomas Maeder [TeamB] Guest Posted: Mon Apr 09, 2007 10:19 pm    Post subject: Re: char to string conversion Roger <aretae (AT) magma (DOT) ca> writes: Quote: I am having trouble with a char to string conversion, e.g. char *pStr; pStr = (char *)lpDevCaps + lpDevCaps->dwLineNameOffset; // points to "Some Text"; string sText = pStr; // sText = { } And what exactly is the trouble? Back to top Roger Guest Posted: Mon Apr 09, 2007 10:44 pm    Post subject: Re: char to string conversion Quote: And what exactly is the trouble? I want sText = "Some Text"; Not sText = { }; Roger Back to top Remy Lebeau (TeamB) Guest Posted: Mon Apr 09, 2007 11:04 pm    Post subject: Re: char to string conversion "Roger" <aretae (AT) magma (DOT) ca> wrote in message news:461a7b5c$1 (AT) newsgroups (DOT) borland.com... Quote: I want sText = "Some Text"; Not sText = { }; You did not show what lpDevCaps is to begin with. Obviously, you are not actually pointing to the right memory offset. Gambit Back to top Roger Guest Posted: Tue Apr 10, 2007 12:30 am    Post subject: Re: char to string conversion Quote: You did not show what lpDevCaps is to begin with. Obviously, you are not actually pointing to the right memory offset. Gambit My apologies, I was obviously not clear. I did use debug to inspect pStr which is actually equal to "AOpen FM56-EXV". and debug showed sText = { }; So I know pStr is pointing to "Some Text", what I don't know is why I can't set string sText = what pStr is point to, i.e. in my specific instance "AOpen FM56-EXV" instead sText = { } EXCEPT now I just tried it again, and it WORKS!!! I have no idea why it didn't work for a couple of hours, I don't know what I did between the time it didn't and now to make it work. I can't replicate the original problem. What I am doing now that seems to work is: string sText = (char *)lpDevCaps + lpDevCaps->dwLineNameOffset; // for debug Roger Back to top Remy Lebeau (TeamB) Guest Posted: Tue Apr 10, 2007 12:40 am    Post subject: Re: char to string conversion "Roger" <aretae (AT) magma (DOT) ca> wrote in message news:461a9443$1 (AT) newsgroups (DOT) borland.com... Quote: My apologies, I was obviously not clear. I did use debug to inspect pStr which is actually equal to "AOpen FM56-EXV". and debug showed sText = { }; That would not be possible given the code you have shown. sText would contain the actual string value. Now, it could be that the debugger itself simply can't show the contents of sText correctly. That is a whole separate issue. Quote: So I know pStr is pointing to "Some Text", what I don't know is why I can't set string sText = what pStr is point to, i.e. in my specific instance "AOpen FM56-EXV" instead sText = { } The code you showed suggests that you are using a std::string from the STL. The STL is not the easiest thing to debug because it uses a lot of internal structures. Try using AnsiString as a test and see what happens. The debugger can handle AnsiString very easily. If it contains the desired result, the the code itself is fine. Gambit Back to top Roger Guest Posted: Tue Apr 10, 2007 12:55 am    Post subject: Re: char to string conversion Quote: The code you showed suggests that you are using a std::string from the STL. The STL is not the easiest thing to debug because it uses a lot of internal structures. Try using AnsiString as a test and see what happens. The debugger can handle AnsiString very easily. If it contains the desired result, the the code itself is fine. Thanks Remy, I will try and remember this. Back to top Chris Uzdavinis (TeamB) Guest Posted: Tue Apr 10, 2007 12:56 am    Post subject: Re: char to string conversion Roger <aretae (AT) magma (DOT) ca> writes: Quote: What I am doing now that seems to work is: string sText = (char *)lpDevCaps + lpDevCaps->dwLineNameOffset; Be wary of code that "seems" to work! I can't help but wonder why you need the cast? What is the type of lpDevCaps? -- Chris (TeamB); Back to top Roger Guest Posted: Tue Apr 10, 2007 1:02 am    Post subject: Re: char to string conversion Chris Uzdavinis (TeamB) wrote: Quote: Roger <aretae (AT) magma (DOT) ca> writes: What I am doing now that seems to work is: string sText = (char *)lpDevCaps + lpDevCaps->dwLineNameOffset; Be wary of code that "seems" to work! I can't help but wonder why you need the cast? What is the type of lpDevCaps? If I leave the cast out I get the following error: [C++ Error] unitTAPI.cpp(188): E2034 Cannot convert 'linedevcaps_tag *' to 'string' lpDevCaps is defined as: LINEDEVCAPS *lpDevCaps = NULL; Roger Back to top Remy Lebeau (TeamB) Guest Posted: Tue Apr 10, 2007 1:45 am    Post subject: Re: char to string conversion "Roger" <aretae (AT) magma (DOT) ca> wrote in message news:461a9bc5$1 (AT) newsgroups (DOT) borland.com... Quote: If I leave the cast out I get the following error: [C++ Error] unitTAPI.cpp(188): E2034 Cannot convert 'linedevcaps_tag *' to 'string' The error is correct in that particular situation, as lpDevCaps is a pointer to a structure. Quote: lpDevCaps is defined as: LINEDEVCAPS *lpDevCaps = NULL; That would have been really useful information to know earlier. In which case, your code should be more like the following instead: char* pName = (char*) (((LPBYTE) lpDevCaps) + lpDevCaps->dwLineNameOffset); string sText(pName, lpDevCaps->dwLineNameSize); You can't rely on the name being null-terminated. That is why Microsoft includes the dwLineNameSize member. Gambit Back to top Roger Guest Posted: Tue Apr 10, 2007 3:25 am    Post subject: Re: char to string conversion Quote: That would have been really useful information to know earlier. In which case, your code should be more like the following instead: char* pName = (char*) (((LPBYTE) lpDevCaps) + lpDevCaps->dwLineNameOffset); string sText(pName, lpDevCaps->dwLineNameSize); You can't rely on the name being null-terminated. That is why Microsoft includes the dwLineNameSize member. Gambit Thanks Remy, I changed my code accordingly. 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