C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  String class, how to implement sprintf?          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message CJ Guest Posted: Tue Oct 28, 2003 9:25 pm    Post subject: String class, how to implement sprintf? Ok, I've got a string class that stores the data in a dynamically allocated "char* m_pData" variable. I'd like to write a member function similiar to "sprintf" for this class. When implementing this member function, I'd like to just call "sprintf" under the covers. The problem is, that I dont' know how large the resulting string will be and thus I don't know how much space I'll need to allocate for my m_pData pointer. Is there any easy what to do this? Thanks! -CJ Back to top Davlet Panech Guest Posted: Tue Oct 28, 2003 10:54 pm    Post subject: Re: String class, how to implement sprintf? "CJ" <cj (AT) nospam (DOT) com> wrote Quote: Ok, I've got a string class that stores the data in a dynamically allocated "char* m_pData" variable. I'd like to write a member function similiar to "sprintf" for this class. When implementing this member function, I'd like to just call "sprintf" under the covers. The problem is, that I dont' know how large the resulting string will be and thus I don't know how much space I'll need to allocate for my m_pData pointer. Is there any easy what to do this? Thanks! -CJ Many environments include a (non-standard) function called "snprintf / vsnprintf". It allows you to provide the maximum length of your buffer, and returns a special value if the buffer is too small. You can call that function repeteadly allocating larger and larger amounts of memory until the whole message fits in the buffer. It'll be a little slower, but it'll work. I guess you could also open a dummy file [like "/dev/null" (UNIX), or "NUL" (DOS, Windows), or just a normal temporary file], fprintf into it, grab the return value, allocate that amount of memory, and then call the normal sprintf. This might be even slower. Note: printf() & friends return the number of characters they emitted. D. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.