Redirecting streams

Posted on 2003-11-11
Last Modified: 2010-04-01
I have a log class that uses C-style I/O. This allows me to have the following situation (simplified):

class Log
   void SetFile(FILE* f) { file = f; }
   FILE* file;

So I can redirect the log output to any file (including stdout or stderr for example) and change it however i want at runtime. I was trying to convert this to use C++ stream I/O and I can't seem to find an equally elegant solution that would allow me to write to a file or cout/cerr etc and change it at runtime. All I can come up with is something like the following:

class Log
   Log(const char* filename) : os(NULL), file(filename) {
      if (file)
   Log(std::ostream& _os) : os.rdbuf(_os.rdbuf()) { }

   void SetFile(const char* filename) {
      if (file.is_open())
      if (file)
   void SetStream(std::ostream& _os) {
      if (file.is_open())
   std::ostream os;
   std::ofstream file;

which is ok, but having to have both an ostream and an ofstream jerks me a little. I tried having just the ofstream but you can't change its rdbuf (at least not using the iostreams library in VC7). I also tried having an ostream* but this isn't really much better overall (although it too seems to work). Can someone enlighten me with a nicer solution? Yes this is a bit pedantic for a log class but hey it might come up somewhere more important one day ;)

Question by:JLevick
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Accepted Solution

havman56 earned 125 total points
ID: 9722086

why cant u used insertion operation on filestream

std::ofstream *file_ptr;

There are lot overloaded function << for output streams u can use appropriately rather than setfunction of urs.



Author Comment

ID: 9745634
thanks - my crappy docs didn't list all the overloads of the insertion operator, there is indeed one that does the job.

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