C++ streambuf用法

class LogStreamBuf : public std::streambuf {

　　public:

　　// REQUIREMENTS: "len" must be >= 2 to account for the '\n' and '\n'.

　　LogStreamBuf(char *buf, int len) {

　　　　setp(buf, buf + len - 2);

　　}

　　// This effectively ignores overflow.

　　virtual int_type overflow(int_type ch) {

　　　　return ch;

　　}



　　// Legacy public ostrstream method.

　　size_t pcount() const { return pptr() - pbase(); }

　　char* pbase() const { return std::streambuf::pbase(); }

};

 

class LogStream : public std::ostream {

   public:

    　　LogStream(char *buf, int len, int ctr)

        　　: std::ostream(NULL),

          　　streambuf_(buf, len),

          　　ctr_(ctr),

          　　self_(this) { rdbuf(&streambuf_);}



    　　int ctr() const { return ctr_; }

    　　void set_ctr(int ctr) { ctr_ = ctr; }

    　　LogStream* self() const { return self_; }



    　　// Legacy std::streambuf methods.

    　　size_t pcount() const { return streambuf_.pcount(); }

   　　 char* pbase() const { return streambuf_.pbase(); }

   　　 char* str() const { return pbase(); }



  private:

   　　 base_logging::LogStreamBuf streambuf_;

    　　int ctr_;  // Counter hack (for the LOG_EVERY_X() macro)

    　　LogStream *self_;  // Consistency check hack

  };