std::basic_streambuf<CharT,Traits>::setg (3) - Linux Manuals

std::basic_streambuf<CharT,Traits>::setg: std::basic_streambuf<CharT,Traits>::setg

NAME

std::basic_streambuf<CharT,Traits>::setg - std::basic_streambuf<CharT,Traits>::setg

Synopsis

void setg( char_type* gbeg, char_type* gcurr, char_type* gend );

Sets the values of the pointers defining the get area. Specifically, after the call eback() == gbeg, gptr() == gcurr, egptr() == gend

Parameters

gbeg - pointer to the new beginning of the get area
gcurr - pointer to the new current character (get pointer) in the get area
gend - pointer to the new end of the get area

Return value

(none)

Example

// Run this code

  #include <iostream>
  #include <sstream>

  class null_filter_buf : public std::streambuf {
      std::streambuf* src;
      char ch; // single-byte buffer
  protected:
      int underflow() {
          while( (ch= src->sbumpc()) == '\0') ; // skip zeroes
          setg(&ch, &ch, &ch+1); // make one read position available
          return ch; // may return EOF
      }
  public:
      null_filter_buf(std::streambuf* buf) : src(buf) {
          setg(&ch, &ch+1, &ch+1); // buffer is initially full
      }
  };

  void filtered_read(std::istream& in)
  {
      std::streambuf* orig = in.rdbuf();
      null_filter_buf buf(orig);
      in.rdbuf(&buf);
      for(char c; in.get(c); )
              std::cout << c;
      in.rdbuf(orig);
  }

  int main()
  {
      char a[] = "This i\0s \0an e\0\0\0xample";
      std::istringstream in(std::string(std::begin(a), std::end(a)));
      filtered_read(in);
  }

Output:

  This is an example