home | help 
std::basic_streambuf::setg(3)  C++ Standard Libary std::basic_streambuf::setg(3)

NAME
     std::basic_streambuf::setg - std::basic_streambuf::setg

Synopsis
	protected:
	void setg( char_type* gbeg, char_type* gcurr, char_type* gend );

	Sets the values of the pointers defining the get area. Specifically, af-
     ter 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()
	  {
	      traits_type::int_type i;
	      while ((i = src->sbumpc()) == '\0')
		  ; // skip zeroes
	      if (!traits_type::eq_int_type(i, traits_type::eof()))
	      {
		  ch = traits_type::to_char_type(i);
		  setg(&ch, &ch, &ch+1); // make one read position available
	      }
	      return i;
	  }
      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

See also
	setp repositions the beginning, next, and end pointers of the output se-
     quence
	     (protected member function)

http://cppreference.com 	   2024.06.10	   std::basic_streambuf::setg(3)
home | help