std::basic_streambuf::setg(3)

💖 NAME 💖

std::basic_streambuf::setg — yes bestie, the name is literally std::basic_streambuf::setg again. We're in the C++ Standard Libary manual, and this is the protected member function that sets the get area's pointers. Slay. 💅

✨ Synopsis ✨

It's a protected member, so it's for you and your streambuf subclasses, not the whole world. The signature is exactly:

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

It sets the values of the pointers that define 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 (the get pointer) in the get area ✨
• gend — pointer to the new end of the get area 🎀

🦋 Return value 🦋

(none) — literally nothing comes back. No return value era. 💀

🌈 Example 🌈

Run this code, bestie:

       // 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 sequence (protected member function) 👑

that's the whole vibe. source/version: http://cppreference.com, date: 2024.06.10, and it's the std::basic_streambuf::setg(3) page. mwah 💋✨