std::basic_...f::sputbackc(3)

💖 std::basic_...f::sputbackc(3) 💖

okay bestie, welcome to the C++ Standard Libary manual page for std::basic_...f::sputbackc(3) — yes, that title is literally abbreviated with ..., and the function we're actually talking about is std::basic_streambuf::sputbackc. No cap, this one is a little unget-flavored icon. 💅

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✨ NAME ✨

std::basic_streambuf::sputbackc — std::basic_streambuf::sputbackc.

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🌸 Synopsis 🌸

int_type sputbackc( char_type c );

okay so sputbackc puts a character back to the get area. 🫶

If a putback position is available in the get area — that's gptr() > eback() — and the character c is equal to the character one position to the left of gptr() (as determined by Traits::eq(c, gptr()[-1])), then it simply decrements the next pointer, gptr(). Easy slay.

Otherwise, it calls pbackfail(Traits::to_int_type(c)) to either back up the get area or to modify both the get area and possibly the associated character sequence. That part is giving "the plot thickens" energy. 😭

The I/O stream function basic_istream::putback is implemented in terms of this function. iykyk.

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🎀 Parameters 🎀

• c — character to put back. That's the whole parameter, bestie.

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💖 Return value 💖

If putback position was available, it returns the character that the next pointer is now pointing at, converted to int_type with Traits::to_int_type(*gptr()). The next single-character input from this streambuf will return this character. Cute.

If putback position was not available, it returns what pbackfail() returns, which is Traits::eof() on failure. Sad but true. 🥀

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🦋 Example 🦋

// Run this code

        #include <iostream>
        #include <sstream>

        int main()
        {
            std::stringstream s("abcdef"); // gptr() points to 'a' in "abcdef"
            std::cout << "Before putback, string holds " << s.str() << '\n';
            char c1 = s.get(); // c1 = 'a', gptr() now points to 'b' in
       "abcdef"
            char c2 = s.rdbuf()->sputbackc('z'); // same as s.putback('z')
                                                 // gptr() now points to 'z' in
       "zbcdef"
            std::cout << "After putback, string holds " << s.str() << '\n';
            char c3 = s.get(); // c3 = 'z', gptr() now points to 'b' in
       "zbcdef"
            char c4 = s.get(); // c4 = 'b', gptr() now points to 'c' in
       "zbcdef"
            std::cout << c1 << c2 << c3 << c4 << '\n';

            s.rdbuf()->sputbackc('b');  // gptr() now points to 'b' in "zbcdef"
            s.rdbuf()->sputbackc('z');  // gptr() now points to 'z' in "zbcdef"
            int eof = s.rdbuf()->sputbackc('x');  // nothing to unget:
       pbackfail() fails
            if (eof == EOF)
                std::cout << "No room to putback after 'z'\n";
        }

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👑 Output: 👑

Before putback, string holds abcdef
After putback, string holds zbcdef
azzb
No room to putback after 'z'

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🌈 See also 🌈

• sungetc — moves the next pointer in the input sequence back by one (public member function).
• putback — puts a character into input stream (public member function of std::basic_istream<CharT,Traits>).

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okay that's the whole page, bestie 💖 source/version: http://cppreference.com · date: 2024.06.10 · footer title: std::basic_...f::sputbackc(3). Mwah 💋✨