std::basic_istream::putback
From cppreference.com
< cpp | io | basic istream
| basic_istream& putback( char_type ch ); |
||
Puts the character ch back to the input stream so the next extracted character will be ch.
First clears eofbit, then constructs a std::basic_istream::sentry object with noskipws set to true. Afterwards, if good()==false, calls setstate(failbit) and returns. Otherwise, if rdbuf() is not null, calls rdbuf()->sputbackc(ch), which calls rdbuf()->pbackfail(ch) if ch does not equal the most recently extracted character.
If rdbuf() is null or if rdbuf->sputbackc(ch) returns Traits::eof(), calls setstate(badbit).
In any case, sets the gcount() counter to zero.
Contents |
[edit] Parameters
(none)
[edit] Return value
*this
[edit] Example
demonstrates the difference between modifying and non-modifying putback()
#include <sstream> #include <iostream> int main() { std::stringstream s1("Hello, world"); // IO stream s1.get(); if(s1.putback('Y')) // modifies the buffer std::cout << s1.rdbuf() << '\n'; else std::cout << "putback failed\n"; std::istringstream s2("Hello, world"); // input-only stream s2.get(); if(s2.putback('Y')) // cannot modify input-only buffer std::cout << s2.rdbuf() << '\n'; else std::cout << "putback failed\n"; s2.clear(); if(s2.putback('H')) // non-modifying putback std::cout << s2.rdbuf() << '\n'; else std::cout << "putback failed\n"; }
Output:
Yello, world putback failed Hello, world
[edit] See also
| unextracts a character (public member function) | |
| reads the next character without extracting it (public member function) | |
