std::basic_...f::pbackfail(3) C++ Standard Libary std::basic_...f::pbackfail(3) NAME std::basic_filebuf::pbackfail - std::basic_filebuf::pbackfail Synopsis protected: virtual int_type pbackfail( int_type c = Traits::eof() ) This protected virtual function is called by the public functions basic_streambuf::sungetc and basic_streambuf::sputbackc (which, in turn, are called by basic_istream::unget and basic_istream::putback). 1) The caller is requesting that the get area is backed up by one char- acter (pbackfail() is called with no arguments), in which case, this function re-reads the file starting one byte earlier and decrements basic_streambuf::gptr(), e.g. by calling gbump(-1). 2) The caller attempts to putback a different character from the one re- trieved earlier (pbackfail() is called with the character that needs to be put back), in which case a) First, checks if there is a putback position, and if there isn't, backs up the get area by re-reading the file starting one byte earlier. a) Then checks what character is in the putback position. If the charac- ter held there is already equal to c, as determined by Traits::eq(to_char_type(c), gptr()[-1]), then simply decrements basic_streambuf::gptr(). b) Otherwise, if the buffer is allowed to modify its own get area, decrements basic_streambuf::gptr() and writes c to the location pointed to gptr() after adjustment. This function never modifies the file, only the get area of the in-mem- ory buffer. If the file is not open (is_open()==false, this function returns Traits::eof() immediately. Parameters c - the character to put back, or Traits::eof() to indicate that backing up of the get area is requested Return value c on success except if c was Traits::eof(), in which case Traits::not_eof(c) is returned. Traits::eof() on failure. Example This section is incomplete Reason: no example See also puts a character back into the input sequence, possibly modi- fying the pbackfail input sequence [virtual] (virtual protected member function of std::basic_stream- buf<CharT,Traits>) sungetc moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf<CharT,Traits>) sputbackc puts one character back in the input sequence (public member function of std::basic_streambuf<CharT,Traits>) unget unextracts a character (public member function of std::basic_istream<CharT,Traits>) putback puts a character into input stream (public member function of std::basic_istream<CharT,Traits>) Category: * Todo no example http://cppreference.com 2024.06.10 std::basic_...f::pbackfail(3)
NAME | Synopsis | Parameters | Return value | Example | See also | Category:
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