std::strstreambuf::pbackfail - cppreference.com (original) (raw)
| protected: virtual int_type pbackfail( int_type c = EOF ); | | (deprecated in C++98) (removed in C++26) | | -------------------------------------------------------------------------- | | ---------------------------------------- |
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).
- The caller is requesting that the get area is backed up by one character (
pbackfail()is called with no arguments or with EOF as the argument)
a) First, checks if there is a putback position, and if there really isn't, fails (strstreambuf has no external character source to re-read).
b) If the caller was wrong and the putback position is in fact available, simply decrements
, e.g. by calling gbump(-1).
- The caller attempts to putback a different character from the one retrieved 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, fails.
b) Then checks what character is in the putback position. If the character held there is already equal to (char)c, then simply decrements
.
c) Otherwise, if the buffer is unmodifiable (this strstreambuf was constructed with a string literal or some other const array), fails.
[edit] Parameters
| c | - | the character to put back, or Traits::eof() to indicate that backing up of the get area is requested |
|---|
[edit] Return value
c on success except if c was EOF, in which case unspecified value other than EOF is returned.
EOF on failure.
[edit] Example
[edit] See also
| | puts a character back into the input sequence, possibly modifying the input sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) [edit] | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf<CharT,Traits>) [edit] | | | puts one character back in the input sequence (public member function of std::basic_streambuf<CharT,Traits>) [edit] | | | unextracts a character (public member function of std::basic_istream<CharT,Traits>) [edit] | | | puts a character into input stream (public member function of std::basic_istream<CharT,Traits>) [edit] |