std::strstreambuf::pbackfail

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Input/output library

I/O manipulators
Print functions(C++23)
C-style I/O
Buffers
basic_streambuf
basic_filebuf
basic_stringbuf
basic_spanbuf (C++23)
strstreambuf (C++98/26*)
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ios_base
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basic_osyncstream (C++20)
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streamoff
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iostream_category (C++11)
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std::strstreambuf

Public member functions
strstreambuf::strstreambuf
strstreambuf::~strstreambuf
strstreambuf::freeze
strstreambuf::str
strstreambuf::pcount
Protected member functions
strstreambuf::underflow
strstreambuf::pbackfail
strstreambuf::overflow
strstreambuf::setbuf
strstreambuf::seekoff
strstreambuf::seekpos

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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 functionsbasic_streambuf::sungetc andbasic_streambuf::sputbackc (which, in turn, are called bybasic_istream::unget andbasic_istream::putback).

1) The caller is requesting that the get area is backed up by one character (pbackfail() is called with no arguments or withEOF 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 decrementsbasic_streambuf::gptr(), e.g. by callinggbump(-1).

2) 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 decrementsbasic_streambuf::gptr().

c) Otherwise, if the buffer is unmodifiable (this strstreambuf was constructed with a string literal or some otherconst array), fails.

d) Otherwise, decrementsbasic_streambuf::gptr() and writesc to the location pointed togptr() after adjustment.

[edit]Parameters

the character to put back, orTraits::eof() to indicate that backing up of the get area is requested

[edit]Return value

c on success except ifc wasEOF, in which case unspecified value other thanEOF is returned.

EOF on failure.

[edit]Example

This section is incomplete
Reason: no example

[edit]See also

pbackfail [virtual]	puts a character back into the input sequence, possibly modifying the input sequence (virtual protected member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sungetc	moves the next pointer in the input sequence back by one (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
sputbackc	puts one character back in the input sequence (public member function of`std::basic_streambuf<CharT,Traits>`)[edit]
unget	unextracts a character (public member function of`std::basic_istream<CharT,Traits>`)[edit]
putback	puts a character into input stream (public member function of`std::basic_istream<CharT,Traits>`)[edit]