man std::basic_ostream_sentry (Fonctions bibliothèques) - Performs setup work for output streams.
NAME
std::basic_ostream::sentry - Performs setup work for output streams.
SYNOPSIS
Public Member Functions
sentry (basic_ostream< CharT, Traits > &__os)
The constructor performs preparatory work.
~sentry ()
Possibly flushes the stream.
operator bool () const
Quick status checking.
Private Attributes
bool M_ok
basic_ostream< CharT, Traits > & M_os
Detailed Description
template<typename CharT, typename Traits> class std::basic_ostream< CharT, Traits >::sentry
Performs setup work for output streams.
Objects of this class are created before all of the standard inserters are run. It is responsible for 'exception-safe prefix and suffix operations.' Additional actions may be added by the implementation, and we list them in http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/howto.html#5 under [27.6] notes.
Definition at line 375 of file ostream.
Constructor & Destructor Documentation
template<typename CharT, typename Traits> std::basic_ostream< CharT, Traits >::sentry::sentry (basic_ostream< CharT, Traits > & __os) [explicit]
The constructor performs preparatory work.
Parameters: os The output stream to guard.
If the stream state is good (os.good() is true), then if the stream is tied to another output stream, is.tie()->flush() is called to synchronize the output sequences.
If the stream state is still good, then the sentry state becomes true ('okay').
Definition at line 46 of file ostream.tcc.
References std::ios_base::failbit, std::basic_ios< CharT, Traits >::good(), std::basic_ios< CharT, Traits >::setstate(), and std::basic_ios< CharT, Traits >::tie().
template<typename CharT, typename Traits> std::basic_ostream< CharT, Traits >::sentry::~sentry () [inline]
Possibly flushes the stream.
If ios_base::unitbuf is set in os.flags(), and std::uncaught_exception() is true, the sentry destructor calls flush() on the output stream.
Definition at line 403 of file ostream.
References std::ios_base::badbit, std::uncaught_exception(), and std::ios_base::unitbuf.
Member Function Documentation
template<typename CharT, typename Traits> std::basic_ostream< CharT, Traits >::sentry::operator bool () const [inline]
Quick status checking.
Returns: The sentry state.
For ease of use, sentries may be converted to booleans. The return value is that of the sentry state (true == okay).
Definition at line 421 of file ostream.
Author
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