Objects of this class are created before all of the standard extractors are run. It is responsible for "exception-safe prefix and suffix operations," although only prefix actions are currently required by the standard. 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 639 of file istream.
typedef _Traits std::basic_istream< _CharT, _Traits >::sentry::traits_type |
std::basic_istream< _CharT, _Traits >::sentry::sentry | ( | basic_istream< _CharT, _Traits > & | __is, | |
bool | __noskipws = false | |||
) | [explicit] |
The constructor performs all the work.
is | The input stream to guard. | |
noskipws | Whether to consume whitespace or not. |
The sentry's preparatory actions are:
is.tie()->flush()
is called to synchronize the output sequenceios_base::skipws
is set in is.flags()
, the sentry extracts and discards whitespace characters from the stream. The currently imbued locale is used to determine whether each character is whitespace.If the stream state is still good, then the sentry state becomes true ("okay").
Definition at line 52 of file istream.tcc.
References std::__check_facet(), std::__ctype_abstract_base< _CharT >::is(), std::basic_streambuf< _CharT, _Traits >::sgetc(), std::skipws(), and std::basic_streambuf< _CharT, _Traits >::snextc().
std::basic_istream< _CharT, _Traits >::sentry::operator bool | ( | ) | const [inline] |