std::basic_istream< _CharT, _Traits >::sentry(3)

NAME
std::basic_istream< _CharT, _Traits >::sentry - Performs setup work for input streams.

SYNOPSIS

#include <istream>

  Public Types
typedef __istream_type::__ctype_type __ctype_type
typedef _Traits::int_type __int_type
typedef basic_istream< _CharT, _Traits > __istream_type
typedef basic_streambuf< _CharT, _Traits > __streambuf_type
typedef _Traits traits_type
Easy access to dependent types.

  Public Member Functions
sentry (basic_istream< _CharT, _Traits > &__is, bool __noskipws=false)
The constructor performs all the work.
operator bool () const
Quick status checking.

Detailed Description

  template<typename _CharT, typename _Traits>
class std::basic_istream< _CharT, _Traits >::sentry"Performs setup work for input streams. 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.

Member Typedef Documentation

  template<typename _CharT, typename _Traits> typedef _Traits std::basic_istream< _CharT, _Traits >::sentry::traits_type

Easy access to dependent types.

Constructor & Destructor Documentation

  template<typename _CharT, typename _Traits> std::basic_istream< _CharT, _Traits >::sentry::sentry (basic_istream< _CharT, _Traits > & __is, bool __noskipws = false) [explicit]

The constructor performs all the work.

Parameters
    __is The input stream to guard.
    __noskipws Whether to consume whitespace or not.

If the stream state is good (__is.good() is true), then the following actions are performed, otherwise the sentry state is false (not okay) and failbit is set in the stream state.

The sentry's preparatory actions are:

1.  if the stream is tied to an output stream, is.tie()->flush() is called to synchronize the output sequence

2.  if __noskipws is false, and ios_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).

References std::basic_istream< _CharT, _Traits >::basic_istream(), std::ios_base::badbit, std::basic_ios< _CharT, _Traits >::good(), and std::ios_base::goodbit.

Member Function Documentation

  template<typename _CharT, typename _Traits> std::basic_istream< _CharT, _Traits >::sentry::operator bool () const [inline], [explicit]

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).

Author

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