DOKK / manpages / debian 13 / libstdc++-13-doc / std::ios_base.3cxx.en
std::ios_base(3cxx) std::ios_base(3cxx)

std::ios_base - The base of the I/O class hierarchy.

#include <ios>

Inherited by std::basic_ios< char, _Traits >, std::basic_ios< _CharT, char_traits< _CharT > >, and std::basic_ios< _CharT, _Traits >.


class failure
These are thrown to indicate problems with io.


enum event { erase_event, imbue_event, copyfmt_event }
The set of events that may be passed to an event callback. typedef void(* event_callback) (event __e, ios_base &__b, int __i)
The type of an event callback function. typedef _Ios_Fmtflags fmtflags
This is a bitmask type. typedef _Ios_Iostate iostate
This is a bitmask type. typedef _Ios_Openmode openmode
This is a bitmask type. typedef _Ios_Seekdir seekdir
This is an enumerated type.


ios_base (const ios_base &)=delete
virtual ~ios_base ()
const locale & _M_getloc () const
Locale access. fmtflags flags () const
Access to format flags. fmtflags flags (fmtflags __fmtfl)
Setting new format flags all at once. locale getloc () const
Locale access. locale imbue (const locale &__loc) throw ()
Setting a new locale. long & iword (int __ix)
Access to integer array. ios_base & operator= (const ios_base &)=delete
streamsize precision () const
Flags access. streamsize precision (streamsize __prec)
Changing flags. void *& pword (int __ix)
Access to void pointer array. void register_callback (event_callback __fn, int __index)
Add the callback __fn with parameter __index. fmtflags setf (fmtflags __fmtfl)
Setting new format flags. fmtflags setf (fmtflags __fmtfl, fmtflags __mask)
Setting new format flags. void unsetf (fmtflags __mask)
Clearing format flags. streamsize width () const
Flags access. streamsize width (streamsize __wide)
Changing flags.


static bool sync_with_stdio (bool __sync=true)
Interaction with the standard C I/O objects. static int xalloc () throw ()
Access to unique indices.


static const openmode __noreplace
static const fmtflags adjustfield
A mask of left|right|internal. Useful for the 2-arg form of setf. static const openmode app
Seek to end before each write. static const openmode ate
Open and seek to end immediately after opening. static const iostate badbit
Indicates a loss of integrity in an input or output sequence (such as an irrecoverable read error from a file). static const fmtflags basefield
A mask of dec|oct|hex. Useful for the 2-arg form of setf. static const seekdir beg
Request a seek relative to the beginning of the stream. static const openmode binary
Perform input and output in binary mode (as opposed to text mode). This is probably not what you think it is; see https://gcc.gnu.org/onlinedocs/libstdc++/manual/fstreams.html#std.io.filestreams.binary. static const fmtflags boolalpha
Insert/extract bool in alphabetic rather than numeric format. static const seekdir cur
Request a seek relative to the current position within the sequence. static const fmtflags dec
Converts integer input or generates integer output in decimal base. static const seekdir end
Request a seek relative to the current end of the sequence. static const iostate eofbit
Indicates that an input operation reached the end of an input sequence. static const iostate failbit
Indicates that an input operation failed to read the expected characters, or that an output operation failed to generate the desired characters. static const fmtflags fixed
Generate floating-point output in fixed-point notation. static const fmtflags floatfield
A mask of scientific|fixed. Useful for the 2-arg form of setf. static const iostate goodbit
Indicates all is well. static const fmtflags hex
Converts integer input or generates integer output in hexadecimal base. static const openmode in
Open for input. Default for ifstream and fstream. static const fmtflags internal
Adds fill characters at a designated internal point in certain generated output, or identical to right if no such point is designated. static const fmtflags left
Adds fill characters on the right (final positions) of certain generated output. (I.e., the thing you print is flush left.) static const fmtflags oct
Converts integer input or generates integer output in octal base. static const openmode out
Open for output. Default for ofstream and fstream. static const fmtflags right
Adds fill characters on the left (initial positions) of certain generated output. (I.e., the thing you print is flush right.) static const fmtflags scientific
Generates floating-point output in scientific notation. static const fmtflags showbase
Generates a prefix indicating the numeric base of generated integer output. static const fmtflags showpoint
Generates a decimal-point character unconditionally in generated floating-point output. static const fmtflags showpos
Generates a + sign in non-negative generated numeric output. static const fmtflags skipws
Skips leading white space before certain input operations. static const openmode trunc
Truncate an existing stream when opening. Default for ofstream. static const fmtflags unitbuf
Flushes output after each output operation. static const fmtflags uppercase
Replaces certain lowercase letters with their uppercase equivalents in generated output.


enum { _S_local_word_size }


void _M_call_callbacks (event __ev) throw ()
void _M_dispose_callbacks (void) throw ()
_Words & _M_grow_words (int __index, bool __iword)
void _M_init () throw ()
void _M_move (ios_base &) noexcept
void _M_swap (ios_base &__rhs) noexcept


_Callback_list * _M_callbacks
iostate _M_exception
fmtflags _M_flags
locale _M_ios_locale
_Words _M_local_word [_S_local_word_size]
streamsize _M_precision
iostate _M_streambuf_state
streamsize _M_width
_Words * _M_word
int _M_word_size
_Words _M_word_zero

The base of the I/O class hierarchy.

This class defines everything that can be defined about I/O that does not depend on the type of characters being input or output. Most people will only see ios_base when they need to specify the full name of the various I/O flags (e.g., the openmodes).

typedef void(* std::ios_base::event_callback) (event __e, ios_base &__b, int __i)

The type of an event callback function.

Parameters

__e One of the members of the event enum.
__b Reference to the ios_base object.
__i The integer provided when the callback was registered.

Event callbacks are user defined functions that get called during several ios_base and basic_ios functions, specifically imbue(), copyfmt(), and ~ios().

typedef _Ios_Fmtflags std::ios_base::fmtflags

This is a bitmask type. _Ios_Fmtflags is implementation-defined, but it is valid to perform bitwise operations on these values and expect the Right Thing to happen. Defined objects of type fmtflags are:

  • boolalpha
  • dec
  • fixed
  • hex
  • internal
  • left
  • oct
  • right
  • scientific
  • showbase
  • showpoint
  • showpos
  • skipws
  • unitbuf
  • uppercase
  • adjustfield
  • basefield
  • floatfield

typedef _Ios_Iostate std::ios_base::iostate

This is a bitmask type. _Ios_Iostate is implementation-defined, but it is valid to perform bitwise operations on these values and expect the Right Thing to happen. Defined objects of type iostate are:

  • badbit
  • eofbit
  • failbit
  • goodbit

typedef _Ios_Openmode std::ios_base::openmode

This is a bitmask type. _Ios_Openmode is implementation-defined, but it is valid to perform bitwise operations on these values and expect the Right Thing to happen. Defined objects of type openmode are:

  • app
  • ate
  • binary
  • in
  • out
  • trunc

typedef _Ios_Seekdir std::ios_base::seekdir

This is an enumerated type. _Ios_Seekdir is implementation-defined. Defined values of type seekdir are:

  • beg
  • cur, equivalent to SEEK_CUR in the C standard library.
  • end, equivalent to SEEK_END in the C standard library.

enum std::ios_base::event

The set of events that may be passed to an event callback. erase_event is used during ~ios() and copyfmt(). imbue_event is used during imbue(). copyfmt_event is used during copyfmt().

virtual std::ios_base::~ios_base () [virtual]

Invokes each callback with erase_event. Destroys local storage.

Note that the ios_base object for the standard streams never gets destroyed. As a result, any callbacks registered with the standard streams will not get invoked with erase_event (unless copyfmt is used).

const locale & std::ios_base::_M_getloc () const [inline]

Locale access.

Returns

A reference to the current locale.

Like getloc above, but returns a reference instead of generating a copy.

fmtflags std::ios_base::flags () const [inline]

Access to format flags.

Returns

The format control flags for both input and output.

fmtflags std::ios_base::flags (fmtflags __fmtfl) [inline]

Setting new format flags all at once.

Parameters

__fmtfl The new flags to set.

Returns

The previous format control flags.

This function overwrites all the format flags with __fmtfl.

locale std::ios_base::getloc () const [inline]

Locale access.

Returns

A copy of the current locale.

If imbue(loc) has previously been called, then this function returns loc. Otherwise, it returns a copy of std::locale(), the global C++ locale.

locale std::ios_base::imbue (const locale & __loc)

Setting a new locale.

Parameters

__loc The new locale.

Returns

The previous locale.

Sets the new locale for this stream, and then invokes each callback with imbue_event.

Referenced by std::basic_ios< _CharT, _Traits >::imbue().

Access to integer array.

Parameters

__ix Index into the array.

Returns

A reference to an integer associated with the index.

The iword function provides access to an array of integers that can be used for any purpose. The array grows as required to hold the supplied index. All integers in the array are initialized to 0.

The implementation reserves several indices. You should use xalloc to obtain an index that is safe to use. Also note that since the array can grow dynamically, it is not safe to hold onto the reference.

streamsize std::ios_base::precision () const [inline]

Flags access.

Returns

The precision to generate on certain output operations.

Be careful if you try to give a definition of precision here; see DR 189.

streamsize std::ios_base::precision (streamsize __prec) [inline]

Changing flags.

Parameters

__prec The new precision value.

Returns

The previous value of precision().

void *& std::ios_base::pword (int __ix) [inline]

Access to void pointer array.

Parameters

__ix Index into the array.

Returns

A reference to a void* associated with the index.

The pword function provides access to an array of pointers that can be used for any purpose. The array grows as required to hold the supplied index. All pointers in the array are initialized to 0.

The implementation reserves several indices. You should use xalloc to obtain an index that is safe to use. Also note that since the array can grow dynamically, it is not safe to hold onto the reference.

void std::ios_base::register_callback (event_callback __fn, int __index)

Add the callback __fn with parameter __index.

Parameters

__fn The function to add.
__index The integer to pass to the function when invoked.

Registers a function as an event callback with an integer parameter to be passed to the function when invoked. Multiple copies of the function are allowed. If there are multiple callbacks, they are invoked in the order they were registered.

fmtflags std::ios_base::setf (fmtflags __fmtfl) [inline]

Setting new format flags.

Parameters

__fmtfl Additional flags to set.

Returns

The previous format control flags.

This function sets additional flags in format control. Flags that were previously set remain set.

fmtflags std::ios_base::setf (fmtflags __fmtfl, fmtflags __mask) [inline]

Setting new format flags.

Parameters

__fmtfl Additional flags to set.
__mask The flags mask for fmtfl.

Returns

The previous format control flags.

This function clears mask in the format flags, then sets fmtfl & mask. An example mask is ios_base::adjustfield.

static bool std::ios_base::sync_with_stdio (bool __sync = true) [static]

Interaction with the standard C I/O objects.

Parameters

__sync Whether to synchronize or not.

Returns

True if the standard streams were previously synchronized.

The synchronization referred to is only that between the standard C facilities (e.g., stdout) and the standard C++ objects (e.g., cout). User-declared streams are unaffected. See https://gcc.gnu.org/onlinedocs/libstdc++/manual/fstreams.html#std.io.filestreams.binary

void std::ios_base::unsetf (fmtflags __mask) [inline]

Clearing format flags.

Parameters

__mask The flags to unset.

This function clears __mask in the format flags.

streamsize std::ios_base::width () const [inline]

Flags access.

Returns

The minimum field width to generate on output operations.

Minimum field width refers to the number of characters.

streamsize std::ios_base::width (streamsize __wide) [inline]

Changing flags.

Parameters

__wide The new width value.

Returns

The previous value of width().

static int std::ios_base::xalloc () [static]

Access to unique indices.

Returns

An integer different from all previous calls.

This function returns a unique integer every time it is called. It can be used for any purpose, but is primarily intended to be a unique index for the iword and pword functions. The expectation is that an application calls xalloc in order to obtain an index in the iword and pword arrays that can be used without fear of conflict.

The implementation maintains a static variable that is incremented and returned on each invocation. xalloc is guaranteed to return an index that is safe to use in the iword and pword arrays.

const fmtflags std::ios_base::adjustfield [static]

A mask of left|right|internal. Useful for the 2-arg form of setf.

Referenced by std::num_put< _CharT, _OutIter >::do_put(), std::internal(), std::left(), and std::right().

const openmode std::ios_base::app [static]

Seek to end before each write.

Referenced by std::basic_filebuf< _CharT, _Traits >::overflow(), and std::basic_filebuf< _CharT, _Traits >::xsputn().

const openmode std::ios_base::ate [static]

Open and seek to end immediately after opening.

Referenced by std::basic_filebuf< _CharT, _Traits >::open().

const iostate std::ios_base::badbit [static]

Indicates a loss of integrity in an input or output sequence (such as an irrecoverable read error from a file).

Referenced by std::basic_istream< _CharT, _Traits >::sentry::sentry(), std::basic_ios< _CharT, _Traits >::bad(), std::basic_ios< _CharT, _Traits >::fail(), std::basic_ostream< _CharT, _Traits >::flush(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< char >::get(), std::basic_istream< _CharT, _Traits >::get(), std::basic_ostream< _CharT, _Traits >::operator<<(), std::operator>>(), std::basic_istream< _CharT, _Traits >::operator>>(), std::basic_ostream< _CharT, _Traits >::put(), std::basic_istream< _CharT, _Traits >::putback(), std::basic_istream< _CharT, _Traits >::read(), std::basic_istream< _CharT, _Traits >::readsome(), std::basic_istream< char >::seekg(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::sync(), std::basic_istream< _CharT, _Traits >::tellg(), std::basic_istream< char >::tellg(), and std::ws().

const fmtflags std::ios_base::basefield [static]

A mask of dec|oct|hex. Useful for the 2-arg form of setf.

Referenced by std::dec(), std::num_get< _CharT, _InIter >::do_get(), std::num_put< _CharT, _OutIter >::do_put(), std::hex(), and std::oct().

const seekdir std::ios_base::beg [static]

Request a seek relative to the beginning of the stream.

Referenced by std::basic_filebuf< _CharT, _Traits >::seekpos().

const openmode std::ios_base::binary [static]

Perform input and output in binary mode (as opposed to text mode). This is probably not what you think it is; see https://gcc.gnu.org/onlinedocs/libstdc++/manual/fstreams.html#std.io.filestreams.binary.

Referenced by std::basic_filebuf< _CharT, _Traits >::showmanyc().

const fmtflags std::ios_base::boolalpha [static]

Insert/extract bool in alphabetic rather than numeric format.

Referenced by std::boolalpha(), std::num_get< _CharT, _InIter >::do_get(), std::num_put< _CharT, _OutIter >::do_put(), and std::noboolalpha().

const seekdir std::ios_base::cur [static]

Request a seek relative to the current position within the sequence.

Referenced by std::basic_filebuf< _CharT, _Traits >::imbue(), std::basic_filebuf< _CharT, _Traits >::overflow(), std::basic_filebuf< _CharT, _Traits >::pbackfail(), std::basic_filebuf< _CharT, _Traits >::seekoff(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_istream< _CharT, _Traits >::tellg(), and std::basic_ostream< _CharT, _Traits >::tellp().

const fmtflags std::ios_base::dec [static]

Converts integer input or generates integer output in decimal base.

Referenced by std::dec().

const seekdir std::ios_base::end [static]

Request a seek relative to the current end of the sequence.

Referenced by std::basic_filebuf< _CharT, _Traits >::open(), and std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff().

const iostate std::ios_base::eofbit [static]

Indicates that an input operation reached the end of an input sequence.

Referenced by std::basic_istream< _CharT, _Traits >::sentry::sentry(), std::time_get< _CharT, _InIter >::do_get(), std::num_get< _CharT, _InIter >::do_get(), std::num_get< _CharT, _InIter >::do_get(), std::num_get< _CharT, _InIter >::do_get(), std::num_get< _CharT, _InIter >::do_get(), std::time_get< _CharT, _InIter >::do_get_date(), std::time_get< _CharT, _InIter >::do_get_monthname(), std::time_get< _CharT, _InIter >::do_get_time(), std::time_get< _CharT, _InIter >::do_get_weekday(), std::time_get< _CharT, _InIter >::do_get_year(), std::basic_ios< _CharT, _Traits >::eof(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< char >::get(), std::time_get< _CharT, _InIter >::get(), std::basic_istream< _CharT, _Traits >::ignore(), std::basic_istream< _CharT, _Traits >::operator>>(), std::operator>>(), std::basic_istream< _CharT, _Traits >::putback(), std::basic_istream< _CharT, _Traits >::read(), std::basic_istream< _CharT, _Traits >::readsome(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< char >::sync(), std::basic_istream< _CharT, _Traits >::unget(), and std::ws().

const iostate std::ios_base::failbit [static]

Indicates that an input operation failed to read the expected characters, or that an output operation failed to generate the desired characters.

Referenced by std::basic_istream< _CharT, _Traits >::sentry::sentry(), std::basic_ostream< _CharT, _Traits >::sentry::sentry(), std::num_get< _CharT, _InIter >::do_get(), std::time_get< _CharT, _InIter >::do_get_monthname(), std::time_get< _CharT, _InIter >::do_get_weekday(), std::time_get< _CharT, _InIter >::do_get_year(), std::basic_ios< _CharT, _Traits >::fail(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< char >::get(), std::time_get< _CharT, _InIter >::get(), std::basic_istream< _CharT, _Traits >::operator>>(), std::operator>>(), std::basic_istream< _CharT, _Traits >::operator>>(), std::basic_istream< _CharT, _Traits >::read(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_ostream< _CharT, _Traits >::seekp(), and std::basic_ostream< _CharT, _Traits >::seekp().

const fmtflags std::ios_base::fixed [static]

Generate floating-point output in fixed-point notation.

Referenced by std::fixed(), and std::hexfloat().

const fmtflags std::ios_base::floatfield [static]

A mask of scientific|fixed. Useful for the 2-arg form of setf.

Referenced by std::defaultfloat(), std::fixed(), std::hexfloat(), and std::scientific().

const iostate std::ios_base::goodbit [static]

Indicates all is well.

Referenced by std::basic_istream< _CharT, _Traits >::sentry::sentry(), std::time_get< _CharT, _InIter >::do_get(), std::num_get< _CharT, _InIter >::do_get(), std::time_get< _CharT, _InIter >::do_get_monthname(), std::time_get< _CharT, _InIter >::do_get_weekday(), std::time_get< _CharT, _InIter >::do_get_year(), std::basic_ostream< _CharT, _Traits >::flush(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< _CharT, _Traits >::get(), std::basic_istream< char >::get(), std::basic_istream< _CharT, _Traits >::get(), std::time_get< _CharT, _InIter >::get(), std::basic_istream< _CharT, _Traits >::ignore(), std::basic_istream< _CharT, _Traits >::ignore(), std::basic_ostream< _CharT, _Traits >::operator<<(), std::basic_istream< _CharT, _Traits >::operator>>(), std::operator>>(), std::basic_istream< _CharT, _Traits >::operator>>(), std::basic_ostream< _CharT, _Traits >::put(), std::basic_istream< _CharT, _Traits >::putback(), std::basic_istream< _CharT, _Traits >::read(), std::basic_istream< _CharT, _Traits >::readsome(), std::basic_istream< char >::readsome(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::sync(), std::basic_istream< _CharT, _Traits >::unget(), and std::ws().

const fmtflags std::ios_base::hex [static]

Converts integer input or generates integer output in hexadecimal base.

Referenced by std::num_get< _CharT, _InIter >::do_get(), std::num_put< _CharT, _OutIter >::do_put(), and std::hex().

const openmode std::ios_base::in [static]

Open for input. Default for ifstream and fstream.

Referenced by std::basic_stringbuf< _CharT, _Traits, _Alloc >::overflow(), std::basic_filebuf< _CharT, _Traits >::pbackfail(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_istream< _CharT, _Traits >::seekg(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), std::basic_filebuf< _CharT, _Traits >::showmanyc(), std::basic_istream< _CharT, _Traits >::tellg(), std::basic_filebuf< _CharT, _Traits >::underflow(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::underflow(), and std::basic_filebuf< _CharT, _Traits >::xsgetn().

const fmtflags std::ios_base::internal [static]

Adds fill characters at a designated internal point in certain generated output, or identical to right if no such point is designated.

Referenced by std::internal().

const fmtflags std::ios_base::left [static]

Adds fill characters on the right (final positions) of certain generated output. (I.e., the thing you print is flush left.)

Referenced by std::num_put< _CharT, _OutIter >::do_put(), and std::left().

const fmtflags std::ios_base::oct [static]

Converts integer input or generates integer output in octal base.

Referenced by std::oct().

const openmode std::ios_base::out [static]

Open for output. Default for ofstream and fstream.

Referenced by std::basic_filebuf< _CharT, _Traits >::overflow(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::overflow(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::pbackfail(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekoff(), std::basic_ostream< _CharT, _Traits >::seekp(), std::basic_ostream< _CharT, _Traits >::seekp(), std::basic_stringbuf< _CharT, _Traits, _Alloc >::seekpos(), std::basic_ostream< _CharT, _Traits >::tellp(), and std::basic_filebuf< _CharT, _Traits >::xsputn().

const fmtflags std::ios_base::right [static]

Adds fill characters on the left (initial positions) of certain generated output. (I.e., the thing you print is flush right.)

Referenced by std::right().

const fmtflags std::ios_base::scientific [static]

Generates floating-point output in scientific notation.

Referenced by std::hexfloat(), and std::scientific().

const fmtflags std::ios_base::showbase [static]

Generates a prefix indicating the numeric base of generated integer output.

Referenced by std::num_put< _CharT, _OutIter >::do_put(), std::noshowbase(), and std::showbase().

const fmtflags std::ios_base::showpoint [static]

Generates a decimal-point character unconditionally in generated floating-point output.

Referenced by std::noshowpoint(), and std::showpoint().

const fmtflags std::ios_base::showpos [static]

Generates a + sign in non-negative generated numeric output.

Referenced by std::noshowpos(), and std::showpos().

const fmtflags std::ios_base::skipws [static]

Skips leading white space before certain input operations.

Referenced by std::basic_istream< _CharT, _Traits >::sentry::sentry(), std::noskipws(), std::__detail::operator>>(), and std::skipws().

const openmode std::ios_base::trunc [static]

Truncate an existing stream when opening. Default for ofstream.

const fmtflags std::ios_base::unitbuf [static]

Flushes output after each output operation.

Referenced by std::nounitbuf(), and std::unitbuf().

const fmtflags std::ios_base::uppercase [static]

Replaces certain lowercase letters with their uppercase equivalents in generated output.

Referenced by std::num_put< _CharT, _OutIter >::do_put(), std::nouppercase(), and std::uppercase().

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