std::ios_base Class Reference
[I/O]

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). More...

Inheritance diagram for std::ios_base:

List of all members.

Classes

class failure
These are thrown to indicate problems with io.
27.4.2.1.1 Class ios_base::failure. More...

Public Types

Public Member Functions

const locale & _M_getloc () const
fmtflags flags (fmtflags __fmtfl)
fmtflags flags () const
locale getloc () const
locale imbue (const locale &__loc)
long & iword (int __ix)
streamsize precision (streamsize __prec)
streamsize precision () const
void *& pword (int __ix)
void register_callback (event_callback __fn, int __index)
fmtflags setf (fmtflags __fmtfl, fmtflags __mask)
fmtflags setf (fmtflags __fmtfl)
void unsetf (fmtflags __mask)
streamsize width (streamsize __wide)
streamsize width () const
virtual ~ios_base ()

Static Public Member Functions

static bool sync_with_stdio (bool __sync=true)
static int xalloc () throw ()

Static Public Attributes

static const fmtflags adjustfield
static const openmode app
static const openmode ate
static const iostate badbit
static const fmtflags basefield
static const seekdir beg
static const openmode binary
static const fmtflags boolalpha
static const seekdir cur
static const fmtflags dec
static const seekdir end
static const iostate eofbit
static const iostate failbit
static const fmtflags fixed
static const fmtflags floatfield
static const iostate goodbit
static const fmtflags hex
static const openmode in
static const fmtflags internal
static const fmtflags left
static const fmtflags oct
static const openmode out
static const fmtflags right
static const fmtflags scientific
static const fmtflags showbase
static const fmtflags showpoint
static const fmtflags showpos
static const fmtflags skipws
static const openmode trunc
static const fmtflags unitbuf
static const fmtflags uppercase

Protected Types

enum { _S_local_word_size }

Protected Member Functions

void _M_call_callbacks (event __ev) throw ()
void _M_dispose_callbacks (void)
_Words & _M_grow_words (int __index, bool __iword)
void _M_init ()

Protected Attributes

_Callback_list * _M_callbacks
locale _M_ios_locale
_Words _M_local_word [_S_local_word_size]
_Words * _M_word
int _M_word_size
_Words _M_word_zero

Detailed Description

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).

Definition at line 207 of file ios_base.h.

Member Typedef Documentation

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

The type of an event callback function.

Parameters:

	event	One of the members of the event enum.
	ios_base	Reference to the ios_base object.
	int	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

Definition at line 263 of file ios_base.h.

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

Definition at line 338 of file ios_base.h.

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

Definition at line 369 of file ios_base.h.

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.

Definition at line 401 of file ios_base.h.

Member Enumeration Documentation

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().

Definition at line 427 of file ios_base.h.

Constructor & Destructor Documentation

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).

Member Function Documentation

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.

Definition at line 710 of file ios_base.h.

Referenced by std::money_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::time_put< _CharT, _OutIter >::do_put(), std::num_put< _CharT, _OutIter >::do_put(), and std::time_put< _CharT, _OutIter >::put().

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.

Definition at line 566 of file ios_base.h.

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

Access to format flags.

Returns:: The format control flags for both input and output.

Definition at line 555 of file ios_base.h.

Referenced by std::basic_ios< _CharT, _Traits >::copyfmt(), std::num_get< _CharT, _InIter >::do_get(), std::num_put< _CharT, _OutIter >::do_put(), std::basic_ostream< _CharT, _Traits >::operator<<(), and std::operator<<().

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.

Definition at line 699 of file ios_base.h.

Referenced by std::basic_ios< _CharT, _Traits >::copyfmt(), std::money_put< _CharT, _OutIter >::do_put(), std::basic_ios< _CharT, _Traits >::imbue(), std::operator>>(), and std::ws().

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.

Reimplemented in std::basic_ios< _CharT, _Traits >, std::basic_ios< _CharT, _Traits >, and std::basic_ios< char, _Traits >.

long& std::ios_base::iword ( int __ix ) [inline]

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.

Definition at line 745 of file ios_base.h.

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

Changing flags.

Parameters:

prec

The new precision value.

Returns:: The previous value of precision().

Definition at line 634 of file ios_base.h.

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.

Definition at line 625 of file ios_base.h.

Referenced by std::basic_ios< _CharT, _Traits >::copyfmt(), and std::operator<<().

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.

Definition at line 766 of file ios_base.h.

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,
		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.

Definition at line 599 of file ios_base.h.

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.

Definition at line 582 of file ios_base.h.

Referenced by std::boolalpha(), std::dec(), std::fixed(), std::hex(), std::internal(), std::left(), std::oct(), std::right(), std::scientific(), std::showbase(), std::showpoint(), std::showpos(), std::skipws(), std::unitbuf(), and std::uppercase().

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 http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch28s02.html

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.

Definition at line 614 of file ios_base.h.

Referenced by std::noboolalpha(), std::noshowbase(), std::noshowpoint(), std::noshowpos(), std::noskipws(), std::nounitbuf(), and std::nouppercase().

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

Changing flags.

Parameters:

wide

The new width value.

Returns:: The previous value of width().

Definition at line 657 of file ios_base.h.

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.

Definition at line 648 of file ios_base.h.

Referenced by std::basic_ios< _CharT, _Traits >::copyfmt(), std::num_put< _CharT, _OutIter >::do_put(), and std::operator>>().

static int std::ios_base::xalloc ( ) throw () [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.