std::basic_ios (3) - Linux Manuals

std::basic_ios: std::basic_ios

NAME

std::basic_ios - std::basic_ios

Synopsis

Defined in header <ios>
template<
class CharT,
class Traits = std::char_traits<CharT>
> class basic_ios : public std::ios_base

The class std::basic_ios provides facilities for interfacing with objects that have std::basic_streambuf interface. Several std::basic_ios objects can refer to one actual std::basic_streambuf object.
 std-basic ios-inheritance.svg
Inheritance diagram
Two specializations for common character types are also provided:

Type Definition
ios basic_ios<char>
wios basic_ios<wchar_t>

Member types

Member type Definition
char_type CharT
traits_type Traits; the program is ill-formed if Traits::char_type is not CharT.
int_type Traits::int_type
pos_type Traits::pos_type
off_type Traits::off_type

Public member functions

               constructs the object
constructor (public member function)

destructor destructs the object
               (virtual public member function)
[virtual]
               the copy assignment operator is deleted
operator= (public member function)

State functions

               checks if no error has occurred i.e. I/O operations are available
good (public member function)
               checks if end-of-file has been reached
eof (public member function)
               checks if an error has occurred
fail (public member function)
               checks if a non-recoverable error has occurred
bad (public member function)
               checks if an error has occurred (synonym of fail())
operator! (public member function)

operator_void*
operator_bool checks if no error has occurred (synonym of !fail())
               (public member function)
(until C++11)
(since C++11)
               returns state flags
rdstate (public member function)
               sets state flags
setstate (public member function)
               modifies state flags
clear (public member function)

Formatting

               copies formatting information
copyfmt (public member function)
               manages the fill character
fill (public member function)

Miscellaneous

               manages exception mask
exceptions (public member function)
               sets the locale
imbue (public member function)
               manages associated stream buffer
rdbuf (public member function)
               manages tied stream
tie (public member function)
               narrows characters
narrow (public member function)
               widens characters
widen (public member function)

Protected member functions

          initializes a default-constructed std::basic_ios
init (protected member function)

move moves from another std::basic_ios except for rdbuf
          (protected member function)
(C++11)

swap swaps with another std::basic_ios except for rdbuf
          (protected member function)
(C++11)
          replaces the rdbuf without clearing its error state
set_rdbuf (protected member function)

Inherited from std::ios_base

Member functions

Formatting

                  manages format flags
flags (public member function of std::ios_base)
                  sets specific format flag
setf (public member function of std::ios_base)
                  clears specific format flag
unsetf (public member function of std::ios_base)
                  manages decimal precision of floating point operations
precision (public member function of std::ios_base)
                  manages field width
width (public member function of std::ios_base)

Locales

                  sets locale
imbue (public member function of std::ios_base)
                  returns current locale
getloc (public member function of std::ios_base)

Internal extensible array

xalloc returns a program-wide unique integer that is safe to use as index to pword() and iword()
                  (public static member function of std::ios_base)
[static]
                  resizes the private storage if necessary and access to the long element at the given index
iword (public member function of std::ios_base)
                  resizes the private storage if necessary and access to the void* element at the given index
pword (public member function of std::ios_base)

Miscellaneous

                  registers event callback function
register_callback (public member function of std::ios_base)

sync_with_stdio sets whether C++ and C IO libraries are interoperable
                  (public static member function of std::ios_base)
[static]

Member classes

                  stream exception
failure (public member class of std::ios_base)
                  initializes standard stream objects
Init (public member class of std::ios_base)

Member types and constants

Type Explanation
               stream open mode type
               The following constants are also defined:

               Constant Explanation
               app seek to the end of stream before each write
               binary open in binary_mode
openmode in open for reading
               out open for writing
               trunc discard the contents of the stream when opening
               ate seek to the end of stream immediately after open

               (typedef)
               formatting flags type
               The following constants are also defined:

               Constant Explanation
               dec use decimal base for integer I/O: see std::dec
               oct use octal base for integer I/O: see std::oct
               hex use hexadecimal base for integer I/O: see std::hex
               basefield dec|oct|hex. Useful for masking operations
               left left adjustment (adds fill characters to the right): see std::left
               right right adjustment (adds fill characters to the left): see std::right
               internal internal adjustment (adds fill characters to the internal designated point): see std::internal
               adjustfield left|right|internal. Useful for masking operations
               scientific generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific
fmtflags fixed generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed
               floatfield scientific|fixed. Useful for masking operations
               boolalpha insert and extract bool type in alphanumeric format: see std::boolalpha
               showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase
               showpoint generate a decimal-point character unconditionally for floating-point number output: see std::showpoint
               showpos generate a + character for non-negative numeric output: see std::showpos
               skipws skip leading whitespace before certain input operations: see std::skipws
               unitbuf flush the output after each output operation: see std::unitbuf
               uppercase replace certain lowercase letters with their uppercase
                           equivalents in certain output operations: see std::uppercase

               (typedef)
               state of the stream type
               The following constants are also defined:

               Constant Explanation
               goodbit no error
iostate badbit irrecoverable stream error
               failbit input/output operation failed (formatting or extraction error)
               eofbit associated input sequence has reached end-of-file

               (typedef)
               seeking direction type
               The following constants are also defined:

               Constant Explanation
               beg the beginning of a stream
seekdir end the ending of a stream
               cur the current position of stream position indicator

               (typedef)
               specifies event type
event (enum)
               callback function type
event_callback (typedef)

Notes

Straightforward implementation of std::basic_ios stores only the following members (which all depend on the template parameters and thus cannot be part of std::ios_base):

* the fill character (see fill())
* the tied stream pointer (see tie())
* the associated stream buffer pointer (see rdbuf())

Actual implementations vary:
Microsoft Visual Studio stores just those three members.
LLVM libc++ stores 1 less member: it maintains the rdbuf pointer as a void* member of ios_base.
GNU libstdc++ stores 4 additional members: three cached facets and a flag to indicate that fill was initialized