std::ios_base (3) - Linux Manuals

std::ios_base: std::ios_base

NAME

std::ios_base - std::ios_base

Synopsis

Defined in header <ios>
class ios_base;

The class ios_base is a multipurpose class that serves as the base class for all I/O stream classes. It maintains several kinds of data:
1) state information: stream status flags
2) control information: flags that control formatting of both input and output sequences and the imbued locale
3) private storage: indexed extensible data structure that allows both long and void* members, which may be implemented as two arbitrary-length arrays or a single array of two-element structs or another container.
4) callbacks: arbitrary number of user-defined functions to be called from imbue(), copyfmt(), and ~ios_base()
Typical implementation holds member constants corresponding to all values of fmtflags, iostate, openmode, and seekdir shown below, member variables to maintain current precision, width, and formatting flags, the exception mask, the buffer error state, a resizeable container holding the callbacks, the currently imbued locale, the private storage, and a static integer variable for xalloc().

Member functions

                  constructs the object
constructor (protected member function)

destructor destructs the object
                  (virtual public member function)
[virtual]

Formatting

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

Locales

                  sets locale
imbue (public member function)
                  returns current locale
getloc (public member function)

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)
[static]
                  resizes the private storage if necessary and access to the long element at the given index
iword (public member function)
                  resizes the private storage if necessary and access to the void* element at the given index
pword (public member function)

Miscellaneous

                  registers event callback function
register_callback (public member function)

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

Member classes

                  stream exception
failure (public member class)
                  initializes standard stream objects
Init (public member class)

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)

Deprecated member types

Type Explanation
io_state(deprecated) integer type that may be used like iostate (until C++17)
open_mode(deprecated) integer type that may be used like openmode
seek_dir(deprecated) integer type that may be used like seekdir
streamoff(deprecated) unspecified type that may be used like off_type, not necessarily std::streamoff
streampos(deprecated) unspecified type that may be used like pos_type, not necessarily std::streampos