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std::ios_base

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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().

Contents

[edit] Member functions

constructs the object
(protected member function) [edit]
[virtual]
destructs the object
(virtual public member function) [edit]
Formatting
manages format flags
(public member function) [edit]
sets specific format flag
(public member function) [edit]
clears specific format flag
(public member function) [edit]
manages decimal precision of floating point operations
(public member function) [edit]
manages field width
(public member function) [edit]
Locales
sets locale
(public member function) [edit]
returns current locale
(public member function) [edit]
Internal extensible array
[static]
returns a program-wide unique integer that is safe to use as index to pword() and iword()
(public static member function) [edit]
resizes the private storage if necessary and access to the long element at the given index
(public member function) [edit]
resizes the private storage if necessary and access to the void* element at the given index
(public member function) [edit]
Miscellaneous
registers event callback function
(public member function) [edit]
sets whether C++ and C IO libraries are interoperable
(public static member function) [edit]

Member classes

stream exception
(public member class) [edit]
initializes standard stream objects
(public member class) [edit]

Member types and constants

Type Explanation
stream open mode type

The following constants are also defined:

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

(typedef) [edit]
formatting flags type

The following constants are also defined:

Constant Explanation[edit]
dec use decimal base for integer I/O[edit]
oct use octal base for integer I/O[edit]
hex use hexadecimal base for integer I/O[edit]
basefield dec|oct|hex|0. Useful for masking operations[edit]
left left adjustment (adds fill characters to the right) [edit]
right right adjustment (adds fill characters to the left) [edit]
internal internal adjustment (adds fill characters to the internal designated point) [edit]
adjustfield left|right|internal. Useful for masking operations [edit]
scientific generate floating point types using scientific notation, or hex notation if combined with fixed [edit]
fixed generate floating point types using fixed notation, or hex notation if combined with scientific [edit]
floatfield scientific|fixed|(scientific|fixed)|0. Useful for masking operations [edit]
boolalpha insert and extract bool type in alphanumeric format [edit]
showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O [edit]
showpoint generate a decimal-point character unconditionally for floating-point number output [edit]
showpos generate a + character for non-negative numeric output [edit]
skipws skip leading whitespace before certain input operations [edit]
unitbuf flush the output after each output operation [edit]
uppercase replace certain lowercase letters with their uppercase
equivalents in certain output output operations [edit]

(typedef) [edit]
state of the stream type

The following constants are also defined:

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

(typedef) [edit]
seeking direction type

The following constants are also defined:

Constant Explanation[edit]
beg the beginning of a stream [edit]
end the ending of a stream [edit]
cur the current position of stream position indicator [edit]

(typedef) [edit]
specifies event type
(enum) [edit]
callback function type
(typedef) [edit]
Deprecated member types
Type Explanation
io_state(deprecated) integer type that may be used like iostate
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