std::ios_base
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ios_base
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std::ios_base
Member functions
Formatting
Locales
Internal extensible array
Miscellaneous
Member classes
Member types
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(), std::basic_ios::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
Formatting
Locales
Internal extensible array
[static]
(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]
(public member function) [edit]
resizes the private storage if necessary and access to the void* element at the given index
(public member function) [edit]
(public member function) [edit]
Miscellaneous
[static]
(public static member function) [edit]
Member classes
Member types and constants
Type
Explanation
stream open mode type
(typedef) [edit]
formatting flags type
(typedef) [edit]
state of the stream type
(typedef) [edit]
seeking direction type
(typedef) [edit]
specifies event type
(enum) [edit]
callback function type
(typedef) [edit]
(until C++17)
The following constants are also defined:
Constant
Explanation[edit]
(typedef) [edit]
The following constants are also defined:
Constant
Explanation[edit]
internal
internal adjustment (adds fill characters to the internal designated point): see std::internal [edit]
scientific
generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific [edit]
fixed
generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed [edit]
showbase
generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase [edit]
showpoint
generate a decimal-point character unconditionally for floating-point number output: see std::showpoint [edit]
uppercase
replace certain lowercase letters with their uppercase equivalents in certain output operations: see std::uppercase [edit]
(typedef) [edit]
The following constants are also defined:
Constant
Explanation[edit]
(typedef) [edit]
The following constants are also defined:
Constant
Explanation[edit]
(typedef) [edit]
(enum) [edit]
(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
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 1357 (N3110) |
C++98 | std::ios_base defined operator~, operator&and operator| for types openmode, fmtflags andiostate, violating the requirements of BitmaskType [1]
|
removed these definitions |
- ↑ A BitmaskType needs to support bitwise opertaions on its own. The bitwise operation support should not be provided externally.