std::ios_base - cppreference.com (original) (raw)
| Defined in header | | | | -------------------------------------------------------------- | | | | 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:
state information: stream status flags.
control information: flags that control formatting of both input and output sequences and the imbued locale.
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.
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
| (constructor) | constructs the object (protected member function) [edit] |
|---|---|
| (destructor)[virtual] | destructs the object (virtual public member function) [edit] |
| operator= | assigns to the stream (public member function) [edit] |
| Formatting | |
| flags | manages format flags (public member function) [edit] |
| setf | sets specific format flag (public member function) [edit] |
| unsetf | clears specific format flag (public member function) [edit] |
| precision | manages decimal precision of floating point operations (public member function) [edit] |
| width | manages field width (public member function) [edit] |
| Locales | |
| imbue | sets locale (public member function) [edit] |
| getloc | returns current locale (public member function) [edit] |
| Internal extensible array | |
| xalloc[static] | returns a program-wide unique integer that is safe to use as index to pword() and iword() (public static member function) [edit] |
| iword | resizes the private storage if necessary and access to the long element at the given index (public member function) [edit] |
| pword | resizes the private storage if necessary and access to the void* element at the given index (public member function) [edit] |
| Miscellaneous | |
| register_callback | registers event callback function (public member function) [edit] |
| sync_with_stdio[static] | sets whether C++ and C I/O libraries are interoperable (public static member function) [edit] |
| Member classes | |
| failure | stream exception (public member class) [edit] |
| Init | initializes standard stream objects (public member class) [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 | (until C++17) |
|---|
[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.