C++ Library - <ios_base>
Introduction
Base class for the entire hierarchy of stream classes in the standard input/output library, describing the most basic part of a stream which is common to all stream objects, independently of their character type.
It has no public constructors, and thus no objects of this class can be declared. Both ios_base and its derived class basic_ios define the components of streams that do not depend on whether the stream is an input or an output stream: ios_base describes the members that are independent of the template parameters (i.e. the character type and traits), while basic_ios describes the members that do depend on them.
More specifically, the ios_base class maintains the following information of a stream −
| field | member functions | description | |
|---|---|---|---|
| Formatting | format flags | flags setf unsetf |
A set of internal flags that affect how certain input/output operations are interpreted or generated. See member type fmtflags. |
| field width | width | Width of the next formatted element to insert. | |
| display precision | precision | Decimal precision for the next floating-point value inserted. | |
| locale | getloc imbue |
The locale object used by the function for formatted input/output operations affected by localization properties. | |
| Other | callback stack | register_callback | Stack of pointers to functions that are called when certain events occur. |
| extensible arrays | iword pword xalloc |
Internal arrays to store objects of type long and void*. |
Definition
Below is definition of ios_base as shown below −
class ios_base;
Member types
| Sr.No. | Member types | Definition |
|---|---|---|
| 1 | event | Type to indicate event type |
| 2 | event_callback | Event callback function type |
| 3 | fmtflags | Type for stream format flags |
| 4 | iostate | Type for stream state flags |
| 5 | openmode | Type for stream opening mode flags |
| 6 | seekdir | Type for stream seeking direction flag |
Public Member Functions
| Sr.No. | Member types | Definition |
|---|---|---|
| 1 | (constructor) | Construct object (public member function ) |
| 2 | (destructor) | Destruct object (public member function ) |
Formatting
| Sr.No. | Member types | Definition |
|---|---|---|
| 1 | flags | It is used to get/set format flags |
| 2 | setf | It is used to set specific format flags |
| 3 | unsetf | It is used to clear specific format flags |
| 4 | precision | It is used to get/Set floating-point decimal precision |
| 5 | width | It is used to get/set field width |
Locales
Internal extensible array
| Sr.No. | Member types | Definition |
|---|---|---|
| 1 | xalloc | It is used to get new index for extensible array [static] |
| 2 | iword | It is used to get integer element of extensible array |
| 3 | pword | It is used to get pointer element of extensible array |
Others
| Sr.No. | Member types | Definition |
|---|---|---|
| 1 | register_callback | Register event callback function |
| 2 | sync_with_stdio | Toggle synchronization with cstdio streams [static] |