- The C Standard Library
- The C Standard Library
- The C++ Standard Library
- C++ Library - Home
- C++ Library - <fstream>
- C++ Library - <iomanip>
- C++ Library - <ios>
- C++ Library - <iosfwd>
- C++ Library - <iostream>
- C++ Library - <istream>
- C++ Library - <ostream>
- C++ Library - <sstream>
- C++ Library - <streambuf>
- C++ Library - <atomic>
- C++ Library - <complex>
- C++ Library - <exception>
- C++ Library - <functional>
- C++ Library - <limits>
- C++ Library - <locale>
- C++ Library - <memory>
- C++ Library - <new>
- C++ Library - <numeric>
- C++ Library - <regex>
- C++ Library - <stdexcept>
- C++ Library - <string>
- C++ Library - <thread>
- C++ Library - <tuple>
- C++ Library - <typeinfo>
- C++ Library - <utility>
- C++ Library - <valarray>
- The C++ STL Library
- C++ Library - <array>
- C++ Library - <bitset>
- C++ Library - <deque>
- C++ Library - <forward_list>
- C++ Library - <list>
- C++ Library - <map>
- C++ Library - <queue>
- C++ Library - <set>
- C++ Library - <stack>
- C++ Library - <unordered_map>
- C++ Library - <unordered_set>
- C++ Library - <vector>
- C++ Library - <algorithm>
- C++ Library - <iterator>
- C++ Programming Resources
- C++ Programming Tutorial
- C++ Useful Resources
- C++ Discussion
C++ IOS Library - Register Callback
Description
It is used to register event callback function. Registers fn as a callback function to be called automatically with index as argument when a stream event occurs.
If more than one callback function is registered, they are all called, in the inverse order of registration.
The callback function shall be of a type convertible to event_callback. And it is called by an expression equivalent to shown below −
void register_callback (event_callback fn, int index);
Declaration
Following is the declaration for ios_base::register_callback function.
void*& pword (int idx);
Parameters
fn − Pointer to the function to be called.
index − Integer value passed as parameter to the callback function.
Return Value
none
Exceptions
Basic guarantee − if an exception is thrown, the stream is in a valid state.
Data races
It modifies the stream object.
Example
In below example explains about ios_base::register_callback function.
#include <iostream> #include <fstream> void testfn (std::ios::event ev, std::ios_base& stream, int index) { switch (ev){ case stream.copyfmt_event: std::cout << "copyfmt_event\n"; break; case stream.imbue_event: std::cout << "imbue_event\n"; break; case stream.erase_event: std::cout << "erase_event\n"; break; } } int main () { std::ofstream filestr; filestr.register_callback (testfn,0); filestr.imbue (std::cout.getloc()); return 0; }
Let us compile and run the above program, this will produce the following result −
imbue_event erase_event