std basic ios copyfmt in C++
Many functions from the Dinkum C++ Library, a conforming implementation of the Standard C++ Library, can be called by a C++ program. These operations carry out necessary tasks like input and output. Additionally, they offer effective executions of commonly utilized functions. These routines come with a tone of function and class definitions to help you get the most out of the library. Iostreams headers and STL headers are the two more general subcategories of the C++ library headers. The Standard C++ Library is utilized alongside the headers derived from the Standard C Library. For further details regarding the Standard C Library, refer to the operating system's documentation.
Copies the values of every internal member of object rhs, with the exception of the stream buffer reference to the relevant members of *this and the status flags. This contains all formatting information, the fill character, the tie pointer, and the format flags. For *this, a freshly built object contains copies of all external objects pointed in rhs.
The following order is followed in this function
- Uses erase_event as a parameter to call each callback that has been registered by register_callback().
- Copies every member object from others to* this, with the exception of rdbuf (), rdstate (), and the exception mask. In addition, it duplicates the contents of the arrays std::ios_base::iword and std::ios_base::pword (but not the word and word pointers themselves), the locale, styling flags, callbacks, and the tied stream. Uses copyfmt_event as a parameter and calls each callback that has been registered by register_callback().
- Assumes to call exceptions(other. exceptions()) in order to copy the exception mask from other to *this.
Parameters
Stream object whose members are copied to *this, with parameters set to rhs.
Return Value
*this is the result.
Copying Formatting:
When copyfmt is called, the formatting state of the rhs stream is copied into the caller stream. This state information includes filling characters, locale, formatting flags (such as std::ios_base::dec, std::ios_base::hex, etc.), and any other state information that modifies the formatting and stream behavior.
The whole contents of the standard output stream cout, excluding the error status and the stream buffer, are copied to the output file stream out using the std::basic_ios<>::copyfmt() member function. You can copy the exception mask individually using the function std::basic_ios<>:: exceptions(), as in std::cout.exceptions(fil.exceptions()). However, copycat () copies the exception mask, so you don't need to do this directly.
For the same goal, Boost offers a more detailed library of IO state savers. Transfers the values of every internal member of rhs to the equivalent members of *this, with the exception of the status flags and the stream buffer.
Following the call, rhs and *this receive the identical return from the following member functions:
The following arrays need to be copied last: array internal extensible array * array internal extensible array * fill character tie tied stream exceptions mask.
ElementDescriptionflagsformat flagswidthfield widthprecisionprecisiongetlocselected localeiarrayinternal extensible array *parrayinternal extensible array *fillfill charactertietied streamNote: The internal extensible array (word, word) is maintained independently by each stream object: Not simply a link to it, but its contents are transferred.
Example 1:
This creates an object called "out" from std::ofstream and makes it operate precisely like std::cout, including formatting and tying() to std::cin.
Program:
#include#include int main () { std::ofstream filestr; filestr.open ("test.txt"); std::cout.fill ('*'); std::cout.width (10); filestr.copyfmt (std::cout); std::cout << 40; filestr << 40; return 0; }Run this code
Output:
********40
Example 2:
You can make the ofstream object "out" behave exactly like std::cout by tying() to std::cin and doing other things.
Program:
#include#include int main() { std::ofstream out; out.copyfmt(std::cout); // copy everything except rdstate and rdbuf out.clear(std::cout.rdstate()); // copy rdstate out.basic_ios ::rdbuf(std::cout.rdbuf()); // share the buffer out << "Hello, world "; }
Output:
Hello, world
Conclusion
std::basic_ios::copyfmt is an effective tool for controlling the formatting state of C++ input/output streams. It makes it simple to keep your program's behavior constant throughout and to synchronize formatting settings across streams. It should be utilized carefully, though, as with any feature, to prevent unexpected side effects and performance problems.heus, the freedom fighters, mount an uprising against the machine army.