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std::basic_filebuf::showmanyc

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< cpp‎ | io‎ | basic filebuf
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protected:
virtual std::streamsize showmanyc()

If implemented, returns the number of characters left to read from the file.

Contents

[edit] Parameters

(none)

[edit] Return value

The number of characters available for reading from the file, or -1 if the end of file was reached.

[edit] Notes

This function is optional. If not implemented, this function returns 0 (since the base class version std::basic_streambuf::showmanyc gets called)

Whether implemented or not, this function is normally called by std::basic_streambuf::in_avail if the get area is empty.

[edit] Example

implementation test to see if showmanyc() is implemented for filebuf

#include <fstream>
#include <iostream>
 
struct mybuf : std::filebuf
{
     using std::filebuf::showmanyc;
};
 
int main()
{
    mybuf fin;
    fin.open("test.in", std::ios_base::in);
    std::cout << "showmanyc() returns " << fin.showmanyc() << '\n';
}

Output:

showmanyc() returns 6626

[edit] See also

obtains the number of characters immediately available in the get area
(public member function of std::basic_streambuf) [edit]
extracts already available blocks of characters
(public member function of std::basic_istream) [edit]