73ef4ff3
 Hu Chunming
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////
Copyright 2021 Glen Joseph Fernandes
(glenjofe@gmail.com)
Distributed under the Boost Software License, Version 1.0.
(http://www.boost.org/LICENSE_1_0.txt)
////
# Null Streams, <boost/io/nullstream.hpp>
:toc:
:toc-title:
:idprefix:
## Description
The header `<boost/io/nullstream.hpp>` provides the class template
`boost::io::basic_nullbuf` which is a null stream buffer and class template
`boost::io::basic_onullstream` which is a null stream.
## Example
The following program passes a null stream to a function.
```
#include <boost/io/ostream_joiner.hpp>
#include <fstream>
void setup(std::ostream& log);
int main(int argc, char* argv[])
{
if (argc == 2) {
std::ofstream file(argv[1]);
setup(file);
} else {
boost::io::onullstream none;
setup(none);
}
}
```
## Reference
### Header Synopsis
```
namespace boost {
namespace io {
template<class CharT, class Traits = std::char_traits<Char> >
class basic_nullbuf
: public std::basic_streambuf<CharT, Traits> {
protected:
typename Traits::int_type overflow(typename Traits::int_type c) override;
std::streamsize xsputn(const CharT*, std::streamsize n) override;
};
template<class CharT, class Traits = std::char_traits<CharT> >
class basic_onullstream
: public std::basic_ostream<CharT, Traits> {
public:
basic_onullstream();
};
typedef basic_onullstream<char> onullstream;
typedef basic_onullstream<wchar_t> wonullstream;
} // io
} // boost
```
## Acknowledgments
Glen Fernandes implemented `basic_nullbuf` and `basic_onullstream`.
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