Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is an older version of Boost and was released in 2013. The current version is 1.91.0.

basic_streambuf::max_size

Return the maximum size of the buffer.

std::size_t max_size() const;