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 2015. The current version is 1.91.0.

buffer_size (2 of 5 overloads)

Get the number of bytes in a modifiable buffer.

std::size_t buffer_size(
    const mutable_buffers_1 & b);