...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Determine the number of bytes available for reading.
std::size_t available() const;
This function is used to determine the number of bytes that may be read without blocking.
The number of bytes that may be read without blocking, or 0 if an error occurs.
Thrown on failure.