std::char_traits<CharT>::to_int_type

From cppreference.com
< cpp‎ | string‎ | char traits
static int_type to_int_type( char_type c );
(until C++11)
static constexpr int_type to_int_type( char_type c ) noexcept;
(since C++11)

Converts a value of char_type to int_type.

Parameters

c - value to convert

Return value

A value equivalent to c.

Complexity

Constant.

Notes

For every valid value of char_type, there must be a unique value of int_type distinct from eof(). For example, a common implementation of char_traits<char>::eof() is return -1, and a corresponding valid implementation of char_traits<char>::to_int_type(c) is return (unsigned char)c.