gistfile1.cpp

// Used to save, modify and restore stream state formatting parameters.
template<class Char, class Trait>
struct stream_state {
    using fmtflags = std::ios_base::fmtflags;

    std::streamsize width;
    std::streamsize precision;
    Char fill;
    fmtflags flags;

    stream_state(const std::basic_ostream<Char, Trait>& s)
    : width(s.width()), precision(s.precision()), fill(s.fill()), flags(s.flags()) { }

    static stream_state default_for_stream(const std::basic_ostream<Char, Trait>& s) {
        stream_state default_state;
        default_state.width = 0;
        default_state.precision = 6;
        default_state.fill = s.widen(' ');
        default_state.flags = s.dec | s.skipws;
        return default_state;
    }

    fmtflags setf(fmtflags new_flags) {
        auto old = flags;
        flags |= new_flags;
        return old;
    }

    fmtflags setf(fmtflags new_flags, fmtflags mask) {
        auto old = flags;
        flags = (flags & ~mask) | (new_flags & mask);
        return old;
    }

    void apply(std::basic_ostream<Char, Trait>& s) {
        s.width(width);
        s.precision(precision);
        s.fill(fill);
        s.flags(flags);
    }

private:
    stream_state() = default;
};