// Copyright 2019 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_HISTOGRAM_DETAIL_COUNTING_STREAMBUF_HPP
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#define BOOST_HISTOGRAM_DETAIL_COUNTING_STREAMBUF_HPP
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#include <boost/core/exchange.hpp>
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#include <ostream>
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#include <streambuf>
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namespace boost {
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namespace histogram {
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namespace detail {
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// detect how many characters will be printed by formatted output
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template <class CharT, class Traits = std::char_traits<CharT>>
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struct counting_streambuf : std::basic_streambuf<CharT, Traits> {
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using base_t = std::basic_streambuf<CharT, Traits>;
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using typename base_t::char_type;
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using typename base_t::int_type;
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std::streamsize* p_count;
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counting_streambuf(std::streamsize& c) : p_count(&c) {}
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std::streamsize xsputn(const char_type* /* s */, std::streamsize n) override {
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*p_count += n;
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return n;
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}
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int_type overflow(int_type ch) override {
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++*p_count;
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return ch;
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}
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};
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template <class C, class T>
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struct count_guard {
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using bos = std::basic_ostream<C, T>;
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using bsb = std::basic_streambuf<C, T>;
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counting_streambuf<C, T> csb;
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bos* p_os;
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bsb* p_rdbuf;
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count_guard(bos& os, std::streamsize& s) : csb(s), p_os(&os), p_rdbuf(os.rdbuf(&csb)) {}
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count_guard(count_guard&& o)
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: csb(o.csb), p_os(boost::exchange(o.p_os, nullptr)), p_rdbuf(o.p_rdbuf) {}
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count_guard& operator=(count_guard&& o) {
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if (this != &o) {
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csb = std::move(o.csb);
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p_os = boost::exchange(o.p_os, nullptr);
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p_rdbuf = o.p_rdbuf;
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}
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return *this;
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}
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~count_guard() {
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if (p_os) p_os->rdbuf(p_rdbuf);
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}
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};
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template <class C, class T>
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count_guard<C, T> make_count_guard(std::basic_ostream<C, T>& os, std::streamsize& s) {
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return {os, s};
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}
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} // namespace detail
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} // namespace histogram
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} // namespace boost
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#endif
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