Added thirdparty: boost library

thirdparty/include/boost/histogram/detail/counting_streambuf.hpp

@@ -0,0 +1,77 @@
+// Copyright 2019 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_HISTOGRAM_DETAIL_COUNTING_STREAMBUF_HPP
+#define BOOST_HISTOGRAM_DETAIL_COUNTING_STREAMBUF_HPP
+
+#include <boost/core/exchange.hpp>
+#include <ostream>
+#include <streambuf>
+
+namespace boost {
+namespace histogram {
+namespace detail {
+
+// detect how many characters will be printed by formatted output
+template <class CharT, class Traits = std::char_traits<CharT>>
+struct counting_streambuf : std::basic_streambuf<CharT, Traits> {
+  using base_t = std::basic_streambuf<CharT, Traits>;
+  using typename base_t::char_type;
+  using typename base_t::int_type;
+
+  std::streamsize* p_count;
+
+  counting_streambuf(std::streamsize& c) : p_count(&c) {}
+
+  std::streamsize xsputn(const char_type* /* s */, std::streamsize n) override {
+    *p_count += n;
+    return n;
+  }
+
+  int_type overflow(int_type ch) override {
+    ++*p_count;
+    return ch;
+  }
+};
+
+template <class C, class T>
+struct count_guard {
+  using bos = std::basic_ostream<C, T>;
+  using bsb = std::basic_streambuf<C, T>;
+
+  counting_streambuf<C, T> csb;
+  bos* p_os;
+  bsb* p_rdbuf;
+
+  count_guard(bos& os, std::streamsize& s) : csb(s), p_os(&os), p_rdbuf(os.rdbuf(&csb)) {}
+
+  count_guard(count_guard&& o)
+      : csb(o.csb), p_os(boost::exchange(o.p_os, nullptr)), p_rdbuf(o.p_rdbuf) {}
+
+  count_guard& operator=(count_guard&& o) {
+    if (this != &o) {
+      csb = std::move(o.csb);
+      p_os = boost::exchange(o.p_os, nullptr);
+      p_rdbuf = o.p_rdbuf;
+    }
+    return *this;
+  }
+
+  ~count_guard() {
+    if (p_os) p_os->rdbuf(p_rdbuf);
+  }
+};
+
+template <class C, class T>
+count_guard<C, T> make_count_guard(std::basic_ostream<C, T>& os, std::streamsize& s) {
+  return {os, s};
+}
+
+} // namespace detail
+} // namespace histogram
+} // namespace boost
+
+#endif