Added fclose_deleter.

fclose_deleter can be used as a deleter function object for std::FILE
pointers returned by std::fopen.

include/boost/core/fclose_deleter.hpp

@@ -0,0 +1,45 @@
+/*
+ *             Copyright Andrey Semashev 2022.
+ * 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)
+ */
+/*!
+ * \file   fclose_deleter.hpp
+ * \author Andrey Semashev
+ * \date   21.09.2022
+ *
+ * This header contains an \c fclose_deleter implementation. This is a deleter
+ * function object that invokes <tt>std::fclose</tt> on the passed pointer to
+ * a <tt>std::FILE</tt> structure.
+ */
+
+#ifndef BOOST_CORE_FCLOSE_DELETER_HPP
+#define BOOST_CORE_FCLOSE_DELETER_HPP
+
+#include <cstdio>
+#include <boost/config.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#pragma once
+#endif
+
+namespace boost {
+
+//! A function object that closes a file
+struct fclose_deleter
+{
+    //! Function object result type
+    typedef void result_type;
+    /*!
+     * Closes the file handle
+     */
+    void operator() (std::FILE* p) const BOOST_NOEXCEPT
+    {
+        std::fclose(p);
+    }
+};
+
+} // namespace boost
+
+#endif // BOOST_CORE_FCLOSE_DELETER_HPP