Convert Markus' IO state saver class to use the interface from

<boost/io/ios_state.hpp>.

While at it, save precision and width in addition to the flags and make sure
it can be used by multiple compilation units.

[[Imported from SVN: r6025]]

dune/common/Makefile.am

@@ -7,6 +7,7 @@ noinst_LTLIBRARIES = libcommon.la
 
 libcommon_la_SOURCES =				\
 	configparser.cc				\
+	ios_state.cc				\
 	stdstreams.cc
 
 commonincludedir = $(includedir)/dune/common
@@ -40,6 +41,7 @@ commoninclude_HEADERS = 			\
 	geometrytype.hh				\
 	gmpfield.hh				\
 	interfaces.hh				\
+	ios_state.hh				\
 	iteratorfacades.hh			\
 	lcm.hh					\
 	lru.hh					\

dune/common/ios_state.cc

+// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+// vi: set et ts=4 sw=2 sts=2:
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <dune/common/ios_state.hh>
+
+namespace Dune {
+
+  //////////////////////////////////////////////////////////////////////
+  //
+  //  class ios_base_all_saver
+  //
+
+  ios_base_all_saver::ios_base_all_saver(state_type& ios_)
+    : ios(ios_), oldflags(ios.flags()), oldprec(ios.precision()),
+      oldwidth(ios.width())
+  {}
+
+  ios_base_all_saver::~ios_base_all_saver()
+  {
+    restore();
+  }
+
+  void ios_base_all_saver::restore()
+  {
+    ios.flags(oldflags);
+    ios.precision(oldprec);
+    ios.width(oldwidth);
+  }
+
+}

dune/common/ios_state.hh

+// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+// vi: set et ts=4 sw=2 sts=2:
+#ifndef DUNE_COMMON_IOS_STATE_HH
+#define DUNE_COMMON_IOS_STATE_HH
+
+#include <ios>
+
+namespace Dune {
+  /** @addtogroup Common
+   *
+   * @{
+   */
+  /**
+   * @file
+   * @brief  Utility class for storing and resetting stream attributes.
+   * @author Markus Blatt
+   */
+  /**
+   * @brief Utility class for storing and resetting stream attributes.
+   *
+   * The constructor saves the attributes currently set in the ios_base
+   * object and the destructor restores these attributes again.  The
+   * attributes can also be restores at any time by calling the method
+   * restore().
+   *
+   * The saved attributes are the format flags, precision, and width.
+   *
+   * @note The interface of this class is meant to be drop-in compatible the
+   *       the class of the same name from <boost/io/ios_state.hpp>.
+   */
+  class ios_base_all_saver
+  {
+  public:
+    /** @brief Export type of object we save the state for */
+    typedef std::ios_base state_type;
+
+    /**
+     * @brief Constructor that stores the currently used flags.
+     * @param ios_ The ios_base object whose flags are to be saved and
+     *             restored.  Any stream object should work here.
+     *
+     * @note A reference to the ios_base object is store in this object.  Thus
+     *       the ios_base object must remain valid until the destructor of
+     *       this object has been called.
+     */
+    ios_base_all_saver(state_type& ios_);
+
+    /**
+     * @brief Destructor that restores the flags stored by the constructor.
+     */
+    ~ios_base_all_saver();
+
+    /**
+     * @brief Restore flags now
+     *
+     * The flags will also be restored at destruction time even if this method
+     * was used.
+     */
+    void restore();
+
+  private:
+    /** @brief the ios object to restore the flags to. */
+    state_type& ios;
+    /** @brief The flags used when the constructor was called. */
+    state_type::fmtflags oldflags;
+    /** @brief The precision in use when the constructor was called. */
+    std::streamsize oldprec;
+    /** @brief The width in use when the constructor was called. */
+    std::streamsize oldwidth;
+  };
+
+  /** }@ */
+}
+
+#endif // DUNE_COMMON_IOS_STATE_HH