xapian-core/include/xapian/derefwrapper.h

   1 /** @file
   2  *  @brief Class for wrapping type returned by an input_iterator.
   3  */
   4 /* Copyright (C) 2004,2008,2009,2013,2014 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  19  * USA
  20  */
  21
  22 #ifndef XAPIAN_INCLUDED_DEREFWRAPPER_H
  23 #define XAPIAN_INCLUDED_DEREFWRAPPER_H
  24
  25 #if !defined XAPIAN_IN_XAPIAN_H && !defined XAPIAN_LIB_BUILD
  26 # error Never use <xapian/derefwraper.h> directly; include <xapian.h> instead.
  27 #endif
  28
  29 namespace Xapian {
  30
  31 /** @private @internal Class which returns a value when dereferenced with
  32  *  operator*.
  33  *
  34  *  We need this wrapper class to implement input_iterator semantics for the
  35  *  postfix operator++ methods of some of our iterator classes.
  36  */
  37 template<typename T>
  38 class DerefWrapper_ {
  39     /// Don't allow assignment.
  40 #if __cplusplus >= 201103L
  41     // Avoid warnings with newer clang.
  42     void operator=(const DerefWrapper_&) = delete;
  43 #else
  44     void operator=(const DerefWrapper_&);
  45 #endif
  46
  47     /// The value.
  48     T res;
  49
  50   public:
  51 #if __cplusplus >= 201103L
  52     /// Default copy constructor.
  53     DerefWrapper_(const DerefWrapper_&) = default;
  54 #endif
  55
  56     explicit DerefWrapper_(const T &res_) : res(res_) { }
  57     const T & operator*() const { return res; }
  58 };
  59
  60 }
  61
  62 #endif // XAPIAN_INCLUDED_DEREFWRAPPER_H