libbase/GnashFactory.h

   1 // GnashFactory.h   A generic class template
   2 //
   3 //   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Free Software
   4 //   Foundation, Inc
   5 //
   6 // This program is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation; either version 3 of the License, or
   9 // (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  USA
  19 //
  20
  21 #ifndef GNASH_FACTORY_H
  22 #define GNASH_FACTORY_H
  23
  24 #ifdef HAVE_CONFIG_H
  25 # include "gnashconfig.h"
  26 #endif
  27
  28 #include <map>
  29 #include <string>
  30 #include <algorithm>
  31 #include <iterator>
  32 #include <boost/type_traits.hpp>
  33 #include <boost/utility/enable_if.hpp>
  34
  35 #include "dsodefs.h"
  36 #include "GnashAlgorithm.h"
  37
  38 namespace gnash {
  39
  40
  41 /// A generic factory class for registering and retrieving objects by key.
  42 //
  43 /// Note: there is only one GnashFactory for any combination of template
  44 /// arguments. It's not advisable to have more than one factory for any
  45 /// type.
  46 //
  47 /// Note that this relies on static initialization, so do not call get()
  48 /// before or after main().
  49 //
  50 /// @tparam T       The base type to be produced by the factory
  51 /// @tparam Init    An object whose constructor ensures that the elements
  52 ///                 are registered. This helps avoid problems with
  53 ///                 unpredictable static initialization.
  54 /// @tparam Key     The type to be used as a key.
  55 template<typename T, typename Init = void, typename Key = std::string>
  56 class DSOEXPORT GnashFactory
  57 {
  58 public:
  59
  60     typedef T value_type;
  61     typedef Key key_type;
  62
  63     template<typename Derived>
  64     struct RegisterHandler
  65     {
  66         static T* createHandler() {
  67             return new Derived();
  68         }
  69
  70         RegisterHandler(const Key& name) {
  71             GnashFactory::instance().registerHandler(name, createHandler);
  72         }
  73     };
  74
  75     typedef T*(*CreateHandler)();
  76     typedef std::map<std::string, CreateHandler> Handlers;
  77
  78     /// Get the GnashFactory singleton.
  79     static GnashFactory& instance() {
  80         static GnashFactory m;
  81         return m;
  82     }
  83
  84     /// Dump the registered keys to the iterator.
  85     //
  86     /// Only usable with output iterators.
  87     template<typename Iterator>
  88     void listKeys(Iterator i, typename boost::enable_if<boost::is_same<
  89               typename std::iterator_traits<Iterator>::iterator_category,
  90               std::output_iterator_tag> >::type* dummy = 0) {
  91         Init();
  92         static_cast<void>(dummy);
  93         std::transform(_handlers.begin(), _handlers.end(), i,
  94                 FirstElement<typename Handlers::value_type>());
  95
  96     }
  97
  98     /// Return a Handler identified by a name.
  99     //
 100     /// @param name     The name of the handler to return. An empty string
 101     ///                 will return the first available handler. If the
 102     ///                 string is not empty and no match is found, a null
 103     ///                 pointer will be returned.
 104     T* get(const Key& name) {
 105         Init();
 106         if (name.empty()) {
 107             return _handlers.empty() ? 0 : _handlers.begin()->second();
 108         }
 109
 110         typename Handlers::const_iterator it = _handlers.find(name);
 111         if (it == _handlers.end()) return 0;
 112         return it->second();
 113     }
 114
 115     /// Register a Handler with a particular name.
 116     //
 117     /// @param name     The name to register the Handler under. Duplicated
 118     ///                 names will replace previous handlers!
 119     /// @param r        A pointer to a function that will return the
 120     ///                 Handler when called.
 121     void registerHandler(const Key& name, CreateHandler r) {
 122         _handlers[name] = r;
 123     }
 124
 125 private:
 126
 127     GnashFactory() {}
 128
 129     Handlers _handlers;
 130
 131 };
 132
 133 } // namespace gnash
 134
 135 #endif