include/KDIS/DataTypes/FactoryDecoder.hpp

   1 /*********************************************************************
   2 Copyright 2013 Karl Jones
   3 All rights reserved.
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   5 Redistribution and use in source and binary forms, with or without
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  27 http://p.sf.net/kdis/UserGuide
  28 *********************************************************************/
  29
  30 /********************************************************************
  31     class:      FactoryDecoder
  32     created:    15/03/2011
  33     author:     Karl Jones
  34
  35     purpose:    This is an Abstract class that can be used to create your own custom decoders for some of the more extendable data types.
  36                     For example the VariableDatum can support many different variations including your own custom ones, using a FactoryDecoder
  37                                 you can add your custom classes into KDIS.
  38
  39                                 If you want KDIS to decode your custom classes simply call the RegisterFactoryDecoder function of the relevant class.
  40
  41                                 Example:
  42
  43                                 // You could create a seperate decoder class just for the decoding task, here I use multiple inheritance...
  44                 class MyCustomVariableDatumClass : public variableDatum, public FactoryDecoder<VariableDatum,
  45                                 {
  46                                         ...
  47                                         variableDatum * FactoryDecode( int TypeEnum, KDataStream & stream )
  48                                         {
  49                                                 // Do you custom decoding in here.
  50                                         }
  51                                         ...
  52                                 }
  53
  54
  55                                 // Now when your application starts up register you new FactoryDecoderClass like so:
  56
  57                                 // 123 could be your type enum value.
  58                                 VariableDatum::RegisterFactoryDecoder( 123, new MyCustomVariableDatumClass );
  59
  60                                 // Now when ever a VariableDatum with type 123 is received it will be decoded with your custom class.
  61
  62                                 // When you no longer need the custom decoders you should call 'ClearFactoryDecoders', which can also free up the memory for you.
  63
  64 *********************************************************************/
  65
  66 #pragma once
  67
  68 #include "./../KDataStream.h"
  69 #include "./../Extras/KRef_Ptr.h"
  70 #include <map>
  71
  72 namespace KDIS {
  73 namespace DATA_TYPE {
  74
  75 template<class DecoderBaseTyp>
  76 class FactoryDecoder
  77 {
  78 public:
  79
  80         FactoryDecoder(){};
  81
  82         virtual ~FactoryDecoder(){};
  83
  84     //************************************
  85     // FullName:    KDIS::DATA_TYPE::FactoryDecoder::FactoryDecode
  86     // Description: This is where you decode the stream into your custom class,
  87         //              the enum value is also passed back so you can perform decoding
  88         //              of multiple types within a single FactoryDecoder.
  89     // Parameter:   KINT32 EnumVal
  90         // Parameter:   KDataStream & stream
  91     //************************************
  92         virtual DecoderBaseTyp * FactoryDecode( KINT32 EnumVal, KDataStream & stream ) = 0;
  93 };
  94
  95 /********************************************************************
  96     class:      FactoryDecoderUser
  97     created:    17/03/2011
  98     author:     Karl Jones
  99
 100     purpose:    This class adds support for custom decoding.
 101 *********************************************************************/
 102
 103 template<class DecoderBaseTyp>
 104 class FactoryDecoderUser
 105 {
 106 public:
 107
 108         typedef KDIS::UTILS::KRef_Ptr< FactoryDecoder<DecoderBaseTyp> > FacDecPtr;
 109
 110 protected:
 111
 112         static std::map<KINT32, FacDecPtr> m_mDecoders;
 113
 114 public:
 115
 116     //************************************
 117     // FullName:    KDIS::DATA_TYPE::FactoryDecoderUser::RegisterFactoryDecoder
 118     // Description: Registers a decoder for a custom class.
 119         //              EnumVal is the relevant enum value representing the new class.
 120         //              E.G DatumID enum for VariableDatum.
 121         //              Exception thrown if a decoder already exists for this enum.
 122     // Parameter:   KINT32 EnumVal
 123         // Parameter:   FacDecPtr Decoder
 124     //************************************
 125         static void RegisterFactoryDecoder( KINT32 EnumVal, FacDecPtr Decoder )
 126         {
 127                 if( m_mDecoders.find( EnumVal ) != m_mDecoders.end() )
 128                 {
 129                         KStringStream ss;
 130                         ss << "A decoder already exists for this enum: " << EnumVal;
 131                         throw KException( __FUNCTION__, INVALID_OPERATION, ss.str() );
 132                 }
 133
 134                 // Register the new decoder.
 135                 m_mDecoders[EnumVal] = Decoder;
 136         }
 137
 138     //************************************
 139     // FullName:    KDIS::DATA_TYPE::FactoryDecoderUser::FactoryDecode
 140     // Description: Attempts to find a decoder for the enum, returns NULL if none are found.
 141         //              Note: An exception may be thrown by a decoder.
 142     // Parameter:   KINT32 EnumVal
 143         // Parameter:   KDataStream & stream
 144     //************************************
 145         static DecoderBaseTyp * FactoryDecode( KINT32 EnumVal, KDataStream & stream )
 146         {
 147                 // Try to find a decoder
 148                 typename std::map<KINT32, FacDecPtr>::iterator itr = m_mDecoders.find( EnumVal );
 149                 if( itr != m_mDecoders.end() )
 150                 {
 151                         return itr->second->FactoryDecode( EnumVal, stream );
 152                 }
 153
 154                 // No decoders found so return NULL.
 155                 return 0;
 156         }
 157
 158     //************************************
 159     // FullName:    KDIS::DATA_TYPE::FactoryDecoderUser::FactoryDecode
 160     // Description: Removes all factory decoders.
 161     //************************************
 162         static void ClearFactoryDecoders()
 163         {
 164                 m_mDecoders.clear();
 165         }
 166 };
 167
 168 // Init static map variable.
 169 template<class DecoderBaseTyp>
 170 std::map<KINT32, KDIS::UTILS::KRef_Ptr< FactoryDecoder<DecoderBaseTyp> > > FactoryDecoderUser<DecoderBaseTyp>::m_mDecoders = std::map<KINT32, KDIS::UTILS::KRef_Ptr< FactoryDecoder<DecoderBaseTyp> > >();
 171
 172 } // END namespace DATA_TYPES
 173 } // END namespace KDIS
 174