zypp/Callback.h

   1 /*---------------------------------------------------------------------\
   2 |                          ____ _   __ __ ___                          |
   3 |                         |__  / \ / / . \ . \                         |
   4 |                           / / \ V /|  _/  _/                         |
   5 |                          / /__ | | | | | |                           |
   6 |                         /_____||_| |_| |_|                           |
   7 |                                                                      |
   8 \---------------------------------------------------------------------*/
   9 /** \file zypp/Callback.h
  10  *
  11 */
  12 #ifndef ZYPP_CALLBACK_H
  13 #define ZYPP_CALLBACK_H
  14
  15 #include "zypp/base/NonCopyable.h"
  16 #include "zypp/UserData.h"
  17
  18 ///////////////////////////////////////////////////////////////////
  19 namespace zypp
  20 { /////////////////////////////////////////////////////////////////
  21
  22   /** \todo Eliminate this! */
  23   namespace HACK {
  24     class Callback
  25     {
  26     };
  27   } // namespace HACK
  28
  29   ///////////////////////////////////////////////////////////////////
  30   /** Callbacks light.
  31    *
  32    * \par The task report structure (SENDER SIDE).
  33    *
  34    * A default constructible struct derived from callback::ReportBase.
  35    * It \b must \b not conatin any data, just virtual methods.
  36    *
  37    * These are the functions the sender invokes, and which will be forwarded
  38    * to some receiver. If no receiver is present, the defined default
  39    * implementations are invoked.
  40    *
  41    * For methods returning non-void, define a reasonable return value,
  42    * because this is what you get back in case no receiver is listening.
  43    *
  44    * That way the sending side does not need to know whether some receiver
  45    * is listening. And it enables the receiver to return a reasonable value,
  46    * in case he's got no idea, what else to return.
  47    *
  48    * \code
  49    *   struct Foo : public callback::ReportBase
  50    *   {
  51    *     virtual void ping( int i )
  52    *     {}
  53    *     virtual int pong()
  54    *     { return -1; }
  55    *
  56    *   };
  57    * \endcode
  58    *
  59    * \par Sending a Task report (SENDER SIDE).
  60    *
  61    * Simply create a callback::SendReport<_Report>, where _Report
  62    * is your task report structure. Invoke the callback functions
  63    * as needed. That's it.
  64    *
  65    * \note Even creation and destruction of a callback::SendReport
  66    * are indicated to a receiver. So even in case of an Exception,
  67    * the receiver is able to recognize, that the task ended.
  68    * So don't create it without need.
  69    *
  70    * \code
  71    * {
  72    *   callback::SendReport<Foo> report;
  73    *   report->ping( 13 );
  74    *   int response = report->pong();
  75    * }
  76    * \endcode
  77    *
  78    * \par Receiving Task reports (RECEIVER SIDE).
  79    *
  80    * To receive task reports of type \c Foo the recipient class
  81    * derives from callback::ReceiveReport\<Foo\>. callback::ReceiveReport
  82    * inherits \c Foo and provides two additional virtual methods:
  83    *
  84    * \code
  85    *   virtual void reportbegin() {}
  86    *   virtual void reportend() {}
  87    * \endcode
  88    *
  89    * These two are automatically invoked, whenever the sender
  90    * creates a callback::SendReport instance, and when it gets
  91    * destructed. So even if the sending task is aborted without
  92    * sending an explicit notification, the reciever may notice it,
  93    * by overloading \c reportend.
  94    *
  95    * Overload the methods you're interested in.
  96    *
  97    * \note In case you must return some value and don't know which,
  98    * return the task structures default. The author of the task
  99    * structure had to provide this value, so it's probabely better
 100    * than anything you \e invent.
 101    * \code
 102    *   int somefunction()
 103    *   {
 104    *     ...// don't know what to return?
 105    *     return Foo::somefunction();
 106    *   }
 107    * \endcode
 108    *
 109    * \par Connecting the Receiver
 110    *
 111    * For this callback::ReceiveReport provides 4 methods:
 112    * \code
 113    *  void connect();
 114    *  void disconnect();
 115    *  bool connected() const;
 116    *  ReceiveReport * whoIsConnected() const;
 117    * \endcode
 118    *
 119    * \li \c connect Connect this ReceiveReport (in case some other
 120    * ReceiveReport is connected, it get disconnected. Remember its
 121    * a Callback light).
 122    * \li \c disconnect Disconnect this ReceiveReport in case it is
 123    * connected. If not connected nothing happens.
 124    * \li \c connected Test whether this ReceiveReport is currently
 125    * connected.
 126    * \li \c whoIsConnected Return a 'ReceiveReport*' to the currently
 127    * connected ReceiveReport, or \c NULL if none is connected.
 128    *
 129    * \par Passing Userdata via Callbacks
 130    *
 131    * For typesafe passing of user data via callbacks \see \ref UserData.
 132    *
 133    */
 134   namespace callback
 135   { /////////////////////////////////////////////////////////////////
 136
 137     /**  */
 138     struct ReportBase
 139     {
 140       typedef callback::UserData UserData;
 141       virtual ~ReportBase()
 142       {}
 143     };
 144
 145     /**  */
 146     template<class _Report>
 147       class DistributeReport;
 148
 149     /**  */
 150     template<class _Report>
 151       struct ReceiveReport : public _Report
 152       {
 153         typedef _Report                   ReportType;
 154         typedef typename ReportType::UserData UserData;
 155         typedef ReceiveReport<_Report>    Receiver;
 156         typedef DistributeReport<_Report> Distributor;
 157
 158         virtual ~ReceiveReport()
 159         { disconnect(); }
 160
 161         ReceiveReport * whoIsConnected() const
 162         { return Distributor::instance().getReceiver(); }
 163
 164         bool connected() const
 165         { return whoIsConnected() == this; }
 166
 167         void connect()
 168         { Distributor::instance().setReceiver( *this ); }
 169
 170         void disconnect()
 171         { Distributor::instance().unsetReceiver( *this ); }
 172
 173         virtual void reportbegin()
 174         {}
 175         virtual void reportend()
 176         {}
 177       };
 178
 179     /**  */
 180     template<class _Report>
 181       struct DistributeReport
 182       {
 183        public:
 184         typedef _Report                   ReportType;
 185         typedef typename ReportType::UserData UserData;
 186         typedef ReceiveReport<_Report>    Receiver;
 187         typedef DistributeReport<_Report> Distributor;
 188
 189          static DistributeReport & instance()
 190          {
 191            static DistributeReport _self;
 192            return _self;
 193          }
 194
 195          Receiver * getReceiver() const
 196          { return _receiver == &_noReceiver ? 0 : _receiver; }
 197
 198          void setReceiver( Receiver & rec_r )
 199          { _receiver = &rec_r; }
 200
 201          void unsetReceiver( Receiver & rec_r )
 202          { if ( _receiver == &rec_r ) noReceiver(); }
 203
 204          void noReceiver()
 205          { _receiver = &_noReceiver; }
 206
 207       public:
 208          Receiver * operator->()
 209          { return _receiver; }
 210
 211       private:
 212         DistributeReport()
 213         : _receiver( &_noReceiver )
 214         {}
 215         Receiver _noReceiver;
 216         Receiver * _receiver;
 217       };
 218
 219     /**  */
 220     template<class _Report>
 221       struct SendReport : private zypp::base::NonCopyable
 222       {
 223         typedef _Report                   ReportType;
 224         typedef typename ReportType::UserData UserData;
 225         typedef ReceiveReport<_Report>    Receiver;
 226         typedef DistributeReport<_Report> Distributor;
 227
 228         SendReport()
 229         { Distributor::instance()->reportbegin(); }
 230
 231         ~SendReport()
 232         { Distributor::instance()->reportend(); }
 233
 234         static Receiver * whoIsConnected()
 235         { return Distributor::instance().getReceiver(); }
 236
 237         static bool connected()
 238         { return whoIsConnected(); }
 239
 240         Distributor & operator->()
 241         { return Distributor::instance(); }
 242       };
 243
 244     /** Temporarily connect a ReceiveReport then restore the previous one.
 245      *
 246      * Pass the ReceiveReport you want to connect temporarily
 247      * to the ctor. The ReceiveReport is connected, a previously
 248      * connected ReceiveReport is remembered and re-connected in
 249      * the dtor.
 250      * Use the default ctpr to temporarily disconnect any connected report.
 251      * \code
 252      *  struct FooReceive : public callback::ReceiveReport<Foo>
 253      *  {..};
 254      *  struct FooReceive2 : public callback::ReceiveReport<Foo>
 255      *  {..};
 256      *
 257      *  FooReceive  r;
 258      *  FooReceive2 r2;
 259      *
 260      *  r.connect();
 261      *  ... // r receiving the report
 262      *  {
 263      *    callback::TempConnect<Foo> temp( r2 );
 264      *    ...// r2 receiving the report
 265      *  }
 266      *  ...// r receiving the report
 267      * \endcode
 268     */
 269     template<class _Report>
 270       struct TempConnect
 271       {
 272         typedef _Report                   ReportType;
 273         typedef typename ReportType::UserData UserData;
 274         typedef ReceiveReport<_Report>    Receiver;
 275         typedef DistributeReport<_Report> Distributor;
 276
 277         TempConnect()
 278         : _oldRec( Distributor::instance().getReceiver() )
 279         {
 280           Distributor::instance().noReceiver();
 281         }
 282
 283         TempConnect( Receiver & rec_r )
 284         : _oldRec( Distributor::instance().getReceiver() )
 285         {
 286           rec_r.connect();
 287         }
 288
 289         ~TempConnect()
 290         {
 291           if ( _oldRec )
 292             Distributor::instance().setReceiver( *_oldRec );
 293           else
 294             Distributor::instance().noReceiver();
 295         }
 296       private:
 297         Receiver * _oldRec;
 298       };
 299
 300     /////////////////////////////////////////////////////////////////
 301   } // namespace callback
 302   ///////////////////////////////////////////////////////////////////
 303   /////////////////////////////////////////////////////////////////
 304 } // namespace zypp
 305 ///////////////////////////////////////////////////////////////////
 306 #endif // ZYPP_CALLBACK_H