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