lumiera_/src/steam/asset/db.hpp

/*
  DB.hpp  -  registry holding known Asset instances.

   Copyright (C)
     2008,            Hermann Vosseler <Ichthyostega@web.de>

  **Lumiera** is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version. See the file COPYING for further details.

*/


/** @file db.hpp
 ** Implementation of the _Asset database_.
 ** Simplistic hash based lookup-table.
 ** @internal implementation details of the AssetManager
 */


#ifndef ASSET_DB_H
#define ASSET_DB_H


#include "lib/sync.hpp"
#include "lib/error.hpp"
#include "steam/asset.hpp"
#include "lib/depend-inject.hpp"

#include <memory>
#include <unordered_map>
#include <boost/utility.hpp>


namespace steam {
namespace asset {
  
  using std::static_pointer_cast;
  using std::dynamic_pointer_cast;
  
  using lib::Sync;
  using lib::RecursiveLock_NoWait;
  
    
  /* ===== hash implementations ===== */
  
  size_t 
  hash_value (Asset::Ident const& idi)
  {
    size_t hash = 0;
    boost::hash_combine(hash, idi.org);
    boost::hash_combine(hash, idi.name);
    boost::hash_combine(hash, idi.category);
    return hash;
  }
  
  size_t
  hash_value (Asset const& asset)
  {
    return asset.getID();
  }
  
  
  /**
   * trivial hash functor
   * returns any hash value unmodified.
   * For building a hashtable with keys
   * already containing valid hash values.
   */
  struct IdentityHash
    {
      size_t 
      operator() (size_t val)  const { return val; }
    };
  
  typedef std::unordered_map<size_t, PAsset, IdentityHash> IdHashtable;
  
  
  
  
  /**
   * Implementation of the registry holding all Asset 
   * instances known to the Asset Manager subsystem. 
   * As of 8/2007 implemented by a hashtable.
   */
  class DB 
    : util::NonCopyable
    , public Sync<RecursiveLock_NoWait>
    {
      IdHashtable table;
      
      DB()
        : table()
        { }
      
     ~DB()
        {
         clear();
        }
      
      friend class lib::DependencyFactory<DB>;
      
      
    public:
      template<class KIND>
      lib::P<KIND> 
      get (ID<KIND> hash)  const
        {
          return dynamic_pointer_cast<KIND,Asset> (find (hash));
        }
      
      template<class KIND>
      void
      put (ID<KIND> hash, lib::P<KIND>& ptr)
        {
          table[hash] = static_pointer_cast (ptr);
        }
      
      void
      put (ID<Asset> hash, PAsset& ptr)
        {
          table[hash] = ptr;
        }
      
      bool
      del (ID<Asset> hash)
        {
          return table.erase (hash); 
        }
      
      /** removes all registered assets and does something similar 
       *  to Asset::unlink() on each to break cyclic dependencies
       *  (we can't use the real unlink()-function, because this 
       *  will propagate, including calls to the AssetManager.
       *  As the destructor of DB needs to call clear(), this
       *  could result in segfaults. This doesn't seem to be
       *  a problem, though, because we register and process
       *  \e all assets and the net effect is just breaking
       *  any cyclic dependencies)
       * @note EX_FREE 
       */ 
      void
      clear ()
        try
          {
            IdHashtable::iterator i = table.begin(); 
            IdHashtable::iterator e = table.end(); 
            for ( ; i!=e ; ++i )
              i->second->dependants.clear();
            
            table.clear();
          }
        ERROR_LOG_AND_IGNORE (progress, "cleaning the Asset registry")
      
      
      /** intended for diagnostics */
      void 
      asList (list<PcAsset>& output)  const  
        { 
          IdHashtable::const_iterator i = table.begin(); 
          IdHashtable::const_iterator e = table.end(); 
          for ( ; i!=e ; ++i )  
            output.push_back (i->second);
        }
      
      
    private:
      const PAsset &
      find (size_t hash)  const
        {
          static const PAsset NULLP;
          IdHashtable::const_iterator i = table.find (hash);
          if (i == table.end())
            return NULLP;  // empty ptr signalling "not found"
          else
            return i->second;
        }
    };
  
    
}} // namespace steam::asset
#endif