Line data    Source code

       1             : /* Copyright (C) 2017 Wildfire Games.
       2             :  * This file is part of 0 A.D.
       3             :  *
       4             :  * 0 A.D. is free software: you can redistribute it and/or modify
       5             :  * it under the terms of the GNU General Public License as published by
       6             :  * the Free Software Foundation, either version 2 of the License, or
       7             :  * (at your option) any later version.
       8             :  *
       9             :  * 0 A.D. is distributed in the hope that it will be useful,
      10             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      11             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12             :  * GNU General Public License for more details.
      13             :  *
      14             :  * You should have received a copy of the GNU General Public License
      15             :  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
      16             :  */
      17             : 
      18             : #ifndef INCLUDED_ENTITY
      19             : #define INCLUDED_ENTITY
      20             : 
      21             : #include "lib/types.h"
      22             : 
      23             : class IComponent;
      24             : 
      25             : /**
      26             :  * Entity ID type.
      27             :  * ID numbers are never reused within a simulation run.
      28             :  */
      29             : typedef u32 entity_id_t;
      30             : 
      31             : /**
      32             :  * Invalid entity ID. Used as an error return value by some functions.
      33             :  * No valid entity will have this ID.
      34             :  */
      35             : const entity_id_t INVALID_ENTITY = 0;
      36             : 
      37             : /**
      38             :  * Entity ID for singleton 'system' components.
      39             :  * Use with QueryInterface to get the component instance.
      40             :  * (This allows those systems to make convenient use of the common infrastructure
      41             :  * for message-passing, scripting, serialisation, etc.)
      42             :  */
      43             : const entity_id_t SYSTEM_ENTITY = 1;
      44             : 
      45             : // Entities are split into two kinds:
      46             : // "Normal" (for most entities)
      47             : // "Local" (for entities that only exist on the local machine, aren't synchronised across the network,
      48             : // aren't retained in saved games, etc)
      49             : // The distinction is encoded in the entity ID, so that they're easily distinguished.
      50             : //
      51             : // We want all entity_id_ts to fit in an integer JS::Value, i.e. 1-2^30 .. 2^30-1 (inclusive)
      52             : // We want them to be unsigned ints (actually it shouldn't matter but unsigned seems simpler)
      53             : // We want 1 tag bit
      54             : // So we have 1 JS-reserved bit, 1 unused sign bit, 1 local tag bit, 29 counter bits
      55             : // (0.5B entities should be plenty)
      56             : 
      57             : #define ENTITY_TAGMASK (1 << 29)
      58             : #define ENTITY_IS_NORMAL(id) (((id) & ENTITY_TAGMASK) == 0)
      59             : #define ENTITY_IS_LOCAL(id) (((id) & ENTITY_TAGMASK) == ENTITY_TAGMASK)
      60             : const entity_id_t FIRST_LOCAL_ENTITY = ENTITY_TAGMASK;
      61             : 
      62             : struct SEntityComponentCache
      63             : {
      64             :     size_t numInterfaces;
      65             :     IComponent* interfaces[1]; /* variable length array */
      66             : };
      67             : 
      68             : /**
      69             :  * Object wrapping an entity_id_t, with a SEntityComponentCache to support fast
      70             :  * QueryInterface() / CmpPtr<>() calls.
      71             :  *
      72             :  * Components can use IComponent::GetSystemEntity() and IComponent::GetEntityHandle()
      73             :  * to get handles to SYSTEM_ENTITY and themselves, and then pass those handles around.
      74             :  *
      75             :  * Be careful not to store a CEntityHandle for longer than the lifetime of the entity
      76             :  * (listen to MT_Destroy messages to know when to release it) - otherwise the handle will
      77             :  * contain a dangling pointer and will probably crash.
      78             :  */
      79             : class CEntityHandle
      80             : {
      81             : public:
      82         742 :     CEntityHandle() : m_Id(INVALID_ENTITY), m_ComponentCache(NULL) { }
      83         129 :     CEntityHandle(entity_id_t id, SEntityComponentCache* componentCache)
      84         129 :         : m_Id(id), m_ComponentCache(componentCache)
      85             :     {
      86         129 :     }
      87             : 
      88         802 :     entity_id_t GetId() const { return m_Id; }
      89         256 :     SEntityComponentCache* GetComponentCache() const { return m_ComponentCache; }
      90             : 
      91             : private:
      92             :     entity_id_t m_Id;
      93             :     SEntityComponentCache* m_ComponentCache;
      94             : };
      95             : 
      96             : #endif // INCLUDED_ENTITY