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/* Copyright (C) 2010 Wildfire Games.
* This file is part of 0 A.D.
*
* 0 A.D. 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.
*
* 0 A.D. is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef INCLUDED_SIM2_ENTITY
#define INCLUDED_SIM2_ENTITY
// (can't call it INCLUDED_ENTITY because that conflicts with simulation/Entity.h)
#include "lib/types.h"
class IComponent;
/**
* Entity ID type.
* ID numbers are never reused within a simulation run.
*/
typedef u32 entity_id_t;
/**
* Invalid entity ID. Used as an error return value by some functions.
* No valid entity will have this ID.
*/
const entity_id_t INVALID_ENTITY = 0;
/**
* Entity ID for singleton 'system' components.
* Use with QueryInterface to get the component instance.
* (This allows those systems to make convenient use of the common infrastructure
* for message-passing, scripting, serialisation, etc.)
*/
const entity_id_t SYSTEM_ENTITY = 1;
// Entities are split into two kinds:
// "Normal" (for most entities)
// "Local" (for entities that only exist on the local machine, aren't synchronised across the network,
// aren't retained in saved games, etc)
// The distinction is encoded in the entity ID, so that they're easily distinguished.
//
// We want all entity_id_ts to fit in jsval ints, i.e. 1-2^30 .. 2^30-1 (inclusive)
// We want them to be unsigned ints (actually it shouldn't matter but unsigned seems simpler)
// We want 1 tag bit
// So we have 1 JS-reserved bit, 1 unused sign bit, 1 local tag bit, 29 counter bits
// (0.5B entities should be plenty)
#define ENTITY_TAGMASK (1 << 29)
#define ENTITY_IS_NORMAL(id) (((id) & ENTITY_TAGMASK) == 0)
#define ENTITY_IS_LOCAL(id) (((id) & ENTITY_TAGMASK) == ENTITY_TAGMASK)
const entity_id_t FIRST_LOCAL_ENTITY = ENTITY_TAGMASK;
struct SEntityComponentCache
{
size_t numInterfaces;
IComponent* interfaces[1]; /* variable length array */
};
/**
* Object wrapping an entity_id_t, with a SEntityComponentCache to support fast
* QueryInterface() / CmpPtr<>() calls.
*
* Components can use IComponent::GetSystemEntity() and IComponent::GetEntityHandle()
* to get handles to SYSTEM_ENTITY and themselves, and then pass those handles around.
*
* Be careful not to store a CEntityHandle for longer than the lifetime of the entity
* (listen to MT_Destroy messages to know when to release it) - otherwise the handle will
* contain a dangling pointer and will probably crash.
*/
class CEntityHandle
{
public:
CEntityHandle() : m_Id(0), m_ComponentCache(NULL) { }
CEntityHandle(entity_id_t id, SEntityComponentCache* componentCache)
: m_Id(id), m_ComponentCache(componentCache)
{
}
entity_id_t GetId() const { return m_Id; }
SEntityComponentCache* GetComponentCache() const { return m_ComponentCache; }
private:
entity_id_t m_Id;
SEntityComponentCache* m_ComponentCache;
};
#endif // INCLUDED_SIM2_ENTITY
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