97 lines
3.2 KiB
C++
97 lines
3.2 KiB
C++
/* Copyright (C) 2015 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef INCLUDED_ENTITY
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#define INCLUDED_ENTITY
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#include "lib/types.h"
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class IComponent;
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/**
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* Entity ID type.
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* ID numbers are never reused within a simulation run.
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*/
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typedef u32 entity_id_t;
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/**
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* Invalid entity ID. Used as an error return value by some functions.
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* No valid entity will have this ID.
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*/
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const entity_id_t INVALID_ENTITY = 0;
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/**
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* Entity ID for singleton 'system' components.
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* Use with QueryInterface to get the component instance.
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* (This allows those systems to make convenient use of the common infrastructure
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* for message-passing, scripting, serialisation, etc.)
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*/
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const entity_id_t SYSTEM_ENTITY = 1;
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// Entities are split into two kinds:
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// "Normal" (for most entities)
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// "Local" (for entities that only exist on the local machine, aren't synchronised across the network,
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// aren't retained in saved games, etc)
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// The distinction is encoded in the entity ID, so that they're easily distinguished.
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//
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// We want all entity_id_ts to fit in jsval ints, i.e. 1-2^30 .. 2^30-1 (inclusive)
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// We want them to be unsigned ints (actually it shouldn't matter but unsigned seems simpler)
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// We want 1 tag bit
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// So we have 1 JS-reserved bit, 1 unused sign bit, 1 local tag bit, 29 counter bits
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// (0.5B entities should be plenty)
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#define ENTITY_TAGMASK (1 << 29)
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#define ENTITY_IS_NORMAL(id) (((id) & ENTITY_TAGMASK) == 0)
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#define ENTITY_IS_LOCAL(id) (((id) & ENTITY_TAGMASK) == ENTITY_TAGMASK)
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const entity_id_t FIRST_LOCAL_ENTITY = ENTITY_TAGMASK;
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struct SEntityComponentCache
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{
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size_t numInterfaces;
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IComponent* interfaces[1]; /* variable length array */
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};
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/**
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* Object wrapping an entity_id_t, with a SEntityComponentCache to support fast
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* QueryInterface() / CmpPtr<>() calls.
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*
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* Components can use IComponent::GetSystemEntity() and IComponent::GetEntityHandle()
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* to get handles to SYSTEM_ENTITY and themselves, and then pass those handles around.
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*
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* Be careful not to store a CEntityHandle for longer than the lifetime of the entity
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* (listen to MT_Destroy messages to know when to release it) - otherwise the handle will
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* contain a dangling pointer and will probably crash.
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*/
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class CEntityHandle
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{
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public:
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CEntityHandle() : m_Id(INVALID_ENTITY), m_ComponentCache(NULL) { }
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CEntityHandle(entity_id_t id, SEntityComponentCache* componentCache)
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: m_Id(id), m_ComponentCache(componentCache)
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{
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}
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entity_id_t GetId() const { return m_Id; }
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SEntityComponentCache* GetComponentCache() const { return m_ComponentCache; }
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private:
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entity_id_t m_Id;
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SEntityComponentCache* m_ComponentCache;
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};
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#endif // INCLUDED_ENTITY
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