99 lines
2.4 KiB
Markdown
99 lines
2.4 KiB
Markdown
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*| [JavaECS](../../README.md) | [docs](../overview.md) | [entity](./dir.md) | EntityManager[]().md*
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# Entity Manager
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| **In this Section** |
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| [About](#about) |
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| [Implementation](#implementation) |
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| [Constructors](#constructors) |
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| [Methods](#methods) |
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| [Fields](#fields) |
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| [Examples](#examples)|
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| [Notes](#notes)|
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## About
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Controls adding and removing entities, and registration and deregistration of components to specific entities.
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## Implementation
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Before attempting to use a system, it must be registered.
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Registration requires a call to `registerSystem(String systemName, ECSSystem system)`, with params of the `String name` and a object reference of the [ECSSystem](./ECSSystem.md). Using the object reference, a system can be invoked at any time.
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See [EntityManager.java](/BrychanD/JaveECS/src/branch/master/javaecs/src/main/java/nz/ac/massey/programming_project_159333_s1_2021/EntityManager.java)
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## Constructors
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``` java
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public EntityManager(){}
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```
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The default constructor initialises [unusedEntities](#unusedEntities) to a new queue containing `1024` unique integers.
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<br>
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``` java
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public EntityManager(int maxEntities){}
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```
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Initialises [unusedEntities](#unusedEntities) to a new queue containing `maxEntities` unique integers.
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<br>
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## Methods
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### addEntity
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``` java
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public Integer addEntity();
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```
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Pops the next available entity index off the queue, and returns its value.
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Returns `-1` if there is no remaining unused entities.
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<br>
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### getRegistrations
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``` java
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public BitSet getRegistrations(int entity);
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```
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Returns the `BitSet` of registrations the `entity` has
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<br>
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### registerComponent
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``` java
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public void registerComponent(int component, int entity);
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```
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Sets the bit `component` in [entityRegistrations](#entityRegistrations) for `entity` to `true`.
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<br>
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### removeEntity
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``` java
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public void removeEntity(int entity);
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```
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Adds the entity's index back to the unused queue, and clears the assigned registration bits
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#### Note
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>This function should not be called directly. Doing so will leave component data in memory, and will cause desynchronisation of the system registrations.
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<br>
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### unregisterComponent
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``` java
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public void unregisterComponent(int component, int entity);
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```
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Sets the bit `component` in [entityRegistrations](#entityRegistrations) for `entity` to `false`.
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<br>
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## Fields
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### entityRegistrations
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``` java
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List<BitSet> entityRegistrations;
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```
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<br>
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### unusedEntities
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``` java
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Queue<Integer> unusedEntities;
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```
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<br>
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