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MemoryAllocator.md

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Memory Allocator

In ME.ECS there is custom Memory Allocator with custom pointers. Memory Allocator stored in State and contains all objects you have create in state.

Warning Keep in mind that MemoryAllocator doesn't thread-safe for now.

// Get state allocator
var allocator = world.GetState().allocator;
// Create collection in state allocator
var arr = new List<int>(ref allocator, 100);
...
arr.Dispose(ref allocator);

The main difference between MemoryAllocator.List<> and NativeList<> (or Generic.List<>) is in pointer inside this collection:

  • Generic.List<> contains array, which points to the C# heap memory.
  • NativeList<> contains void*, which points to the Unity heap memory.
  • MemoryAllocator.List<> contains long, which doesn't point to the native memory, it points to the allocator, so you can store this collection everywhere: in UI, in components, etc. You can store collections inside collections and doesn't matter about copying.

Warning Do not forget to call Dispose() on MemoryAllocator collections.

For now ME.ECS has these collections implemented:

Collection Description Burst
MemArrayAllocator Default array implementation. ✔️
List Default list implementation. ✔️
HashSet Default HashSet implementation without IEquatable restriction (uses default EqualityComparer).
Stack Default Stack implementation. ✔️
Queue Default Queue implementation. ✔️
Dictionary Default Dictionary implementation without IEquatable restriction (uses default EqualityComparer).
EquatableDictionary Custom Dictionary implementation with default IEquatable restriction. Use this for primitive or types which has IEquatable<> interface. ✔️
EquatableHashSet Custom HashSet implementation with default IEquatable restriction. Use this for primitive or types which has IEquatable<> interface. ✔️
NativeHashSet Custom HashSet implementation with IEquatableAllocator<> restriction. Required for types which needs to check Equals using MemoryAllocator. ✔️ 
using ME.ECS.Collections.MemoryAllocator;

public struct YourComponent : IComponent {
    // You don't need to use ICopyable<> interface here because List<> is stored as unmanaged pointer
    public List<int> list;
}

Static Allocators

By default ME.ECS has 2 static allocators:

// Max size of temp allocator is 256 KB
var tempAllocator = StaticAllocators.GetAllocator(AllocatorType.Temp);
// Initial size of persistent allocator is 4MB and max size is not defined
var persistentAllocator = StaticAllocators.GetAllocator(AllocatorType.Persistent);

You can use any of these allocators to store your data. Btw, you can create your own allocator with options:

var customAllocator = new MemoryAllocator().Initialize(initialSizeInBytes, maxSizeInBytes);