99 lines
8.3 KiB
Markdown
99 lines
8.3 KiB
Markdown
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# Unity.Collections
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A C# collections library providing data structures that can be used in jobs, and
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optimized by Burst compiler.
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### Package CI Summary
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[](https://badges.cds.internal.unity3d.com/packages/com.unity.collections/build-info?branch=master) [](https://badges.cds.internal.unity3d.com/packages/com.unity.collections/dependencies-info?branch=master) [](https://badges.cds.internal.unity3d.com/packages/com.unity.collections/dependants-info)  
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## Documentation
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https://docs.unity3d.com/Packages/com.unity.collections@0.14/manual/index.html
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## Data structures
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The Unity.Collections package includes the following data structures:
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Data structure | Description | Documentation
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---------------------------- | ----------- | -------------
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`BitField32` | Fixed size 32-bit array of bits. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.BitField32.html)
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`BitField64` | Fixed size 64-bit array of bits. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.BitField64.html)
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`NativeBitArray` | Arbitrary sized array of bits. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeBitArray.html)
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`UnsafeBitArray` | Arbitrary sized array of bits, without any thread safety check features. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeBitArray.html)
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`NativeList` | An unmanaged, resizable list. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeList-1.html)
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`UnsafeList` | An unmanaged, resizable list, without any thread safety check features. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeList-1.html)
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`NativeParallelHashMap` | Unordered associative array, a collection of keys and values. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeParallelHashMap-2.html)
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`UnsafeParallelHashMap` | Unordered associative array, a collection of keys and values, without any thread safety check features. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeParallelHashMap-2.html)
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`NativeParallelHashSet` | Set of values. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeParallelHashSet-1.html)
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`UnsafeParallelHashSet` | Set of values, without any thread safety check features. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeParallelHashSet-1.html)
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`NativeParallelMultiHashMap` | Unordered associative array, a collection of keys and values. This container can store multiple values for every key. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeParallelMultiHashMap-2.html)
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`UnsafeParallelMultiHashMap` | Unordered associative array, a collection of keys and values, without any thread safety check features. This container can store multiple values for every key. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeParallelMultiHashMap-2.html)
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`NativeStream` | A deterministic data streaming supporting parallel reading and parallel writing. Allows you to write different types or arrays into a single stream. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeStream.html)
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`UnsafeStream` | A deterministic data streaming supporting parallel reading and parallel writings, without any thread safety check features. Allows you to write different types or arrays into a single stream. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeStream.html)
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`NativeReference` | An unmanaged, reference container. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.NativeReference-1.html)
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`UnsafeAppendBuffer` | An unmanaged, untyped, buffer, without any thread safety check features. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeAppendBuffer.html)
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`UnsafeRingQueue` | Fixed-size circular buffer, without any thread safety check features. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeRingQueue-1.html)
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`UnsafeAtomicCounter32` | 32-bit atomic counter. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeAtomicCounter32.html)
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`UnsafeAtomicCounter64` | 64-bit atomic counter. | [Documentation](https://docs.unity3d.com/Packages/com.unity.collections@0.14/api/Unity.Collections.LowLevel.Unsafe.UnsafeAtomicCounter64.html)
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[...](https://docs.unity3d.com/Packages/com.unity.collections@0.14/manual/index.html)
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The items in this package build upon the [NativeArray<T0>](https://docs.unity3d.com/ScriptReference/Unity.Collections.NativeArray_1),
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[NativeSlice<T0>](https://docs.unity3d.com/ScriptReference/Unity.Collections.NativeSlice_1),
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and other members of the Unity.Collections namespace, which Unity includes in
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the [core module](https://docs.unity3d.com/ScriptReference/UnityEngine.CoreModule).
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## Notation
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`Native*` container prefix signifies that containers have debug safety mechanisms
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which will warn users when a container is used incorrectly in regard with thread-safety,
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or memory management. `Unsafe*` containers do not provide those safety warnings, and
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the user is fully responsible to guarantee that code will execute correctly. Almost all
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`Native*` containers are implemented by using `Unsafe*` container of the same kind
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internally. In the release build, since debug safety mechanism is disabled, there
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should not be any significant performance difference between `Unsafe*` and `Native*`
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containers. `Unsafe*` containers are in `Unity.Collections.LowLevel.Unsafe`
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namespace, while `Native*` containers are in `Unity.Collections` namespace.
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## Determinism
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Populating containers from parallel jobs is never deterministic, except when
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using `NativeStream` or `UnsafeStream`. If determinism is required, consider
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sorting the container as a separate step or post-process it on a single thread.
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## Known Issues
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All containers allocated with `Allocator.Temp` on the same thread use a shared
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`AtomicSafetyHandle` instance. This is problematic when using `NativeParallelHashMap`,
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`NativeParallelMultiHashMap`, `NativeParallelHashSet` and `NativeList` together in situations
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where their secondary safety handle is used. This means that operations that
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invalidate an enumerator for either of these collections (or the `NativeArray`
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returned by `NativeList.AsArray`) will also invalidate all other previously
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acquired enumerators. For example, this will throw when safety checks are enabled:
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```
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var list = new NativeList<int>(Allocator.Temp);
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list.Add(1);
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// This array uses the secondary safety handle of the list, which is
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// shared between all Allocator.Temp allocations.
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var array = list.AsArray();
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var list2 = new NativeParallelHashSet<int>(Allocator.Temp);
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// This invalidates the secondary safety handle, which is also used
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// by the list above.
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list2.TryAdd(1);
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// This throws an InvalidOperationException because the shared safety
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// handle was invalidated.
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var x = array[0];
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```
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This defect will be addressed in a future release.
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## Licensing
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Unity Companion License (“License”) Software Copyright © 2017-2020 Unity Technologies ApS
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For licensing details see [LICENSE.md](LICENSE.md)
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