30 lines
1.6 KiB
Markdown
30 lines
1.6 KiB
Markdown
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## DllImport and internal calls
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To call native functions, use [`[DllImport]`](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.dllimportattribute?view=net-6.0):
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```c#
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[DllImport("MyNativeLibrary")]
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public static extern int Foo(int arg);
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```
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Burst also supports internal calls implemented inside Unity:
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```c#
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// In UnityEngine.Mathf
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[MethodImpl(MethodImplOptions.InternalCall)]
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public static extern int ClosestPowerOfTwo(int value);
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```
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`DllImport` is only supported for [native plug-ins](https://docs.unity3d.com/Manual/NativePlugins.html), not platform-dependent libraries like `kernel32.dll`.
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For all `DllImport` and internal calls, you can only use the following types as parameter or return types:
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|**Type**|**Supported type**|
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|---|---|
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|Built-in and intrinsic types|`byte` / `sbyte`<br/>`short` / `ushort`<br/>`int` / `uint`<br/>`long` / `ulong`<br/>`float`<br/>`double`<br/>`System.IntPtr` / `System.UIntPtr`<br/>`Unity.Burst.Intrinsics.v64` / `Unity.Burst.Intrinsics.v128` / `Unity.Burst.Intrinsics.v256`|
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|Pointers and references|`sometype*` : Pointer to any of the other types in this list<br/>`ref sometype` : Reference to any of the other types in this list
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|Handle structs|`unsafe struct MyStruct { void* Ptr; }` : Struct containing a single pointer field<br/>`unsafe struct MyStruct { int Value; }` : Struct containing a single integer field
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> [!NOTE]
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>Passing structs by value isn't supported; you need to pass them through a pointer or reference. The only exception is that handle structs are supported. These are structs that contain a single field of pointer or integer type.
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