UnsafeElementAt(int)
Provides read-only access to NativeArray<T>.ReadOnly elements by index.
Read time 1 minuteLast updated 10 days ago
Definition
- Type: Method
- Namespace: Unity.Collections
- Assembly: UnityEngine.ManagedKernelModule
public ref readonly T UnsafeElementAt(int index)
Parameters
The index of the element.
Returns
Type | Description |
|---|---|
| T | A |
Remarks
This method is dangerous because it returns reference to the memory that can be destroyed (with NativeArray<T>.Dispose, for instance) and if the is accessed that might lead to undefined results including crashes.
ref localExamples
public readonly struct BigStruct{ public readonly long a; public readonly long b; public readonly long c; public readonly long d;}static void ProcessByte(byte b){ ...}static void ProcessBigStructWithoutCopy(in BigStruct bigStruct) // see 'in' modificator{ ...}static void Example(){ const int n = 32; var nativeArrayOfBytes = new NativeArray<byte>(n, Allocator.Temp); var nativeArrayOfBigStructures = new NativeArray<FixedString4096Bytes>(n, Allocator.Temp); // ... fill the arrays with some data ... var readOnlyBytes = nativeArrayOfBytes.AsReadOnly(); for (var i = 0; i < n; ++i) { ProcessByte(readOnlyBytes[i]); //ProcessByte(readOnlyBytes.UnsafeElementAt(i)); is more expensive, since pointer on x64 platforms is 8 times bigger than a byte } var readOnlyBigStructures = nativeArrayOfBigStructures.AsReadOnly(); for (var i = 0; i < n; ++i) { //ProcessBigStructWithoutCopy(readOnlyBigStructures[i]); copy - expensive in this case ProcessBigStructWithoutCopy(readOnlyBigStructures.UnsafeElementAt(i)); } // dangerous part ref var element = ref readOnlyBigStructures.UnsafeElementAt(4); // element is valid here ProcessBigStructWithoutCopy(element); nativeArrayOfBigStructures.Dispose(); // access to element here is undefined, can lead to a crash or wrong results // ProcessBigStructWithoutCopy(element); <-- do not do this!}