system.memory

C# 7.2 introduces two new types: Span<T> and Memory<T> that have better performance over earlier C# types like string[] . Question: What is the difference between Span<T> and Memory<T> ? Why would I use one over the other? Hussein Salman Span<T> is stack-only in nature while Memory<T> can exist on the heap. Span<T> is a new type we are adding to the platform to represent contiguous regions of arbitrary memory, with performance characteristics on par with T[]. Its APIs are similar to the array, but unlike arrays, it can point to either managed or native memory, or to memory allocated on the

For a network protocol implementation I want to make use of the new Memory and Span classes to achieve zero-copy of the buffer while accessing the data through a struct . I have the following contrived example: [StructLayout(LayoutKind.Sequential, Pack = 1)] public struct Data { public int IntValue; public short ShortValue; public byte ByteValue; } static void Prepare() { var buffer = new byte[1024]; var dSpan = MemoryMarshal.Cast<byte, Data>(buffer); ref var d = ref dSpan[0]; d.ByteValue = 1; d.ShortValue = (2 << 8) + 3; d.IntValue = (4 << 24) + (5 << 16) + (6 << 8) + 7; } The result is that

I notice that the following will compile and execute even though the local variables are not initialized. Is this a feature of Span? void Uninitialized() { Span<char> s1; var l1 = s1.Length; Span<char> s2; UninitializedOut(out s2); var l2 = s2.Length; } void UninitializedOut(out Span<char> s) {} This looks like an issue caused by reference assemblies, required because of the way that Span<T> has framework-specific internals. This means that in the reference assembly : there are no fields (edit: this isn't quite true - see footnote). A struct is considered assigned (for the purposes of