span item access.fsx

#time 


let a : byte[] = Array.zeroCreate 1000000
let b : int[] = Array.zeroCreate (1000000/4)

open System.Runtime.InteropServices
open System

let test1() = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- a.[i]

let test2 (a : byte []) = 
    let a = a.AsSpan()
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- a.[i]

        
let test3() = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- a.AsSpan().[i]
        
let test4() = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- MemoryMarshal.Cast<int,byte>(MemoryMarshal.Cast<byte,int>(a.AsSpan())).[i]

let test5 (m : Memory<int>) = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- MemoryMarshal.Cast<int,byte>(m.Span).[i]

let test6() =
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- Span<byte>(&&b.[0] |> NativeInterop.NativePtr.toVoidPtr,b.Length*sizeof<int>).[i]

let mm = 
    {new MemoryManager<byte>() with 
        member x.GetSpan() = MemoryMarshal.Cast<int,byte>(b.AsSpan())
        member x.Pin(_) = failwith "pin"
        member x.Unpin() = failwith "unpin"
        member x.Dispose(_) = ()
        }


let test7() =
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- mm.GetSpan().[i]
        
let test8() =
    let mutable s = 0
    for i = 0 to b.Length - 1 do 
        s <- b.AsSpan().[i]
let test9() =
    let mutable s = 0
    for i = 0 to b.Length - 1 do 
        s <- System.Buffers.Binary.BinaryPrimitives.ReadInt32LittleEndian(Span.op_Implicit(a.AsSpan().Slice(i)))


let test10() =
    let mutable s = 0uy
    let ptr = &&b.[0]|> NativeInterop.NativePtr.toVoidPtr
    for i = 0 to a.Length - 1 do 
        s <- Span<byte>(ptr ,b.Length*sizeof<int>).[i]
        
let test11() =
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        use ptr = fixed &b.[0]
        s <- Span<byte>(ptr |> NativeInterop.NativePtr.toVoidPtr, b.Length*sizeof<int>).[i]
        
        
let test12 (m : Memory<int>) = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        use p = m.Pin()
        s <- Span<byte>(p.Pointer, b.Length*sizeof<int>).[i]
        
let test13 (m : Memory<int>) = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- Span<byte>(&&(m.Span.[0]) |> NativeInterop.NativePtr.toVoidPtr, b.Length*sizeof<int>).[i]


let test14 (m : Memory<byte>) = 
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- m.Span.[i]
       
let inline cast<'T>(p : Memory<byte>): byref<'T> = (# "" p : byref<'T> #) 
let inline retype (t : ^t) : ^tm = (# "" t : ^tm #)
//let inline retype (t : byte Span) : int Span = (# "" t : int Span #)

let test = new Memory<byte>([|11uy; 11uy; 11uy; 11uy|])
let mem : int = (retype test.Span).[0]
printfn "same: %d" mem
0
do
    let test = new Memory<byte>([|11uy; 11uy; 11uy; 11uy|])
    use p = test.Pin()
    let mem : int = retype p.Pointer
    printfn "mem %d %d" mem (Span(p.Pointer,1).[0])


BitConverter.ToInt32([|11uy; 11uy; 11uy; 11uy|],0)
let test11() =
    let mutable s = 0uy
    for i = 0 to a.Length - 1 do 
        s <- retype (b.AsSpan().[i])