Combine Strings using ArrayPool

combine-strings.fs

open System
open System.Buffers
open System.Text

let toOneArrayToRuleThemAll(strs: string[]) =
    
    let ascii = System.Text.Encoding.ASCII
    
    let totalBytes = Seq.sumBy String.length strs
    let result = Array.zeroCreate totalBytes
    
    let mutable i = 0
    
    let pool: ArrayPool<byte> = ArrayPool.Shared
    for str in strs do
        let byteArray = pool.Rent str.Length
        let span = byteArray.AsSpan()
        let bytes = ascii.GetBytes(str.AsSpan(), span)
        
        for j = 0 to bytes-1 do
            result.[j+i] <- byteArray.[j]
        pool.Return byteArray
        i <- i + bytes
    result
      
let testArr = [|"123";"345";"bcdasdkjh";"ABASD234"|]

let byteResult = toOneArrayToRuleThemAll testArr
//  [|49uy; 50uy; 51uy; 51uy; 52uy; 53uy; 98uy; 99uy; 100uy; 97uy; 115uy; 100uy;
//    107uy; 106uy; 104uy; 65uy; 66uy; 65uy; 83uy; 68uy; 50uy; 51uy; 52uy|]

let testString = Encoding.ASCII.GetString byteResult
// "123345bcdasdkjhABASD234"