GuidToSN prototype

GuidToSN.fs

open System
open System.Collections.Generic
open Force.Crc32
open System.Text
open Murmur
open HashLib

let check keys e name =
    let hsahes = new HashSet<string>()
    let stopWatch = System.Diagnostics.Stopwatch.StartNew()
    let add_hash x =  hsahes.Add(e(x)) |> not
    let collisions = Array.filter add_hash keys |> Array.length
    stopWatch.Stop()
    printfn "%s %f sec %d collisions (%f %%)" name stopWatch.Elapsed.TotalSeconds collisions (double(collisions) / double(keys.Length)*100.0)


let baseChars = "abcdefghijklmnopqrstuvwxyz23456789".ToCharArray()

let intToString(value: int64 ) =
        let mutable i = 8
        let mutable value = value
        let buffer = Array.create<char> i 'a'
        let targetBase = int64(baseChars.Length)
        while value > 0L do
            i <- i - 1
            buffer.[i] <- baseChars.[int(value % targetBase)]
            value <- value / targetBase
        new string(buffer)

let toString(bytes : byte[])=
    let buffer = Array.zeroCreate<byte> 8
    Array.Copy(bytes, buffer, if bytes.Length > 5 then 5 else bytes.Length)
    let value = BitConverter.ToInt64(buffer,0)
    intToString value

let keys gen = seq{
    while true do
        yield gen()
}

let E2 = new Crc32CAlgorithm()
let crc40c (key : Guid) = 
    let key = key.ToByteArray()
    let buffer = Array.create 5 0uy
    let hash32 = E2.ComputeHash(key)
    Array.Copy(hash32, buffer, 4)
    let hash32_2 = E2.ComputeHash(key.[0..8])
    buffer.[4] <- hash32_2.[0]
    buffer |> toString

let crc32c (key : Guid) = E2.ComputeHash(key.ToByteArray()) |> toString
let E = new Crc32Algorithm()
let crc32 (key : Guid) = E.ComputeHash(key.ToByteArray()) |> toString
let m32 = MurmurHash.Create32(managed=false); // returns a 128-bit algorithm using "unsafe" code with default seed
let murmur32 (key : Guid) = m32.ComputeHash(key.ToByteArray()) |> toString

let m128 = MurmurHash.Create128(managed=false); // returns a 128-bit algorithm using "unsafe" code with default seed
let murmur128 (key : Guid) = 
    let ba =m128.ComputeHash(key.ToByteArray())
    ba |> toString

let E64 = HashFactory.Checksum.CreateCRC64(HashLib.Checksum.CRC64Polynomials.ECMA_182);
let crc64 (key : Guid) = 
    let ba =E64.ComputeBytes(key.ToByteArray())
    ba.GetBytes() |> toString

let E64zeroISO = HashFactory.Checksum.CreateCRC64(HashLib.Checksum.CRC64Polynomials.ISO);
let crc64ISO (key : Guid) = 
    let ba =E64zeroISO.ComputeBytes(key.ToByteArray())
    ba.GetBytes() |> toString

let sha256E = HashFactory.Crypto.CreateSHA256()
let sha256 (key : Guid) = 
    let ba =sha256E.ComputeBytes(key.ToByteArray())
    ba.GetBytes() |> toString

let fnv = HashFactory.Hash64.CreateFNV1a();

let fnv1a (key : Guid) = 
    let ba =fnv.ComputeBytes(key.ToByteArray())
    ba.GetBytes() |> toString

let checkGuidGen gen name =
    let count = 15000000
    let keysSeq = keys gen
    printfn "checking %d keys generated by %s " count name 
    printfn "Keys sample"
    for k in keysSeq |> Seq.take 10 do
        printfn "%A" k
    let keys = keysSeq |> Seq.take count |> Array.ofSeq
    printfn "results:"
    //check keys sha256 "sha256"
    check keys crc40c "crc40c"
    
    //check keys crc64ISO "crc64 ISO poly"
    check keys crc64 "crc64 ECMA_182 poly"
    //check keys crc32 "crc32"

    //check keys crc32c "crc32c"
    //check keys murmur32 "murmur32"
    //check keys murmur128 "murmur128"
    //check keys fnv1a "FNV1a(64)"

let generateComb() =
    let guidArray = Guid.NewGuid().ToByteArray()
    let baseDate = new DateTime(1900, 1, 1)
    let now = DateTime.Now
    // Get the days and milliseconds which will be used to build the byte string 
    let days = new TimeSpan(now.Ticks - baseDate.Ticks)
    let msecs = now.TimeOfDay
    // Convert to a byte array 
    // Note that SQL Server is accurate to 1/300th of a millisecond so we divide by 3.333333 
    let daysArray = BitConverter.GetBytes(days.Days)
    let msecsArray = BitConverter.GetBytes(int64 (msecs.TotalMilliseconds / 3.333333))
    // Reverse the bytes to match SQL Servers ordering 
    Array.Reverse(daysArray)
    Array.Reverse(msecsArray)
    // Copy the bytes into the guid 
    Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2)
    Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4)
    new Guid(guidArray)

let mutable i = Array.create 16 0uy
let mutable rev = false
let rec incArr (arr:byte[]) index = 
    if -1 = index then ()
    else arr.[index] <- arr.[index] + 1uy
         if arr.[index] = 0uy then incArr arr (index-1)
         else ()

let incrementalGenerator()=
    incArr i 15
    rev<- not rev
    new Guid(if rev then i else Array.rev i)

[<EntryPoint>]
let main argv = 
    let mutable a = 0;
    checkGuidGen incrementalGenerator "Incremental guids"
    checkGuidGen Guid.NewGuid "Guid.NewGuid"
    checkGuidGen generateComb "Comb guids"
    
    Console.ReadLine() |> ignore
    0 // return an integer exit code