PDP-11 binary F# Mono Xamarin Mac

gistfile1.fs

open System.IO
open System.Text

let mem = Array.zeroCreate<byte>(0x10000)

mem.[0] <- 0x10uy
mem.[1] <- byte 0x20

printfn "0:%d %02x" mem.[0] mem.[0]
printfn "1:%d %02x" mem.[1] mem.[1]

let read16 i = (uint16 mem.[i]) ||| ( (uint16 mem.[i+1] ) <<< 8 )

printfn "read16 0 = %04x" (read16 0)

//let args = System.Environment.GetCommandLineArgs()

let f = new FileStream("a.out" , FileMode.Open)
f.Read( mem, 0, 16) |> ignore
let textsize = int (read16 2)
let datasize = int (read16 4)
f.Read( mem, 0, textsize + datasize) |> ignore
f.Close()

let disasm () =
    // .text
    let mutable i = 0
    while i < textsize do
        printf "%04x %04x \t" i (read16 i)
        match int mem.[i+1], int mem.[i] with
        | 0x15, 0xc0 ->
            i <- i + 2
            printfn "mov $%x, r0" (read16 i)
        | 0x89, n ->
            printfn "sys %d" n
        | 0x00, 0x06 ->
            printfn "rtt"
        | _ ->
            printfn ".word %o" (read16 i)
        i <- i + 2

let run () =
    let mutable i = 0
    let mutable r0 = uint16 0
    while i < textsize do
        match int mem.[i+1], int mem.[i] with
        | 0x15, 0xc0 ->
            i <- i + 2
            r0 <- read16 i
        | 0x89, 0x04 ->
            let str = int (read16 (i + 2))
            let len = int (read16 (i + 4))
            i <- i + 4
            printf "%s" (Encoding.ASCII.GetString(mem, str, len))
            //printfn "write(%x, %x, %x)" r0 str len
        | 0x89, 0x01 ->
            exit (int r0)
        | _ ->
            printfn "error %x" i
        i <- i + 2

run()