Last V8 SID file melody finder

#!/usr/bin/env luajit

local function main()
    local fd = assert(io.open("Last_V8.sid"))
    local d={}
    repeat
        local char = fd:read(1)
        if char then
            table.insert(d,string.byte(char))
        end
    until not char
    fd:close()
    print(#d.." bytes read")

    local notes = {[0]="C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "H"}

    for i = 1, #d - 3 do
        local result = nil
        if d[i] == 255 and d[i+1] ~= 255 then
            result = {"@"..bit.tohex(i-1)..":"}
            j = i + 1
            local done = nil
            repeat
                local len = bit.band(d[j], 0x9f)
                if len > 127 then
                    len = len - 128
                    j=j+1
                end
                j=j+1
                local note = d[j]
                j=j+1
                if note < 100 and note > 1 then
                    local oct = math.floor(note / 12)
                    note = note - oct * 12
                    table.insert(result, notes[note]..oct..","..len + 1)
                else
                    done = true
                    result = nil
                end
            until done or d[j] == 255
            if result and #result > 4 then
                table.insert(result, 2, "("..(#result - 1)..")")
                print(table.concat(result,"  "))
            end
        end
    end
end

main()