libdatatape

local ser = require "ser"
if not ser then
    -- Download random library squid recommended
local function a(b,c)local d=fs.open(b,"w")d.write(c)d.close()end;local function e(b)local d=fs.open(b,"r")local c=d.readAll()d.close()return c end;local function f(g)local h=http.get(g)local c=h.readAll()h.close()return c end;local function i(g,d)a(d,f(g))end;i("https://pastebin.com/raw/KXHSsHkt","ser")
end

local function move_to_start(tape)
    tape.seek(-tape.getSize())
end

local function get_byte(num, byte)
    return bit.band(bit.brshift(num, byte * 8), 0xFF)
end

local function from_bytes(b)
    local n = 0
    for ix, byte in pairs(b) do
        n = bit.bor(n, bit.blshift(byte, (ix - 1) * 8))
    end
    return n
end

local function write_string(tape, str, ignore_out_of_space)
    if tape.getSize() < (#str + 4) and not ignore_out_of_space then
        return false, "Not enough space"
    end

    move_to_start(tape)

    tape.write(get_byte(#str, 0))
    tape.write(get_byte(#str, 1))
    tape.write(get_byte(#str, 2))
    tape.write(get_byte(#str, 3))

    return tape.write(str)
end

local function read_string(tape)
    move_to_start(tape)

    local data_length = from_bytes {tape.read(), tape.read(), tape.read(), tape.read()}
    local data_remaining = data_length

    if data_length > (tape.getSize() - 4) then
        return false, "Invalid data length."
    end

    local data = ""

    repeat
        local block = tape.read(256)
        block = block:sub(1, data_remaining)
        data_remaining = data_remaining - #block
        data = data .. block -- for some reason, only 256 chars at once can be read?
        sleep()
    until data_remaining == 0

    return data
end

local function write(tape, dat, ignore_out_of_space)
    return write_string(tape, ser.serialize(dat), ignore_out_of_space)
end

local function read(tape)
    return ser.deserialize(read_string(tape))
end

return { read_string = read_string, read = read, write_string = write_string, write = write }