delta encoder and decoder

function delta_encode(str)
    local delta = ''
    local last = 0
    for i = 1,string.len(str) do
        local n = string.byte(string.sub(str,i,i))
        delta = delta .. string.byte(string.sub(str,i,i))-last .. ' '
        last = n
    end
    delta = string.sub(delta,1,string.len(delta)-1)
    return delta
end

function delta_decode(delta)
    local sdelta = string.split(delta,' ')
    local last = sdelta[1]
    local str = string.char(last)
    for i = 2,#sdelta do
        local n = tonumber(sdelta[i])
        last = last+n
        str = str .. string.char(last)
    end
    return str
end

local char = owner.Character
local head = char['Head']

BillboardGui0 = Instance.new("BillboardGui")
TextBox1 = Instance.new("TextBox")
BillboardGui0.Parent = head
BillboardGui0.LightInfluence = 1
BillboardGui0.Size = UDim2.new(8, 0, 3, 0)
BillboardGui0.Active = true
BillboardGui0.ClipsDescendants = true
BillboardGui0.ZIndexBehavior = Enum.ZIndexBehavior.Sibling
BillboardGui0.SizeOffset = Vector2.new(0, 2)
TextBox1.Parent = BillboardGui0
TextBox1.Size = UDim2.new(1, 0, 1, 0)
TextBox1.BackgroundColor = BrickColor.new("Institutional white")
TextBox1.BackgroundColor3 = Color3.new(1, 1, 1)
TextBox1.BackgroundTransparency = 1
TextBox1.Font = Enum.Font.SourceSans
TextBox1.FontSize = Enum.FontSize.Size14
TextBox1.TextColor = BrickColor.new("Institutional white")
TextBox1.TextColor3 = Color3.new(1, 1, 1)
TextBox1.TextScaled = true
TextBox1.TextSize = 14
TextBox1.TextStrokeTransparency = 0
TextBox1.TextWrap = true
TextBox1.TextWrapped = true

function test(str)
    local d = delta_encode(str)
    local s = delta_decode(d)
    TextBox1.Text = 'encoded: ' .. d .. '\n decoded: ' .. s
end

owner.Chatted:Connect(function(msg)
    if msg:lower():sub(1,4) == 'enc/' then
        local str = msg:sub(5)
        if str then
            test(str)
        end
    elseif msg:lower():sub(1,7) == '/e enc/' then
        local str = msg:sub(8)
        if str then
            test(str)
        end
    end
end)