RLE decoder that supports Pico-8's subset of Lua

rle_dec.lua

-- Helper function to repeat string
function rep(char, multiplier)
    local out = ""

    for i=1, multiplier do
        out = out..char
    end

    return out
end

-- RLE Decoder
function drle(data)
    local decode, count, i = "", "", 1

    while i <= #data do
        local char = sub(data, i, i)

        if type(tonum(char)) then
            count = count..char
        else
            multiplier = tonum(count) or 1
            decode = decode..rep(char, multiplier)
            count = ""
        end

        i = i + 1
    end

    return decode
end