lua binary data packing

binary.lua

-- Fast functions for working with binary data
return {
    decode_uint8 = function(str, ofs)
        ofs = ofs or 0
        return string.byte(str, ofs + 1)
    end,

    decode_uint16 = function(str, ofs)
        ofs = ofs or 0
        local a, b = string.byte(str, ofs + 1, ofs + 2)
        return a + b * 0x100
    end,

    decode_uint32 = function(str, ofs)
        ofs = ofs or 0
        local a, b, c, d = string.byte(str, ofs + 1, ofs + 4)
        return a + b * 0x100 + c * 0x10000 + d * 0x1000000
    end,

    encode_uint8 = function(int)
        return string.char(int)
    end,

    encode_uint16 = function(int)
        local a, b = int % 0x100, int / 0x100
        return string.char(a, b)
    end,

    encode_uint32 = function(int)
        local a, b, c, d = 
            int % 0x100, 
            int / 0x100 % 0x100, 
            int / 0x10000 % 0x100, 
            int / 0x1000000
        return string.char(a, b, c, d)
    end,
}