LuaURL编码：不安全字符的百分号转义

local function urlencode(s)
    local out = {}
    for i = 1, #s do
        local b = s:byte(i)
        if b == 45 or b == 46 or b == 95 or b == 126
            or (b >= 48 and b <= 57)
            or (b >= 65 and b <= 90)
            or (b >= 97 and b <= 122) then
            out[#out + 1] = string.char(b)
        else
            out[#out + 1] = string.format("%%%02X", b)
        end
    end
    return table.concat(out)
end

local function urldecode(s)
    local out, i = {}, 1
    while i <= #s do
        if s:sub(i, i) == "%" then
            out[#out + 1] = string.char(
                tonumber(s:sub(i + 1, i + 2), 16))
            i = i + 3
        else
            out[#out + 1] = s:sub(i, i)
            i = i + 1
        end
    end
    return table.concat(out)
end
local p = getplayerbyname("url01")
sendmsg(p, 1, urldecode(urlencode("a b&c")))