something is wrong when using tostring method with big number

[openresty]

something is wrong when using tostring method with big number

[agentzh]

@theoneqq Better not in that redis library. It might be a good idea to simply change the LuaJIT's tostring() method. The LL suffix is indeed not very helpful usually.

[agentzh]

10^14 already exceeds a 32-bit integer's range and LuaJIT will store it as a double-precision floating point number. You need 64-bit integers, in LuaJIT, should use cdata instead. Like this:

$ resty -e 'print(1234567901234567890LL)'
1234567901234567890LL

Or to remove the LL suffix:

$ resty -e 'print(string.sub(tostring(1234567901234567890LL), 0, -3))'
1234567901234567890

If you do no want to do arithmetic on the 64-bit integer values, then you should just use strings from the very beginning instead of using Lua numbers or Lua cdata objects.

BTW, the code you quoted is from minilua (you have a type in your message, not minlua). The minilua is only used when building the LuaJIT itself. It no longer exists in the final installed LuaJIT tree.

[theoneqq]

openresty/bundle/lua-resty-redis/lib/resty/redis.lua

local function _gen_req(args)
    local nargs = #args

    local req = new_tab(nargs * 5 + 1, 0)
    req[1] = "*" .. nargs .. "\r\n"
    local nbits = 2

    for i = 1, nargs do
        local arg = args[i]
        if type(arg) ~= "string" then
            arg = tostring(arg)
        end

        req[nbits] = "$"
        req[nbits + 1] = #arg
        req[nbits + 2] = "\r\n"
        req[nbits + 3] = arg
        req[nbits + 4] = "\r\n"

        nbits = nbits + 5
    end

    -- it is much faster to do string concatenation on the C land
    -- in real world (large number of strings in the Lua VM)
    return req
end

Thanks, I got it. I wander if I can modify above tostring method, instead of to distinguish common number and big number.

[theoneqq]

It's really a good idea, I will try