lua/rng32jit.lua at main · tkers/lua · GitHub

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local bit = require("bit")

local function xorshift(x)
    -- x = (x ~ x << 13) & 2147483647
    -- x = (x ~ x >> 17) & 2147483647
    -- x = (x ~ x << 5) & 2147483647
    x = bit.band(bit.bxor(x, bit.lshift(x, 13)), 2147483647)
    x = bit.band(bit.bxor(x, bit.rshift(x, 17)), 2147483647)
    x = bit.band(bit.bxor(x, bit.lshift(x, 5)), 2147483647)
    return x
end

local RNG = {}
RNG.__index = RNG

function RNG.new(seed)
    local self = setmetatable({}, RNG)
    self:seed(seed or 1)
    return self
end

function RNG:seed(seed)
    -- self.state = (seed * 23456789) & 2147483647
    self.state = bit.band(seed * 23456789, 2147483647)
end

function RNG:next()
    local x = xorshift(self.state)
    self.state = x
    return x
end

function RNG:random(a, b)
    local x = self:next()
    if not a then
        return x / 2147483647
    elseif not b then
        return x % a + 1
    else
        return x % (b - a + 1) + a
    end
end

return RNG