shaper.lua

local gettime = require "socket".gettime;

module "shaper"

local shaper = {};

function shaper:update()
	local newt = gettime();
	local elapsed = newt - self.t;
	self.t = newt;
	local balance = self.rate * elapsed + self.balance;
	if balance > self.max then
		self.balance = self.max;
	else
		self.balance = balance;
	end
	return self.balance;
end

function shaper:peek(cost)
	cost = cost or 1;
	return shaper.balance >= cost or shaper:update() >= cost;
end

function shaper:poll(cost)
	if shaper:peek(cost) then
		self.balance = self.balance - cost;
		return true;
	else
		return false;
	end
end

function create(max, period)
	return setmetatable({ rate = max / period, max = max, t = 0, balance = max }, shaper);
end

return _M;