--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/throttle.lua	Mon Aug 29 13:00:33 2011 -0400
@@ -0,0 +1,44 @@
+
+local gettime = require "socket".gettime;
+
+module "throttle"
+
+local throttle = {};
+local throttle_mt = { __index = throttle };
+
+function throttle: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 throttle:peek(cost)
+	cost = cost or 1;
+	return self.balance >= cost or self:update() >= cost;
+end
+
+function throttle:poll(cost, split)
+	if self:peek(cost) then
+		self.balance = self.balance - cost;
+		return true;
+	else
+		local balance = self.balance;
+		if split then
+			self.balance = 0;
+		end
+		return false, balance, (cost-self.balance);
+	end
+end
+
+function create(max, period)
+	return setmetatable({ rate = max / period, max = max, t = 0, balance = max }, throttle_mt);
+end
+
+return _M;