stack in luajit

Stack.lua

-- Stack.lua
-- Last in, first out
-- poopbarrel/magicoal_nerb :^)
local Stack = {}
Stack.__index = Stack;

function Stack.new(capacityPow)
	local mask = bit.lshift(1, capacityPow) - 1
	
	-- create an array beforehand so lua doesn't
	-- need to rehash it
	local arr = table.new(mask + 1, 0)
	return setmetatable({
		mask = mask,
		ptr = 0,
		count = 0,
		arr = arr,
	}, Stack);
end

function Stack:clear()
	self.count = 0
	self.ptr = 0
end

function Stack:getCount()
	return self.count
end

function Stack:iterate(fn)
	local raw = self.ptr - 1
	local arr = self.arr
	for i = 0, self.count - 1 do
		local ptr = bit.band(raw - i, self.mask) + 1
		fn(arr[ptr])
	end
end

function Stack:peek()
	return self.arr[self.ptr]
end

function Stack:push(value)
	self.ptr = bit.band(self.ptr, self.mask) + 1
	self.count = self.count + 1
	self.arr[self.ptr] = value
end

function Stack:empty()
	return self.count == 0
end

function Stack:pop()
	local object = self.arr[self.ptr]
	self.ptr = bit.band(self.ptr - 2, self.mask) + 1
	self.count = self.count - 1
	assert(self.count < self.mask, "Wtf")

	return object
end

return Stack;