mirror of
https://github.com/sbrl/Minetest-WorldEditAdditions.git
synced 2024-11-15 20:52:59 +00:00
74 lines
2 KiB
Lua
74 lines
2 KiB
Lua
-------------------------------------------------------------------------------
|
|
--- A Queue implementation
|
|
-- Taken & adapted from https://www.lua.org/pil/11.4.html
|
|
-- @submodule worldeditadditions.utils.queue
|
|
-- @class
|
|
local Queue = {}
|
|
Queue.__index = Queue
|
|
|
|
--- Creates a new queue instance.
|
|
-- @returns Queue
|
|
function Queue.new()
|
|
local result = { first = 0, last = -1, items = {} }
|
|
setmetatable(result, Queue)
|
|
return result
|
|
end
|
|
|
|
--- Adds a new value to the end of the queue.
|
|
-- @param value any The new value to add to the end of the queue.
|
|
-- @returns number The index of the value that was added to the queue.
|
|
function Queue:enqueue(value)
|
|
local new_last = self.last + 1
|
|
self.last = new_last
|
|
self.items[new_last] = value
|
|
return new_last
|
|
end
|
|
|
|
--- Determines whether a given value is present in this queue or not.
|
|
-- @param value any The value to check.
|
|
-- @returns bool Whether the given value exists in the queue or not.
|
|
function Queue:contains(value)
|
|
for i=self.first,self.last do
|
|
if self.items[i] == value then
|
|
return true
|
|
end
|
|
end
|
|
return false
|
|
end
|
|
|
|
--- Returns whether the queue is empty or not.
|
|
-- @returns bool Whether the queue is empty or not.
|
|
function Queue:is_empty()
|
|
return self.first > self.last
|
|
end
|
|
|
|
--- Removes the item with the given index from the queue.
|
|
-- Item indexes do not change as the items in a queue are added and removed.
|
|
-- @param number The index of the item to remove from the queue.
|
|
-- @returns nil
|
|
function Queue:remove_index(index)
|
|
self.items[index] = nil
|
|
end
|
|
|
|
--- Dequeues an item from the front of the queue.
|
|
-- @returns any|nil Returns the item at the front of the queue, or nil if no items are currently enqueued.
|
|
function Queue:dequeue()
|
|
if Queue.is_empty(self) then
|
|
error("Error: The self is empty!")
|
|
end
|
|
|
|
local first = self.first
|
|
-- Find the next non-nil item
|
|
local value
|
|
while value == nil do
|
|
if first >= self.last then return nil end
|
|
value = self.items[first]
|
|
self.items[first] = nil -- Help the garbage collector out
|
|
first = first + 1
|
|
end
|
|
self.first = first
|
|
return value
|
|
end
|
|
|
|
|
|
return Queue
|