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