File

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−-- Prosody IM
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−-- Copyright (C) 2008-2015 Matthew Wild
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−-- Copyright (C) 2008-2015 Waqas Hussain
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−--
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−-- This project is MIT/X11 licensed. Please see the
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−-- COPYING file in the source package for more information.
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−--
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−
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−-- Small ringbuffer library (i.e. an efficient FIFO queue with a size limit)
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−-- (because unbounded dynamically-growing queues are a bad thing...)
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−
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−local have_utable, utable = pcall(require, "util.table"); -- For pre-allocation of table
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−
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−local function new(size, allow_wrapping)
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−	-- Head is next insert, tail is next read
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−	local head, tail = 1, 1;
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−	local items = 0; -- Number of stored items
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−	local t = have_utable and utable.create(size, 0) or {}; -- Table to hold items
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−	--luacheck: ignore 212/self
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−	return {
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−		_items = t;
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−		size = size;
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−		count = function (self) return items; end;
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−		push = function (self, item)
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−			if items >= size then
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−				if allow_wrapping then
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−					tail = (tail%size)+1; -- Advance to next oldest item
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−					items = items - 1;
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−				else
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−					return nil, "queue full";
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−				end
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−			end
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−			t[head] = item;
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−			items = items + 1;
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−			head = (head%size)+1;
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−			return true;
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−		end;
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−		pop = function (self)
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−			if items == 0 then
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−				return nil;
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−			end
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−			local item;
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−			item, t[tail] = t[tail], 0;
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−			tail = (tail%size)+1;
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−			items = items - 1;
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−			return item;
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−		end;
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−		peek = function (self)
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−			if items == 0 then
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−				return nil;
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−			end
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−			return t[tail];
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−		end;
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−		replace = function (self, data)
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−			if items == 0 then
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−				return self:push(data);
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−			end
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−			t[tail] = data;
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−			return true;
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−		end;
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−		items = function (self)
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−			return function (_, pos)
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−				if pos >= items then
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−					return nil;
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−				end
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−				local read_pos = tail + pos;
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−				if read_pos > self.size then
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−					read_pos = (read_pos%size);
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−				end
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−				return pos+1, t[read_pos];
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−			end, self, 0;
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−		end;
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−		consume = function (self)
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−			return self.pop, self;
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−		end;
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−	};
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−end
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−
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−return {
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−	new = new;
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−};
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−