File

util/queue.lua @ 10390:82705ec87253 0.11

util.startup: Ensure prosody.paths are absolute (see #1430) Normally these paths are injected into the installed 'prosody' executable as absolute paths, but it is possible to override at least the config path via environment variable or command line argument. This makes sure a path relative to pwd stays relative to that instead of the data directory.
author Kim Alvefur <zash@zash.se>
date Mon, 04 Nov 2019 00:29:49 +0100
parent 6912:cb5b14c95b7b
child 9901:c8b75239846c
child 11103:73b8aaf55775
line wrap: on
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-- Prosody IM
-- Copyright (C) 2008-2015 Matthew Wild
-- Copyright (C) 2008-2015 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

-- Small ringbuffer library (i.e. an efficient FIFO queue with a size limit)
-- (because unbounded dynamically-growing queues are a bad thing...)

local have_utable, utable = pcall(require, "util.table"); -- For pre-allocation of table

local function new(size, allow_wrapping)
	-- Head is next insert, tail is next read
	local head, tail = 1, 1;
	local items = 0; -- Number of stored items
	local t = have_utable and utable.create(size, 0) or {}; -- Table to hold items
	--luacheck: ignore 212/self
	return {
		_items = t;
		size = size;
		count = function (self) return items; end;
		push = function (self, item)
			if items >= size then
				if allow_wrapping then
					tail = (tail%size)+1; -- Advance to next oldest item
					items = items - 1;
				else
					return nil, "queue full";
				end
			end
			t[head] = item;
			items = items + 1;
			head = (head%size)+1;
			return true;
		end;
		pop = function (self)
			if items == 0 then
				return nil;
			end
			local item;
			item, t[tail] = t[tail], 0;
			tail = (tail%size)+1;
			items = items - 1;
			return item;
		end;
		peek = function (self)
			if items == 0 then
				return nil;
			end
			return t[tail];
		end;
		items = function (self)
			--luacheck: ignore 431/t
			return function (t, pos)
				if pos >= t:count() then
					return nil;
				end
				local read_pos = tail + pos;
				if read_pos > t.size then
					read_pos = (read_pos%size);
				end
				return pos+1, t._items[read_pos];
			end, self, 0;
		end;
	};
end

return {
	new = new;
};