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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
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)
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;
};
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