--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/util/queue.lua Thu Apr 07 18:11:33 2022 +0100
@@ -0,0 +1,82 @@
+-- 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;
+ replace = function (self, data)
+ if items == 0 then
+ return self:push(data);
+ end
+ t[tail] = data;
+ return true;
+ end;
+ items = function (self)
+ return function (_, pos)
+ if pos >= items then
+ return nil;
+ end
+ local read_pos = tail + pos;
+ if read_pos > self.size then
+ read_pos = (read_pos%size);
+ end
+ return pos+1, t[read_pos];
+ end, self, 0;
+ end;
+ consume = function (self)
+ return self.pop, self;
+ end;
+ };
+end
+
+return {
+ new = new;
+};
+