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| -rw-r--r-- | util/queue.lua | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/util/queue.lua b/util/queue.lua new file mode 100644 index 00000000..afdcaf45 --- /dev/null +++ b/util/queue.lua @@ -0,0 +1,54 @@ +-- 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) + -- 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 { + size = size; + count = function (self) return items; end; + push = function (self, item) + if items >= size then + return nil, "queue full"; + 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; + }; +end + +return { + new = new; +}; + |