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https://github.com/bjc/prosody.git
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254b65a030
Similar to util.ringbuffer (and shares almost identical API). Differences: - size limit is optional and dynamic - does not allocate a fixed buffer of max_size bytes - focus on simply storing references to existing string objects where possible, avoiding unnecessary allocations - references are still stored in a ring buffer to enable use as a fast FIFO Optional second parameter to new() provides the number of ring buffer segments. On Lua 5.2 on my laptop, a segment is ~19 bytes. If the ring buffer fills up, the next write will compact all strings into a single item.
82 lines
1.8 KiB
Lua
82 lines
1.8 KiB
Lua
-- 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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-- 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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local have_utable, utable = pcall(require, "util.table"); -- For pre-allocation of table
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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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return {
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new = new;
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};
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