comparison: scansion/queue.lua
scansion/queue.lua
- changeset 40
- ecad8c75ba87
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| 39:814b06660220 | 40:ecad8c75ba87 |
|---|---|
| 1 -- Prosody IM | |
| 2 -- Copyright (C) 2008-2015 Matthew Wild | |
| 3 -- Copyright (C) 2008-2015 Waqas Hussain | |
| 4 -- | |
| 5 -- This project is MIT/X11 licensed. Please see the | |
| 6 -- COPYING file in the source package for more information. | |
| 7 -- | |
| 8 | |
| 9 -- Small ringbuffer library (i.e. an efficient FIFO queue with a size limit) | |
| 10 -- (because unbounded dynamically-growing queues are a bad thing...) | |
| 11 | |
| 12 local have_utable, utable = pcall(require, "util.table"); -- For pre-allocation of table | |
| 13 | |
| 14 local function new(size, allow_wrapping) | |
| 15 -- Head is next insert, tail is next read | |
| 16 local head, tail = 1, 1; | |
| 17 local items = 0; -- Number of stored items | |
| 18 local t = have_utable and utable.create(size, 0) or {}; -- Table to hold items | |
| 19 | |
| 20 return { | |
| 21 _items = t; | |
| 22 size = size; | |
| 23 count = function (self) return items; end; | |
| 24 push = function (self, item) | |
| 25 if items >= size then | |
| 26 if allow_wrapping then | |
| 27 tail = (tail%size)+1; -- Advance to next oldest item | |
| 28 items = items - 1; | |
| 29 else | |
| 30 return nil, "queue full"; | |
| 31 end | |
| 32 end | |
| 33 t[head] = item; | |
| 34 items = items + 1; | |
| 35 head = (head%size)+1; | |
| 36 return true; | |
| 37 end; | |
| 38 pop = function (self) | |
| 39 if items == 0 then | |
| 40 return nil; | |
| 41 end | |
| 42 local item; | |
| 43 item, t[tail] = t[tail], 0; | |
| 44 tail = (tail%size)+1; | |
| 45 items = items - 1; | |
| 46 return item; | |
| 47 end; | |
| 48 peek = function (self) | |
| 49 if items == 0 then | |
| 50 return nil; | |
| 51 end | |
| 52 return t[tail]; | |
| 53 end; | |
| 54 items = function (self) | |
| 55 return function (t, pos) | |
| 56 if pos >= t:count() then | |
| 57 return nil; | |
| 58 end | |
| 59 local read_pos = tail + pos; | |
| 60 if read_pos > t.size then | |
| 61 read_pos = (read_pos%size); | |
| 62 end | |
| 63 return pos+1, t._items[read_pos]; | |
| 64 end, self, 0; | |
| 65 end; | |
| 66 }; | |
| 67 end | |
| 68 | |
| 69 return { | |
| 70 new = new; | |
| 71 }; | |
| 72 |
