core/history.lua

   1
   2 local os = require("os")
   3 local io = require("io")
   4 local string = require("string")
   5 --       local posix = require("posix")
   6 --       local table = require("table")
   7 --       local math = require("math")
   8 --       local type = type
   9 --       local error = error
  10 local print = print
  11 --       local pcall = pcall
  12 --       local pairs = pairs
  13 --       local package = package
  14 --       local require = require
  15 local tostring = tostring
  16 --       local tonumber = tonumber
  17 local setmetatable = setmetatable
  18
  19 module("history")
  20
  21
  22 history = {}
  23 function new (size)
  24         local o = {}
  25
  26         setmetatable (o,history)
  27         history.__index = history
  28
  29         o.data = {}
  30         o.data[size] = nil
  31         o.size = size
  32         o.count = 0
  33         o.last = 0
  34
  35         return o
  36 end
  37
  38 function history:add (entry)
  39         if self.count < self.size then
  40                 self.count = self.count + 1
  41                 self.last = self.count
  42                 self.data[self.last] = entry
  43         else
  44                 self.last = 1 + (self.last % self.size)
  45                 self.data[self.last] = entry
  46         end
  47 end
  48
  49 function history:oldest ()
  50         if self.count then
  51                 local i = 1 + ((self.last + self.size - self.count) % self.size)
  52                 return self.data[i]
  53         end
  54         return nil
  55 end
  56
  57 function history:newest ()
  58         if self.count then
  59                 return self.data[self.last]
  60         end
  61         return nil
  62 end
  63
  64 function history:walk_reverse ()
  65         local s = self
  66         local count = s.count
  67         local index = s.last
  68
  69         return function ()
  70                 local ret = nil
  71                 if count > 0 then
  72                         local i = 1 + (s.size + index - 1) % s.size
  73                         ret = s.data[i]
  74                         count = count - 1
  75                         index = index - 1
  76                 end
  77                 return ret
  78         end
  79 end
  80
  81