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--[[
Copyright (c) 2012 Kaarle Ritvanen
See LICENSE file for license details
--]]
module(..., package.seeall)
-- TODO each transaction backend (i.e. persistence manager or
-- transaction proper) should be implemented as a thread or have its
-- internal state stored in shared storage (with appropriate locking)
local generation = 0
function gen_number()
generation = generation + 1
return generation
end
TransactionBackend = require('acf.object').class()
function TransactionBackend:init() self.mod_time = {} end
function TransactionBackend:get_if_older(path, timestamp)
local value, ts = self:get(path)
if ts > timestamp then error('Concurrent modification: '..path) end
return value, ts
end
function TransactionBackend:set(path, t, value)
self:set_multiple{{path, t, value}}
end
function TransactionBackend:set_multiple(mods)
-- TODO delegate to PM backends?
local timestamp = gen_number()
for _, mod in ipairs(mods) do
self.mod_time[mod[1]] = timestamp
end
end
-- TODO should be atomic, mutex with set_multiple
function TransactionBackend:comp_and_setm(accessed, mods)
for path, timestamp in pairs(accessed) do
self:get_if_older(path, timestamp)
end
self:set_multiple(mods)
end
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