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--[[
Copyright (c) 2012-2013 Kaarle Ritvanen
See LICENSE file for license details
--]]
local M = {}
local err = require('acf.error')
-- 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 M.gen_number()
generation = generation + 1
return generation
end
M.TransactionBackend = require('acf.object').class()
function M.TransactionBackend:init() self.mod_time = {} end
function M.TransactionBackend:get_if_older(path, timestamp)
local value, ts = self:get(path)
if ts > timestamp then err.raise('conflict', path) end
return value, ts
end
function M.TransactionBackend:set(path, value)
self:set_multiple{{path, value}}
end
function M.TransactionBackend:set_multiple(mods)
-- TODO delegate to PM backends?
local timestamp = M.gen_number()
local effective = {}
local function tostr(s) return s ~= nil and tostring(s) or nil end
for _, mod in ipairs(mods) do
local path, value = unpack(mod)
if type(value) == 'table' or type(
self:get(path)
) == 'table' or self:get(path) ~= value then
table.insert(effective, mod)
self.mod_time[path] = timestamp
end
end
self:_set_multiple(effective)
end
-- TODO should be atomic, mutex with set_multiple
function M.TransactionBackend:comp_and_setm(accessed, mods)
local errors = err.ErrorDict()
for path, timestamp in pairs(accessed) do
errors:collect(self.get_if_older, self, path, timestamp)
end
errors:raise()
self:set_multiple(mods)
end
return M
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