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--[[
Copyright (c) 2012-2014 Kaarle Ritvanen
See LICENSE file for license details
--]]
local M = {}
local err = require('aconf.error')
local object = require('aconf.object')
local class = object.class
local pth = require('aconf.path')
local copy = require('aconf.util').copy
-- 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
local function gen_number()
generation = generation + 1
return generation
end
M.TransactionBackend = 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 = 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
local function remove_list_value(list, value)
value = tostring(value)
for i, v in ipairs(list) do
if tostring(v) == value then
table.remove(list, i)
return
end
end
end
M.Transaction = class(M.TransactionBackend)
function M.Transaction:init(backend)
object.super(self, M.Transaction):init()
self.backend = backend
self:reset()
end
function M.Transaction:reset()
self.started = gen_number()
self.access_time = {}
self.added = {}
self.modified = {}
self.deleted = {}
end
function M.Transaction:get(path)
if self.deleted[path] then return nil, self.mod_time[path] end
for _, tbl in ipairs{self.added, self.modified} do
if tbl[path] ~= nil then
return copy(tbl[path]), self.mod_time[path]
end
end
local value, timestamp = self.backend:get_if_older(path, self.started)
self.access_time[path] = timestamp
return value, timestamp
end
function M.Transaction:_set_multiple(mods)
local function set(path, value, new)
local delete = value == nil
if self.added[path] == nil and (not new or self.deleted[path]) then
self.modified[path] = value
self.deleted[path] = delete
else self.added[path] = value end
end
for _, mod in ipairs(mods) do
local path, value = unpack(mod)
local ppath = pth.parent(path)
local parent = self:get(ppath)
if parent == nil then
parent = {}
self:set(ppath, parent)
end
local name = pth.name(path)
local old = self:get(path)
local is_table = type(value) == 'table'
local delete = value == nil
if delete then self:check_deleted(path) end
if type(old) == 'table' then
if delete then
for _, child in ipairs(old) do self:set(pth.join(path, child)) end
elseif is_table then return
elseif #old > 0 then
error('Cannot assign a primitive value to non-leaf node '..path)
end
end
if is_table then value = {} end
set(path, value, old == nil)
local function set_parent()
set(ppath, parent)
self.mod_time[ppath] = self.mod_time[path]
end
if old == nil and not delete then
table.insert(parent, name)
set_parent()
elseif old ~= nil and delete then
remove_list_value(parent, name)
set_parent()
end
end
end
function M.Transaction:check_deleted(path) end
function M.Transaction:commit()
local mods = {}
local handled = {}
local function insert(path, value)
assert(not handled[path])
table.insert(mods, {path, value})
handled[path] = true
end
local function insert_add(path)
if not handled[path] then
local pp = pth.parent(path)
if self.added[pp] then insert_add(pp) end
insert(path, self.added[path])
end
end
local function insert_del(path)
if not handled[path] then
local value = self.backend:get(path)
if type(value) == 'table' then
for _, child in ipairs(value) do
local cp = pth.join(path, child)
assert(self.deleted[cp])
insert_del(cp)
end
end
insert(path)
end
end
for path, deleted in pairs(self.deleted) do
if deleted then insert_del(path) end
end
for path, value in pairs(self.modified) do
if type(value) ~= 'table' then insert(path, value) end
end
for path, _ in pairs(self.added) do insert_add(path) end
self.backend:comp_and_setm(self.access_time, mods)
self:reset()
end
return M
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