lsyncd/mantle/queue.lua
Axel Kittenberger 902b2c77cd cleanups
2018-03-30 15:15:49 +02:00

295 lines
3.6 KiB
Lua

--
-- queue.lua from Lsyncd -- the Live (Mirror) Syncing Demon
--
--
-- The queue is optimized for FILO operation.
--
--
-- License: GPLv2 (see COPYING) or any later version
-- Authors: Axel Kittenberger <axkibe@gmail.com>
--
if lsyncd_version
then
print( 'Error, Lsyncd mantle already loaded' )
os.exit( -1 )
end
--
-- Metatable.
--
local mt = { }
--
-- Key to native table.
--
local k_nt = { }
--
-- On accessing a nil index.
--
mt.__index = function
(
self,
k -- key used to access
)
if type( k ) ~= 'number'
then
error( 'Queue, key "'..k..'" invalid', 2 )
end
return self[ k_nt ][ k ]
end
--
-- On assigning a new index.
--
mt.__newindex = function
(
self,
k, -- key value to assign to
v -- value to assign
)
error( 'Queues are not directly assignable.', 2 )
end
--
-- Returns the size of the queue.
--
mt.__len = function
(
self
)
return self[ k_nt ].size
end
--
-- Returns the first item of the Queue.
--
local function first
(
self
)
local nt = self[ k_nt ]
return nt[ nt.first ]
end
--
-- Returns the last item of the Queue.
--
local function last
(
self
)
local nt = self[ k_nt ]
return nt[ nt.last ]
end
--
-- Pushes a value on the queue.
-- Returns the last value
--
local function push
(
self,
value -- value to push
)
if not value
then
error( 'Queue pushing nil value', 2 )
end
local nt = self[ k_nt ]
local last = nt.last + 1
nt.last = last
nt[ last ] = value
nt.size = nt.size + 1
return last
end
--
-- Removes an item at pos from the Queue.
--
local function remove
(
self,
pos -- position to remove
)
local nt = self[ k_nt ]
if nt[ pos ] == nil
then
error( 'Removing nonexisting item in Queue', 2 )
end
nt[ pos ] = nil
-- if removing first or last element,
-- the queue limits are adjusted.
if pos == nt.first
then
local last = nt.last
while nt[ pos ] == nil and pos <= last
do
pos = pos + 1
end
nt.first = pos
elseif pos == nt.last
then
local first = nt.first
while nt[ pos ] == nil and pos >= first
do
pos = pos - 1
end
nt.last = pos
end
-- reset the indizies if the queue is empty
if nt.last < nt.first
then
nt.first = 1
nt.last = 0
end
nt.size = nt.size - 1
end
--
-- Replaces a value.
--
local function replace
(
self,
pos, -- position to replace
value -- the new entry
)
local nt = self[ k_nt ]
if nt[ pos ] == nil
then
error( 'Trying to replace an unset Queue entry.' )
end
nt[ pos ] = value
end
--
-- Queue iterator ( stateless )
--
local function iter
(
self,
pos
)
local nt = self[ k_nt ]
pos = pos + 1
while nt[ pos ] == nil and pos <= nt.last
do
pos = pos + 1
end
if pos > nt.last then return nil end
return pos, nt[ pos ]
end
--
-- Reverse queue iterator (stateless)
--
local function revIter
(
self,
pos
)
local nt = self[ k_nt ]
pos = pos - 1
while nt[ pos ] == nil and pos >= nt.first
do
pos = pos - 1
end
if pos < nt.first
then
return nil
end
return pos, nt[ pos ]
end
--
-- Iteraters through the queue
-- returning all non-nil pos-value entries.
--
local function qpairs
(
self
)
return iter, self, self[ k_nt ].first - 1
end
--
-- Iteraters backwards through the queue
-- returning all non-nil pos-value entries.
--
local function qpairsReverse
(
self
)
return revIter, self, self[ k_nt ].last + 1
end
--
-- Creates a new queue.
--
local function new
( )
local q =
{
first = first,
last = last,
push = push,
qpairs = qpairs,
qpairsReverse = qpairsReverse,
remove = remove,
replace = replace,
[ k_nt ] =
{
first = 1,
last = 0,
size = 0
}
}
setmetatable( q, mt )
return q
end
--
-- Exported interface
--
Queue = { new = new }