flm01/mote/v2/openwrt/package/flukso/luasrc/rrd/server.lua

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--[[
rrd.pipe - Lua 5.1 submodule for connecting to rrdtool in pipe mode
Copyright (C) 2010 Bart Van Der Meerssche <bart.vandermeerssche@flukso.net>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
]]--
local nixio = require 'nixio'
local getfenv, setmetatable =
getfenv, setmetatable
module (...)
local modenv = getfenv()
--- Start an rrdtool server in pipe mode.
--
-- +----------+ +-----------+
-- | | fd[4] ---> fd[3] | |
-- | parent | | rrdtool |
-- | | fd[5] <--- fd[6] | |
-- +----------+ +-----------+
--
-- @return rrd.server (RS) object
function start()
local fd = {}
fd[3], fd[4] = nixio.pipe()
fd[5], fd[6] = nixio.pipe()
local pid, code, err = nixio.fork()
if pid and pid ~= 0 then -- parent
fd[3]:close()
fd[6]:close()
fd[5]:setblocking(false)
return setmetatable({pid = pid, fdr = fd[5], fdw = fd[4]}, {__index = modenv})
elseif pid == 0 then -- child
fd[4]:close()
fd[5]:close()
nixio.dup(fd[3], nixio.stdin)
nixio.dup(fd[6], nixio.stdout)
nixio.execp('rrdtool', '-')
else -- error
nixio.syslog("err", "Unable to fork(): " .. err)
return nil, code, err
end
end
--- Stop the rrdtool server.
-- @param rrd.server (RS) object
-- @return true
function stop(RS)
RS.fdr:close()
RS.fdw:close()
return nixio.kill(RS.pid, nixio.const.SIGKILL)
end