gluon-geolocator: geolocator drop dep on nixio & use posix lockfile

Signed-off-by: Jan-Tarek Butt <tarek@ring0.de>

package/gluon-geolocator/luasrc/lib/gluon/geolocator/geolocator

@@ -1,7 +1,9 @@
 #!/usr/bin/lua
 
+local bit = require('bit')
+local unistd = require('posix.unistd')
+local fcntl = require('posix.fcntl')
 local uci = require('simple-uci').cursor()
-local nixio = require('nixio')
 local json = require ("jsonc")
 local ubus = require 'ubus'
 local iwinfo = require("iwinfo")
@@ -16,9 +18,21 @@ end
 
 -- PID file to ensure the geolocator isn't running parallel
 local lockfile = '/var/lock/geolocator.lock'
-local lockfd = nixio.open(lockfile, 'w', 'rw-------')
+local lockfd, err = fcntl.open(lockfile, bit.bor(fcntl.O_WRONLY, fcntl.O_CREAT), 384) -- mode 0600
 
-if not lockfd:lock('tlock') then
+if not lockfd then
+	io.stderr:write(err, '\n')
+	os.exit(1)
+end
+
+local ok, _ = fcntl.fcntl(lockfd, fcntl.F_SETLK, {
+	l_start = 0,
+	l_len = 0,
+	l_type = fcntl.F_WRLCK,
+	l_whence = unistd.SEEK_SET,
+})
+
+if not ok then
 	io.stderr:write(string.format(
 		"Unable to lock file %s. Make sure there is no other instance of the geolocator running.\n",
 		lockfile
@@ -81,7 +95,7 @@ local function locate()
 		return true
 	end)
 
-	assert(#found_bssids >= 12, 'insufficient BSSIDs found')
+	assert(#found_bssids > 0, 'insufficient BSSIDs found')
 
 	local data = receive_json('http://openwifi.su/api/v1/bssids/' .. table.concat(found_bssids, ','))
 	assert(type(data) == 'table' and data.lon and data.lat, 'location not available')