83 lines
1.6 KiB
Lua
83 lines
1.6 KiB
Lua
-- tz -- A simple timezone module for interpreting zone files
|
|
|
|
local M = {}
|
|
|
|
local tstart = 0
|
|
local tend = 0
|
|
local toffset = 0
|
|
local thezone = "eastern"
|
|
|
|
function M.setzone(zone)
|
|
thezone = zone
|
|
return M.exists(thezone)
|
|
end
|
|
|
|
function M.exists(zone)
|
|
return file.exists(zone .. ".zone")
|
|
end
|
|
|
|
function M.getzones()
|
|
local result = {}
|
|
for fn, _ in pairs(file.list()) do
|
|
local _, _, prefix = string.find(fn, "(.*).zone")
|
|
if prefix then
|
|
table.insert(result, prefix)
|
|
end
|
|
end
|
|
return result
|
|
end
|
|
|
|
local function load(t)
|
|
local z = file.open(thezone .. ".zone", "r")
|
|
|
|
local hdr = z:read(20)
|
|
local magic = struct.unpack("c4 B", hdr)
|
|
|
|
if magic == "TZif" then
|
|
local lens = z:read(24)
|
|
local ttisgmt_count, ttisdstcnt, leapcnt, timecnt, typecnt, charcnt -- luacheck: no unused
|
|
= struct.unpack("> LLLLLL", lens)
|
|
|
|
local times = z:read(4 * timecnt)
|
|
local typeindex = z:read(timecnt)
|
|
local ttinfos = z:read(6 * typecnt)
|
|
|
|
z:close()
|
|
|
|
local offset = 1
|
|
local tt
|
|
for i = 1, timecnt do
|
|
tt = struct.unpack(">l", times, (i - 1) * 4 + 1)
|
|
if t < tt then
|
|
offset = (i - 2)
|
|
tend = tt
|
|
break
|
|
end
|
|
tstart = tt
|
|
end
|
|
|
|
local tindex = struct.unpack("B", typeindex, offset + 1)
|
|
toffset = struct.unpack(">l", ttinfos, tindex * 6 + 1)
|
|
else
|
|
tend = 0x7fffffff
|
|
tstart = 0
|
|
end
|
|
end
|
|
|
|
|
|
function M.getoffset(t)
|
|
if t < tstart or t >= tend then
|
|
-- Ignore errors
|
|
local ok, msg = pcall(function ()
|
|
load(t)
|
|
end)
|
|
if not ok then
|
|
print (msg)
|
|
end
|
|
end
|
|
|
|
return toffset, tstart, tend
|
|
end
|
|
|
|
return M
|