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