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koreader/frontend/random.lua

35 lines
982 B
Lua

--- A set of functions to extend math.random and math.randomseed.
local bit = require("bit")
local random = {}
--- Uses current time as seed to randomize.
function random.seed()
math.randomseed(os.time())
end
random.seed()
--- Returns a UUID (v4, random).
function random.uuid(with_dash)
local array = {}
for i = 1, 16 do
table.insert(array, math.random(256) - 1)
end
-- The 13th character should be 4.
array[7] = bit.band(array[7], 79)
array[7] = bit.bor(array[7], 64)
-- The 17th character should be 8 / 9 / a / b.
array[9] = bit.band(array[9], 191)
array[9] = bit.bor(array[9], 128)
if with_dash then
return string.format("%02X%02X%02X%02X-%02X%02X-%02X%02X-%02X%02X-%02X%02X%02X%02X%02X%02X",
unpack(array))
else
return string.format("%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
unpack(array))
end
end
return random