Generate a squuid in nginx (openresty)

datomic-squuid.lua

-- Datomic SQUUID layout:
-- xxxxxxxx-xxxx-4xxx-Vxxx-xxxxxxxxxxxx
-- ^^^^^^^^ ^^^^ ^
--     |     |   |^^^ ^
--     |     |   | |  |^^^-^^^^^^^^^^^^
--     |     |   | |  | |
--     |     |   | |  | |- random
--     |     |   | |  |- IETF variant {8,9,a,b}
--     |     |   | |- random
--     |     |   |- Version 4
--     |     |- random
--     |- ms since epoch rounded to seconds

local str = require "resty.string"
local random = require "resty.random"

ngx.say("-----------------------------------------------------")

function squuid(hash)
  -- elapsed seconds from the epoch
  local t_epoch = ngx.time()
  local p1 = bit.tohex(t_epoch, 8)
  local p2 = string.sub(hash, 9, 12)
  local p3 = "4" .. string.sub(hash, 14, 16)
  local variant = "0x" .. string.sub(hash,17,18);
  variant = bit.band( variant , 0x3f) -- clear variant
  variant = bit.bor( variant, 0x80) -- set to IETF variant
  local p4 = bit.tohex(variant,2) .. string.sub(hash, 19, 20)
  local p5 = string.sub(hash, 21)
  return p1 .. "-" .. p2 .. "-" .. p3 .. "-" .. p4 .. "-" .. p5
  --return p1 ..  p2 .. p3 .. p4 .. p5
end

-- A random filename for upload before renaming:
local rnd_file = str.to_hex( random.bytes(16) )
local md5 = ngx.md5(rnd_file)

ngx.say(md5)
ngx.say(squuid(md5))