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util/id.lua @ 13186:affaf6d08d26
util.datamanager: Pad list writes to avoid crossing block boundaries
By padding items so that they do not cross block boundaries, it becomes
eaiser to delete whole blocks with fallocate() without cutting items
in half, improving efficiency of such operations.
Since list stores are used for message archives, where the most common
deletion operation would be of the oldest entires, at the top of the
file. With this, all blocks that contain items to be removed could be
deleted without needing to read, delete and write out the whole file.
author | Kim Alvefur <zash@zash.se> |
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date | Wed, 07 Jun 2023 00:39:30 +0200 |
parent | 12975:d10957394a3c |
rev | line source |
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util.id: New util for producing random identifiers of varying sizes
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1 -- Prosody IM |
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2 -- Copyright (C) 2008-2017 Matthew Wild |
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3 -- Copyright (C) 2008-2017 Waqas Hussain |
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4 -- Copyright (C) 2008-2017 Kim Alvefur |
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5 -- |
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6 -- This project is MIT/X11 licensed. Please see the |
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7 -- COPYING file in the source package for more information. |
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8 -- |
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9 |
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10 local s_gsub = string.gsub; |
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11 local random_bytes = require "prosody.util.random".bytes; |
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12 local base64_encode = require "prosody.util.encodings".base64.encode; |
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13 |
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14 local b64url = { ["+"] = "-", ["/"] = "_", ["="] = "" }; |
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15 local function b64url_random(len) |
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16 return (s_gsub(base64_encode(random_bytes(len)), "[+/=]", b64url)); |
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17 end |
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18 |
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19 return { |
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20 -- sizes divisible by 3 fit nicely into base64 without padding== |
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21 |
12111 | 22 -- for short lived things with low risk of collisions |
23 tiny = function() return b64url_random(3); end; | |
24 | |
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25 -- close to 8 bytes, should be good enough for relatively short lived or uses |
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26 -- scoped by host or users, half the size of an uuid |
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27 short = function() return b64url_random(9); end; |
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28 |
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29 -- more entropy than uuid at 2/3 the size |
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30 -- should be okay for globally scoped ids or security token |
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31 medium = function() return b64url_random(18); end; |
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32 |
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33 -- as long as an uuid but MOAR entropy |
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34 long = function() return b64url_random(27); end; |
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35 |
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36 -- pick your own adventure |
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37 custom = function (size) |
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38 return function () return b64url_random(size); end; |
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39 end; |
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40 } |