prosody
affaf6d08d26
util/uuid.lua

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util/uuid.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>
date Wed, 07 Jun 2023 00:39:30 +0200
parent 12975:d10957394a3c
line wrap: on
line source

-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

local random = require "prosody.util.random";
local random_bytes = random.bytes;
local hex = require "prosody.util.hex".encode;
local m_ceil = math.ceil;

local function get_nibbles(n)
	return hex(random_bytes(m_ceil(n/2))):sub(1, n);
end

local function get_twobits()
	return ("%x"):format(random_bytes(1):byte() % 4 + 8);
end

local function generate()
	-- generate RFC 4122 complaint UUIDs (version 4 - random)
	return get_nibbles(8).."-"..get_nibbles(4).."-4"..get_nibbles(3).."-"..(get_twobits())..get_nibbles(3).."-"..get_nibbles(12);
end

return {
	get_nibbles=get_nibbles;
	generate = generate ;
	-- COMPAT
	seed = random.seed;
};