purposes
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path: root/builtin/game/forceloading.lua
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-- Prevent anyone else accessing those functions
local forceload_block = core.forceload_block
local forceload_free_block = core.forceload_free_block
core.forceload_block = nil
core.forceload_free_block = nil

local blocks_forceloaded
local blocks_temploaded = {}
local total_forceloaded = 0

local BLOCKSIZE = core.MAP_BLOCKSIZE
local function get_blockpos(pos)
	return {
		x = math.floor(pos.x/BLOCKSIZE),
		y = math.floor(pos.y/BLOCKSIZE),
		z = math.floor(pos.z/BLOCKSIZE)}
end

-- When we create/free a forceload, it's either transient or persistent. We want
-- to add to/remove from the table that corresponds to the type of forceload, but
-- we also need the other table because whether we forceload a block depends on
-- both tables.
-- This function returns the "primary" table we are adding to/removing from, and
-- the other table.
local function get_relevant_tables(transient)
	if transient then
		return blocks_temploaded, blocks_forceloaded
	else
		return blocks_forceloaded, blocks_temploaded
	end
end

function core.forceload_block(pos, transient)
	local blockpos = get_blockpos(pos)
	local hash = core.hash_node_position(blockpos)
	local relevant_table, other_table = get_relevant_tables(transient)
	if relevant_table[hash] ~= nil then
		relevant_table[hash] = relevant_table[hash] + 1
		return true
	elseif other_table[hash] ~= nil then
		relevant_table[hash] = 1
	else
		if total_forceloaded >= (tonumber(core.settings:get("max_forceloaded_blocks")) or 16) then
			return false
		end
		total_forceloaded = total_forceloaded+1
		relevant_table[hash] = 1
		forceload_block(blockpos)
		return true
	end
end

function core.forceload_free_block(pos, transient)
	local blockpos = get_blockpos(pos)
	local hash = core.hash_node_position(blockpos)
	local relevant_table, other_table = get_relevant_tables(transient)
	if relevant_table[hash] == nil then return end
	if relevant_table[hash] > 1 then
		relevant_table[hash] = relevant_table[hash] - 1