Replace DFS with BFS.

Replace the recursive depth-first search of a wire network with an
iterative breadth-first search, primarily to reduce memory footprint and
eliminate the possibility of stack overflow.
This commit is contained in:
Christopher Head 2016-11-16 21:42:17 -08:00 committed by Auke Kok
parent 7ecb29e87f
commit 514fb2e289

@ -63,27 +63,54 @@ function digiline:rules_link_anydir(output, input)
or digiline:rules_link(input, output)
end
local function queue_new()
return {nextRead = 1, nextWrite = 1}
end
local function queue_empty(queue)
return queue.nextRead == queue.nextWrite
end
local function queue_enqueue(queue, object)
local nextWrite = queue.nextWrite
queue[nextWrite] = object
queue.nextWrite = nextWrite + 1
end
local function queue_dequeue(queue)
local nextRead = queue.nextRead
local object = queue[nextRead]
queue[nextRead] = nil
queue.nextRead = nextRead + 1
return object
end
function digiline:transmit(pos, channel, msg, checked)
local checkedid = tostring(pos.x).."_"..tostring(pos.y).."_"..tostring(pos.z)
if checked[checkedid] then return end
checked[checkedid] = true
local queue = queue_new()
queue_enqueue(queue, pos)
while not queue_empty(queue) do
local curPos = queue_dequeue(queue)
local node = minetest.get_node(curPos)
local spec = digiline:getspec(node)
if spec then
-- Effector actions --> Receive
if spec.effector then
spec.effector.action(curPos, node, channel, msg)
end
local node = minetest.get_node(pos)
local spec = digiline:getspec(node)
if not spec then return end
-- Effector actions --> Receive
if spec.effector then
spec.effector.action(pos, node, channel, msg)
end
-- Cable actions --> Transmit
if spec.wire then
local rules = digiline:importrules(spec.wire.rules, node)
for _,rule in ipairs(rules) do
if digiline:rules_link(pos, digiline:addPosRule(pos, rule)) then
digiline:transmit(digiline:addPosRule(pos, rule), channel, msg, checked)
-- Cable actions --> Transmit
if spec.wire then
local rules = digiline:importrules(spec.wire.rules, node)
for _, rule in ipairs(rules) do
local nextPos = digiline:addPosRule(curPos, rule)
if digiline:rules_link(curPos, nextPos) then
local checkedID = tostring(nextPos.x) .. "_" .. tostring(nextPos.y) .. "_" .. tostring(nextPos.z)
if not checked[checkedID] then
checked[checkedID] = true
queue_enqueue(queue, nextPos)
end
end
end
end
end
end