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InventoryTransaction: beware of conflicting slot change actions with the same origin/target

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these types of chains would never normally occur, but they've been seen in the wild. Attempting to resolve such chains has exponentially increasing complexity.
This commit is contained in:
Dylan K. Taylor 2020-11-10 16:45:20 +00:00
parent fa920aa868
commit c368ebb5e7
1 changed files with 22 additions and 9 deletions
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31
src/pocketmine/inventory/transaction/InventoryTransaction.php
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@ -230,21 +230,34 @@ class InventoryTransaction{
protected function findResultItem(Item $needOrigin, array $possibleActions) : ?Item{
assert(count($possibleActions) > 0);
$candidate = null;
$newList = $possibleActions;
foreach($possibleActions as $i => $action){
if($action->getSourceItem()->equalsExact($needOrigin)){
$newList = $possibleActions;
if($candidate !== null){
/*
* we found multiple possible actions that match the origin action
* this means that there are multiple ways that this chain could play out
* if we cared so much about this, we could build all the possible chains in parallel and see which
* variation managed to complete the chain, but this has an extremely high complexity which is not
* worth the trouble for this scenario (we don't usually expect to see chains longer than a couple
* of actions in here anyway), and might still result in multiple possible results.
*/
return null;
}
$candidate = $action;
unset($newList[$i]);
if(count($newList) === 0){
return $action->getTargetItem();
}
$result = $this->findResultItem($action->getTargetItem(), $newList);
if($result !== null){
return $result;
}
}
}
if($candidate === null){
//chaining is not possible with this origin, none of the actions are valid
return null;
}
return null;
if(count($newList) === 0){
return $candidate->getTargetItem();
}
return $this->findResultItem($candidate->getTargetItem(), $newList);
}
/**