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<?php |
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namespace Doctrine\DBAL\Internal; |
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use function array_reverse; |
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/** |
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* DependencyOrderCalculator implements topological sorting, which is an ordering |
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* algorithm for directed graphs (DG) and/or directed acyclic graphs (DAG) by |
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* using a depth-first searching (DFS) to traverse the graph built in memory. |
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* This algorithm have a linear running time based on nodes (V) and dependency |
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* between the nodes (E), resulting in a computational complexity of O(V + E). |
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*/ |
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final class DependencyOrderCalculator |
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{ |
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public const NOT_VISITED = 0; |
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public const IN_PROGRESS = 1; |
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public const VISITED = 2; |
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/** |
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* Matrix of nodes (aka. vertex). |
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* Keys are provided hashes and values are the node definition objects. |
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* |
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* @var array<string,DependencyOrderNode> |
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*/ |
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private $nodeList = []; |
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/** |
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* Volatile variable holding calculated nodes during sorting process. |
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* |
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* @var array<object> |
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*/ |
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private $sortedNodeList = []; |
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/** |
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* Checks for node (vertex) existence in graph. |
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*/ |
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public function hasNode(string $hash) : bool |
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{ |
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return isset($this->nodeList[$hash]); |
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} |
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/** |
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* Adds a new node (vertex) to the graph, assigning its hash and value. |
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* |
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* @param object $node |
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*/ |
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public function addNode(string $hash, $node) : void |
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{ |
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$vertex = new DependencyOrderNode(); |
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$vertex->hash = $hash; |
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$vertex->state = self::NOT_VISITED; |
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$vertex->value = $node; |
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$this->nodeList[$hash] = $vertex; |
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} |
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/** |
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* Adds a new dependency (edge) to the graph using their hashes. |
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*/ |
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public function addDependency(string $fromHash, string $toHash) : void |
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{ |
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$vertex = $this->nodeList[$fromHash]; |
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$edge = new DependencyOrderEdge(); |
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$edge->from = $fromHash; |
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$edge->to = $toHash; |
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$vertex->dependencyList[$toHash] = $edge; |
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} |
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/** |
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* Return a valid order list of all current nodes. |
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* The desired topological sorting is the reverse post order of these searches. |
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* |
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* {@internal Highly performance-sensitive method.} |
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* |
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* @return array<object> |
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*/ |
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public function sort() : array |
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{ |
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foreach ($this->nodeList as $vertex) { |
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if ($vertex->state !== self::NOT_VISITED) { |
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continue; |
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} |
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$this->visit($vertex); |
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} |
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$sortedList = $this->sortedNodeList; |
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$this->nodeList = []; |
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$this->sortedNodeList = []; |
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return array_reverse($sortedList); |
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} |
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/** |
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* Visit a given node definition for reordering. |
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* |
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* {@internal Highly performance-sensitive method.} |
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*/ |
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private function visit(DependencyOrderNode $vertex) |
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{ |
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$vertex->state = self::IN_PROGRESS; |
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foreach ($vertex->dependencyList as $edge) { |
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$adjacentVertex = $this->nodeList[$edge->to]; |
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switch ($adjacentVertex->state) { |
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case self::VISITED: |
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case self::IN_PROGRESS: |
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// Do nothing, since node was already visited or is |
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// currently visited |
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break; |
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case self::NOT_VISITED: |
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$this->visit($adjacentVertex); |
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} |
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} |
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if ($vertex->state === self::VISITED) { |
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return; |
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} |
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$vertex->state = self::VISITED; |
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$this->sortedNodeList[] = $vertex->value; |
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} |
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} |
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doctrine /
dbal
