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<?php |
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namespace Hexogen\KDTree; |
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use Hexogen\KDTree\Interfaces\ItemInterface; |
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use Hexogen\KDTree\Interfaces\KDTreeInterface; |
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use Hexogen\KDTree\Interfaces\NodeInterface; |
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use Hexogen\KDTree\Interfaces\TreePersisterInterface; |
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class FSTreePersister implements TreePersisterInterface |
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{ |
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/** |
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* @var string path to the file |
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*/ |
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private $path; |
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/** |
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* @var resource file handler |
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*/ |
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private $handler; |
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/** |
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* @var int |
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*/ |
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private $dimensions; |
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/** |
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* @var int |
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*/ |
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private $nodeMemorySize; |
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public function __construct(string $path) |
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{ |
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$this->path = $path; |
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} |
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/** |
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* @api |
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* @param KDTreeInterface $tree |
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* @param string $identifier that identifies persisted tree(may be a filename, database name etc.) |
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* @return mixed |
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*/ |
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public function convert(KDTreeInterface $tree, string $identifier) |
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{ |
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$this->initTree($identifier); |
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$this->dimensions = $tree->getDimensionCount(); |
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$this->calculateNodeSize(); |
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$this->specifyNumberOfDimensions(); |
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$this->specifyNumberOfItems($tree); |
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$upperBound = $tree->getMaxBoundary(); |
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$this->writeCoordinate($upperBound); |
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$lowerBound = $tree->getMinBoundary(); |
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$this->writeCoordinate($lowerBound); |
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$root = $tree->getRoot(); |
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if ($root) { |
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$this->writeNode($root); |
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} |
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fclose($this->handler); |
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} |
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/** |
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* @param NodeInterface $node |
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*/ |
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private function writeNode(NodeInterface $node) |
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{ |
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$position = ftell($this->handler); |
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$item = $node->getItem(); |
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$this->writeItemId($item); |
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$dataChunk = pack('V', 0); // left position currently unknown so it equal 0/null |
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fwrite($this->handler, $dataChunk); |
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$rightNode = $node->getRight(); |
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$rightPosition = 0; |
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if ($rightNode) { |
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$rightPosition = $position + $this->nodeMemorySize; |
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} |
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$dataChunk = pack('V', $rightPosition); |
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fwrite($this->handler, $dataChunk); |
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$this->saveItemCoordinate($item); |
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if ($rightNode) { |
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$this->writeNode($rightNode); |
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} |
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$leftNode = $node->getLeft(); |
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if ($leftNode == null) { |
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return; |
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} |
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$this->persistLeftLink($position); |
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$this->writeNode($leftNode); |
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} |
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/** |
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* @param array $coordinate |
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*/ |
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private function writeCoordinate(array $coordinate) |
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{ |
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$dataChunk = pack('d'.$this->dimensions, ...$coordinate); |
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fwrite($this->handler, $dataChunk); |
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} |
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/** |
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* @param string $identifier |
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*/ |
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private function initTree(string $identifier) |
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{ |
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$this->handler = fopen($this->path . '/' . $identifier, 'wb'); |
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} |
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/** |
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* Calculate memory size in file needed for single node |
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*/ |
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private function calculateNodeSize() |
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{ |
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$this->nodeMemorySize = 3 * FSKDTree::INT_LENGTH + $this->dimensions * FSKDTree::FLOAT_LENGTH; |
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} |
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/** |
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* Specify number of dimensions according to file format |
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*/ |
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private function specifyNumberOfDimensions() |
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{ |
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$dataChunk = pack('V', $this->dimensions); |
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fwrite($this->handler, $dataChunk); |
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} |
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/** |
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* @param KDTreeInterface $tree |
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*/ |
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private function specifyNumberOfItems(KDTreeInterface $tree) |
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{ |
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$itemCount = $tree->getItemCount(); |
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$dataChunk = pack('V', $itemCount); |
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fwrite($this->handler, $dataChunk); |
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} |
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/** |
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* @param $item |
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*/ |
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private function saveItemCoordinate(ItemInterface $item) |
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{ |
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$coordinate = []; |
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for ($i = 0; $i < $this->dimensions; $i++) { |
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$coordinate[] = $item->getNthDimension($i); |
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} |
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$this->writeCoordinate($coordinate); |
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} |
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/** |
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* Persist current position before writing left node |
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* @param int $position |
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*/ |
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private function persistLeftLink(int $position) |
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{ |
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$leftPosition = ftell($this->handler); |
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fseek($this->handler, $position + FSKDTree::INT_LENGTH); |
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$dataChunk = pack('V', $leftPosition); |
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fwrite($this->handler, $dataChunk); |
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fseek($this->handler, $leftPosition); |
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} |
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/** |
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* @param $item |
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*/ |
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private function writeItemId(ItemInterface $item) |
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{ |
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$itemId = $item->getId(); |
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$dataChunk = pack('V', $itemId); |
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fwrite($this->handler, $dataChunk); |
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} |
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} |
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hexogen /
kdtree
