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<?php
namespace itertools;
use IteratorIterator;
use Traversable;
use ArrayIterator;
/**
* splits a iterator into smaller chunks. this can be used for batch processing.
*
* Example:
* $iterator = new rangeiterator();
* $batchsize = 100;
* foreach(new hunkingiterator($iterator, $batchsize) as $chunk) {
* $pdo->starttransaction();
* foreach($chunk as $element) {
* // process the iterator elements. using the transaction inside the chunkiterator makes sure the transaction stays small
* }
* $pdo->commit();
*/
class ChunkingIterator extends IteratorIterator
{
protected $chunkSize;
protected $chunk;
protected $chunkIndex;
public function __construct($iterator, $chunkSize)
parent::__construct(is_array($iterator) ? new ArrayIterator($iterator) : $iterator);
$this->chunkSize = $chunkSize;
$this->chunk = array();
}
public function rewind()
$this->getInnerIterator()->rewind();
$this->chunkIndex = 0;
protected function ensureBatchPresent()
if(!is_null(key($this->chunk))) {
// chunk not completely fetched;
return;
$inner = $this->getInnerIterator();
for($i = 0; $i < $this->chunkSize && $inner->valid(); $i++) {
$this->chunk[] = $inner->current();
$inner->next();
public function key()
return $this->chunkIndex;
public function next()
$this->chunkIndex += 1;
public function current()
$this->ensureBatchPresent();
return $this->chunk;
public function valid()
return count($this->chunk) != 0;
SuRaMoN /
itertools
