itertools\ChunkingIterator

Complexity

Total Complexity

11

Size/Duplication

Total Lines	56
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	0

Importance

Changes

0

7 Methods

Rating	Name	Duplication	Size	Complexity
A	__construct()	0	6	2
A	rewind()	0	6	1
A	ensureBatchPresent()	0	12	4
A	key()	0	4	1
A	next()	0	5	1
A	current()	0	5	1
A	valid()	0	5	1

<?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->chunk = array();
        $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->chunk = array();
        $this->chunkIndex += 1;
    }

    public function current()
    {
        $this->ensureBatchPresent();
        return $this->chunk;
    }

    public function valid()
    {
        $this->ensureBatchPresent();
        return count($this->chunk) != 0;
    }
}