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<?php
/*
* This file is part of the Predis package.
*
* (c) 2009-2020 Daniele Alessandri
* (c) 2021-2023 Till Krüss
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Predis\Collection\Iterator;
use InvalidArgumentException;
use Iterator;
use Predis\ClientInterface;
use Predis\NotSupportedException;
use ReturnTypeWillChange;
/**
* Abstracts the iteration of items stored in a list by leveraging the LRANGE
* command wrapped in a fully-rewindable PHP iterator.
*
* This iterator tries to emulate the behaviour of cursor-based iterators based
* on the SCAN-family of commands introduced in Redis <= 2.8, meaning that due
* to its incremental nature with multiple fetches it can only offer limited
* guarantees on the returned elements because the collection can change several
* times (trimmed, deleted, overwritten) during the iteration process.
*
* @see http://redis.io/commands/lrange
*/
class ListKey implements Iterator
{
protected $client;
protected $count;
protected $key;
protected $valid;
protected $fetchmore;
protected $elements;
protected $position;
protected $current;
/**
* @param ClientInterface $client Client connected to Redis.
* @param string $key Redis list key.
* @param int $count Number of items retrieved on each fetch operation.
*
* @throws InvalidArgumentException
*/
public function __construct(ClientInterface $client, $key, $count = 10)
{
$this->requiredCommand($client, 'LRANGE');
if ((false === $count = filter_var($count, FILTER_VALIDATE_INT)) || $count < 0) {
throw new InvalidArgumentException('The $count argument must be a positive integer.');
}
$this->client = $client;
$this->key = $key;
$this->count = $count;
$this->reset();
}
/**
* Ensures that the client instance supports the specified Redis command
* required to fetch elements from the server to perform the iteration.
*
* @param ClientInterface $client Client connected to Redis.
* @param string $commandID Command ID.
*
* @throws NotSupportedException
*/
protected function requiredCommand(ClientInterface $client, $commandID)
{
if (!$client->getCommandFactory()->supports($commandID)) {
throw new NotSupportedException("'$commandID' is not supported by the current command factory.");
}
}
/**
* Resets the inner state of the iterator.
*/
protected function reset()
{
$this->valid = true;
$this->fetchmore = true;
$this->elements = [];
$this->position = -1;
$this->current = null;
}
/**
* Fetches a new set of elements from the remote collection, effectively
* advancing the iteration process.
*
* @return array
*/
protected function executeCommand()
{
return $this->client->lrange($this->key, $this->position + 1, $this->position + $this->count);
}
/**
* Populates the local buffer of elements fetched from the server during the
* iteration.
*/
protected function fetch()
{
$elements = $this->executeCommand();
if (count($elements) < $this->count) {
$this->fetchmore = false;
}
$this->elements = $elements;
}
/**
* Extracts next values for key() and current().
*/
protected function extractNext()
{
++$this->position;
$this->current = array_shift($this->elements);
}
/**
* {@inheritdoc}
*/
#[ReturnTypeWillChange]
public function rewind()
{
$this->reset();
$this->next();
}
/**
* {@inheritdoc}
*/
#[ReturnTypeWillChange]
public function current()
{
return $this->current;
}
/**
* {@inheritdoc}
*/
#[ReturnTypeWillChange]
public function key()
{
return $this->position;
}
/**
* {@inheritdoc}
*/
#[ReturnTypeWillChange]
public function next()
{
if (!$this->elements && $this->fetchmore) {
$this->fetch();
}
if ($this->elements) {
$this->extractNext();
} else {
$this->valid = false;
}
}
/**
* {@inheritdoc}
*/
#[ReturnTypeWillChange]
public function valid()
{
return $this->valid;
}
}
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