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    <h3>Editing: InputStream.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Process;

use Symfony\Component\Process\Exception\RuntimeException;

/**
 * Provides a way to continuously write to the input of a Process until the InputStream is closed.
 *
 * @author Nicolas Grekas &lt;p@tchwork.com&gt;
 *
 * @implements \IteratorAggregate&lt;int, string&gt;
 */
class InputStream implements \IteratorAggregate
{
    /** @var callable|null */
    private $onEmpty = null;
    private $input = [];
    private $open = true;

    /**
     * Sets a callback that is called when the write buffer becomes empty.
     */
    public function onEmpty(?callable $onEmpty = null)
    {
        $this-&gt;onEmpty = $onEmpty;
    }

    /**
     * Appends an input to the write buffer.
     *
     * @param resource|string|int|float|bool|\Traversable|null $input The input to append as scalar,
     *                                                                stream resource or \Traversable
     */
    public function write($input)
    {
        if (null === $input) {
            return;
        }
        if ($this-&gt;isClosed()) {
            throw new RuntimeException(sprintf('&quot;%s&quot; is closed.', static::class));
        }
        $this-&gt;input[] = ProcessUtils::validateInput(__METHOD__, $input);
    }

    /**
     * Closes the write buffer.
     */
    public function close()
    {
        $this-&gt;open = false;
    }

    /**
     * Tells whether the write buffer is closed or not.
     */
    public function isClosed()
    {
        return !$this-&gt;open;
    }

    /**
     * @return \Traversable&lt;int, string&gt;
     */
    #[\ReturnTypeWillChange]
    public function getIterator()
    {
        $this-&gt;open = true;

        while ($this-&gt;open || $this-&gt;input) {
            if (!$this-&gt;input) {
                yield '';
                continue;
            }
            $current = array_shift($this-&gt;input);

            if ($current instanceof \Iterator) {
                yield from $current;
            } else {
                yield $current;
            }
            if (!$this-&gt;input &amp;&amp; $this-&gt;open &amp;&amp; null !== $onEmpty = $this-&gt;onEmpty) {
                $this-&gt;write($onEmpty($this));
            }
        }
    }
}
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