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    <h3>Editing: SMimePart.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\Mime\Part;

use Symfony\Component\Mime\Header\Headers;

/**
 * @author Sebastiaan Stok &lt;s.stok@rollerscapes.net&gt;
 */
class SMimePart extends AbstractPart
{
    /** @internal */
    protected $_headers;

    private $body;
    private $type;
    private $subtype;
    private $parameters;

    /**
     * @param iterable|string $body
     */
    public function __construct($body, string $type, string $subtype, array $parameters)
    {
        unset($this-&gt;_headers);

        parent::__construct();

        if (!\is_string($body) &amp;&amp; !is_iterable($body)) {
            throw new \TypeError(sprintf('The body of &quot;%s&quot; must be a string or a iterable (got &quot;%s&quot;).', self::class, get_debug_type($body)));
        }

        $this-&gt;body = $body;
        $this-&gt;type = $type;
        $this-&gt;subtype = $subtype;
        $this-&gt;parameters = $parameters;
    }

    public function getMediaType(): string
    {
        return $this-&gt;type;
    }

    public function getMediaSubtype(): string
    {
        return $this-&gt;subtype;
    }

    public function bodyToString(): string
    {
        if (\is_string($this-&gt;body)) {
            return $this-&gt;body;
        }

        $body = '';
        foreach ($this-&gt;body as $chunk) {
            $body .= $chunk;
        }
        $this-&gt;body = $body;

        return $body;
    }

    public function bodyToIterable(): iterable
    {
        if (\is_string($this-&gt;body)) {
            yield $this-&gt;body;

            return;
        }

        $body = '';
        foreach ($this-&gt;body as $chunk) {
            $body .= $chunk;
            yield $chunk;
        }
        $this-&gt;body = $body;
    }

    public function getPreparedHeaders(): Headers
    {
        $headers = clone parent::getHeaders();

        $headers-&gt;setHeaderBody('Parameterized', 'Content-Type', $this-&gt;getMediaType().'/'.$this-&gt;getMediaSubtype());

        foreach ($this-&gt;parameters as $name =&gt; $value) {
            $headers-&gt;setHeaderParameter('Content-Type', $name, $value);
        }

        return $headers;
    }

    public function __sleep(): array
    {
        // convert iterables to strings for serialization
        if (is_iterable($this-&gt;body)) {
            $this-&gt;body = $this-&gt;bodyToString();
        }

        $this-&gt;_headers = $this-&gt;getHeaders();

        return ['_headers', 'body', 'type', 'subtype', 'parameters'];
    }

    public function __wakeup(): void
    {
        $r = new \ReflectionProperty(AbstractPart::class, 'headers');
        $r-&gt;setAccessible(true);
        $r-&gt;setValue($this, $this-&gt;_headers);
        unset($this-&gt;_headers);
    }
}
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