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    <h3>Editing: Rfc2231Encoder.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\Encoder;

use Symfony\Component\Mime\CharacterStream;

/**
 * @author Chris Corbyn
 */
final class Rfc2231Encoder implements EncoderInterface
{
    /**
     * Takes an unencoded string and produces a string encoded according to RFC 2231 from it.
     */
    public function encodeString(string $string, ?string $charset = 'utf-8', int $firstLineOffset = 0, int $maxLineLength = 0): string
    {
        $lines = [];
        $lineCount = 0;
        $lines[] = '';
        $currentLine = &amp;$lines[$lineCount++];

        if (0 &gt;= $maxLineLength) {
            $maxLineLength = 75;
        }

        $charStream = new CharacterStream($string, $charset);
        $thisLineLength = $maxLineLength - $firstLineOffset;

        while (null !== $char = $charStream-&gt;read(4)) {
            $encodedChar = rawurlencode($char);
            if ('' !== $currentLine &amp;&amp; \strlen($currentLine.$encodedChar) &gt; $thisLineLength) {
                $lines[] = '';
                $currentLine = &amp;$lines[$lineCount++];
                $thisLineLength = $maxLineLength;
            }
            $currentLine .= $encodedChar;
        }

        return implode(&quot;\r\n&quot;, $lines);
    }
}
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