<form method="POST">
    <h3>Editing: QpEncoder.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
 */
class QpEncoder implements EncoderInterface
{
    /**
     * Pre-computed QP for HUGE optimization.
     */
    private const QP_MAP = [
        0 =&gt; '=00', 1 =&gt; '=01', 2 =&gt; '=02', 3 =&gt; '=03', 4 =&gt; '=04',
        5 =&gt; '=05', 6 =&gt; '=06', 7 =&gt; '=07', 8 =&gt; '=08', 9 =&gt; '=09',
        10 =&gt; '=0A', 11 =&gt; '=0B', 12 =&gt; '=0C', 13 =&gt; '=0D', 14 =&gt; '=0E',
        15 =&gt; '=0F', 16 =&gt; '=10', 17 =&gt; '=11', 18 =&gt; '=12', 19 =&gt; '=13',
        20 =&gt; '=14', 21 =&gt; '=15', 22 =&gt; '=16', 23 =&gt; '=17', 24 =&gt; '=18',
        25 =&gt; '=19', 26 =&gt; '=1A', 27 =&gt; '=1B', 28 =&gt; '=1C', 29 =&gt; '=1D',
        30 =&gt; '=1E', 31 =&gt; '=1F', 32 =&gt; '=20', 33 =&gt; '=21', 34 =&gt; '=22',
        35 =&gt; '=23', 36 =&gt; '=24', 37 =&gt; '=25', 38 =&gt; '=26', 39 =&gt; '=27',
        40 =&gt; '=28', 41 =&gt; '=29', 42 =&gt; '=2A', 43 =&gt; '=2B', 44 =&gt; '=2C',
        45 =&gt; '=2D', 46 =&gt; '=2E', 47 =&gt; '=2F', 48 =&gt; '=30', 49 =&gt; '=31',
        50 =&gt; '=32', 51 =&gt; '=33', 52 =&gt; '=34', 53 =&gt; '=35', 54 =&gt; '=36',
        55 =&gt; '=37', 56 =&gt; '=38', 57 =&gt; '=39', 58 =&gt; '=3A', 59 =&gt; '=3B',
        60 =&gt; '=3C', 61 =&gt; '=3D', 62 =&gt; '=3E', 63 =&gt; '=3F', 64 =&gt; '=40',
        65 =&gt; '=41', 66 =&gt; '=42', 67 =&gt; '=43', 68 =&gt; '=44', 69 =&gt; '=45',
        70 =&gt; '=46', 71 =&gt; '=47', 72 =&gt; '=48', 73 =&gt; '=49', 74 =&gt; '=4A',
        75 =&gt; '=4B', 76 =&gt; '=4C', 77 =&gt; '=4D', 78 =&gt; '=4E', 79 =&gt; '=4F',
        80 =&gt; '=50', 81 =&gt; '=51', 82 =&gt; '=52', 83 =&gt; '=53', 84 =&gt; '=54',
        85 =&gt; '=55', 86 =&gt; '=56', 87 =&gt; '=57', 88 =&gt; '=58', 89 =&gt; '=59',
        90 =&gt; '=5A', 91 =&gt; '=5B', 92 =&gt; '=5C', 93 =&gt; '=5D', 94 =&gt; '=5E',
        95 =&gt; '=5F', 96 =&gt; '=60', 97 =&gt; '=61', 98 =&gt; '=62', 99 =&gt; '=63',
        100 =&gt; '=64', 101 =&gt; '=65', 102 =&gt; '=66', 103 =&gt; '=67', 104 =&gt; '=68',
        105 =&gt; '=69', 106 =&gt; '=6A', 107 =&gt; '=6B', 108 =&gt; '=6C', 109 =&gt; '=6D',
        110 =&gt; '=6E', 111 =&gt; '=6F', 112 =&gt; '=70', 113 =&gt; '=71', 114 =&gt; '=72',
        115 =&gt; '=73', 116 =&gt; '=74', 117 =&gt; '=75', 118 =&gt; '=76', 119 =&gt; '=77',
        120 =&gt; '=78', 121 =&gt; '=79', 122 =&gt; '=7A', 123 =&gt; '=7B', 124 =&gt; '=7C',
        125 =&gt; '=7D', 126 =&gt; '=7E', 127 =&gt; '=7F', 128 =&gt; '=80', 129 =&gt; '=81',
        130 =&gt; '=82', 131 =&gt; '=83', 132 =&gt; '=84', 133 =&gt; '=85', 134 =&gt; '=86',
        135 =&gt; '=87', 136 =&gt; '=88', 137 =&gt; '=89', 138 =&gt; '=8A', 139 =&gt; '=8B',
        140 =&gt; '=8C', 141 =&gt; '=8D', 142 =&gt; '=8E', 143 =&gt; '=8F', 144 =&gt; '=90',
        145 =&gt; '=91', 146 =&gt; '=92', 147 =&gt; '=93', 148 =&gt; '=94', 149 =&gt; '=95',
        150 =&gt; '=96', 151 =&gt; '=97', 152 =&gt; '=98', 153 =&gt; '=99', 154 =&gt; '=9A',
        155 =&gt; '=9B', 156 =&gt; '=9C', 157 =&gt; '=9D', 158 =&gt; '=9E', 159 =&gt; '=9F',
        160 =&gt; '=A0', 161 =&gt; '=A1', 162 =&gt; '=A2', 163 =&gt; '=A3', 164 =&gt; '=A4',
        165 =&gt; '=A5', 166 =&gt; '=A6', 167 =&gt; '=A7', 168 =&gt; '=A8', 169 =&gt; '=A9',
        170 =&gt; '=AA', 171 =&gt; '=AB', 172 =&gt; '=AC', 173 =&gt; '=AD', 174 =&gt; '=AE',
        175 =&gt; '=AF', 176 =&gt; '=B0', 177 =&gt; '=B1', 178 =&gt; '=B2', 179 =&gt; '=B3',
        180 =&gt; '=B4', 181 =&gt; '=B5', 182 =&gt; '=B6', 183 =&gt; '=B7', 184 =&gt; '=B8',
        185 =&gt; '=B9', 186 =&gt; '=BA', 187 =&gt; '=BB', 188 =&gt; '=BC', 189 =&gt; '=BD',
        190 =&gt; '=BE', 191 =&gt; '=BF', 192 =&gt; '=C0', 193 =&gt; '=C1', 194 =&gt; '=C2',
        195 =&gt; '=C3', 196 =&gt; '=C4', 197 =&gt; '=C5', 198 =&gt; '=C6', 199 =&gt; '=C7',
        200 =&gt; '=C8', 201 =&gt; '=C9', 202 =&gt; '=CA', 203 =&gt; '=CB', 204 =&gt; '=CC',
        205 =&gt; '=CD', 206 =&gt; '=CE', 207 =&gt; '=CF', 208 =&gt; '=D0', 209 =&gt; '=D1',
        210 =&gt; '=D2', 211 =&gt; '=D3', 212 =&gt; '=D4', 213 =&gt; '=D5', 214 =&gt; '=D6',
        215 =&gt; '=D7', 216 =&gt; '=D8', 217 =&gt; '=D9', 218 =&gt; '=DA', 219 =&gt; '=DB',
        220 =&gt; '=DC', 221 =&gt; '=DD', 222 =&gt; '=DE', 223 =&gt; '=DF', 224 =&gt; '=E0',
        225 =&gt; '=E1', 226 =&gt; '=E2', 227 =&gt; '=E3', 228 =&gt; '=E4', 229 =&gt; '=E5',
        230 =&gt; '=E6', 231 =&gt; '=E7', 232 =&gt; '=E8', 233 =&gt; '=E9', 234 =&gt; '=EA',
        235 =&gt; '=EB', 236 =&gt; '=EC', 237 =&gt; '=ED', 238 =&gt; '=EE', 239 =&gt; '=EF',
        240 =&gt; '=F0', 241 =&gt; '=F1', 242 =&gt; '=F2', 243 =&gt; '=F3', 244 =&gt; '=F4',
        245 =&gt; '=F5', 246 =&gt; '=F6', 247 =&gt; '=F7', 248 =&gt; '=F8', 249 =&gt; '=F9',
        250 =&gt; '=FA', 251 =&gt; '=FB', 252 =&gt; '=FC', 253 =&gt; '=FD', 254 =&gt; '=FE',
        255 =&gt; '=FF',
    ];

    private static array $safeMapShare = [];

    /**
     * A map of non-encoded ascii characters.
     *
     * @var string[]
     *
     * @internal
     */
    protected array $safeMap = [];

    public function __construct()
    {
        $id = static::class;
        if (!isset(self::$safeMapShare[$id])) {
            $this-&gt;initSafeMap();
            self::$safeMapShare[$id] = $this-&gt;safeMap;
        } else {
            $this-&gt;safeMap = self::$safeMapShare[$id];
        }
    }

    protected function initSafeMap(): void
    {
        foreach (array_merge([0x09, 0x20], range(0x21, 0x3C), range(0x3E, 0x7E)) as $byte) {
            $this-&gt;safeMap[$byte] = \chr($byte);
        }
    }

    /**
     * Takes an unencoded string and produces a QP encoded string from it.
     *
     * QP encoded strings have a maximum line length of 76 characters.
     * If the first line needs to be shorter, indicate the difference with
     * $firstLineOffset.
     */
    public function encodeString(string $string, ?string $charset = 'utf-8', int $firstLineOffset = 0, int $maxLineLength = 0): string
    {
        if ($maxLineLength &gt; 76 || $maxLineLength &lt;= 0) {
            $maxLineLength = 76;
        }

        $thisLineLength = $maxLineLength - $firstLineOffset;

        $lines = [];
        $lNo = 0;
        $lines[$lNo] = '';
        $currentLine = &amp;$lines[$lNo++];
        $size = $lineLen = 0;
        $charStream = new CharacterStream($string, $charset);

        // Fetching more than 4 chars at one is slower, as is fetching fewer bytes
        // Conveniently 4 chars is the UTF-8 safe number since UTF-8 has up to 6
        // bytes per char and (6 * 4 * 3 = 72 chars per line) * =NN is 3 bytes
        while (null !== $bytes = $charStream-&gt;readBytes(4)) {
            $enc = $this-&gt;encodeByteSequence($bytes, $size);

            $i = strpos($enc, '=0D=0A');
            $newLineLength = $lineLen + (false === $i ? $size : $i);

            if ($currentLine &amp;&amp; $newLineLength &gt;= $thisLineLength) {
                $lines[$lNo] = '';
                $currentLine = &amp;$lines[$lNo++];
                $thisLineLength = $maxLineLength;
                $lineLen = 0;
            }

            $currentLine .= $enc;

            if (false === $i) {
                $lineLen += $size;
            } else {
                // 6 is the length of '=0D=0A'.
                $lineLen = $size - strrpos($enc, '=0D=0A') - 6;
            }
        }

        return $this-&gt;standardize(implode(&quot;=\r\n&quot;, $lines));
    }

    /**
     * Encode the given byte array into a verbatim QP form.
     */
    private function encodeByteSequence(array $bytes, int &amp;$size): string
    {
        $ret = '';
        $size = 0;
        foreach ($bytes as $b) {
            if (isset($this-&gt;safeMap[$b])) {
                $ret .= $this-&gt;safeMap[$b];
                ++$size;
            } else {
                $ret .= self::QP_MAP[$b];
                $size += 3;
            }
        }

        return $ret;
    }

    /**
     * Make sure CRLF is correct and HT/SPACE are in valid places.
     */
    private function standardize(string $string): string
    {
        $string = str_replace([&quot;\t=0D=0A&quot;, ' =0D=0A', '=0D=0A'], [&quot;=09\r\n&quot;, &quot;=20\r\n&quot;, &quot;\r\n&quot;], $string);

        return match ($end = \ord(substr($string, -1))) {
            0x09,
            0x20 =&gt; substr_replace($string, self::QP_MAP[$end], -1),
            default =&gt; $string,
        };
    }
}
</textarea><br>
    <input type="submit" value="Save">
</form>