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    <h3>Editing: HeaderUtils.php</h3>
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/*
 * 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\HttpFoundation;

/**
 * HTTP header utility functions.
 *
 * @author Christian Schmidt &lt;github@chsc.dk&gt;
 */
class HeaderUtils
{
    public const DISPOSITION_ATTACHMENT = 'attachment';
    public const DISPOSITION_INLINE = 'inline';

    /**
     * This class should not be instantiated.
     */
    private function __construct()
    {
    }

    /**
     * Splits an HTTP header by one or more separators.
     *
     * Example:
     *
     *     HeaderUtils::split(&quot;da, en-gb;q=0.8&quot;, &quot;,;&quot;)
     *     // =&gt; ['da'], ['en-gb', 'q=0.8']]
     *
     * @param string $separators List of characters to split on, ordered by
     *                           precedence, e.g. &quot;,&quot;, &quot;;=&quot;, or &quot;,;=&quot;
     *
     * @return array Nested array with as many levels as there are characters in
     *               $separators
     */
    public static function split(string $header, string $separators): array
    {
        $quotedSeparators = preg_quote($separators, '/');

        preg_match_all('
            /
                (?!\s)
                    (?:
                        # quoted-string
                        &quot;(?:[^&quot;\\\\]|\\\\.)*(?:&quot;|\\\\|$)
                    |
                        # token
                        [^&quot;'.$quotedSeparators.']+
                    )+
                (?&lt;!\s)
            |
                # separator
                \s*
                (?&lt;separator&gt;['.$quotedSeparators.'])
                \s*
            /x', trim($header), $matches, \PREG_SET_ORDER);

        return self::groupParts($matches, $separators);
    }

    /**
     * Combines an array of arrays into one associative array.
     *
     * Each of the nested arrays should have one or two elements. The first
     * value will be used as the keys in the associative array, and the second
     * will be used as the values, or true if the nested array only contains one
     * element. Array keys are lowercased.
     *
     * Example:
     *
     *     HeaderUtils::combine([[&quot;foo&quot;, &quot;abc&quot;], [&quot;bar&quot;]])
     *     // =&gt; [&quot;foo&quot; =&gt; &quot;abc&quot;, &quot;bar&quot; =&gt; true]
     */
    public static function combine(array $parts): array
    {
        $assoc = [];
        foreach ($parts as $part) {
            $name = strtolower($part[0]);
            $value = $part[1] ?? true;
            $assoc[$name] = $value;
        }

        return $assoc;
    }

    /**
     * Joins an associative array into a string for use in an HTTP header.
     *
     * The key and value of each entry are joined with &quot;=&quot;, and all entries
     * are joined with the specified separator and an additional space (for
     * readability). Values are quoted if necessary.
     *
     * Example:
     *
     *     HeaderUtils::toString([&quot;foo&quot; =&gt; &quot;abc&quot;, &quot;bar&quot; =&gt; true, &quot;baz&quot; =&gt; &quot;a b c&quot;], &quot;,&quot;)
     *     // =&gt; 'foo=abc, bar, baz=&quot;a b c&quot;'
     */
    public static function toString(array $assoc, string $separator): string
    {
        $parts = [];
        foreach ($assoc as $name =&gt; $value) {
            if (true === $value) {
                $parts[] = $name;
            } else {
                $parts[] = $name.'='.self::quote($value);
            }
        }

        return implode($separator.' ', $parts);
    }

    /**
     * Encodes a string as a quoted string, if necessary.
     *
     * If a string contains characters not allowed by the &quot;token&quot; construct in
     * the HTTP specification, it is backslash-escaped and enclosed in quotes
     * to match the &quot;quoted-string&quot; construct.
     */
    public static function quote(string $s): string
    {
        if (preg_match('/^[a-z0-9!#$%&amp;\'*.^_`|~-]+$/i', $s)) {
            return $s;
        }

        return '&quot;'.addcslashes($s, '&quot;\\&quot;').'&quot;';
    }

    /**
     * Decodes a quoted string.
     *
     * If passed an unquoted string that matches the &quot;token&quot; construct (as
     * defined in the HTTP specification), it is passed through verbatimly.
     */
    public static function unquote(string $s): string
    {
        return preg_replace('/\\\\(.)|&quot;/', '$1', $s);
    }

    /**
     * Generates an HTTP Content-Disposition field-value.
     *
     * @param string $disposition      One of &quot;inline&quot; or &quot;attachment&quot;
     * @param string $filename         A unicode string
     * @param string $filenameFallback A string containing only ASCII characters that
     *                                 is semantically equivalent to $filename. If the filename is already ASCII,
     *                                 it can be omitted, or just copied from $filename
     *
     * @throws \InvalidArgumentException
     *
     * @see RFC 6266
     */
    public static function makeDisposition(string $disposition, string $filename, string $filenameFallback = ''): string
    {
        if (!\in_array($disposition, [self::DISPOSITION_ATTACHMENT, self::DISPOSITION_INLINE])) {
            throw new \InvalidArgumentException(sprintf('The disposition must be either &quot;%s&quot; or &quot;%s&quot;.', self::DISPOSITION_ATTACHMENT, self::DISPOSITION_INLINE));
        }

        if ('' === $filenameFallback) {
            $filenameFallback = $filename;
        }

        // filenameFallback is not ASCII.
        if (!preg_match('/^[\x20-\x7e]*$/', $filenameFallback)) {
            throw new \InvalidArgumentException('The filename fallback must only contain ASCII characters.');
        }

        // percent characters aren't safe in fallback.
        if (str_contains($filenameFallback, '%')) {
            throw new \InvalidArgumentException('The filename fallback cannot contain the &quot;%&quot; character.');
        }

        // path separators aren't allowed in either.
        if (str_contains($filename, '/') || str_contains($filename, '\\') || str_contains($filenameFallback, '/') || str_contains($filenameFallback, '\\')) {
            throw new \InvalidArgumentException('The filename and the fallback cannot contain the &quot;/&quot; and &quot;\\&quot; characters.');
        }

        $params = ['filename' =&gt; $filenameFallback];
        if ($filename !== $filenameFallback) {
            $params['filename*'] = &quot;utf-8''&quot;.rawurlencode($filename);
        }

        return $disposition.'; '.self::toString($params, ';');
    }

    /**
     * Like parse_str(), but preserves dots in variable names.
     */
    public static function parseQuery(string $query, bool $ignoreBrackets = false, string $separator = '&amp;'): array
    {
        $q = [];

        foreach (explode($separator, $query) as $v) {
            if (false !== $i = strpos($v, &quot;\0&quot;)) {
                $v = substr($v, 0, $i);
            }

            if (false === $i = strpos($v, '=')) {
                $k = urldecode($v);
                $v = '';
            } else {
                $k = urldecode(substr($v, 0, $i));
                $v = substr($v, $i);
            }

            if (false !== $i = strpos($k, &quot;\0&quot;)) {
                $k = substr($k, 0, $i);
            }

            $k = ltrim($k, ' ');

            if ($ignoreBrackets) {
                $q[$k][] = urldecode(substr($v, 1));

                continue;
            }

            if (false === $i = strpos($k, '[')) {
                $q[] = bin2hex($k).$v;
            } else {
                $q[] = bin2hex(substr($k, 0, $i)).rawurlencode(substr($k, $i)).$v;
            }
        }

        if ($ignoreBrackets) {
            return $q;
        }

        parse_str(implode('&amp;', $q), $q);

        $query = [];

        foreach ($q as $k =&gt; $v) {
            if (false !== $i = strpos($k, '_')) {
                $query[substr_replace($k, hex2bin(substr($k, 0, $i)).'[', 0, 1 + $i)] = $v;
            } else {
                $query[hex2bin($k)] = $v;
            }
        }

        return $query;
    }

    private static function groupParts(array $matches, string $separators, bool $first = true): array
    {
        $separator = $separators[0];
        $partSeparators = substr($separators, 1);

        $i = 0;
        $partMatches = [];
        $previousMatchWasSeparator = false;
        foreach ($matches as $match) {
            if (!$first &amp;&amp; $previousMatchWasSeparator &amp;&amp; isset($match['separator']) &amp;&amp; $match['separator'] === $separator) {
                $previousMatchWasSeparator = true;
                $partMatches[$i][] = $match;
            } elseif (isset($match['separator']) &amp;&amp; $match['separator'] === $separator) {
                $previousMatchWasSeparator = true;
                ++$i;
            } else {
                $previousMatchWasSeparator = false;
                $partMatches[$i][] = $match;
            }
        }

        $parts = [];
        if ($partSeparators) {
            foreach ($partMatches as $matches) {
                $parts[] = self::groupParts($matches, $partSeparators, false);
            }
        } else {
            foreach ($partMatches as $matches) {
                $parts[] = self::unquote($matches[0][0]);
            }

            if (!$first &amp;&amp; 2 &lt; \count($parts)) {
                $parts = [
                    $parts[0],
                    implode($separator, \array_slice($parts, 1)),
                ];
            }
        }

        return $parts;
    }
}
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