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Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

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Pantheon Automation 2015-08-17 17:00:26 -07:00 • committed by Greg Anderson
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core/lib/Drupal/Component/Utility/UserAgent.php Normal file
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<?php
/**
* @file
* Contains \Drupal\Component\Utility\UserAgent.
*/
namespace Drupal\Component\Utility;
/**
* Provides user agent related utility functions.
*
* @ingroup utility
*/
class UserAgent {
/**
* Identifies user agent language from the Accept-language HTTP header.
*
* The algorithm works as follows:
* - map user agent language codes to available language codes.
* - order all user agent language codes by qvalue from high to low.
* - add generic user agent language codes if they aren't already specified
* but with a slightly lower qvalue.
* - find the most specific available language code with the highest qvalue.
* - if 2 or more languages are having the same qvalue, respect the order of
* them inside the $languages array.
*
* We perform user agent accept-language parsing only if page cache is
* disabled, otherwise we would cache a user-specific preference.
*
* @param string $http_accept_language
* The value of the "Accept-Language" HTTP header.
* @param array $langcodes
* An array of available language codes to pick from.
* @param array $mappings
* (optional) Custom mappings to support user agents that are sending non
* standard language codes. No mapping is assumed by default.
*
* @return string
* The selected language code or FALSE if no valid language can be
* identified.
*/
public static function getBestMatchingLangcode($http_accept_language, $langcodes, $mappings = array()) {
// The Accept-Language header contains information about the language
// preferences configured in the user's user agent / operating system.
// RFC 2616 (section 14.4) defines the Accept-Language header as follows:
// Accept-Language = "Accept-Language" ":"
// 1#( language-range [ ";" "q" "=" qvalue ] )
// language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" )
// Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
$ua_langcodes = array();
if (preg_match_all('@(?<=[, ]|^)([a-zA-Z-]+|\*)(?:;q=([0-9.]+))?(?:$|\s*,\s*)@', trim($http_accept_language), $matches, PREG_SET_ORDER)) {
foreach ($matches as $match) {
if ($mappings) {
$langcode = strtolower($match[1]);
foreach ($mappings as $ua_langcode => $standard_langcode) {
if ($langcode == $ua_langcode) {
$match[1] = $standard_langcode;
}
}
}
// We can safely use strtolower() here, tags are ASCII.
// RFC2616 mandates that the decimal part is no more than three digits,
// so we multiply the qvalue by 1000 to avoid floating point
// comparisons.
$langcode = strtolower($match[1]);
$qvalue = isset($match[2]) ? (float) $match[2] : 1;
// Take the highest qvalue for this langcode. Although the request
// supposedly contains unique langcodes, our mapping possibly resolves
// to the same langcode for different qvalues. Keep the highest.
$ua_langcodes[$langcode] = max(
(int) ($qvalue * 1000),
(isset($ua_langcodes[$langcode]) ? $ua_langcodes[$langcode] : 0)
);
}
}
// We should take pristine values from the HTTP headers, but Internet
// Explorer from version 7 sends only specific language tags (eg. fr-CA)
// without the corresponding generic tag (fr) unless explicitly configured.
// In that case, we assume that the lowest value of the specific tags is the
// value of the generic language to be as close to the HTTP 1.1 spec as
// possible.
// See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4 and
// http://blogs.msdn.com/b/ie/archive/2006/10/17/accept-language-header-for-internet-explorer-7.aspx
asort($ua_langcodes);
foreach ($ua_langcodes as $langcode => $qvalue) {
// For Chinese languages the generic tag is either zh-hans or zh-hant, so
// we need to handle this separately, we can not split $langcode on the
// first occurrence of '-' otherwise we get a non-existing language zh.
// All other languages use a langcode without a '-', so we can safely
// split on the first occurrence of it.
if (strlen($langcode) > 7 && (substr($langcode, 0, 7) == 'zh-hant' || substr($langcode, 0, 7) == 'zh-hans')) {
$generic_tag = substr($langcode, 0, 7);
}
else {
$generic_tag = strtok($langcode, '-');
}
if (!empty($generic_tag) && !isset($ua_langcodes[$generic_tag])) {
// Add the generic langcode, but make sure it has a lower qvalue as the
// more specific one, so the more specific one gets selected if it's
// defined by both the user agent and us.
$ua_langcodes[$generic_tag] = $qvalue - 0.1;
}
}
// Find the added language with the greatest qvalue, following the rules
// of RFC 2616 (section 14.4). If several languages have the same qvalue,
// prefer the one with the greatest weight.
$best_match_langcode = FALSE;
$max_qvalue = 0;
foreach ($langcodes as $langcode_case_sensitive) {
// Language tags are case insensitive (RFC2616, sec 3.10).
$langcode = strtolower($langcode_case_sensitive);
// If nothing matches below, the default qvalue is the one of the wildcard
// language, if set, or is 0 (which will never match).
$qvalue = isset($ua_langcodes['*']) ? $ua_langcodes['*'] : 0;
// Find the longest possible prefix of the user agent supplied language
// ('the language-range') that matches this site language ('the language
// tag').
$prefix = $langcode;
do {
if (isset($ua_langcodes[$prefix])) {
$qvalue = $ua_langcodes[$prefix];
break;
}
}
while ($prefix = substr($prefix, 0, strrpos($prefix, '-')));
// Find the best match.
if ($qvalue > $max_qvalue) {
$best_match_langcode = $langcode_case_sensitive;
$max_qvalue = $qvalue;
}
}
return $best_match_langcode;
}
}