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Diffstat (limited to 'www/wiki/includes/libs/http/HttpAcceptNegotiator.php')
| -rw-r--r-- | www/wiki/includes/libs/http/HttpAcceptNegotiator.php | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/www/wiki/includes/libs/http/HttpAcceptNegotiator.php b/www/wiki/includes/libs/http/HttpAcceptNegotiator.php new file mode 100644 index 00000000..4de8e77e --- /dev/null +++ b/www/wiki/includes/libs/http/HttpAcceptNegotiator.php @@ -0,0 +1,138 @@ +<?php + +namespace Wikimedia\Http; + +/** + * Utility for negotiating a value from a set of supported values using a preference list. + * This is intended for use with HTTP headers like Accept, Accept-Language, Accept-Encoding, etc. + * See RFC 2616 section 14 for details. + * + * To use this with a request header, first parse the header value into an array of weights + * using HttpAcceptParser, then call getBestSupportedKey. + * + * @license GPL-2.0-or-later + * @author Daniel Kinzler + * @author Thiemo Kreuz + */ +class HttpAcceptNegotiator { + + /** + * @var string[] + */ + private $supportedValues; + + /** + * @var string + */ + private $defaultValue; + + /** + * @param string[] $supported A list of supported values. + */ + public function __construct( array $supported ) { + $this->supportedValues = $supported; + $this->defaultValue = reset( $supported ); + } + + /** + * Returns the best supported key from the given weight map. Of the keys from the + * $weights parameter that are also in the list of supported values supplied to + * the constructor, this returns the key that has the highest weight associated + * with it. If two keys have the same weight, the more specific key is preferred, + * as required by RFC2616 section 14. Keys that map to 0 or false are ignored. + * If no matching key is found, $default is returned. + * + * @param float[] $weights An associative array mapping accepted values to their + * respective weights. + * + * @param null|string $default The value to return if non of the keys in $weights + * is supported (null per default). + * + * @return null|string The best supported key from the $weights parameter. + */ + public function getBestSupportedKey( array $weights, $default = null ) { + // Make sure we correctly bias against wildcards and ranges, see RFC2616, section 14. + foreach ( $weights as $name => &$weight ) { + if ( $name === '*' || $name === '*/*' ) { + $weight -= 0.000002; + } elseif ( substr( $name, -2 ) === '/*' ) { + $weight -= 0.000001; + } + } + + // Sort $weights by value and... + asort( $weights ); + + // remove any keys with values equal to 0 or false (HTTP/1.1 section 3.9) + $weights = array_filter( $weights ); + + // ...use the ordered list of keys + $preferences = array_reverse( array_keys( $weights ) ); + + $value = $this->getFirstSupportedValue( $preferences, $default ); + return $value; + } + + /** + * Returns the first supported value from the given preference list. Of the values from + * the $preferences parameter that are also in the list of supported values supplied + * to the constructor, this returns the value that has the lowest index in the list. + * If no such value is found, $default is returned. + * + * @param string[] $preferences A list of acceptable values, in order of preference. + * + * @param null|string $default The value to return if non of the keys in $weights + * is supported (null per default). + * + * @return null|string The best supported key from the $weights parameter. + */ + public function getFirstSupportedValue( array $preferences, $default = null ) { + foreach ( $preferences as $value ) { + foreach ( $this->supportedValues as $supported ) { + if ( $this->valueMatches( $value, $supported ) ) { + return $supported; + } + } + } + + return $default; + } + + /** + * Returns true if the given acceptable value matches the given supported value, + * according to the HTTP specification. The following rules are used: + * + * - comparison is case-insensitive + * - if $accepted and $supported are equal, they match + * - if $accepted is `*` or `*` followed by `/*`, it matches any $supported value. + * - if both $accepted and $supported contain a `/`, and $accepted ends with `/*`, + * they match if the part before the first `/` is equal. + * + * @param string $accepted An accepted value (may contain wildcards) + * @param string $supported A supported value. + * + * @return bool Whether the given supported value matches the given accepted value. + */ + private function valueMatches( $accepted, $supported ) { + // RDF 2045: MIME types are case insensitive. + // full match + if ( strcasecmp( $accepted, $supported ) === 0 ) { + return true; + } + + // wildcard match (HTTP/1.1 section 14.1, 14.2, 14.3) + if ( $accepted === '*' || $accepted === '*/*' ) { + return true; + } + + // wildcard match (HTTP/1.1 section 14.1) + if ( substr( $accepted, -2 ) === '/*' + && strncasecmp( $accepted, $supported, strlen( $accepted ) - 2 ) === 0 + ) { + return true; + } + + return false; + } + +} |