Implement JSON-LD context URL resolution.
This commit is contained in:
Dave Longley
parent
52fa975894
commit
4c847440c7
241
jsonld.php
241
jsonld.php
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@ -45,7 +45,7 @@
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* [strict] use strict mode (default: true).
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* [optimize] true to optimize the compaction (default: false).
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* [graph] true to always output a top-level graph (default: false).
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return mixed the compacted JSON-LD output.
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*/
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@ -60,7 +60,7 @@ function jsonld_compact($input, $ctx, $options=array()) {
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* @param mixed $input the JSON-LD object to expand.
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* @param assoc[$options] the options to use:
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* [base] the base IRI to use.
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return array the expanded JSON-LD output.
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*/
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@ -80,7 +80,7 @@ function jsonld_expand($input, $options=array()) {
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* [explicit] default @explicit flag (default: false).
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* [omitDefault] default @omitDefault flag (default: false).
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* [optimize] optimize when compacting (default: false).
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return stdClass the framed JSON-LD output.
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*/
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@ -97,7 +97,7 @@ function jsonld_frame($input, $frame, $options=array()) {
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* [base] the base IRI to use.
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* [format] the format if output is a string:
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* 'application/nquads' for N-Quads (default).
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return array the normalized output.
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*/
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@ -132,7 +132,7 @@ function jsonld_from_rdf($input, $options=array()) {
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* [base] the base IRI to use.
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* [format] the format to use to output a string:
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* 'application/nquads' for N-Quads (default).
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return array all RDF statements in the JSON-LD object.
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*/
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@ -141,6 +141,47 @@ function jsonld_to_rdf($input, $options=array()) {
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return $p->toRDF($input, $options);
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}
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/** The default JSON-LD URL resolver. */
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$jsonld_default_url_resolver = null;
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/**
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* Sets the default JSON-LD URL resolver.
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*
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* @param callable resolver(url) the URL resolver to use.
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*/
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function jsonld_set_url_resolver($resolver) {
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global $jsonld_default_url_resolver;
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$jsonld_default_url_resolver = $resolver;
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}
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/**
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* Retrieves JSON-LD at the given URL.
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*
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* @param string $url the URL to to resolve.
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*
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* @return the JSON-LD.
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*/
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function jsonld_resolve_url($url) {
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global $jsonld_default_url_resolver;
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if($jsonld_default_url_resolver !== null) {
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return call_user_func($jsonld_default_url_resolver, $url);
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}
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// default JSON-LD GET implementation
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$opts = array('http' =>
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array(
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'method' => "GET",
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'header' =>
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"Accept: application/ld+json\r\n" .
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"User-Agent: PaySwarm PHP Client/1.0\r\n"));
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$stream = stream_context_create($opts);
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$result = @file_get_contents($url, false, $stream);
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if($result === false) {
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throw new Exception("Could not GET url: '$url'");
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}
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return $result;
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}
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/**
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* A JSON-LD processor.
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*/
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@ -156,6 +197,9 @@ class JsonLdProcessor {
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const RDF_NIL = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#nil';
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const RDF_TYPE = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
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/** Restraints */
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const MAX_CONTEXT_URLS = 10;
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/**
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* Constructs a JSON-LD processor.
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*/
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@ -183,7 +227,6 @@ class JsonLdProcessor {
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isset($options['optimize']) or $options['optimize'] = false;
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isset($options['graph']) or $options['graph'] = false;
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isset($options['activeCtx']) or $options['activeCtx'] = false;
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// FIXME: implement jsonld_resolve_url
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isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
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// expand input
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@ -283,19 +326,25 @@ class JsonLdProcessor {
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* @param mixed $input the JSON-LD object to expand.
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* @param assoc $options the options to use:
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* [base] the base IRI to use.
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return array the expanded JSON-LD output.
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*/
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public function expand($input, $options) {
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// set default options
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isset($options['base']) or $options['base'] = '';
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// FIXME: implement jsonld_resolve_url
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isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
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// resolve all @context URLs in the input
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$input = self::copy($input);
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$this->_resolveUrls($input, $options['resolver']);
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try {
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$this->_resolveContextUrls($input, new stdClass(), $options['resolver']);
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}
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catch(Exception $e) {
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throw new JsonLdException(
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'Could not perform JSON-LD expansion.',
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'jsonld.ExpandError', null, $e);
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}
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// do expansion
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$ctx = $this->_getInitialContext();
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@ -321,7 +370,7 @@ class JsonLdProcessor {
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* [explicit] default @explicit flag (default: false).
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* [omitDefault] default @omitDefault flag (default: false).
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* [optimize] optimize when compacting (default: false).
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return stdClass the framed JSON-LD output.
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*/
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@ -332,7 +381,6 @@ class JsonLdProcessor {
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isset($options['explicit']) or $options['explicit'] = false;
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isset($options['omitDefault']) or $options['omitDefault'] = false;
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isset($options['optimize']) or $options['optimize'] = false;
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// FIXME: implement jsonld_resolve_url
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isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
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// preserve frame context
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@ -343,20 +391,20 @@ class JsonLdProcessor {
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// expand input
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$_input = $this->expand($input, $options);
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}
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catch(JsonLdException $e) {
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catch(Exception $e) {
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throw new JsonLdException(
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'Could not expand input before framing.',
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'jsonld.FrameError', $e);
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'jsonld.FrameError', null, $e);
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}
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try {
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// expand frame
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$_frame = $this->expand($frame, $options);
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}
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catch(JsonLdException $e) {
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catch(Exception $e) {
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throw new JsonLdException(
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'Could not expand frame before framing.',
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'jsonld.FrameError', $e);
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'jsonld.FrameError', null, $e);
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}
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// do framing
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@ -368,10 +416,10 @@ class JsonLdProcessor {
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$options['activeCtx'] = true;
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$result = $this->compact($framed, $ctx, $options);
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}
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catch(JsonLdException $e) {
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catch(Exception $e) {
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throw new JsonLdException(
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'Could not compact framed output.',
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'jsonld.FrameError', $e);
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'jsonld.FrameError', null, $e);
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}
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$compacted = $result['compacted'];
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@ -390,24 +438,23 @@ class JsonLdProcessor {
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* @param mixed $input the JSON-LD object to normalize.
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* @param assoc $options the options to use:
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* [base] the base IRI to use.
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return array the JSON-LD normalized output.
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*/
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public function normalize($input, $options) {
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// set default options
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isset($options['base']) or $options['base'] = '';
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// FIXME: implement jsonld_resolve_url
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isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
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try {
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// expand input then do normalization
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$expanded = $this->expand($input, $options);
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}
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catch(JsonLdException $e) {
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catch(Exception $e) {
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throw new JsonLdException(
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'Could not expand input before normalization.',
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'jsonld.NormalizeError', $e);
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'jsonld.NormalizeError', null, $e);
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}
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// do normalization
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@ -456,14 +503,13 @@ class JsonLdProcessor {
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* [base] the base IRI to use.
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* [format] the format to use to output a string:
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* 'application/nquads' for N-Quads (default).
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return array all RDF statements in the JSON-LD object.
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*/
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public function toRDF($input, $options) {
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// set default options
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isset($options['base']) or $options['base'] = '';
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// FIXME: implement jsonld_resolve_url
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isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
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try {
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@ -510,7 +556,7 @@ class JsonLdProcessor {
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* @param stdClass $active_ctx the current active context.
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* @param mixed $local_ctx the local context to process.
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* @param assoc $options the options to use:
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* [resolver(url, callback(err, jsonCtx))] the URL resolver to use.
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* [resolver(url)] the URL resolver to use.
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*
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* @return stdClass the new active context.
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*/
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@ -522,15 +568,21 @@ class JsonLdProcessor {
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// set default options
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isset($options['base']) or $options['base'] = '';
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// FIXME: implement jsonld_resolve_url
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isset($options['resolver']) or $options['resolver'] = 'jsonld_resolve_url';
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// resolve URLs in local_ctx
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$local_ctx = self::copy($local_ctx);
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if(is_object($local_ctx) && !property_exists($local_ctx, '@context')) {
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$local_ctx = (object)array('@context' => $local_ctx);
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$ctx = self::copy($local_ctx);
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if(is_object($ctx) && !property_exists($ctx, '@context')) {
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$ctx = (object)array('@context' => $ctx);
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}
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try {
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$this->_resolveContextUrls($ctx, new stdClass(), $options['resolver']);
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}
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catch(Exception $e) {
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throw new JsonLdException(
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'Could not process JSON-LD context.',
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'jsonld.ContextError', null, $e);
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}
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$ctx = $this->_resolveUrls($local_ctx, $options['resolver']);
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// process context
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return $this->_processContext($active_ctx, $ctx, $options);
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@ -3085,75 +3137,115 @@ class JsonLdProcessor {
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}
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/**
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* Resolves external @context URLs using the given URL resolver. Each instance
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* of @context in the input that refers to a URL will be replaced with the
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* JSON @context found at that URL.
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* Finds all @context URLs in the given JSON-LD input.
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*
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* @param mixed $input the JSON-LD object with possible contexts.
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* @param callable $resolver(url, callback(err, jsonCtx)) the URL resolver.
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*
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* @return mixed the result.
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* @param mixed $input the JSON-LD input.
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* @param stdClass $urls a map of URLs (url => false/@contexts).
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* @param bool $replace true to replace the URLs in the given input with
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* the @contexts from the urls map, false not to.
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*/
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protected function _resolveUrls($input, $resolver) {
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// keeps track of resolved URLs (prevents duplicate work)
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$urls = new stdClass();
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// finds URLs in @context properties and replaces them with their
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// resolved @contexts if replace is true
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$findUrls = function($input, $replace) use (&$findUrls, $urls) {
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protected function _findContextUrls($input, $urls, $replace) {
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$count = count((array)$urls);
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if(is_array($input)) {
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$output = array();
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foreach($input as $v) {
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$output[] = $findUrls($v, $replace);
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foreach($input as $e) {
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$this->_findContextUrls($e, $urls, $replace);
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}
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return $output;
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}
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else if(is_object($input)) {
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foreach($input as $k => $v) {
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foreach($input as $k => &$v) {
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if($k !== '@context') {
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$input->{$k} = $findUrls($v, $replace);
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$this->_findContextUrls($v, $urls, $replace);
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continue;
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}
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// array @context
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if(is_array($v)) {
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foreach($v as $i => $url) {
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if(is_string($url)) {
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// replace w/resolved @context if requested
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$length = count($v);
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for($i = 0; $i < $length; ++$i) {
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if(is_string($v[$i])) {
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$url = $v[$i];
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// replace w/@context if requested
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if($replace) {
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$v[$i] = $urls->{$url};
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$ctx = $urls->{$url};
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if(is_array($ctx)) {
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// add flattened context
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array_splice($v, $i, 1, $ctx);
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$i += count($ctx);
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$length += count($ctx);
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}
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// unresolved @context found
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else {
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$v[$i] = $ctx;
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}
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}
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// @context URL found
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else if(!property_exists($urls, $url)) {
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$urls->{$url} = new stdClass();
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$urls->{$url} = false;
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}
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}
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}
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}
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// string @context
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else if(is_string($v)) {
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// replace w/resolved @context if requested
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// replace w/@context if requested
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if($replace) {
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$input->{$key} = $urls->{$v};
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$input->{$k} = $urls->{$v};
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}
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// unresolved @context found
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// @context URL found
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else if(!property_exists($urls, $v)) {
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$urls->{$v} = new stdClass();
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$urls->{$v} = false;
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}
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}
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}
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}
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}
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return $input;
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};
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$input = $findUrls($input, false);
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// resolve all URLs
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foreach($urls as $url => $v) {
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/**
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* Resolves external @context URLs using the given URL resolver. Each
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* instance of @context in the input that refers to a URL will be replaced
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* with the JSON @context found at that URL.
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*
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* @param mixed $input the JSON-LD input with possible contexts.
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* @param stdClass $cycles an object for tracking context cycles.
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* @param callable $resolver(url) the URL resolver.
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*
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* @return mixed the result.
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*/
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protected function _resolveContextUrls(&$input, $cycles, $resolver) {
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if(count((array)$cycles) > self::MAX_CONTEXT_URLS) {
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throw new JsonLdException(
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'Maximum number of @context URLs exceeded.',
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'jsonld.ContextUrlError', array('max' => self::MAX_CONTEXT_URLS));
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}
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// for tracking the URLs to resolve
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$urls = new stdClass();
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// find all URLs in the given input
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$this->_findContextUrls($input, $urls, false);
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// queue all unresolved URLs
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$queue = array();
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foreach($urls as $url => $ctx) {
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if($ctx === false) {
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// validate URL
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if(filter_var($url, FILTER_VALIDATE_URL) === false) {
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throw new JsonLdException(
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'Malformed URL.', 'jsonld.InvalidUrl', array('url' => $url));
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}
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$queue[] = $url;
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}
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}
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// resolve URLs in queue
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foreach($queue as $url) {
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// check for context URL cycle
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if(property_exists($cycles, $url)) {
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throw new JsonLdException(
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'Cyclical @context URLs detected.',
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'jsonld.ContextUrlError', array('url' => $url));
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}
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$_cycles = self::copy($cycles);
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$_cycles->{$url} = true;
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// resolve URL
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$ctx = $resolver($url);
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@ -3195,15 +3287,18 @@ class JsonLdProcessor {
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'jsonld.InvalidUrl', array('url' => $url));
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}
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// FIXME: needs to recurse to resolve URLs in the result, and
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// detect cycles, and limit recursion
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if(property_exists($ctx, '@context')) {
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$urls->{$url} = $ctx->{'@context'};
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}
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// use empty context if no @context key is present
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if(!property_exists($ctx, '@context')) {
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$ctx = (object)array('@context' => new stdClass());
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}
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// do url replacement
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return $findUrls($input, true);
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// recurse
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$this->_resolveContextUrls($ctx, $_cycles, $resolver);
|
||||
$urls->{$url} = $ctx->{'@context'};
|
||||
}
|
||||
|
||||
// replace all URLS in the input
|
||||
$this->_findContextUrls($input, $urls, true);
|
||||
}
|
||||
|
||||
/**
|
||||
|
|
@ -3634,10 +3729,10 @@ class JsonLdException extends Exception {
|
|||
public function __toString() {
|
||||
$rval = __CLASS__ . ": [{$this->type}]: {$this->message}\n";
|
||||
if($this->details) {
|
||||
$rval .= 'details: ' . print_r($this->details, true) . "\n";
|
||||
$rval .= 'Details: ' . print_r($this->details, true) . "\n";
|
||||
}
|
||||
if($this->cause) {
|
||||
$rval .= 'cause: ' . $this->cause;
|
||||
$rval .= 'Cause: ' . $this->cause;
|
||||
}
|
||||
$rval .= $this->getTraceAsString() . "\n";
|
||||
return $rval;
|
||||
|
|
|
|||
Loading…
Reference in a new issue