File indexing completed on 2024-12-22 05:36:20

 <?php
 
 /**
  * Takes a well formed list of tokens and fixes their nesting.
  *
  * HTML elements dictate which elements are allowed to be their children,
  * for example, you can't have a p tag in a span tag.  Other elements have
  * much more rigorous definitions: tables, for instance, require a specific
  * order for their elements.  There are also constraints not expressible by
  * document type definitions, such as the chameleon nature of ins/del
  * tags and global child exclusions.
  *
  * The first major objective of this strategy is to iterate through all
  * the nodes and determine whether or not their children conform to the
  * element's definition.  If they do not, the child definition may
  * optionally supply an amended list of elements that is valid or
  * require that the entire node be deleted (and the previous node
  * rescanned).
  *
  * The second objective is to ensure that explicitly excluded elements of
  * an element do not appear in its children.  Code that accomplishes this
  * task is pervasive through the strategy, though the two are distinct tasks
  * and could, theoretically, be seperated (although it's not recommended).
  *
  * @note Whether or not unrecognized children are silently dropped or
  *       translated into text depends on the child definitions.
  *
  * @todo Enable nodes to be bubbled out of the structure.  This is
  *       easier with our new algorithm.
  */
 
 class HTMLPurifier_Strategy_FixNesting extends HTMLPurifier_Strategy
 {
 
     /**
      * @param HTMLPurifier_Token[] $tokens
      * @param HTMLPurifier_Config $config
      * @param HTMLPurifier_Context $context
      * @return array|HTMLPurifier_Token[]
      */
     public function execute($tokens, $config, $context)
     {
 
         //####################################################################//
         // Pre-processing
 
         // O(n) pass to convert to a tree, so that we can efficiently
         // refer to substrings
         $top_node = HTMLPurifier_Arborize::arborize($tokens, $config, $context);
 
         // get a copy of the HTML definition
         $definition = $config->getHTMLDefinition();
 
         $excludes_enabled = !$config->get('Core.DisableExcludes');
 
         // setup the context variable 'IsInline', for chameleon processing
         // is 'false' when we are not inline, 'true' when it must always
         // be inline, and an integer when it is inline for a certain
         // branch of the document tree
         $is_inline = $definition->info_parent_def->descendants_are_inline;
         $context->register('IsInline', $is_inline);
 
         // setup error collector
         $e =& $context->get('ErrorCollector', true);
 
         //####################################################################//
         // Loop initialization
 
         // stack that contains all elements that are excluded
         // it is organized by parent elements, similar to $stack,
         // but it is only populated when an element with exclusions is
         // processed, i.e. there won't be empty exclusions.
         $exclude_stack = array($definition->info_parent_def->excludes);
 
         // variable that contains the start token while we are processing
         // nodes. This enables error reporting to do its job
         $node = $top_node;
         // dummy token
         list($token, $d) = $node->toTokenPair();
         $context->register('CurrentNode', $node);
         $context->register('CurrentToken', $token);
 
         //####################################################################//
         // Loop
 
         // We need to implement a post-order traversal iteratively, to
         // avoid running into stack space limits.  This is pretty tricky
         // to reason about, so we just manually stack-ify the recursive
         // variant:
         //
         //  function f($node) {
         //      foreach ($node->children as $child) {
         //          f($child);
         //      }
         //      validate($node);
         //  }
         //
         // Thus, we will represent a stack frame as array($node,
         // $is_inline, stack of children)
         // e.g. array_reverse($node->children) - already processed
         // children.
 
         $parent_def = $definition->info_parent_def;
         $stack = array(
             array($top_node,
                   $parent_def->descendants_are_inline,
                   $parent_def->excludes, // exclusions
                   0)
             );
 
         while (!empty($stack)) {
             list($node, $is_inline, $excludes, $ix) = array_pop($stack);
             // recursive call
             $go = false;
             $def = empty($stack) ? $definition->info_parent_def : $definition->info[$node->name];
             while (isset($node->children[$ix])) {
                 $child = $node->children[$ix++];
                 if ($child instanceof HTMLPurifier_Node_Element) {
                     $go = true;
                     $stack[] = array($node, $is_inline, $excludes, $ix);
                     $stack[] = array($child,
                         // ToDo: I don't think it matters if it's def or
                         // child_def, but double check this...
                         $is_inline || $def->descendants_are_inline,
                         empty($def->excludes) ? $excludes
                                               : array_merge($excludes, $def->excludes),
                         0);
                     break;
                 }
             };
             if ($go) continue;
             list($token, $d) = $node->toTokenPair();
             // base case
             if ($excludes_enabled && isset($excludes[$node->name])) {
                 $node->dead = true;
                 if ($e) $e->send(E_ERROR, 'Strategy_FixNesting: Node excluded');
             } else {
                 // XXX I suppose it would be slightly more efficient to
                 // avoid the allocation here and have children
                 // strategies handle it
                 $children = array();
                 foreach ($node->children as $child) {
                     if (!$child->dead) $children[] = $child;
                 }
                 $result = $def->child->validateChildren($children, $config, $context);
                 if ($result === true) {
                     // nop
                     $node->children = $children;
                 } elseif ($result === false) {
                     $node->dead = true;
                     if ($e) $e->send(E_ERROR, 'Strategy_FixNesting: Node removed');
                 } else {
                     $node->children = $result;
                     if ($e) {
                         // XXX This will miss mutations of internal nodes. Perhaps defer to the child validators
                         if (empty($result) && !empty($children)) {
                             $e->send(E_ERROR, 'Strategy_FixNesting: Node contents removed');
                         } else if ($result != $children) {
                             $e->send(E_WARNING, 'Strategy_FixNesting: Node reorganized');
                         }
                     }
                 }
             }
         }
 
         //####################################################################//
         // Post-processing
 
         // remove context variables
         $context->destroy('IsInline');
         $context->destroy('CurrentNode');
         $context->destroy('CurrentToken');
 
         //####################################################################//
         // Return
 
         return HTMLPurifier_Arborize::flatten($node, $config, $context);
     }
 }
 
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