php-src/ext/dom/dom_iterators.c
Niels Dossche c3f0797385
Implement iteration cache, item cache and length cache for node list iteration (#11330)
* Implement iteration cache, item cache and length cache for node list iteration

The current implementation follows the spec requirement that the list
must be "live". This means that changes in the document must be
reflected in the existing node lists without requiring the user to
refetch the node list.
The consequence is that getting any item, or the length of the list,
always starts searching from the root element of the node list. This
results in O(n) time to get any item or the length. If there's a for
loop over the node list, this means the iterations will take O(n²) time
in total. This causes real-world performance issues with potential for
downtime (see GH-11308 and its references for details).

We fix this by introducing a caching strategy. We cache the last
iterated object in the iterator, the last requested item in the node
list, and the last length computation. To invalidate the cache, we
simply count the number of modifications made to the containing
document. If the modification number does not match what the number was
during caching, we know the document has been modified and the cache is
invalid. If this ever overflows, we saturate the modification number and
don't do any caching anymore. Note that we don't check for overflow on
64-bit systems because it would take hundreds of years to overflow.

Fixes GH-11308.
2023-06-03 00:13:14 +02:00

339 lines
9.4 KiB
C

/*
+----------------------------------------------------------------------+
| Copyright (c) The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| https://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: Christian Stocker <chregu@php.net> |
| Rob Richards <rrichards@php.net> |
+----------------------------------------------------------------------+
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "php.h"
#if defined(HAVE_LIBXML) && defined(HAVE_DOM)
#include "php_dom.h"
#include "dom_ce.h"
typedef struct _nodeIterator nodeIterator;
struct _nodeIterator {
int cur;
int index;
xmlNode *node;
};
typedef struct _notationIterator notationIterator;
struct _notationIterator {
int cur;
int index;
xmlNotation *notation;
};
#if LIBXML_VERSION >= 20908
static void itemHashScanner (void *payload, void *data, const xmlChar *name) /* {{{ */
#else
static void itemHashScanner (void *payload, void *data, xmlChar *name)
#endif
{
nodeIterator *priv = (nodeIterator *)data;
if(priv->cur < priv->index) {
priv->cur++;
} else {
if(priv->node == NULL) {
priv->node = (xmlNode *)payload;
}
}
}
/* }}} */
xmlNodePtr create_notation(const xmlChar *name, const xmlChar *ExternalID, const xmlChar *SystemID) /* {{{ */
{
xmlEntityPtr ret;
ret = (xmlEntityPtr) xmlMalloc(sizeof(xmlEntity));
memset(ret, 0, sizeof(xmlEntity));
ret->type = XML_NOTATION_NODE;
ret->name = xmlStrdup(name);
ret->ExternalID = xmlStrdup(ExternalID);
ret->SystemID = xmlStrdup(SystemID);
ret->length = 0;
ret->content = NULL;
ret->URI = NULL;
ret->orig = NULL;
ret->children = NULL;
ret->parent = NULL;
ret->doc = NULL;
ret->_private = NULL;
ret->last = NULL;
ret->prev = NULL;
return((xmlNodePtr) ret);
}
/* }}} */
xmlNode *php_dom_libxml_hash_iter(xmlHashTable *ht, int index) /* {{{ */
{
xmlNode *nodep = NULL;
nodeIterator *iter;
int htsize;
if ((htsize = xmlHashSize(ht)) > 0 && index < htsize) {
iter = emalloc(sizeof(nodeIterator));
iter->cur = 0;
iter->index = index;
iter->node = NULL;
xmlHashScan(ht, itemHashScanner, iter);
nodep = iter->node;
efree(iter);
return nodep;
} else {
return NULL;
}
}
/* }}} */
xmlNode *php_dom_libxml_notation_iter(xmlHashTable *ht, int index) /* {{{ */
{
notationIterator *iter;
xmlNotation *notep = NULL;
int htsize;
if ((htsize = xmlHashSize(ht)) > 0 && index < htsize) {
iter = emalloc(sizeof(notationIterator));
iter->cur = 0;
iter->index = index;
iter->notation = NULL;
xmlHashScan(ht, itemHashScanner, iter);
notep = iter->notation;
efree(iter);
return create_notation(notep->name, notep->PublicID, notep->SystemID);
} else {
return NULL;
}
}
/* }}} */
static void php_dom_iterator_dtor(zend_object_iterator *iter) /* {{{ */
{
php_dom_iterator *iterator = (php_dom_iterator *)iter;
zval_ptr_dtor(&iterator->intern.data);
zval_ptr_dtor(&iterator->curobj);
}
/* }}} */
static int php_dom_iterator_valid(zend_object_iterator *iter) /* {{{ */
{
php_dom_iterator *iterator = (php_dom_iterator *)iter;
if (Z_TYPE(iterator->curobj) != IS_UNDEF) {
return SUCCESS;
} else {
return FAILURE;
}
}
/* }}} */
zval *php_dom_iterator_current_data(zend_object_iterator *iter) /* {{{ */
{
php_dom_iterator *iterator = (php_dom_iterator *)iter;
return &iterator->curobj;
}
/* }}} */
static void php_dom_iterator_current_key(zend_object_iterator *iter, zval *key) /* {{{ */
{
php_dom_iterator *iterator = (php_dom_iterator *)iter;
zval *object = &iterator->intern.data;
if (instanceof_function(Z_OBJCE_P(object), dom_nodelist_class_entry)) {
ZVAL_LONG(key, iter->index);
} else {
dom_object *intern = Z_DOMOBJ_P(&iterator->curobj);
if (intern != NULL && intern->ptr != NULL) {
xmlNodePtr curnode = (xmlNodePtr)((php_libxml_node_ptr *)intern->ptr)->node;
ZVAL_STRINGL(key, (char *) curnode->name, xmlStrlen(curnode->name));
} else {
ZVAL_NULL(key);
}
}
}
/* }}} */
static void php_dom_iterator_move_forward(zend_object_iterator *iter) /* {{{ */
{
zval *object;
xmlNodePtr curnode = NULL, basenode;
dom_object *intern;
dom_object *nnmap;
dom_nnodemap_object *objmap;
int previndex;
HashTable *nodeht;
zval *entry;
bool do_curobj_undef = 1;
php_dom_iterator *iterator = (php_dom_iterator *)iter;
object = &iterator->intern.data;
nnmap = Z_DOMOBJ_P(object);
objmap = (dom_nnodemap_object *)nnmap->ptr;
intern = Z_DOMOBJ_P(&iterator->curobj);
if (intern != NULL && intern->ptr != NULL) {
if (objmap->nodetype != XML_ENTITY_NODE &&
objmap->nodetype != XML_NOTATION_NODE) {
if (objmap->nodetype == DOM_NODESET) {
nodeht = HASH_OF(&objmap->baseobj_zv);
zend_hash_move_forward_ex(nodeht, &iterator->pos);
if ((entry = zend_hash_get_current_data_ex(nodeht, &iterator->pos))) {
zval_ptr_dtor(&iterator->curobj);
ZVAL_UNDEF(&iterator->curobj);
ZVAL_COPY(&iterator->curobj, entry);
do_curobj_undef = 0;
}
} else {
if (objmap->nodetype == XML_ATTRIBUTE_NODE ||
objmap->nodetype == XML_ELEMENT_NODE) {
curnode = (xmlNodePtr)((php_libxml_node_ptr *)intern->ptr)->node;
curnode = curnode->next;
} else {
/* The collection is live, we nav the tree from the base object if we cannot
* use the cache to restart from the last point. */
basenode = dom_object_get_node(objmap->baseobj);
if (UNEXPECTED(!basenode)) {
goto err;
}
if (php_dom_is_cache_tag_stale_from_node(&iterator->cache_tag, basenode)) {
php_dom_mark_cache_tag_up_to_date_from_node(&iterator->cache_tag, basenode);
previndex = 0;
if (basenode && (basenode->type == XML_DOCUMENT_NODE ||
basenode->type == XML_HTML_DOCUMENT_NODE)) {
curnode = xmlDocGetRootElement((xmlDoc *) basenode);
} else {
curnode = basenode->children;
}
} else {
previndex = iter->index - 1;
curnode = (xmlNodePtr)((php_libxml_node_ptr *)intern->ptr)->node;
}
curnode = dom_get_elements_by_tag_name_ns_raw(
basenode, curnode, (char *) objmap->ns, (char *) objmap->local, &previndex, iter->index);
}
}
} else {
if (objmap->nodetype == XML_ENTITY_NODE) {
curnode = php_dom_libxml_hash_iter(objmap->ht, iter->index);
} else {
curnode = php_dom_libxml_notation_iter(objmap->ht, iter->index);
}
}
}
err:
if (do_curobj_undef) {
zval_ptr_dtor(&iterator->curobj);
ZVAL_UNDEF(&iterator->curobj);
}
if (curnode) {
php_dom_create_object(curnode, &iterator->curobj, objmap->baseobj);
}
}
/* }}} */
static const zend_object_iterator_funcs php_dom_iterator_funcs = {
php_dom_iterator_dtor,
php_dom_iterator_valid,
php_dom_iterator_current_data,
php_dom_iterator_current_key,
php_dom_iterator_move_forward,
NULL,
NULL,
NULL, /* get_gc */
};
zend_object_iterator *php_dom_get_iterator(zend_class_entry *ce, zval *object, int by_ref) /* {{{ */
{
dom_object *intern;
dom_nnodemap_object *objmap;
xmlNodePtr curnode=NULL;
int curindex = 0;
HashTable *nodeht;
zval *entry;
php_dom_iterator *iterator;
if (by_ref) {
zend_throw_error(NULL, "An iterator cannot be used with foreach by reference");
return NULL;
}
iterator = emalloc(sizeof(php_dom_iterator));
zend_iterator_init(&iterator->intern);
iterator->cache_tag.modification_nr = 0;
ZVAL_OBJ_COPY(&iterator->intern.data, Z_OBJ_P(object));
iterator->intern.funcs = &php_dom_iterator_funcs;
ZVAL_UNDEF(&iterator->curobj);
intern = Z_DOMOBJ_P(object);
objmap = (dom_nnodemap_object *)intern->ptr;
if (objmap != NULL) {
if (objmap->nodetype != XML_ENTITY_NODE &&
objmap->nodetype != XML_NOTATION_NODE) {
if (objmap->nodetype == DOM_NODESET) {
nodeht = HASH_OF(&objmap->baseobj_zv);
zend_hash_internal_pointer_reset_ex(nodeht, &iterator->pos);
if ((entry = zend_hash_get_current_data_ex(nodeht, &iterator->pos))) {
ZVAL_COPY(&iterator->curobj, entry);
}
} else {
xmlNodePtr basep = (xmlNode *)dom_object_get_node(objmap->baseobj);
if (!basep) {
goto err;
}
if (objmap->nodetype == XML_ATTRIBUTE_NODE || objmap->nodetype == XML_ELEMENT_NODE) {
if (objmap->nodetype == XML_ATTRIBUTE_NODE) {
curnode = (xmlNodePtr) basep->properties;
} else {
curnode = (xmlNodePtr) basep->children;
}
} else {
xmlNodePtr nodep = basep;
if (nodep->type == XML_DOCUMENT_NODE || nodep->type == XML_HTML_DOCUMENT_NODE) {
nodep = xmlDocGetRootElement((xmlDoc *) nodep);
} else {
nodep = nodep->children;
}
curnode = dom_get_elements_by_tag_name_ns_raw(
basep, nodep, (char *) objmap->ns, (char *) objmap->local, &curindex, 0);
}
}
} else {
if (objmap->nodetype == XML_ENTITY_NODE) {
curnode = php_dom_libxml_hash_iter(objmap->ht, 0);
} else {
curnode = php_dom_libxml_notation_iter(objmap->ht, 0);
}
}
}
err:
if (curnode) {
php_dom_create_object(curnode, &iterator->curobj, objmap->baseobj);
}
return &iterator->intern;
}
/* }}} */
#endif