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c3f0797385
* 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.
154 lines
5.5 KiB
C
154 lines
5.5 KiB
C
/*
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+----------------------------------------------------------------------+
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| Copyright (c) The PHP Group |
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+----------------------------------------------------------------------+
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| This source file is subject to version 3.01 of the PHP license, |
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| that is bundled with this package in the file LICENSE, and is |
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| available through the world-wide-web at the following url: |
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| https://www.php.net/license/3_01.txt |
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| If you did not receive a copy of the PHP license and are unable to |
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| obtain it through the world-wide-web, please send a note to |
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| license@php.net so we can mail you a copy immediately. |
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+----------------------------------------------------------------------+
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| Authors: Shane Caraveo <shane@php.net> |
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| Wez Furlong <wez@thebrainroom.com> |
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+----------------------------------------------------------------------+
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*/
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#ifndef PHP_LIBXML_H
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#define PHP_LIBXML_H
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#ifdef HAVE_LIBXML
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extern zend_module_entry libxml_module_entry;
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#define libxml_module_ptr &libxml_module_entry
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#include "php_version.h"
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#define PHP_LIBXML_VERSION PHP_VERSION
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#ifdef PHP_WIN32
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# define PHP_LIBXML_API __declspec(dllexport)
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#elif defined(__GNUC__) && __GNUC__ >= 4
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# define PHP_LIBXML_API __attribute__ ((visibility("default")))
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#else
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# define PHP_LIBXML_API
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#endif
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#include "zend_smart_str.h"
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#include <libxml/tree.h>
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#define LIBXML_SAVE_NOEMPTYTAG 1<<2
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ZEND_BEGIN_MODULE_GLOBALS(libxml)
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zval stream_context;
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smart_str error_buffer;
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zend_llist *error_list;
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zend_fcall_info_cache entity_loader_callback;
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bool entity_loader_disabled;
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ZEND_END_MODULE_GLOBALS(libxml)
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typedef struct _libxml_doc_props {
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HashTable *classmap;
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bool formatoutput;
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bool validateonparse;
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bool resolveexternals;
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bool preservewhitespace;
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bool substituteentities;
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bool stricterror;
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bool recover;
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} libxml_doc_props;
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typedef struct _php_libxml_ref_obj {
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void *ptr;
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int refcount;
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libxml_doc_props *doc_props;
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} php_libxml_ref_obj;
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typedef struct _php_libxml_node_ptr {
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xmlNodePtr node;
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int refcount;
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void *_private;
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} php_libxml_node_ptr;
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typedef struct {
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size_t modification_nr;
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} php_libxml_cache_tag;
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/* extends php_libxml_node_ptr */
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typedef struct {
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php_libxml_node_ptr node_ptr;
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php_libxml_cache_tag cache_tag;
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} php_libxml_doc_ptr;
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typedef struct _php_libxml_node_object {
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php_libxml_node_ptr *node;
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php_libxml_ref_obj *document;
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HashTable *properties;
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zend_object std;
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} php_libxml_node_object;
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static inline php_libxml_node_object *php_libxml_node_fetch_object(zend_object *obj) {
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return (php_libxml_node_object *)((char*)(obj) - obj->handlers->offset);
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}
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static zend_always_inline void php_libxml_invalidate_node_list_cache(php_libxml_doc_ptr *doc_ptr)
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{
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#if SIZEOF_SIZE_T == 8
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/* If one operation happens every nanosecond, then it would still require 584 years to overflow
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* the counter. So we'll just assume this never happens. */
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doc_ptr->cache_tag.modification_nr++;
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#else
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size_t new_modification_nr = doc_ptr->cache_tag.modification_nr + 1;
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if (EXPECTED(new_modification_nr > 0)) { /* unsigned overflow; checking after addition results in one less instruction */
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doc_ptr->cache_tag.modification_nr = new_modification_nr;
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}
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#endif
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}
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static zend_always_inline void php_libxml_invalidate_node_list_cache_from_doc(xmlDocPtr docp)
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{
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if (docp && docp->_private) { /* docp is NULL for detached nodes */
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php_libxml_invalidate_node_list_cache(docp->_private);
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}
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}
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#define Z_LIBXML_NODE_P(zv) php_libxml_node_fetch_object(Z_OBJ_P((zv)))
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typedef void * (*php_libxml_export_node) (zval *object);
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PHP_LIBXML_API int php_libxml_increment_node_ptr(php_libxml_node_object *object, xmlNodePtr node, void *private_data);
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PHP_LIBXML_API int php_libxml_decrement_node_ptr(php_libxml_node_object *object);
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PHP_LIBXML_API int php_libxml_increment_doc_ref(php_libxml_node_object *object, xmlDocPtr docp);
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PHP_LIBXML_API int php_libxml_decrement_doc_ref(php_libxml_node_object *object);
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PHP_LIBXML_API xmlNodePtr php_libxml_import_node(zval *object);
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PHP_LIBXML_API zval *php_libxml_register_export(zend_class_entry *ce, php_libxml_export_node export_function);
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/* When an explicit freeing of node and children is required */
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PHP_LIBXML_API void php_libxml_node_free_list(xmlNodePtr node);
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PHP_LIBXML_API void php_libxml_node_free_resource(xmlNodePtr node);
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/* When object dtor is called as node may still be referenced */
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PHP_LIBXML_API void php_libxml_node_decrement_resource(php_libxml_node_object *object);
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PHP_LIBXML_API void php_libxml_error_handler(void *ctx, const char *msg, ...);
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PHP_LIBXML_API void php_libxml_ctx_warning(void *ctx, const char *msg, ...);
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PHP_LIBXML_API void php_libxml_ctx_error(void *ctx, const char *msg, ...);
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PHP_LIBXML_API int php_libxml_xmlCheckUTF8(const unsigned char *s);
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PHP_LIBXML_API void php_libxml_switch_context(zval *context, zval *oldcontext);
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PHP_LIBXML_API void php_libxml_issue_error(int level, const char *msg);
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PHP_LIBXML_API bool php_libxml_disable_entity_loader(bool disable);
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/* Init/shutdown functions*/
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PHP_LIBXML_API void php_libxml_initialize(void);
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PHP_LIBXML_API void php_libxml_shutdown(void);
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#define LIBXML(v) ZEND_MODULE_GLOBALS_ACCESSOR(libxml, v)
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#if defined(ZTS) && defined(COMPILE_DL_LIBXML)
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ZEND_TSRMLS_CACHE_EXTERN()
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#endif
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#else /* HAVE_LIBXML */
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#define libxml_module_ptr NULL
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#endif
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#define phpext_libxml_ptr libxml_module_ptr
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#endif /* PHP_LIBXML_H */
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