| libxml2 Reference Manual |
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xpath - XML Path Language implementation
API for the XML Path Language implementation XML Path Language implementation XPath is a language for addressing parts of an XML document, designed to be used by both XSLT and XPointer
Author(s): Daniel Veillard
#define XML_XPATH_CHECKNS; #define XML_XPATH_NOVAR; #define xmlXPathNodeSetGetLength(ns); #define xmlXPathNodeSetIsEmpty(ns); #define xmlXPathNodeSetItem(ns, index); typedef struct _xmlNodeSet xmlNodeSet; typedef xmlNodeSet * xmlNodeSetPtr; typedef struct _xmlXPathAxis xmlXPathAxis; typedef xmlXPathAxis * xmlXPathAxisPtr; typedef struct _xmlXPathCompExpr xmlXPathCompExpr; typedef xmlXPathCompExpr * xmlXPathCompExprPtr; typedef struct _xmlXPathContext xmlXPathContext; typedef xmlXPathContext * xmlXPathContextPtr; typedef enum xmlXPathError; typedef xmlXPathFunct * xmlXPathFuncPtr; typedef struct _xmlXPathFunct xmlXPathFunct; typedef struct _xmlXPathObject xmlXPathObject; typedef xmlXPathObject * xmlXPathObjectPtr; typedef enum xmlXPathObjectType; typedef struct _xmlXPathParserContext xmlXPathParserContext; typedef xmlXPathParserContext * xmlXPathParserContextPtr; typedef struct _xmlXPathType xmlXPathType; typedef xmlXPathType * xmlXPathTypePtr; typedef struct _xmlXPathVariable xmlXPathVariable; typedef xmlXPathVariable * xmlXPathVariablePtr; typedef xmlXPathObjectPtr xmlXPathAxisFunc (xmlXPathParserContextPtr ctxt,
xmlXPathObjectPtr cur); double xmlXPathCastBooleanToNumber (int val); xmlChar * xmlXPathCastBooleanToString (int val); int xmlXPathCastNodeSetToBoolean (xmlNodeSetPtr ns); double xmlXPathCastNodeSetToNumber (xmlNodeSetPtr ns); xmlChar * xmlXPathCastNodeSetToString (xmlNodeSetPtr ns); double xmlXPathCastNodeToNumber (xmlNodePtr node); xmlChar * xmlXPathCastNodeToString (xmlNodePtr node); int xmlXPathCastNumberToBoolean (double val); xmlChar * xmlXPathCastNumberToString (double val); int xmlXPathCastStringToBoolean (const xmlChar * val); double xmlXPathCastStringToNumber (const xmlChar * val); int xmlXPathCastToBoolean (xmlXPathObjectPtr val); double xmlXPathCastToNumber (xmlXPathObjectPtr val); xmlChar * xmlXPathCastToString (xmlXPathObjectPtr val); int xmlXPathCmpNodes (xmlNodePtr node1,
xmlNodePtr node2); xmlXPathCompExprPtr xmlXPathCompile (const xmlChar * str); xmlXPathObjectPtr xmlXPathCompiledEval (xmlXPathCompExprPtr comp,
xmlXPathContextPtr ctx); int xmlXPathCompiledEvalToBoolean (xmlXPathCompExprPtr comp,
xmlXPathContextPtr ctxt); int xmlXPathContextSetCache (xmlXPathContextPtr ctxt,
int active,
int value,
int options); xmlXPathObjectPtr xmlXPathConvertBoolean (xmlXPathObjectPtr val); typedef int xmlXPathConvertFunc (xmlXPathObjectPtr obj,
int type); xmlXPathObjectPtr xmlXPathConvertNumber (xmlXPathObjectPtr val); xmlXPathObjectPtr xmlXPathConvertString (xmlXPathObjectPtr val); xmlXPathCompExprPtr xmlXPathCtxtCompile (xmlXPathContextPtr ctxt,
const xmlChar * str); xmlXPathObjectPtr xmlXPathEval (const xmlChar * str,
xmlXPathContextPtr ctx); xmlXPathObjectPtr xmlXPathEvalExpression (const xmlChar * str,
xmlXPathContextPtr ctxt); typedef void xmlXPathEvalFunc (xmlXPathParserContextPtr ctxt,
int nargs); int xmlXPathEvalPredicate (xmlXPathContextPtr ctxt,
xmlXPathObjectPtr res); void xmlXPathFreeCompExpr (xmlXPathCompExprPtr comp); void xmlXPathFreeContext (xmlXPathContextPtr ctxt); void xmlXPathFreeNodeSet (xmlNodeSetPtr obj); void xmlXPathFreeNodeSetList (xmlXPathObjectPtr obj); void xmlXPathFreeObject (xmlXPathObjectPtr obj); typedef xmlXPathFunction xmlXPathFuncLookupFunc (void * ctxt,
const xmlChar * name,
const xmlChar * ns_uri); typedef void xmlXPathFunction (xmlXPathParserContextPtr ctxt,
int nargs); void xmlXPathInit (void); int xmlXPathIsInf (double val); int xmlXPathIsNaN (double val); xmlXPathContextPtr xmlXPathNewContext (xmlDocPtr doc); xmlXPathObjectPtr xmlXPathNodeEval (xmlNodePtr node,
const xmlChar * str,
xmlXPathContextPtr ctx); xmlNodeSetPtr xmlXPathNodeSetCreate (xmlNodePtr val); xmlXPathObjectPtr xmlXPathObjectCopy (xmlXPathObjectPtr val); long xmlXPathOrderDocElems (xmlDocPtr doc); int xmlXPathSetContextNode (xmlNodePtr node,
xmlXPathContextPtr ctx); void xmlXPathSetErrorHandler (xmlXPathContextPtr ctxt,
xmlStructuredErrorFunc handler,
void * data); typedef xmlXPathObjectPtr xmlXPathVariableLookupFunc (void * ctxt,
const xmlChar * name,
const xmlChar * ns_uri);
#define xmlXPathNodeSetGetLength(ns);
Implement a functionality similar to the DOM NodeList.length. Returns the number of nodes in the node-set.
| ns: | a node-set |
#define xmlXPathNodeSetIsEmpty(ns);
Checks whether @ns is empty or not. Returns %TRUE if @ns is an empty node-set.
| ns: | a node-set |
#define xmlXPathNodeSetItem(ns, index);
Implements a functionality similar to the DOM NodeList.item(). Returns the xmlNodePtr at the given @index in @ns or NULL if @index is out of range (0 to length-1)
| ns: | a node-set |
| index: | index of a node in the set |
struct _xmlNodeSet {
int nodeNr
int nodeMax
xmlNodePtr * nodeTab
} xmlNodeSet;
xmlNodeSet * xmlNodeSetPtr;
struct _xmlXPathAxis {
const xmlChar * name
xmlXPathAxisFunc func
} xmlXPathAxis;
xmlXPathAxis * xmlXPathAxisPtr;
struct _xmlXPathCompExpr {
The content of this structure is not made public by the API.
} xmlXPathCompExpr;
xmlXPathCompExpr * xmlXPathCompExprPtr;
struct _xmlXPathContext {
xmlDocPtr doc
xmlNodePtr node
int nb_variables_unused
int max_variables_unused
xmlHashTablePtr varHash
int nb_types
int max_types
xmlXPathTypePtr types
int nb_funcs_unused
int max_funcs_unused
xmlHashTablePtr funcHash
int nb_axis
int max_axis
xmlXPathAxisPtr axis
xmlNsPtr * namespaces
int nsNr
void * user
int contextSize
int proximityPosition
int xptr
xmlNodePtr here
xmlNodePtr origin
xmlHashTablePtr nsHash
xmlXPathVariableLookupFunc varLookupFunc
void * varLookupData
void * extra
const xmlChar * function
const xmlChar * functionURI
xmlXPathFuncLookupFunc funcLookupFunc
void * funcLookupData
xmlNsPtr * tmpNsList
int tmpNsNr
void * userData
xmlStructuredErrorFunc error
xmlError lastError
xmlNodePtr debugNode
xmlDictPtr dict
int flags
void * cache
unsigned long opLimit
unsigned long opCount
int depth
} xmlXPathContext;
xmlXPathContext * xmlXPathContextPtr;
enum xmlXPathError { XPATH_EXPRESSION_OK = 0 XPATH_NUMBER_ERROR = 1 XPATH_UNFINISHED_LITERAL_ERROR = 2 XPATH_START_LITERAL_ERROR = 3 XPATH_VARIABLE_REF_ERROR = 4 XPATH_UNDEF_VARIABLE_ERROR = 5 XPATH_INVALID_PREDICATE_ERROR = 6 XPATH_EXPR_ERROR = 7 XPATH_UNCLOSED_ERROR = 8 XPATH_UNKNOWN_FUNC_ERROR = 9 XPATH_INVALID_OPERAND = 10 XPATH_INVALID_TYPE = 11 XPATH_INVALID_ARITY = 12 XPATH_INVALID_CTXT_SIZE = 13 XPATH_INVALID_CTXT_POSITION = 14 XPATH_MEMORY_ERROR = 15 XPTR_SYNTAX_ERROR = 16 XPTR_RESOURCE_ERROR = 17 XPTR_SUB_RESOURCE_ERROR = 18 XPATH_UNDEF_PREFIX_ERROR = 19 XPATH_ENCODING_ERROR = 20 XPATH_INVALID_CHAR_ERROR = 21 XPATH_INVALID_CTXT = 22 XPATH_STACK_ERROR = 23 XPATH_FORBID_VARIABLE_ERROR = 24 XPATH_OP_LIMIT_EXCEEDED = 25 XPATH_RECURSION_LIMIT_EXCEEDED = 26 };
xmlXPathFunct * xmlXPathFuncPtr;
struct _xmlXPathFunct {
const xmlChar * name
xmlXPathEvalFunc func
} xmlXPathFunct;
struct _xmlXPathObject {
xmlXPathObjectType type
xmlNodeSetPtr nodesetval
int boolval
double floatval
xmlChar * stringval
void * user
int index
void * user2
int index2
} xmlXPathObject;
xmlXPathObject * xmlXPathObjectPtr;
enum xmlXPathObjectType { XPATH_UNDEFINED = 0 XPATH_NODESET = 1 XPATH_BOOLEAN = 2 XPATH_NUMBER = 3 XPATH_STRING = 4 XPATH_USERS = 8 XPATH_XSLT_TREE = 9 /* An XSLT value tree, non modifiable */ };
struct _xmlXPathParserContext {
const xmlChar * cur
const xmlChar * base
int error
xmlXPathContextPtr context
xmlXPathObjectPtr value
int valueNr
int valueMax
xmlXPathObjectPtr * valueTab
xmlXPathCompExprPtr comp
int xptr
xmlNodePtr ancestor
int valueFrame
} xmlXPathParserContext;
xmlXPathParserContext * xmlXPathParserContextPtr;
struct _xmlXPathType {
const xmlChar * name
xmlXPathConvertFunc func
} xmlXPathType;
xmlXPathType * xmlXPathTypePtr;
struct _xmlXPathVariable {
const xmlChar * name
xmlXPathObjectPtr value
} xmlXPathVariable;
xmlXPathVariable * xmlXPathVariablePtr;
xmlXPathObjectPtr xmlXPathAxisFunc (xmlXPathParserContextPtr ctxt,
xmlXPathObjectPtr cur)
An axis traversal function. To traverse an axis, the engine calls the first time with cur == NULL and repeat until the function returns NULL indicating the end of the axis traversal.
| ctxt: | the XPath interpreter context |
| cur: | the previous node being explored on that axis |
| Returns: | the next node in that axis or NULL if at the end of the axis. |
int xmlXPathConvertFunc (xmlXPathObjectPtr obj,
int type)
A conversion function is associated to a type and used to cast the new type to primitive values.
| obj: | an XPath object |
| type: | the number of the target type |
| Returns: | -1 in case of error, 0 otherwise |
void xmlXPathEvalFunc (xmlXPathParserContextPtr ctxt,
int nargs)
An XPath evaluation function, the parameters are on the XPath context stack.
| ctxt: | an XPath parser context |
| nargs: | the number of arguments passed to the function |
xmlXPathFunction xmlXPathFuncLookupFunc (void * ctxt,
const xmlChar * name,
const xmlChar * ns_uri)
Prototype for callbacks used to plug function lookup in the XPath engine.
| ctxt: | an XPath context |
| name: | name of the function |
| ns_uri: | the namespace name hosting this function |
| Returns: | the XPath function or NULL if not found. |
void xmlXPathFunction (xmlXPathParserContextPtr ctxt,
int nargs)
An XPath function. The arguments (if any) are popped out from the context stack and the result is pushed on the stack.
| ctxt: | the XPath interprestation context |
| nargs: | the number of arguments |
xmlXPathObjectPtr xmlXPathVariableLookupFunc (void * ctxt,
const xmlChar * name,
const xmlChar * ns_uri)
Prototype for callbacks used to plug variable lookup in the XPath engine.
| ctxt: | an XPath context |
| name: | name of the variable |
| ns_uri: | the namespace name hosting this variable |
| Returns: | the XPath object value or NULL if not found. |
double xmlXPathNAN;
double xmlXPathNINF;
double xmlXPathPINF;
double xmlXPathCastBooleanToNumber (int val)
Converts a boolean to its number value
| val: | a boolean |
| Returns: | the number value |
xmlChar * xmlXPathCastBooleanToString (int val)
Converts a boolean to its string value.
| val: | a boolean |
| Returns: | a newly allocated string. |
int xmlXPathCastNodeSetToBoolean (xmlNodeSetPtr ns)
Converts a node-set to its boolean value
| ns: | a node-set |
| Returns: | the boolean value |
double xmlXPathCastNodeSetToNumber (xmlNodeSetPtr ns)
Converts a node-set to its number value
| ns: | a node-set |
| Returns: | the number value |
xmlChar * xmlXPathCastNodeSetToString (xmlNodeSetPtr ns)
Converts a node-set to its string value.
| ns: | a node-set |
| Returns: | a newly allocated string. |
double xmlXPathCastNodeToNumber (xmlNodePtr node)
Converts a node to its number value
| node: | a node |
| Returns: | the number value |
xmlChar * xmlXPathCastNodeToString (xmlNodePtr node)
Converts a node to its string value.
| node: | a node |
| Returns: | a newly allocated string. |
int xmlXPathCastNumberToBoolean (double val)
Converts a number to its boolean value
| val: | a number |
| Returns: | the boolean value |
xmlChar * xmlXPathCastNumberToString (double val)
Converts a number to its string value.
| val: | a number |
| Returns: | a newly allocated string. |
int xmlXPathCastStringToBoolean (const xmlChar * val)
Converts a string to its boolean value
| val: | a string |
| Returns: | the boolean value |
double xmlXPathCastStringToNumber (const xmlChar * val)
Converts a string to its number value
| val: | a string |
| Returns: | the number value |
int xmlXPathCastToBoolean (xmlXPathObjectPtr val)
Converts an XPath object to its boolean value
| val: | an XPath object |
| Returns: | the boolean value |
double xmlXPathCastToNumber (xmlXPathObjectPtr val)
Converts an XPath object to its number value
| val: | an XPath object |
| Returns: | the number value |
xmlChar * xmlXPathCastToString (xmlXPathObjectPtr val)
Converts an existing object to its string() equivalent
| val: | an XPath object |
| Returns: | the allocated string value of the object, NULL in case of error. It's up to the caller to free the string memory with xmlFree(). |
int xmlXPathCmpNodes (xmlNodePtr node1,
xmlNodePtr node2)
Compare two nodes w.r.t document order
| node1: | the first node |
| node2: | the second node |
| Returns: | -2 in case of error 1 if first point < second point, 0 if it's the same node, -1 otherwise |
xmlXPathCompExprPtr xmlXPathCompile (const xmlChar * str)
Compile an XPath expression
| str: | the XPath expression |
| Returns: | the xmlXPathCompExprPtr resulting from the compilation or NULL. the caller has to free the object. |
xmlXPathObjectPtr xmlXPathCompiledEval (xmlXPathCompExprPtr comp,
xmlXPathContextPtr ctx)
Evaluate the Precompiled XPath expression in the given context.
| comp: | the compiled XPath expression |
| ctx: | the XPath context |
| Returns: | the xmlXPathObjectPtr resulting from the evaluation or NULL. the caller has to free the object. |
int xmlXPathCompiledEvalToBoolean (xmlXPathCompExprPtr comp,
xmlXPathContextPtr ctxt)
Applies the XPath boolean() function on the result of the given compiled expression.
| comp: | the compiled XPath expression |
| ctxt: | the XPath context |
| Returns: | 1 if the expression evaluated to true, 0 if to false and -1 in API and internal errors. |
int xmlXPathContextSetCache (xmlXPathContextPtr ctxt,
int active,
int value,
int options)
Creates/frees an object cache on the XPath context. If activates XPath objects (xmlXPathObject) will be cached internally to be reused. @options: 0: This will set the XPath object caching: @value: This will set the maximum number of XPath objects to be cached per slot There are two slots for node-set and misc objects. Use <0 for the default number (100). Other values for @options have currently no effect.
| ctxt: | the XPath context |
| active: | enables/disables (creates/frees) the cache |
| value: | a value with semantics dependent on @options |
| options: | options (currently only the value 0 is used) |
| Returns: | 0 if the setting succeeded, and -1 on API or internal errors. |
xmlXPathObjectPtr xmlXPathConvertBoolean (xmlXPathObjectPtr val)
Converts an existing object to its boolean() equivalent
| val: | an XPath object |
| Returns: | the new object, the old one is freed (or the operation is done directly on @val) |
xmlXPathObjectPtr xmlXPathConvertNumber (xmlXPathObjectPtr val)
Converts an existing object to its number() equivalent
| val: | an XPath object |
| Returns: | the new object, the old one is freed (or the operation is done directly on @val) |
xmlXPathObjectPtr xmlXPathConvertString (xmlXPathObjectPtr val)
Converts an existing object to its string() equivalent
| val: | an XPath object |
| Returns: | the new object, the old one is freed (or the operation is done directly on @val) |
xmlXPathCompExprPtr xmlXPathCtxtCompile (xmlXPathContextPtr ctxt,
const xmlChar * str)
Compile an XPath expression
| ctxt: | an XPath context |
| str: | the XPath expression |
| Returns: | the xmlXPathCompExprPtr resulting from the compilation or NULL. the caller has to free the object. |
xmlXPathObjectPtr xmlXPathEval (const xmlChar * str,
xmlXPathContextPtr ctx)
Evaluate the XPath Location Path in the given context.
| str: | the XPath expression |
| ctx: | the XPath context |
| Returns: | the xmlXPathObjectPtr resulting from the evaluation or NULL. the caller has to free the object. |
xmlXPathObjectPtr xmlXPathEvalExpression (const xmlChar * str,
xmlXPathContextPtr ctxt)
Alias for xmlXPathEval().
| str: | the XPath expression |
| ctxt: | the XPath context |
| Returns: | the xmlXPathObjectPtr resulting from the evaluation or NULL. the caller has to free the object. |
int xmlXPathEvalPredicate (xmlXPathContextPtr ctxt,
xmlXPathObjectPtr res)
Evaluate a predicate result for the current node. A PredicateExpr is evaluated by evaluating the Expr and converting the result to a boolean. If the result is a number, the result will be converted to true if the number is equal to the position of the context node in the context node list (as returned by the position function) and will be converted to false otherwise; if the result is not a number, then the result will be converted as if by a call to the boolean function.
| ctxt: | the XPath context |
| res: | the Predicate Expression evaluation result |
| Returns: | 1 if predicate is true, 0 otherwise |
void xmlXPathFreeCompExpr (xmlXPathCompExprPtr comp)
Free up the memory allocated by @comp
| comp: | an XPATH comp |
void xmlXPathFreeContext (xmlXPathContextPtr ctxt)
Free up an xmlXPathContext
| ctxt: | the context to free |
void xmlXPathFreeNodeSet (xmlNodeSetPtr obj)
Free the NodeSet compound (not the actual nodes !).
| obj: | the xmlNodeSetPtr to free |
void xmlXPathFreeNodeSetList (xmlXPathObjectPtr obj)
Free up the xmlXPathObjectPtr @obj but don't deallocate the objects in the list contrary to xmlXPathFreeObject().
| obj: | an existing NodeSetList object |
void xmlXPathFreeObject (xmlXPathObjectPtr obj)
Free up an xmlXPathObjectPtr object.
| obj: | the object to free |
int xmlXPathIsInf (double val)
Checks whether a double is an infinity.
| val: | a double value |
| Returns: | 1 if the value is +Infinite, -1 if -Infinite, 0 otherwise |
int xmlXPathIsNaN (double val)
Checks whether a double is a NaN.
| val: | a double value |
| Returns: | 1 if the value is a NaN, 0 otherwise |
xmlXPathContextPtr xmlXPathNewContext (xmlDocPtr doc)
Create a new xmlXPathContext
| doc: | the XML document |
| Returns: | the xmlXPathContext just allocated. The caller will need to free it. |
xmlXPathObjectPtr xmlXPathNodeEval (xmlNodePtr node,
const xmlChar * str,
xmlXPathContextPtr ctx)
Evaluate the XPath Location Path in the given context. The node 'node' is set as the context node. The context node is not restored.
| node: | the node to to use as the context node |
| str: | the XPath expression |
| ctx: | the XPath context |
| Returns: | the xmlXPathObjectPtr resulting from the evaluation or NULL. the caller has to free the object. |
xmlNodeSetPtr xmlXPathNodeSetCreate (xmlNodePtr val)
Create a new xmlNodeSetPtr of type double and of value @val
| val: | an initial xmlNodePtr, or NULL |
| Returns: | the newly created object. |
xmlXPathObjectPtr xmlXPathObjectCopy (xmlXPathObjectPtr val)
allocate a new copy of a given object
| val: | the original object |
| Returns: | the newly created object. |
long xmlXPathOrderDocElems (xmlDocPtr doc)
Call this routine to speed up XPath computation on static documents. This stamps all the element nodes with the document order Like for line information, the order is kept in the element->content field, the value stored is actually - the node number (starting at -1) to be able to differentiate from line numbers.
| doc: | an input document |
| Returns: | the number of elements found in the document or -1 in case of error. |
int xmlXPathSetContextNode (xmlNodePtr node,
xmlXPathContextPtr ctx)
Sets 'node' as the context node. The node must be in the same document as that associated with the context.
| node: | the node to to use as the context node |
| ctx: | the XPath context |
| Returns: | -1 in case of error or 0 if successful |
void xmlXPathSetErrorHandler (xmlXPathContextPtr ctxt,
xmlStructuredErrorFunc handler,
void * data)
Register a callback function that will be called on errors and warnings. If handler is NULL, the error handler will be deactivated. Available since 2.13.0.
| ctxt: | the XPath context |
| handler: | error handler |
| data: | user data which will be passed to the handler |