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 xmlXPathNodeSetGetLength(ns); #define XML_XPATH_CHECKNS; #define XML_XPATH_NOVAR; #define xmlXPathNodeSetItem(ns, index); #define xmlXPathNodeSetIsEmpty(ns); typedef enum xmlXPathObjectType; typedef xmlXPathVariable * xmlXPathVariablePtr; typedef struct _xmlXPathContext xmlXPathContext; typedef enum xmlXPathError; typedef struct _xmlXPathFunct xmlXPathFunct; typedef xmlXPathType * xmlXPathTypePtr; typedef struct _xmlXPathType xmlXPathType; typedef xmlNodeSet * xmlNodeSetPtr; typedef xmlXPathFunct * xmlXPathFuncPtr; typedef xmlXPathCompExpr * xmlXPathCompExprPtr; typedef struct _xmlXPathObject xmlXPathObject; typedef struct _xmlXPathCompExpr xmlXPathCompExpr; typedef xmlXPathContext * xmlXPathContextPtr; typedef xmlXPathParserContext * xmlXPathParserContextPtr; typedef struct _xmlNodeSet xmlNodeSet; typedef struct _xmlXPathVariable xmlXPathVariable; typedef xmlXPathObject * xmlXPathObjectPtr; typedef struct _xmlXPathAxis xmlXPathAxis; typedef xmlXPathAxis * xmlXPathAxisPtr; typedef struct _xmlXPathParserContext xmlXPathParserContext; int xmlXPathCastNodeSetToBoolean (xmlNodeSetPtr ns); typedef xmlXPathFunction xmlXPathFuncLookupFunc (void * ctxt,
const xmlChar * name,
const xmlChar * ns_uri); xmlXPathObjectPtr xmlXPathNodeEval (xmlNodePtr node,
const xmlChar * str,
xmlXPathContextPtr ctx); xmlChar * xmlXPathCastNodeToString (xmlNodePtr node); int xmlXPathIsNaN (double val); int xmlXPathContextSetCache (xmlXPathContextPtr ctxt,
int active,
int value,
int options); xmlXPathObjectPtr xmlXPathConvertString (xmlXPathObjectPtr val); int xmlXPathCompiledEvalToBoolean (xmlXPathCompExprPtr comp,
xmlXPathContextPtr ctxt); int xmlXPathIsInf (double val); long xmlXPathOrderDocElems (xmlDocPtr doc); xmlNodeSetPtr xmlXPathNodeSetCreate (xmlNodePtr val); double xmlXPathCastBooleanToNumber (int val); double xmlXPathCastNodeToNumber (xmlNodePtr node); double xmlXPathCastStringToNumber (const xmlChar * val); typedef xmlXPathObjectPtr xmlXPathAxisFunc (xmlXPathParserContextPtr ctxt,
xmlXPathObjectPtr cur); double xmlXPathCastToNumber (xmlXPathObjectPtr val); int xmlXPathCastStringToBoolean (const xmlChar * val); xmlChar * xmlXPathCastNumberToString (double val); typedef xmlXPathObjectPtr xmlXPathVariableLookupFunc (void * ctxt,
const xmlChar * name,
const xmlChar * ns_uri); void xmlXPathFreeObject (xmlXPathObjectPtr obj); int xmlXPathEvalPredicate (xmlXPathContextPtr ctxt,
xmlXPathObjectPtr res); void xmlXPathFreeContext (xmlXPathContextPtr ctxt); xmlXPathObjectPtr xmlXPathObjectCopy (xmlXPathObjectPtr val); void xmlXPathFreeNodeSetList (xmlXPathObjectPtr obj); xmlXPathObjectPtr xmlXPathEval (const xmlChar * str,
xmlXPathContextPtr ctx); xmlChar * xmlXPathCastNodeSetToString (xmlNodeSetPtr ns); xmlXPathObjectPtr xmlXPathCompiledEval (xmlXPathCompExprPtr comp,
xmlXPathContextPtr ctx); xmlXPathObjectPtr xmlXPathEvalExpression (const xmlChar * str,
xmlXPathContextPtr ctxt); void xmlXPathInit (void); xmlXPathObjectPtr xmlXPathConvertBoolean (xmlXPathObjectPtr val); typedef int xmlXPathConvertFunc (xmlXPathObjectPtr obj,
int type); typedef void xmlXPathFunction (xmlXPathParserContextPtr ctxt,
int nargs); int xmlXPathCmpNodes (xmlNodePtr node1,
xmlNodePtr node2); xmlChar * xmlXPathCastToString (xmlXPathObjectPtr val); xmlXPathCompExprPtr xmlXPathCtxtCompile (xmlXPathContextPtr ctxt,
const xmlChar * str); typedef void xmlXPathEvalFunc (xmlXPathParserContextPtr ctxt,
int nargs); xmlChar * xmlXPathCastBooleanToString (int val); int xmlXPathSetContextNode (xmlNodePtr node,
xmlXPathContextPtr ctx); int xmlXPathCastNumberToBoolean (double val); void xmlXPathFreeNodeSet (xmlNodeSetPtr obj); void xmlXPathFreeCompExpr (xmlXPathCompExprPtr comp); xmlXPathContextPtr xmlXPathNewContext (xmlDocPtr doc); xmlXPathObjectPtr xmlXPathConvertNumber (xmlXPathObjectPtr val); xmlXPathCompExprPtr xmlXPathCompile (const xmlChar * str); double xmlXPathCastNodeSetToNumber (xmlNodeSetPtr ns); int xmlXPathCastToBoolean (xmlXPathObjectPtr val);
#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 : number of nodes in the set int nodeMax : size of the array as allocated xmlNodePtr * nodeTab : array of nodes in no particular order @@ with_ns to check whether nam } xmlNodeSet;
xmlNodeSet * xmlNodeSetPtr;
struct _xmlXPathAxis { const xmlChar * name : the axis name xmlXPathAxisFunc func : the search function } xmlXPathAxis;
xmlXPathAxis * xmlXPathAxisPtr;
struct _xmlXPathCompExpr { The content of this structure is not made public by the API. } xmlXPathCompExpr;
xmlXPathCompExpr * xmlXPathCompExprPtr;
struct _xmlXPathContext { xmlDocPtr doc : The current document xmlNodePtr node : The current node int nb_variables_unused : unused (hash table) int max_variables_unused : unused (hash table) xmlHashTablePtr varHash : Hash table of defined variables int nb_types : number of defined types int max_types : max number of types xmlXPathTypePtr types : Array of defined types int nb_funcs_unused : unused (hash table) int max_funcs_unused : unused (hash table) xmlHashTablePtr funcHash : Hash table of defined funcs int nb_axis : number of defined axis int max_axis : max number of axis xmlXPathAxisPtr axis : Array of defined axis the namespace nodes of the context node xmlNsPtr * namespaces : Array of namespaces int nsNr : number of namespace in scope void * user : function to free extra variables int contextSize : the context size int proximityPosition : the proximity position extra stuff for XPointer int xptr : is this an XPointer context? xmlNodePtr here : for here() xmlNodePtr origin : for origin() the set of namespace declarations in scope for the expre xmlHashTablePtr nsHash : The namespaces hash table xmlXPathVariableLookupFunc varLookupFunc : variable lookup func void * varLookupData : variable lookup data Possibility to link in an extra item void * extra : needed for XSLT The function name and URI when calling a function const xmlChar * function const xmlChar * functionURI : function lookup function and data xmlXPathFuncLookupFunc funcLookupFunc : function lookup func void * funcLookupData : function lookup data temporary namespace lists kept for walking the n xmlNsPtr * tmpNsList : Array of namespaces int tmpNsNr : number of namespaces in scope error reporting mechanism void * userData : user specific data block xmlStructuredErrorFunc error : the callback in case of errors xmlError lastError : the last error xmlNodePtr debugNode : the source node XSLT dictionary xmlDictPtr dict : dictionary if any int flags : flags to control compilation Cache for reusal of XPath objects void * cache : Resource limits 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 : the function name xmlXPathEvalFunc func : the evaluation function } 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_POINT = 5 XPATH_RANGE = 6 XPATH_LOCATIONSET = 7 XPATH_USERS = 8 XPATH_XSLT_TREE = 9 /* An XSLT value tree, non modifiable */ };
struct _xmlXPathParserContext { const xmlChar * cur : the current char being parsed const xmlChar * base : the full expression int error : error code xmlXPathContextPtr context : the evaluation context xmlXPathObjectPtr value : the current value int valueNr : number of values stacked int valueMax : max number of values stacked xmlXPathObjectPtr * valueTab : stack of values xmlXPathCompExprPtr comp : the precompiled expression int xptr : it this an XPointer expression xmlNodePtr ancestor : used for walking preceding axis int valueFrame : used to limit Pop on the stack } xmlXPathParserContext;
xmlXPathParserContext * xmlXPathParserContextPtr;
struct _xmlXPathType { const xmlChar * name : the type name xmlXPathConvertFunc func : the conversion function } xmlXPathType;
xmlXPathType * xmlXPathTypePtr;
struct _xmlXPathVariable { const xmlChar * name : the variable name xmlXPathObjectPtr value : the 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 5 slots for: node-set, string, number, boolean, 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)
val: | a double value |
Returns: | 1 if the value is +Infinite, -1 if -Infinite, 0 otherwise |
int xmlXPathIsNaN (double val)
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 |