Class: LibXML::XML::XPath::Context

Inherits:
Object
  • Object
show all
Defined in:
ext/libxml/ruby_xml_xpath_context.c,
ext/libxml/ruby_xml_xpath_context.c

Overview

The XML::XPath::Context class is used to evaluate XPath expressions. Generally, you should not directly use this class, but instead use the XML::Document#find and XML::Node#find methods.

doc = XML::Document.string('<header>content</header>')
context = XPath::Context.new(doc)
context.node = doc.root
context.register_namespaces_from_node(doc.root)
nodes = context.find('/header')

Instance Method Summary collapse

Constructor Details

#XPath::Context.new(doc) ⇒ XPath::Context

Creates a new XPath context for the specified document. The context can then be used to evaluate an XPath expression.

doc = XML::Document.string('<header><first>hi</first></header>')
context = XPath::Context.new(doc)
nodes = XPath::Object.new('//first', context)
nodes.length == 1



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 56

static VALUE rxml_xpath_context_initialize(VALUE self, VALUE document)
{
  xmlDocPtr xdoc;

  if (rb_obj_is_kind_of(document, cXMLDocument) != Qtrue)
  {
    rb_raise(rb_eTypeError, "Supplied argument must be a document or node.");
  }

  Data_Get_Struct(document, xmlDoc, xdoc);
  DATA_PTR(self) = xmlXPathNewContext(xdoc);

  return self;
}

Instance Method Details

#disable_cache ⇒ Object

Disables an XPath::Context’s built-in cache.



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 332

static VALUE
rxml_xpath_context_disable_cache(VALUE self)
{
  xmlXPathContextPtr xctxt;
  Data_Get_Struct(self, xmlXPathContext, xctxt);

  if (xmlXPathContextSetCache(xctxt, 0, 0, 0) == -1)
    rxml_raise(&xmlLastError);

  return self;
}

#doc ⇒ Object

Obtain the XML::Document this node belongs to.



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 77

static VALUE rxml_xpath_context_doc(VALUE self)
{
  xmlDocPtr xdoc = NULL;
  xmlXPathContextPtr ctxt;
  Data_Get_Struct(self, xmlXPathContext, ctxt);
  
  xdoc = ctxt->doc;
  return rxml_document_wrap(xdoc);
}

#enable_cache(size = nil) ⇒ Object

Enables an XPath::Context’s built-in cache. If the cache is enabled then XPath objects will be cached internally for reuse. The size parameter controls sets the maximum number of XPath objects that will be cached per XPath object type (node-set, string, number, boolean, and misc objects). Set size to nil to use the default cache size of 100.



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 306

static VALUE
rxml_xpath_context_enable_cache(int argc,  VALUE *argv, VALUE self)
{
  xmlXPathContextPtr xctxt;
  VALUE size;
  int value = -1;

  Data_Get_Struct(self, xmlXPathContext, xctxt);

  if (rb_scan_args(argc, argv, "01", &size) == 1)
  {
	  value = NUM2INT(size);
  }

  if (xmlXPathContextSetCache(xctxt, 1, value, 0) == -1)
    rxml_raise(&xmlLastError);

  return self;
}

#find("xpath") ⇒ true|false|number|string|XML::XPath::Object

Executes the provided xpath function. The result depends on the execution of the xpath statement. It may be true, false, a number, a string or a node set.

Returns:



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 267

static VALUE rxml_xpath_context_find(VALUE self, VALUE xpath_expr)
{
  xmlXPathContextPtr xctxt;
  xmlXPathObjectPtr xobject;
  xmlXPathCompExprPtr xcompexpr;

  Data_Get_Struct(self, xmlXPathContext, xctxt);

  if (TYPE(xpath_expr) == T_STRING)
  {
    VALUE expression = rb_check_string_type(xpath_expr);
    xobject = xmlXPathEval((xmlChar*) StringValueCStr(expression), xctxt);
  }
  else if (rb_obj_is_kind_of(xpath_expr, cXMLXPathExpression))
  {
    Data_Get_Struct(xpath_expr, xmlXPathCompExpr, xcompexpr);
    xobject = xmlXPathCompiledEval(xcompexpr, xctxt);
  }
  else
  {
    rb_raise(rb_eTypeError,
        "Argument should be an instance of a String or XPath::Expression");
  }

  return rxml_xpath_to_value(xctxt, xobject);
}

#node=(node) ⇒ Object

Set the current node used by the XPath engine

doc = XML::Document.string('<header><first>hi</first></header>')
context.node = doc.root.first



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 248

static VALUE rxml_xpath_context_node_set(VALUE self, VALUE node)
{
  xmlXPathContextPtr xctxt;
  xmlNodePtr xnode;

  Data_Get_Struct(self, xmlXPathContext, xctxt);
  Data_Get_Struct(node, xmlNode, xnode);
  xctxt->node = xnode;
  return node;
}

#register_namespace(prefix, uri) ⇒ Object

Register the specified namespace URI with the specified prefix in this context.

context.register_namespace('xi', 'http://www.w3.org/2001/XInclude')



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# File 'ext/libxml/ruby_xml_xpath_context.c', line 96

static VALUE rxml_xpath_context_register_namespace(VALUE self, VALUE prefix, VALUE uri)
{
  xmlXPathContextPtr ctxt;
  Data_Get_Struct(self, xmlXPathContext, ctxt);

  /* Prefix could be a symbol. */
  prefix = rb_obj_as_string(prefix);
  
  if (xmlXPathRegisterNs(ctxt, (xmlChar*) StringValuePtr(prefix),
      (xmlChar*) StringValuePtr(uri)) == 0)
  {
    return (Qtrue);
  }
  else
  {
    /* Should raise an exception, IMHO (whose?, why shouldnt it? -danj)*/
    rb_warning("register namespace failed");
    return (Qfalse);
  }
}

#register_namespaces(["prefix: uri"]) ⇒ self

Register the specified namespaces in this context. There are three different forms that libxml accepts. These include a string, an array of strings, or a hash table:

context.register_namespaces('xi:http://www.w3.org/2001/XInclude')
context.register_namespaces(['xlink:http://www.w3.org/1999/xlink',
                             'xi:http://www.w3.org/2001/XInclude')
context.register_namespaces('xlink' => 'http://www.w3.org/1999/xlink',
                               'xi' => 'http://www.w3.org/2001/XInclude')

Returns:

  • (self) 


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# File 'ext/libxml/ruby_xml_xpath_context.c', line 194

static VALUE rxml_xpath_context_register_namespaces(VALUE self, VALUE nslist)
{
  char *cp;
  long i;
  VALUE rprefix, ruri;
  xmlXPathContextPtr xctxt;

  Data_Get_Struct(self, xmlXPathContext, xctxt);

  /* Need to loop through the 2nd argument and iterate through the
   * list of namespaces that we want to allow */
  switch (TYPE(nslist))
  {
  case T_STRING:
    cp = strchr(StringValuePtr(nslist), (int) ':');
    if (cp == NULL)
    {
      rprefix = nslist;
      ruri = Qnil;
    }
    else
    {
      rprefix = rb_str_new(StringValuePtr(nslist), (long) ((intptr_t) cp - (intptr_t)StringValuePtr(nslist)));
      ruri = rxml_new_cstr((const xmlChar*)&cp[1], xctxt->doc->encoding);
    }
    /* Should test the results of this */
    rxml_xpath_context_register_namespace(self, rprefix, ruri);
    break;
  case T_ARRAY:
    for (i = 0; i < RARRAY_LEN(nslist); i++)
    {
      rxml_xpath_context_register_namespaces(self, RARRAY_PTR(nslist)[i]);
    }
    break;
  case T_HASH:
    rb_hash_foreach(nslist, iterate_ns_hash, self);
    break;
  default:
    rb_raise(
        rb_eArgError,
        "Invalid argument type, only accept string, array of strings, or an array of arrays");
  }
  return self;
}

#register_namespaces_from_node(node) ⇒ self

Helper method to read in namespaces defined on a node.

doc = XML::Document.string('<header><first>hi</first></header>')
context = XPath::Context.new(doc)
context.register_namespaces_from_node(doc.root)

Returns:

  • (self) 


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# File 'ext/libxml/ruby_xml_xpath_context.c', line 126

static VALUE rxml_xpath_context_register_namespaces_from_node(VALUE self,
    VALUE node)
{
  xmlXPathContextPtr xctxt;
  xmlNodePtr xnode;
  xmlNsPtr *xnsArr;

  Data_Get_Struct(self, xmlXPathContext, xctxt);

  if (rb_obj_is_kind_of(node, cXMLDocument) == Qtrue)
  {
    xmlDocPtr xdoc;
    Data_Get_Struct(node, xmlDoc, xdoc);
    xnode = xmlDocGetRootElement(xdoc);
  }
  else if (rb_obj_is_kind_of(node, cXMLNode) == Qtrue)
  {
    Data_Get_Struct(node, xmlNode, xnode);
  }
  else
  {
    rb_raise(rb_eTypeError, "The first argument must be a document or node.");
  }

  xnsArr = xmlGetNsList(xnode->doc, xnode);

  if (xnsArr)
  {
    xmlNsPtr xns = *xnsArr;

    while (xns)
    {
      /* If there is no prefix, then this is the default namespace.
       Skip it for now. */
      if (xns->prefix)
      {
        VALUE prefix = rxml_new_cstr(xns->prefix, xctxt->doc->encoding);
        VALUE uri = rxml_new_cstr(xns->href, xctxt->doc->encoding);
        rxml_xpath_context_register_namespace(self, prefix, uri);
      }
      xns = xns->next;
    }
    xmlFree(xnsArr);
  }

  return self;
}