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 Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#XPath::Context.new(node) ⇒ 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 54

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

  if (rb_obj_is_kind_of(node, cXMLNode) == Qtrue)
  {
    document = rb_funcall(node, rb_intern("doc"), 0);
    if (NIL_P(document))
    rb_raise(rb_eTypeError, "Supplied node must belong to a document.");
  }
  else if (rb_obj_is_kind_of(node, cXMLDocument) == Qtrue)
  {
    document = node;
  }
  else
  {
    rb_raise(rb_eTypeError, "Supplied argument must be a document or node.");
  }

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

  /* Save the doc as an attribute, this will expose it to Ruby's GC. */
  rb_ivar_set(self, DOC_ATTRIBUTE, document);

  return self;
}

Instance Attribute Details

#doc ⇒ Object (readonly)

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 357

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;
}

#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 331

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 261

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

  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 intance of a String or XPath::Expression");
  }

  if (xobject == NULL)
  {
    /* xmlLastError is different than xctxt->lastError.  Use
     xmlLastError since it has the message set while xctxt->lastError
     does not. */
    xmlErrorPtr xerror = xmlGetLastError();
    rxml_raise(xerror);
  }

  switch (xobject->type)
  {
  case XPATH_NODESET:
    result = rxml_xpath_object_wrap(xctxt->doc, xobject);
    break;
  case XPATH_BOOLEAN:
    result = (xobject->boolval != 0) ? Qtrue : Qfalse;
    xmlXPathFreeObject(xobject);
    break;
  case XPATH_NUMBER:
    result = rb_float_new(xobject->floatval);
    xmlXPathFreeObject(xobject);
    break;
  case XPATH_STRING:
    result = rb_str_new2((const char*)xobject->stringval);
    xmlXPathFreeObject(xobject);
    break;
  default:
    result = Qnil;
    xmlXPathFreeObject(xobject);
  }
  return result;
}

#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 242

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 92

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 190

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

  /* 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), (int) ((long) cp
          - (long) StringValuePtr(nslist)));
      ruri = rb_str_new2(&cp[1]);
    }
    /* 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:
    st_foreach(RHASH_TBL(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 122

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 = rb_str_new2((const char*)xns->prefix);
        VALUE uri = rb_str_new2((const char*)xns->href);
        rxml_xpath_context_register_namespace(self, prefix, uri);
      }
      xns = xns->next;
    }
    xmlFree(xnsArr);
  }

  return self;
}