R: Identifies function as expecting an xmlParserContext argument

xmlParserContextFunction {XML} | R Documentation

## Identifies function as expecting an xmlParserContext argument

### Description

This is a convenience function for setting the class of the specified function to include `"XMLParserContextFunction"`. This identifies it as expecting an `xmlParserCtxt` object as its first argument. The resulting function can be passed to the internal/native XML parser as a handler/callback function. When the parser calls it, it recognizes this class information and includes a reference to the C-level `xmlParserCtxt` object as the first argument in the call.

This `xmlParserCtxt` object can be used to gracefully terminate the parsing (without an error), and in the future will also provide access to details about the current state of the parser, e.g. the encoding of the file, the XML version, whether entities are being replaced, line and column number for each node processed.

### Usage

     xmlParserContextFunction(f, class = "XMLParserContextFunction")

### Arguments

`f` | the function whose class information is to be augmented.
`class` | the name of the class which is to be added to the `class` attribute of the function.

### Value

The function object `f` whose class attribute has been prepended with the value of `class`.

### Author(s)

Duncan Temple Lang

### See Also

`xmlInternalTreeParse`/`xmlParse` and the `branches` parameter of `xmlEventParse`.

### Examples

      fun = function(context, ...) {
                 # do things to parse the node
                 # using the context if necessary.
               cat("In XMLParserContextFunction\n")
               xmlStopParser(context)
             }
      fun = xmlParserContextFunction(fun)

      txt = "<doc><a/></doc>"
      # doesn't work for xmlTreeParse()
      #   xmlTreeParse(txt, handlers = list(a = fun))

      #  but does in xmlEventParse().
      xmlEventParse(txt, handlers = list(startElement = fun), asText = TRUE)

[Package XML version 3.98-1.19 Index]