https://github.com/cran/XML
Tip revision: 89e6494d4b3572d033b44942a0b324c221773f47 authored by CRAN Team on 28 October 2022, 09:15:39 UTC
version 3.99-0.12
version 3.99-0.12
Tip revision: 89e6494
xmlSerializeHook.Rd
\name{xmlSerializeHook}
\alias{xmlSerializeHook}
\alias{xmlDeserializeHook}
\title{Functions that help serialize and deserialize XML internal objects}
\description{
These functions can be used to control
how the C-level data structures associated with XML documents, nodes,
XPath queries, etc. are serialized to a a file or connection
and deserialized back into an R session.
Since these C-level data structures are represented
in R as external pointers, they would normally be serialized
and deserialized in a way that loses all the information about
the contents of the memory being referenced.
\code{xmlSerializeHook} arranges to serialize these pointers
by saving the corresponding XML content as a string
and also the class of the object.
The deserialize function converts such objects back to their
original form.
These functions are used in calls to \code{\link{saveRDS}}
and \code{\link{readRDS}} via the
\code{refhook} argument.
\code{
saveRDS(obj, filename, refhook = xmlSerializeHook)
readRDS(filename, refhook = xmlDeserializeHook)
}
}
\usage{
xmlSerializeHook(x)
xmlDeserializeHook(x)
}
\arguments{
\item{x}{the object to be deserialized, and the character vector to be
deserialized.}
}
\value{
\code{xmlSerializeHook} returns a character version of the XML
document or node, along with the basic class.
If it is called with an object that is not an native/internal XML
object, it returns \code{NULL}
\code{xmlDeserializeHook} returns the parsed XML object, either a
document or a node.
}
\references{
The R Internals Manual.
}
\author{
Duncan Temple Lang
}
\seealso{
\code{\link{saveRDS}} and \code{\link{readRDS}}
}
\examples{
z = newXMLNode("foo")
f = system.file("exampleData", "tides.xml", package = "XML")
doc = xmlParse(f)
hdoc = as(doc, "XMLHashTree")
nodes = getNodeSet(doc, "//pred")
ff <- file.path(tempdir(), "tmp.rda")
saveRDS(list(a = 1:10, z = z, doc = doc, hdoc = hdoc, nodes = nodes), ff,
refhook = xmlSerializeHook)
v = readRDS(ff, refhook = xmlDeserializeHook)
unlink(ff)
}
\keyword{IO}