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#' Read HTML or XML.
#'
#' @param x A string, a connection, or a raw vector.
#'
#' A string can be either a path, a url or literal xml. Urls will
#' be converted into connections either using \code{base::url} or, if
#' installed, \code{curl::curl}. Local paths ending in \code{.gz},
#' \code{.bz2}, \code{.xz}, \code{.zip} will be automatically uncompressed.
#'
#' If a connection, the complete connection is read into a raw vector before
#' being parsed.
#' @param encoding Specify a default encoding for the document. Unless
#' otherwise specified XML documents are assumed to be in UTF-8 or
#' UTF-16. If the document is not UTF-8/16, and lacks an explicit
#' encoding directive, this allows you to supply a default.
#' @param ... Additional arguments passed on to methods.
#' @param as_html Optionally parse an xml file as if it's html.
#' @param base_url When loading from a connection, raw vector or literal
#' html/xml, this allows you to specify a base url for the document. Base
#' urls are used to turn relative urls into absolute urls.
#' @param n If \code{file} is a connection, the number of bytes to read per
#' iteration. Defaults to 64kb.
#' @param verbose When reading from a slow connection, this prints some
#' output on every iteration so you know its working.
#' @param options Set parsing options for the libxml2 parser. Zero of more of
#' \Sexpr[results=rd]{xml2:::describe_options(xml2:::xml_parse_options())}
#' @return An XML document. HTML is normalised to valid XML - this may not
#' be exactly the same transformation performed by the browser, but it's
#' a reasonable approximation.
#' @export
#' @examples
#' # Literal xml/html is useful for small examples
#' read_xml("<foo><bar /></foo>")
#' read_html("<html><title>Hi<title></html>")
#' read_html("<html><title>Hi")
#'
#' # From a local path
#' read_html(system.file("extdata", "r-project.html", package = "xml2"))
#'
#' # From a url
#' cd <- read_xml("http://www.xmlfiles.com/examples/cd_catalog.xml")
#' me <- read_html("http://had.co.nz")
read_xml <- function(x, encoding = "", ..., as_html = FALSE, options = "NOBLANKS") {
UseMethod("read_xml")
}
#' @export
#' @rdname read_xml
read_html <- function(x, encoding = "", ..., options = c("RECOVER", "NOERROR", "NOBLANKS")) {
UseMethod("read_html")
}
#' @export
read_html.default <- function(x, encoding = "", ..., options = c("RECOVER", "NOERROR", "NOBLANKS")) {
options <- parse_options(options, xml_parse_options())
suppressWarnings(read_xml(x, encoding = encoding, ..., as_html = TRUE, options = options))
}
#' @export
read_html.response <- function(x, encoding = "", options = c("RECOVER",
"NOERROR", "NOBLANKS"), ...) {
need_package("httr")
options <- parse_options(options, xml_parse_options())
content <- httr::content(x, as = "raw")
xml2::read_html(content, encoding = encoding, options = options, ...)
}
#' @export
#' @rdname read_xml
read_xml.character <- function(x, encoding = "", ..., as_html = FALSE,
options = "NOBLANKS") {
options <- parse_options(options, xml_parse_options())
if (grepl("<|>", x)) {
read_xml.raw(charToRaw(enc2utf8(x)), "UTF-8", ..., as_html = as_html, options = options)
} else {
con <- path_to_connection(x)
if (inherits(con, "connection")) {
read_xml.connection(con, encoding = encoding, ..., as_html = as_html,
base_url = x, options = options)
} else {
doc <- doc_parse_file(con, encoding = encoding, as_html = as_html,
options = options)
xml_document(doc)
}
}
}
#' @export
#' @rdname read_xml
read_xml.raw <- function(x, encoding = "", base_url = "", ...,
as_html = FALSE, options = "NOBLANKS") {
options <- parse_options(options, xml_parse_options())
doc <- doc_parse_raw(x, encoding = encoding, base_url = base_url,
as_html = as_html, options = options)
xml_document(doc)
}
#' @export
#' @rdname read_xml
read_xml.connection <- function(x, encoding = "", n = 64 * 1024,
verbose = FALSE, ..., base_url = "",
as_html = FALSE, options = "NOBLANKS") {
options <- parse_options(options, xml_parse_options())
if (!isOpen(x)) {
open(x, "rb")
on.exit(close(x))
}
raw <- read_connection_(x, n)
read_xml.raw(raw, encoding = encoding, base_url = base_url, as_html =
as_html, options = options)
}
#' @export
read_xml.response <- function(x, encoding = "", base_url = "", ...,
as_html = FALSE, options = "NOBLANKS") {
need_package("httr")
options <- parse_options(options, xml_parse_options())
content <- httr::content(x, as = "raw")
xml2::read_xml(content, encoding = encoding, base_url = base_url,
as_html = as_html, option = options, ...)
}
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