Add parse_http_date. #129

NAMESPACE

@@ -59,6 +59,7 @@ export(oauth_exchanger)
 export(oauth_header)
 export(oauth_listener)
 export(oauth_signature)
+export(parse_http_date)
 export(parse_media)
 export(parse_url)
 export(parsed_content)

NEWS.md

@@ -18,6 +18,11 @@
 * `url_ok()` works correctly now, instead of always returning `FALSE`,
   a bug since version 0.4 (#133).
 
+## Caching
+
+* `parse_http_date()` parses http dates according RFC2616 spec.
+
+
 # httr 0.4
 
 ## New features

R/date.R

@@ -0,0 +1,37 @@
+#' Parse an http date
+#'
+#' As defined in RFC2616,
+#' \url{http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3}, there are
+#' three valid formats:
+#' \itemize{
+#'  \item Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
+#'  \item Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
+#'  \item Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
+#' }
+#' @param x A character vector of strings to parse. All elements must be of
+#'   the same type.
+#' @export
+#' @return A POSIXct object if succesful, otherwise NA.
+#' @examples
+#' parse_http_date("Sun, 06 Nov 1994 08:49:37 GMT")
+#' parse_http_date("Sunday, 06-Nov-94 08:49:37 GMT")
+#' parse_http_date("Sun Nov  6 08:49:37 1994")
+parse_http_date <- function(x) {
+  fmts <- c(
+    "%a, %d %b %Y %H:%M:%S",
+    "%A, %d-%b-%y %H:%M:%S",
+    "%a %b %d %H:%M:%S %Y"
+  )
+
+  # Need to set C locale to ensure that months/days are parsed in English
+  old <- Sys.getlocale(category = "LC_TIME")
+  Sys.setlocale(category = "LC_TIME", locale = "C")
+  on.exit(Sys.setlocale(category = "LC_TIME", locale = old))
+
+  for (fmt in fmts) {
+    parsed <- as.POSIXct(strptime(x, fmt, tz = "GMT"))
+    if (all(!is.na(parsed))) return(parsed)
+  }
+
+  rep(NA, length(x))
+}

man/parse_http_date.Rd

@@ -0,0 +1,30 @@
+% Generated by roxygen2 (4.0.1): do not edit by hand
+\name{parse_http_date}
+\alias{parse_http_date}
+\title{Parse an http date}
+\usage{
+parse_http_date(x)
+}
+\arguments{
+\item{x}{A character vector of strings to parse. All elements must be of
+the same type.}
+}
+\value{
+A POSIXct object if succesful, otherwise NA.
+}
+\description{
+As defined in RFC2616,
+\url{http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3}, there are
+three valid formats:
+\itemize{
+ \item Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
+ \item Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
+ \item Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
+}
+}
+\examples{
+parse_http_date("Sun, 06 Nov 1994 08:49:37 GMT")
+parse_http_date("Sunday, 06-Nov-94 08:49:37 GMT")
+parse_http_date("Sun Nov  6 08:49:37 1994")
+}
+