add reopen_connection generic

Author: ben-schwen

NAMESPACE

@@ -20,6 +20,7 @@ export(rbindlist)
 export(fifelse)
 export(fcase)
 export(fread)
+export(reopen_connection)
 export(fwrite)
 export(foverlaps)
 export(shift)

R/fread.R

@@ -1,3 +1,33 @@
+# S3 generic for reopening connections in binary mode
+reopen_connection = function(con, ...) {
+  UseMethod("reopen_connection")
+}
+
+reopen_connection.default = function(con, ...) {
+  con_class = class(con)[1L]
+  stopf("Don't know how to reopen connection type '%s'. Need a connection opened in binary mode to continue.", con_class)
+}
+
+reopen_connection.file = function(con, ...) {
+  file(summary(con)$description, "rb")
+}
+
+reopen_connection.gzfile = function(con, ...) {
+  gzfile(summary(con)$description, "rb")
+}
+
+reopen_connection.bzfile = function(con, ...) {
+  bzfile(summary(con)$description, "rb")
+}
+
+reopen_connection.url = function(con, ...) {
+  url(summary(con)$description, "rb")
+}
+
+reopen_connection.pipe = function(con, ...) {
+  pipe(summary(con)$description, "rb")
+}
+
 fread = function(
 input="", file=NULL, text=NULL, cmd=NULL, sep="auto", sep2="auto", dec="auto", quote="\"", nrows=Inf, header="auto",
 na.strings=getOption("datatable.na.strings","NA"), stringsAsFactors=FALSE, verbose=getOption("datatable.verbose",FALSE),
@@ -112,13 +142,7 @@ yaml=FALSE, tmpdir=tempdir(), tz="UTC")
 
     if (needs_reopen) {
       close(input)
-      input = switch(con_class,
-                     "file" = file(con_desc, "rb"),
-                     "gzfile" = gzfile(con_desc, "rb"),
-                     "bzfile" = bzfile(con_desc, "rb"),
-                     "url" = url(con_desc, "rb"),
-                     "pipe" = pipe(con_desc, "rb"),
-                     stopf("Don't know how to reopen connection type '%s'. Need a connection opened in binary mode to continue.", con_class))
+      input = reopen_connection(input)
       close_con = input
     } else if (!con_open) {
       open(input, "rb")

man/reopen_connection.Rd

@@ -0,0 +1,25 @@
+\name{reopen_connection}
+\alias{reopen_connection}
+\title{ Reopen a connection in binary mode }
+\description{
+  S3 generic to reopen a connection in binary read mode. Used internally by \code{fread}. Exported so packages with custom connection classes can define methods.
+}
+\usage{
+reopen_connection(con, ...)
+}
+\arguments{
+  \item{con}{ A connection object. }
+  \item{...}{ Additional arguments for methods. }
+}
+\details{
+  Reopens a connection in binary read mode (\code{"rb"}). Methods are provided for \code{file}, \code{gzfile}, \code{bzfile}, \code{url}, and \code{pipe} connections.
+
+  To support custom connection types with \code{fread}, define a method for your connection class that returns a new connection opened in binary mode.
+}
+\value{
+  A connection object opened in binary read mode.
+}
+\seealso{
+  \code{\link{fread}}
+}
+\keyword{ data }