isfiletext() checks whether a file is text or binary in a cross platf…

…orm matter, completing ticket gesistsa#236. This can be useful when a file extension is missing or ambiguous

NAMESPACE

@@ -83,6 +83,7 @@ export(get_ext)
 export(import)
 export(import_list)
 export(install_formats)
+export(isfiletext)
 export(spread_attrs)
 importFrom(curl,curl_fetch_memory)
 importFrom(curl,parse_headers)

R/isfiletext.R

@@ -0,0 +1,34 @@
+#' Determine whether a file is "plain-text" or some sort of binary format
+#'
+#' @param filename Path to the file
+#' @param maxsize  Maximum number of bytes to read
+#' @param textbytes Which characters are used by normal (though not necessarily 
+#'                  just ASCII) text. To detect just ASCII, the following value
+#'                  can be used: `as.raw(c(7:16,18,19,32:127))`
+#' @param tf       If `TRUE` (default) simply return `TRUE` when `filename` 
+#'                 references a text-only file and `FALSE` otherwise. If set to
+#'                 `FALSE` then returns the "non text" bytes found in the file.
+#'
+#' @return boolean or raw
+#' @export
+#' @examples
+#' library(datasets)
+#' export(iris,"iris.yml")
+#' isfiletext("iris.yml")
+#' ## TRUE
+#' 
+#' export(iris,"iris.sav")
+#' isfiletext("iris.sav")
+#' ## FALSE
+#' isfiletext("iris.sav", tf=FALSE)
+#' ## These are the characters found in "iris.sav" that are not printable text
+#' ## 02 00 05 03 06 04 01 14 15 11 17 16 1c 19 1b 1a 18 1e 1d 1f
+isfiletext <- function(filename,maxsize=Inf,
+                       textbytes=as.raw(c(0x7:0x10,0x12,0x13,0x20:0xFF)),
+                       tf=TRUE){
+  bytes <- readBin(ff<-file(filename,'rb'),raw(),n=min(file.info(filename)$size,
+                                                       maxsize));
+  close(ff);
+  nontextbytes <- setdiff(bytes,textbytes);
+  if(tf) return(length(nontextbytes)==0) else return(nontextbytes);
+}

tests/testthat/test_isfiletext.R

@@ -0,0 +1,71 @@
+context("correctly identifying files as text vs binary")
+require("datasets")
+
+txtformats <- c("arff","csv","csv2","dump","fwf","psv","r","tsv","txt","fwf")
+binformats <- c("dbf","dta","rda","rdata","rds","sas7bdat","sav","xlsx","xpt")
+names(iris) <- gsub("\\.","_",names(iris))
+
+test_that("Required text formats recognized as text", {
+  for(xx in txtformats) expect_true(isfiletext(export(iris,
+                                                      paste0("iris.",xx))),
+                                    label = paste0(xx," should be text"))
+  })
+
+test_that("Required non-text formats recognized as non-text", {
+  for(xx in binformats) expect_false(isfiletext(export(iris,
+                                                       paste0("iris.",xx))),
+                                     label = paste0(xx," should be text"))
+  })
+
+test_that("csvy recognized as text", {
+  skip_if_not_installed(pkg="csvy")
+  expect_true(isfiletext(export(iris,'iris.csvy')))
+  })
+
+test_that("xml and html recognized as text", {
+  skip_if_not_installed(pkg="xml2")
+  expect_true(isfiletext(export(iris,'iris.xml')))
+  expect_true(isfiletext(export(iris,'iris.html')))
+  })
+
+test_that("json recognized as text", {
+  skip_if_not_installed(pkg="jsonlite")
+  expect_true(isfiletext(export(iris,'iris.json')))
+  })
+
+test_that("yml recognized as text", {
+  skip_if_not_installed(pkg="yaml")
+  expect_true(isfiletext(export(iris,'iris.yml')))
+  })
+
+test_that("pzfx recognized as text", {
+  skip_if_not_installed(pkg="pzfx")
+  expect_true(isfiletext(export(iris[,-5],"iris.pzfx")))
+  })
+
+# binformats_suggest <- c("matlab","ods","fst","feather")
+test_that("matlab recognized as binary", {
+  skip_if_not_installed(pkg="rmatio")
+  expect_false(isfiletext(export(iris,'iris.matlab')))
+})
+
+test_that("ods recognized as binary", {
+  skip_if_not_installed(pkg="readODS")
+  expect_false(isfiletext(export(iris,'iris.ods')))
+})
+
+test_that("fst recognized as binary", {
+  skip_if_not_installed(pkg="fst")
+  expect_false(isfiletext(export(iris,'iris.fst')))
+})
+
+test_that("feather recognized as binary", {
+  skip_if_not_installed(pkg="feather")
+  expect_false(isfiletext(export(iris,'iris.feather')))
+})
+
+unlink(paste0('iris.',c(txtformats,binformats,'csvy','xml','html','json',
+                        'yml','pzfx','matlab','ods',
+                        'fst','feather')))
+rm(iris,txtformats,binformats)
+