Factor out make_readable_file

r/R/RecordBatchReader.R

@@ -92,13 +92,6 @@ RecordBatchFileReader <- R6Class("RecordBatchFileReader", inherit = Object,
 )
 
 RecordBatchFileReader$create <- function(file) {
-  if (inherits(file, c("raw", "Buffer"))) {
-    file <- BufferReader$create(file)
-  } else if (is.character(file)) {
-    assert_that(length(file) == 1L)
-    file <- ReadableFile$create(file)
-  }
-  assert_that(inherits(file, "RandomAccessFile"))
-
+  file <- make_readable_file(file)
   shared_ptr(RecordBatchFileReader, ipc___RecordBatchFileReader__Open(file))
 }

r/R/csv.R

@@ -32,7 +32,7 @@
 #' `parse_options`, `convert_options`, or `read_options` arguments, or you can
 #' call [csv_table_reader()] directly for lower-level access.
 #'
-#' @param file A character path to a local file, or an Arrow input stream
+#' @inheritParams make_readable_file
 #' @param delim Single character used to separate fields within a record.
 #' @param quote Single character used to quote strings.
 #' @param escape_double Does the file escape quotes by doubling them?
@@ -202,16 +202,11 @@ CsvTableReader$create <- function(file,
                                   parse_options = csv_parse_options(),
                                   convert_options = csv_convert_options(),
                                   ...) {
-  if (is.character(file)) {
-    file <- mmap_open(file)
-  }
-  if (inherits(file, "InputStream")) {
-    file <- shared_ptr(CsvTableReader,
-      csv___TableReader__Make(file, read_options, parse_options, convert_options)
-    )
-  }
-  assert_that(inherits(file, c("CsvTableReader", "TableReader")))
-  file
+  file <- make_readable_file(file)
+  shared_ptr(
+    CsvTableReader,
+    csv___TableReader__Make(file, read_options, parse_options, convert_options)
+  )
 }
 
 #' Arrow CSV and JSON table readers

r/R/feather.R

@@ -113,17 +113,7 @@ FeatherTableReader <- R6Class("FeatherTableReader", inherit = Object,
   )
 )
 
-FeatherTableReader$create <- function(stream, mmap = TRUE, ...) {
-  if (is.character(stream)) {
-    if (isTRUE(mmap)) {
-      stream <- mmap_open(stream, ...)
-    } else {
-      stream <- ReadableFile$create(stream, ...)
-    }
-  } else if (is.raw(stream)) {
-    stream <- BufferReader$create(stream)
-  }
-
-  assert_that(inherits(stream, "InputStream"))
-  unique_ptr(FeatherTableReader, ipc___feather___TableReader__Open(stream))
+FeatherTableReader$create <- function(file, mmap = TRUE, ...) {
+  file <- make_readable_file(file, mmap)
+  unique_ptr(FeatherTableReader, ipc___feather___TableReader__Open(file))
 }

r/R/io.R

@@ -295,3 +295,23 @@ mmap_open <- function(path, mode = c("read", "write", "readwrite")) {
   path <- normalizePath(path)
   shared_ptr(MemoryMappedFile, io___MemoryMappedFile__Open(path, mode))
 }
+
+#' Handle a range of possible input sources
+#' @param file A character file name, raw vector, or an Arrow input stream
+#' @param mmap Logical: whether to memory-map the file (default `TRUE`)
+#' @return An `InputStream` or a subclass of one.
+#' @keywords internal
+make_readable_file <- function(file, mmap = TRUE) {
+  if (is.character(file)) {
+    assert_that(length(file) == 1L)
+    if (isTRUE(mmap)) {
+      file <- mmap_open(file)
+    } else {
+      file <- ReadableFile$create(file)
+    }
+  } else if (inherits(file, c("raw", "Buffer"))) {
+    file <- BufferReader$create(file)
+  }
+  assert_that(inherits(file, "InputStream"))
+  file
+}

r/R/json.R

@@ -70,16 +70,11 @@ JsonTableReader$create <- function(file,
                                    parse_options = json_parse_options(),
                                    ...) {
 
-  if (is.character(file)) {
-    file <- mmap_open(file)
-  }
-  if (inherits(file, "InputStream")) {
-    file <- shared_ptr(JsonTableReader,
-      json___TableReader__Make(file, read_options, parse_options)
-    )
-  }
-  assert_that(inherits(file, c("JsonTableReader", "TableReader")))
-  file
+  file <- make_readable_file(file)
+  shared_ptr(
+    JsonTableReader,
+    json___TableReader__Make(file, read_options, parse_options)
+  )
 }
 
 #' @rdname csv_table_reader

r/R/parquet.R

@@ -105,16 +105,7 @@ ParquetFileReader$create <- function(file,
                                      props = ParquetReaderProperties$create(),
                                      mmap = TRUE,
                                      ...) {
-  if (is.character(file)) {
-    if (isTRUE(mmap)) {
-      file <- mmap_open(file)
-    } else {
-      file <- ReadableFile$create(file)
-    }
-  } else if (is.raw(file)) {
-    file <- BufferReader$create(file)
-  }
-  assert_that(inherits(file, "RandomAccessFile"))
+  file <- make_readable_file(file, mmap)
   assert_that(inherits(props, "ParquetReaderProperties"))
 
   unique_ptr(ParquetFileReader, parquet___arrow___FileReader__OpenFile(file, props))

r/R/read_table.R

@@ -69,7 +69,7 @@ read_table.character <- function(stream) {
 }
 
 #' @export
-`read_table.raw` <- function(stream) {
+read_table.raw <- function(stream) {
   stream <- BufferReader$create(stream)
   on.exit(stream$close())
   batch_reader <- RecordBatchStreamReader$create(stream)
@@ -78,6 +78,6 @@ read_table.character <- function(stream) {
 
 #' @rdname read_table
 #' @export
-read_arrow <- function(stream){
+read_arrow <- function(stream) {
   as.data.frame(read_table(stream))
 }