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# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
#' Write Arrow IPC stream format
#'
#' Apache Arrow defines two formats for [serializing data for interprocess
#' communication
#' (IPC)](https://arrow.apache.org/docs/format/Columnar.html#serialization-and-interprocess-communication-ipc):
#' a "stream" format and a "file" format, known as Feather. `write_ipc_stream()`
#' and [write_feather()] write those formats, respectively.
#'
#' `write_arrow()`, a wrapper around `write_ipc_stream()` and `write_feather()`
#' with some nonstandard behavior, is deprecated. You should explicitly choose
#' the function that will write the desired IPC format (stream or file) since
#' either can be written to a file or `OutputStream`.
#'
#' @inheritParams write_feather
#' @param ... extra parameters passed to `write_feather()`.
#'
#' @return `x`, invisibly.
#' @seealso [write_feather()] for writing IPC files. [write_to_raw()] to
#' serialize data to a buffer.
#' [RecordBatchWriter] for a lower-level interface.
#' @export
#' @examplesIf arrow_available()
#' tf <- tempfile()
#' on.exit(unlink(tf))
#' write_ipc_stream(mtcars, tf)
write_ipc_stream <- function(x, sink, ...) {
x_out <- x # So we can return the data we got
if (is.data.frame(x)) {
x <- Table$create(x)
}
assert_that(is_writable_table(x))
if (!inherits(sink, "OutputStream")) {
sink <- make_output_stream(sink)
on.exit(sink$close())
}
writer <- RecordBatchStreamWriter$create(sink, x$schema)
writer$write(x)
writer$close()
invisible(x_out)
}
#' Write Arrow data to a raw vector
#'
#' [write_ipc_stream()] and [write_feather()] write data to a sink and return
#' the data (`data.frame`, `RecordBatch`, or `Table`) they were given.
#' This function wraps those so that you can serialize data to a buffer and
#' access that buffer as a `raw` vector in R.
#' @inheritParams write_feather
#' @param format one of `c("stream", "file")`, indicating the IPC format to use
#' @return A `raw` vector containing the bytes of the IPC serialized data.
#' @examplesIf arrow_available()
#' # The default format is "stream"
#' mtcars_raw <- write_to_raw(mtcars)
#' @export
write_to_raw <- function(x, format = c("stream", "file")) {
sink <- BufferOutputStream$create()
if (match.arg(format) == "stream") {
write_ipc_stream(x, sink)
} else {
write_feather(x, sink)
}
as.raw(buffer(sink))
}
#' Read Arrow IPC stream format
#'
#' Apache Arrow defines two formats for [serializing data for interprocess
#' communication
#' (IPC)](https://arrow.apache.org/docs/format/Columnar.html#serialization-and-interprocess-communication-ipc):
#' a "stream" format and a "file" format, known as Feather. `read_ipc_stream()`
#' and [read_feather()] read those formats, respectively.
#'
#' `read_arrow()`, a wrapper around `read_ipc_stream()` and `read_feather()`,
#' is deprecated. You should explicitly choose
#' the function that will read the desired IPC format (stream or file) since
#' a file or `InputStream` may contain either.
#'
#' @param file A character file name or URI, `raw` vector, an Arrow input stream,
#' or a `FileSystem` with path (`SubTreeFileSystem`).
#' If a file name or URI, an Arrow [InputStream] will be opened and
#' closed when finished. If an input stream is provided, it will be left
#' open.
#' @param as_data_frame Should the function return a `data.frame` (default) or
#' an Arrow [Table]?
#' @param ... extra parameters passed to `read_feather()`.
#'
#' @return A `data.frame` if `as_data_frame` is `TRUE` (the default), or an
#' Arrow [Table] otherwise
#' @seealso [read_feather()] for writing IPC files. [RecordBatchReader] for a
#' lower-level interface.
#' @export
read_ipc_stream <- function(file, as_data_frame = TRUE, ...) {
if (!inherits(file, "InputStream")) {
file <- make_readable_file(file)
on.exit(file$close())
}
# TODO: this could take col_select, like the other readers
# https://issues.apache.org/jira/browse/ARROW-6830
out <- RecordBatchStreamReader$create(file)$read_table()
if (as_data_frame) {
out <- as.data.frame(out)
}
out
}
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