r/R/read_record_batch.R

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#' read [arrow::RecordBatch][arrow__RecordBatch] as encapsulated IPC message, given a known [arrow::Schema][arrow__Schema]
#'
#' @param obj a [arrow::ipc::Message][arrow__ipc__Message], a [arrow::io::InputStream][arrow__io__InputStream], a [arrow::Buffer][arrow__Buffer], or a raw vector
#' @param schema a [arrow::Schema][arrow__Schema]
#'
#' @return a [arrow::RecordBatch][arrow__RecordBatch]
#'
#' @export
read_record_batch <- function(obj, schema){
  UseMethod("read_record_batch")
}

#' @export
`read_record_batch.arrow::ipc::Message` <- function(obj, schema) {
  assert_that(inherits(schema, "arrow::Schema"))
  shared_ptr(`arrow::RecordBatch`, ipc___ReadRecordBatch__Message__Schema(obj, schema))
}

#' @export
`read_record_batch.arrow::io::InputStream` <- function(obj, schema) {
  assert_that(inherits(schema, "arrow::Schema"))
  shared_ptr(`arrow::RecordBatch`, ipc___ReadRecordBatch__InputStream__Schema(obj, schema))
}

#' @export
read_record_batch.raw <- function(obj, schema){
  stream <- BufferReader(obj)
  on.exit(stream$close())
  read_record_batch(stream, schema)
}

#' @export
`read_record_batch.arrow::Buffer` <- function(obj, schema){
  stream <- BufferReader(obj)
  on.exit(stream$close())
  read_record_batch(stream, schema)
}