R/count_lines.R

In r-hyperspec/hySpc.read.Witec: File Import Functions for Spectra in Various ASCII or Text File Formats

# Function -------------------------------------------------------------------

#' Count Lines (of an ASCII File)
#'
#' @param file the file name or connection
#' @param chunksize `file` is read in chunks of `chunksize` lines.
#'
#'
#' @return Number of lines in file.
#'
#'
#' @export
#'
#' @concept io
#'
#' @author C. Beleites
count_lines <- function(file, chunksize = 1e4) {
  nlines <- 0

  con <- file(file, open = "r")
  on.exit(close(con))

  while ((n <- length(readLines(con, n = chunksize))) > 0L) {
    nlines <- nlines + n
  }

  nlines
}


# Unit tests -----------------------------------------------------------------

hySpc.testthat::test(count_lines) <- function() {
  context("count_lines")

  local_edition(3)

  tmpfile <- tempfile()
  on.exit(unlink(tmpfile))

  writeLines("blabla\nblubb", con = tmpfile)

  test_that("file read in one chunk", {
    expect_equal(count_lines(tmpfile), 2)
  })

  test_that("file read in more chunks", {
    expect_equal(count_lines(tmpfile, chunksize = 1L), 2)
  })
}