R/count_lines.R

In hyperSpec: Work with Hyperspectral Data, i.e. Spectra + Meta Information (Spatial, Time, Concentration, ...)

##' 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
##' @md
##' @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
}

.test (count_lines) <- function (){
  context ("count_lines")
  
  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)
  )
  
}