R/util.R

In dfsp-spirit/pcx: Read and Write 'PCX' Bitmap Image Files

#' @title Download test PCX files for the package.
#'
#' @return invisible list of files, usually ignored. This function is called for the side effect of downloading the data.
#'
#' @keywords internal
download_test_data <- function() {
  pkg_info = pkgfilecache::get_pkg_info("pcx");

  md5_info = read_md5sum_file(system.file('extdata', 'md5sum_libav_pcx', package = 'pcx', mustWork = TRUE));
  base_url= 'https://samples.libav.org/image-samples/pcx/';
  urls = paste(base_url, md5_info$filename, sep='');

  cfiles = pkgfilecache::ensure_files_available(pkg_info, md5_info$filename, urls, md5sums=md5_info$md5sum);
  cfiles$file_status = NULL; # not exposed to end user
  return(invisible(cfiles));
}


#' @title Download test PCX files for the package.
#'
#' @return invisible list of files, usually ignored. This function is called for the side effect of downloading the data.
#'
#' @keywords internal
download_test_data_cga <- function() {
  pkg_info = pkgfilecache::get_pkg_info("pcx");

  md5_info = read_md5sum_file(system.file('extdata', 'md5sum_libav_pcx_cga', package = 'pcx', mustWork = TRUE));
  base_url= 'https://samples.libav.org/image-samples/pcx/cga/';
  urls = paste(base_url, md5_info$filename, sep='');

  cfiles = pkgfilecache::ensure_files_available(pkg_info, md5_info$filename, urls, md5sums=md5_info$md5sum);
  cfiles$file_status = NULL; # not exposed to end user
  return(invisible(cfiles));
}


#' @title Access a single file from the package cache by its file name.
#'
#' @param filename, string. The filename of the file in the package cache.
#'
#' @param mustWork, logical. Whether an error should be created if the file does not exist. If mustWork=FALSE and the file does not exist, the empty string is returned.
#'
#' @return string. The full path to the file in the package cache or the empty string if there is no such file available. Use this in your application code to open the file.
#'
#' @keywords internal
#' @importFrom pkgfilecache get_pkg_info get_filepath
get_opt_data_filepath <- function(filename, mustWork=TRUE) {
  pkg_info = pkgfilecache::get_pkg_info("pcx");
  return(pkgfilecache::get_filepath(pkg_info, filename, mustWork=mustWork));
}


#' @title Read md5sum file written by md5sum program.
#'
#' @param filepath character string, the path the the md5sum file
#'
#' @return data.frame with 3 columns: md5sum, is_binary, and filename.
#'
#' @note File names entries must not include whitespace.
#' @importFrom utils read.table
#' @keywords internal
read_md5sum_file <- function(filepath) {
  df = read.table(filepath, sep="", stringsAsFactors = FALSE, col.names = c('md5sum', 'filename'));
  rows_with_asterisk = startsWith(df$filename, '*'); # there may be a '*' to mark the input mode as binary in front of the file name.
  df$is_binary = rows_with_asterisk;
  df$filename[rows_with_asterisk] = substring(df$filename[rows_with_asterisk], 2, nchar(df$filename[rows_with_asterisk]));
  return(df);
}