[R] Utility to convert a file into an encrypted string using `base64enc` package and vice versa

FileStringR.R

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# FileStringR
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# author  : talegari (Srikanth KS)
# license : GNU AGPLv3 (http://choosealicense.com/licenses/agpl-3.0/)
# about   : a utility to convert a file into an encrypted string using
#           `base64enc` package and vice versa
# depends : R (>= 3)with packages: `tools`, `base64enc`, `assertthat`
#           `sodium`

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# file_string
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# convert a file to a string
# string is written to a file with name of the inputFile appened by .txt
# encrypt the string using a key(a string)

file_string = function(inputFile
                       , key    = NULL
                       , silent = FALSE){
  
  assertthat::assert_that(file.exists(inputFile))
  assertthat::assert_that(assertthat::is.readable(inputFile))
  outputFile <- paste0(inputFile, ".", "txt")
  assertthat::assert_that(!file.exists(outputFile))
  assertthat::assert_that(is.null(key) || assertthat::is.string(key))
  assertthat::assert_that(assertthat::is.flag(silent))
  
  
  if(!is.null(key)){
    key     <- sodium::hash(charToRaw(key), size = 32)
    
    # get sodium output
    so <- sodium::data_encrypt(
      msg     = charToRaw(base64enc::base64encode(what = inputFile))
      , key   = key
      , nonce = base64enc::base64decode("TMfldNKuD1N191QTIooIZ49xrwnRzdqa")
      ) 
    
    aString <- base64enc::base64encode(so)

  } else{
    aString <- base64enc::base64encode(what = inputFile)
  }
  
  ofc        <- file(outputFile, "w")
  on.exit(close(ofc))
  writeLines(text = aString  , con = ofc)
  
  if(silent == FALSE){
    message(paste0("    DONE! encoded output written to: ", outputFile))
  }
  
  return(invisible(TRUE))
  
}


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# string_file
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# convert a string to a file
# string is read from the inputFile and output file is created by removing
# ".txt" extension from the inputFile's name

string_file  = function(inputFile
                        , key    = NULL
                        , silent = FALSE
                        , remove = FALSE){
  
  assertthat::assert_that(file.exists(inputFile))
  assertthat::assert_that(assertthat::is.readable(inputFile))
  outputFile <- tools::file_path_sans_ext(inputFile)
  assertthat::assert_that(!file.exists(outputFile))
  
  if(is.null(key)){
    
    # write the base64 decoded msg to file
    ofc <- file(outputFile, "wb")
    base64enc::base64decode(file = inputFile, output = ofc)
    
  } else{
    
      msg_bin <- base64enc::base64decode(file = inputFile)
      if(length(msg_bin) == 0){
        stop("Invalid input file.")
      }
      key   <- sodium::hash(charToRaw(key), size = 32)
      nonce <- base64enc::base64decode("TMfldNKuD1N191QTIooIZ49xrwnRzdqa")
      
      # check whether the msg and key correspond
      msg_ser <- try(sodium::data_decrypt(bin     = msg_bin
                                          , key   = key
                                          , nonce = nonce)
                     , silent = TRUE)
      
      if(class(msg_ser) == "try-error"){
        stop("The file is corrupted OR the key is wrong.")
      }
      
      ofc <- file(outputFile, "wb")
      base64enc::base64decode(what = rawToChar(msg_ser)
                              , output = ofc
                              )
        }
  close(ofc)
  
  if(silent == FALSE){
    message(paste0("    DONE! decoded output written to: ", outputFile))
  }
  if(remove == TRUE){
    unlink(inputFile)
  }
  
  return(invisible(TRUE))
}