ArtemGr / alternative, using regex

Created May 21, 2009


    
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      alternative, using regex
    
    
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                val pattern = java.util.regex.Pattern.compile ("""(?xs) ("(.*?)"|) ; ("(.*?)"|) (?: \r?\n | \z ) """)
    val matcher = pattern.matcher (input)
    while (matcher.find) {
      val col1 = matcher.group (2)
      val col2 = matcher.group (4)
      // ...
    }

          
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      csvParser.scala
    
    
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            import scala.util.parsing.combinator._
import scala.util.parsing.combinator.syntactical._
object csvParser extends RegexParsers {
  test // Perform unit-testing on first load.
 
  // Turns off whitespace removal: line separators are an important part of the CSV format... 
  override def skipWhitespace = false
 
  def CRLF = "\r\n" | "\n"
  def EOF = "\\z".r
 
  // Any number of columns, but no backtracking over accidental double-quotes.
  def stringInQuotes = """(?xs) ".*?" |""".r ^^ {case qstr => if (qstr.length != 0) qstr.substring (1, qstr.length - 1) else ""}
  def line = stringInQuotes ~ ';' ~ stringInQuotes ~ (CRLF | EOF) ^^ {case col1 ~ _ ~ col2 ~ _ => col1 :: col2 :: Nil}
 
  // Fixed number of columns, but backtracking over accidental double-quotes works.
  def unquote (str: String) = str.substring (1, str.length - (str.charAt (str.length - 1) match {case ';'|'\r'|'\n' => 2; case _ => 1}))
  def col1 = ("(?s)\".*?\";".r ^^ unquote _) | (";" ^^ (_ => ""))
  def col2 = ("(?s)\".*?\"(\\r|\\n)?".r ^^ unquote _) | (("\r" | "\n" | EOF) ^^ (_ => ""))
  def twoColumns = col1 ~ col2 ~ opt ("\n") ^^ {case v1 ~ v2 ~ _ => v1 :: v2 :: Nil}
 
  def csv: Parser[List[List[String]]] = rep1 (twoColumns)
 
  def unwrap[T] (result: ParseResult[T]) = result match {
    case Success (data, _) => data
    case f@Failure (message, _) => throw new Exception (f.toString)
    case e@Error (message, _) => throw new Exception (e.toString)
  }
 
  def test = {
    def check[T] (s: String, expect: AnyRef): AnyRef = {
      val result = unwrap (parse (csv, s))
      assert (result.toString == expect.toString, "expected: \n" + expect + "\n; got: \n" + result)
    }
    check (";", List (List ("", ""))) // One string with both columns absent.
    check ("\"qq\nqq\";", List (List ("qq\nqq", "")))
    check (";\" name1 \n name2 \"", List (List ("", " name1 \n name2 ")))
    check ("\"qq\";\"zz\nzz\"", List (List ("qq", "zz\nzz")))
    check ("\"qq\";\"zz\"\n", List (List ("qq", "zz")))
    check (";\n;\n;", List (List ("", ""), List ("", ""), List ("", "")))
    check ("\"qq\";\"zz\"\n\"qq\";\"zz\"\n\"qq\";\"zz\"", List (List ("qq", "zz"), List ("qq", "zz"), List ("qq", "zz")))
  }
}