Method: CSV#shift

Defined in:

lib/csv.rb

#shift ⇒ Object Also known as: gets, readline

The primary read method for wrapped Strings and IOs, a single row is pulled from the data source, parsed and returned as an Array of fields (if header rows are not used) or a CSV::Row (when header rows are used).

The data source must be open for reading.

# File 'lib/csv.rb', line 1782

def shift
  #########################################################################
  ### This method is purposefully kept a bit long as simple conditional ###
  ### checks are faster than numerous (expensive) method calls.         ###
  #########################################################################

  # handle headers not based on document content
  if header_row? and @return_headers and
     [Array, String].include? @use_headers.class
    if @unconverted_fields
      return add_unconverted_fields(parse_headers, Array.new)
    else
      return parse_headers
    end
  end

  #
  # it can take multiple calls to <tt>@io.gets()</tt> to get a full line,
  # because of \r and/or \n characters embedded in quoted fields
  #
  in_extended_col = false
  csv             = Array.new

  loop do
    # add another read to the line
    unless parse = @io.gets(@row_sep)
      return nil
    end

    parse.sub!(@parsers[:line_end], "")

    if csv.empty?
      #
      # I believe a blank line should be an <tt>Array.new</tt>, not Ruby 1.8
      # CSV's <tt>[nil]</tt>
      #
      if parse.empty?
        @lineno += 1
        if @skip_blanks
          next
        elsif @unconverted_fields
          return add_unconverted_fields(Array.new, Array.new)
        elsif @use_headers
          return self.class::Row.new(Array.new, Array.new)
        else
          return Array.new
        end
      end
    end

    next if @skip_lines and @skip_lines.match parse

    parts =  parse.split(@col_sep, -1)
    if parts.empty?
      if in_extended_col
        csv[-1] << @col_sep   # will be replaced with a @row_sep after the parts.each loop
      else
        csv << nil
      end
    end

    # This loop is the hot path of csv parsing. Some things may be non-dry
    # for a reason. Make sure to benchmark when refactoring.
    parts.each do |part|
      if in_extended_col
        # If we are continuing a previous column
        if part[-1] == @quote_char && part.count(@quote_char) % 2 != 0
          # extended column ends
          csv.last << part[0..-2]
          if csv.last =~ @parsers[:stray_quote]
            raise MalformedCSVError,
                  "Missing or stray quote in line #{lineno + 1}"
          end
          csv.last.gsub!(@quote_char * 2, @quote_char)
          in_extended_col = false
        else
          csv.last << part
          csv.last << @col_sep
        end
      elsif part[0] == @quote_char
        # If we are starting a new quoted column
        if part[-1] != @quote_char || part.count(@quote_char) % 2 != 0
          # start an extended column
          csv             << part[1..-1]
          csv.last        << @col_sep
          in_extended_col =  true
        else
          # regular quoted column
          csv << part[1..-2]
          if csv.last =~ @parsers[:stray_quote]
            raise MalformedCSVError,
                  "Missing or stray quote in line #{lineno + 1}"
          end
          csv.last.gsub!(@quote_char * 2, @quote_char)
        end
      elsif part =~ @parsers[:quote_or_nl]
        # Unquoted field with bad characters.
        if part =~ @parsers[:nl_or_lf]
          raise MalformedCSVError, "Unquoted fields do not allow " +
                                   "\\r or \\n (line #{lineno + 1})."
        else
          raise MalformedCSVError, "Illegal quoting in line #{lineno + 1}."
        end
      else
        # Regular ole unquoted field.
        csv << (part.empty? ? nil : part)
      end
    end

    # Replace tacked on @col_sep with @row_sep if we are still in an extended
    # column.
    csv[-1][-1] = @row_sep if in_extended_col

    if in_extended_col
      # if we're at eof?(), a quoted field wasn't closed...
      if @io.eof?
        raise MalformedCSVError,
              "Unclosed quoted field on line #{lineno + 1}."
      elsif @field_size_limit and csv.last.size >= @field_size_limit
        raise MalformedCSVError, "Field size exceeded on line #{lineno + 1}."
      end
      # otherwise, we need to loop and pull some more data to complete the row
    else
      @lineno += 1

      # save fields unconverted fields, if needed...
      unconverted = csv.dup if @unconverted_fields

      # convert fields, if needed...
      csv = convert_fields(csv) unless @use_headers or @converters.empty?
      # parse out header rows and handle CSV::Row conversions...
      csv = parse_headers(csv)  if     @use_headers

      # inject unconverted fields and accessor, if requested...
      if @unconverted_fields and not csv.respond_to? :unconverted_fields
        add_unconverted_fields(csv, unconverted)
      end

      # return the results
      break csv
    end
  end
end