# class CSV::Parser::InputsScanner

CSV::InputsScanner receives `IO` inputs, encoding and the chunk_size. It also controls the life cycle of the object with its methods `keep_start`, `keep_end`, `keep_back`, `keep_drop`.

CSV::InputsScanner.scan() tries to match with pattern at the current position. If there’s a match, the scanner advances the “scan pointer” and returns the matched string. Otherwise, the scanner returns nil.

CSV::InputsScanner.rest() returns the “rest” of the string (i.e. everything after the scan pointer). If there is no more data (eos? = true), it returns “”.

### Public Class Methods

new(inputs, encoding, row_separator, chunk_size: 8192) click to toggle source

    # File lib/csv/parser.rb, line 87
    def initialize(inputs, encoding, row_separator, chunk_size: 8192)
      @inputs = inputs.dup
      @encoding = encoding
      @row_separator = row_separator
      @chunk_size = chunk_size
      @last_scanner = @inputs.empty?
      @keeps = []
      read_chunk
    end

### Public Instance Methods

check(pattern) click to toggle source

    # File lib/csv/parser.rb, line 248
    def check(pattern)
      @scanner.check(pattern)
    end

each_line(row_separator) { |buffer| ... } click to toggle source

    # File lib/csv/parser.rb, line 97
    def each_line(row_separator)
      return enum_for(__method__, row_separator) unless block_given?
      buffer = nil
      input = @scanner.rest
      position = @scanner.pos
      offset = 0
      n_row_separator_chars = row_separator.size
      # trace(__method__, :start, input)
      while true
        input.each_line(row_separator) do |line|
          @scanner.pos += line.bytesize
          if buffer
            if n_row_separator_chars == 2 and
              buffer.end_with?(row_separator[0]) and
              line.start_with?(row_separator[1])
              buffer << line[0]
              line = line[1..-1]
              position += buffer.bytesize + offset
              @scanner.pos = position
              offset = 0
              yield(buffer)
              buffer = nil
              next if line.empty?
            else
              buffer << line
              line = buffer
              buffer = nil
            end
          end
          if line.end_with?(row_separator)
            position += line.bytesize + offset
            @scanner.pos = position
            offset = 0
            yield(line)
          else
            buffer = line
          end
        end
        break unless read_chunk
        input = @scanner.rest
        position = @scanner.pos
        offset = -buffer.bytesize if buffer
      end
      yield(buffer) if buffer
    end

eos?() click to toggle source

    # File lib/csv/parser.rb, line 170
    def eos?
      @scanner.eos?
    end

keep_back() click to toggle source

    # File lib/csv/parser.rb, line 197
    def keep_back
      # trace(__method__, :start)
      scanner, start, buffer = @keeps.pop
      if buffer
        # trace(__method__, :rescan, start, buffer)
        string = @scanner.string
        if scanner == @scanner
          keep = string.byteslice(start,
                                  string.bytesize - @scanner.pos - start)
        else
          keep = string
        end
        if keep and not keep.empty?
          @inputs.unshift(StringIO.new(keep))
          @last_scanner = false
        end
        @scanner = StringScanner.new(buffer)
      else
        if @scanner != scanner
          message = "scanners are different but no buffer: "
          message += "#{@scanner.inspect}(#{@scanner.object_id}): "
          message += "#{scanner.inspect}(#{scanner.object_id})"
          raise UnexpectedError, message
        end
        # trace(__method__, :repos, start, buffer)
        @scanner.pos = start
      end
      read_chunk if @scanner.eos?
    end

keep_drop() click to toggle source

    # File lib/csv/parser.rb, line 227
    def keep_drop
      _, _, buffer = @keeps.pop
      # trace(__method__, :done, :empty) unless buffer
      return unless buffer

      last_keep = @keeps.last
      # trace(__method__, :done, :no_last_keep) unless last_keep
      return unless last_keep

      if last_keep[2]
        last_keep[2] << buffer
      else
        last_keep[2] = buffer
      end
      # trace(__method__, :done)
    end

keep_end() click to toggle source

    # File lib/csv/parser.rb, line 181
    def keep_end
      # trace(__method__, :start)
      scanner, start, buffer = @keeps.pop
      if scanner == @scanner
        keep = @scanner.string.byteslice(start, @scanner.pos - start)
      else
        keep = @scanner.string.byteslice(0, @scanner.pos)
      end
      if buffer
        buffer << keep
        keep = buffer
      end
      # trace(__method__, :done, keep)
      keep
    end

keep_start() click to toggle source

    # File lib/csv/parser.rb, line 174
    def keep_start
      # trace(__method__, :start)
      adjust_last_keep
      @keeps.push([@scanner, @scanner.pos, nil])
      # trace(__method__, :done)
    end

rest() click to toggle source

    # File lib/csv/parser.rb, line 244
    def rest
      @scanner.rest
    end

scan(pattern) click to toggle source

    # File lib/csv/parser.rb, line 143
    def scan(pattern)
      # trace(__method__, pattern, :start)
      value = @scanner.scan(pattern)
      # trace(__method__, pattern, :done, :last, value) if @last_scanner
      return value if @last_scanner

      read_chunk if value and @scanner.eos?
      # trace(__method__, pattern, :done, value)
      value
    end

scan_all(pattern) click to toggle source

    # File lib/csv/parser.rb, line 154
    def scan_all(pattern)
      # trace(__method__, pattern, :start)
      value = @scanner.scan(pattern)
      # trace(__method__, pattern, :done, :last, value) if @last_scanner
      return value if @last_scanner

      # trace(__method__, pattern, :done, :nil) if value.nil?
      return nil if value.nil?
      while @scanner.eos? and read_chunk and (sub_value = @scanner.scan(pattern))
        # trace(__method__, pattern, :sub, sub_value)
        value << sub_value
      end
      # trace(__method__, pattern, :done, value)
      value
    end

### Private Instance Methods

adjust_last_keep() click to toggle source

    # File lib/csv/parser.rb, line 257
    def adjust_last_keep
      # trace(__method__, :start)

      keep = @keeps.last
      # trace(__method__, :done, :empty) if keep.nil?
      return if keep.nil?

      scanner, start, buffer = keep
      string = @scanner.string
      if @scanner != scanner
        start = 0
      end
      if start == 0 and @scanner.eos?
        keep_data = string
      else
        keep_data = string.byteslice(start, @scanner.pos - start)
      end
      if keep_data
        if buffer
          buffer << keep_data
        else
          keep[2] = keep_data.dup
        end
      end

      # trace(__method__, :done)
    end

read_chunk() click to toggle source

    # File lib/csv/parser.rb, line 285
    def read_chunk
      return false if @last_scanner

      adjust_last_keep

      input = @inputs.first
      case input
      when StringIO
        string = input.read
        raise InvalidEncoding unless string.valid_encoding?
        # trace(__method__, :stringio, string)
        @scanner = StringScanner.new(string)
        @inputs.shift
        @last_scanner = @inputs.empty?
        true
      else
        chunk = input.gets(@row_separator, @chunk_size)
        if chunk
          raise InvalidEncoding unless chunk.valid_encoding?
          # trace(__method__, :chunk, chunk)
          @scanner = StringScanner.new(chunk)
          if input.respond_to?(:eof?) and input.eof?
            @inputs.shift
            @last_scanner = @inputs.empty?
          end
          true
        else
          # trace(__method__, :no_chunk)
          @scanner = StringScanner.new("".encode(@encoding))
          @inputs.shift
          @last_scanner = @inputs.empty?
          if @last_scanner
            false
          else
            read_chunk
          end
        end
      end
    end

trace(*args) click to toggle source

    # File lib/csv/parser.rb, line 253
    def trace(*args)
      pp([*args, @scanner, @scanner&.string, @scanner&.pos, @keeps])
    end