class CSV::Parser::Scanner

CSV::Scanner 接收 CSV 输出，扫描它并返回内容。它还通过其方法 keep_start、keep_end、keep_back、keep_drop 控制对象的生命周期。

使用 StringScanner（官方 strscan gem）。Strscan 提供对 String 的词法扫描操作。我们继承它的对象并利用其方法。更多信息，请访问：ruby-doc.org/stdlib-2.6.1/libdoc/strscan/rdoc/StringScanner.html

公共类方法

new(*args) 点击以切换源代码

调用父类方法

# File csv-3.3.2/lib/csv/parser.rb, line 42
def initialize(*args)
  super
  @keeps = []
end

公共实例方法

each_line(row_separator) { |line| ... } 点击以切换源代码

# File csv-3.3.2/lib/csv/parser.rb, line 47
def each_line(row_separator)
  position = pos
  rest.each_line(row_separator) do |line|
    position += line.bytesize
    self.pos = position
    yield(line)
  end
end

keep_back() 点击以切换源代码

# File csv-3.3.2/lib/csv/parser.rb, line 65
def keep_back
  self.pos = @keeps.pop
end

keep_drop() 点击以切换源代码

# File csv-3.3.2/lib/csv/parser.rb, line 69
def keep_drop
  @keeps.pop
end

keep_end() 点击以切换源代码

# File csv-3.3.2/lib/csv/parser.rb, line 60
def keep_end
  start = @keeps.pop
  string.byteslice(start, pos - start)
end

keep_start() 点击以切换源代码

# File csv-3.3.2/lib/csv/parser.rb, line 56
def keep_start
  @keeps.push(pos)
end