--- StringIO.new([string[, mode]])
--- StringIO.open([string[, mode]])
--- StringIO.open([string[, mode]]) {|io| ... }

    StringIO ֥Ȥޤ

        require 'stringio'

        io = StringIO.new("foo")
        p io.getc       # => 102
        p io.pos        # => 1
        p io.size       # => 3
        io << "bar"
        p io.size       # => 4
        io.rewind
        p io.gets       # => "fbar"

