How do I unescape c-style escape sequences from ruby?

Okay, if you don't like eval solution, I've hacked a simple state machine in Ruby to parse simple "\n" and "\t" in strings correctly, including pre-escaping of backslash itself. Here it is:

BACKSLASH = "\\"

def unescape_c_string(s)
    state = 0
    res = ''
    s.each_char { |c|
        case state
        when 0
            case c
            when BACKSLASH then state = 1
            else res << c
            end
        when 1
            case c
            when 'n' then res << "\n"; state = 0
            when 't' then res << "\t"; state = 0
            when BACKSLASH then res << BACKSLASH; state = 0
            else res << BACKSLASH; res << c; state = 0
            end
        end
    }
    return res
end

This one can be easily extended to support more characters, including multi-character entities, like \123. Test unit to prove that it works:

require 'test/unit'

class TestEscapeCString < Test::Unit::TestCase
    def test_1
        assert_equal("abc\nasd", unescape_c_string('abc\nasd'))
    end
    def test_2
        assert_equal("abc\tasd", unescape_c_string('abc\tasd'))
    end
    def test_3
        assert_equal("abc\\asd", unescape_c_string('abc' + BACKSLASH * 2 + 'asd'))
    end
    def test_4
        assert_equal("abc\\nasd", unescape_c_string('abc' + BACKSLASH * 2 + 'nasd'))
    end
    def test_5
        assert_equal("abc\\\nasd", unescape_c_string('abc' + BACKSLASH * 3 + 'nasd'))
    end
    def test_6
        assert_equal("abc\\\\nasd", unescape_c_string('abc' + BACKSLASH * 4 + 'nasd'))
    end
end

Shorter, even more hacky and fairly dangerous, due to eval:

eval "\"#{string}\""

> a = '1\t2\n3'
> puts a
1\t2\n3
> puts eval "\"#{a}\""
1       2
3