What is the Ruby way to convert a value to an ASCII string?

Question

What is the cleanest Ruby way to convert a number to an ASCII string?

for example, a = 0x68656c6c6f should become a = "hello".

In normal C without libraries, I would use a 0xFF mask which I kept shifting. Somehow I've the feeling Ruby has shorter/less explicit ways to do this.

I'm using Ruby 1.8.7.

While I dont like the fact that I need to convert it to a string first ("68656c6c6f"), Array#pack("H*") seems the way to go — Len
– Len, Commented Jan 23, 2012 at 15:53
I dont like the fact that I need to convert it to a string first, then use .to_s(16) — the Tin Man
– the Tin Man, Commented Jan 23, 2012 at 16:11
Then I still convert it to a string :). What I meant is I hoped for a ruby-ish solution that could convert it to a ascii string without having to convert it to a hex string first. — Len
– Len, Commented Jan 24, 2012 at 7:46
Converting it to a string and then unpacking it IS a Ruby-like way to do it. You could also do it the C/assembler way and shift and mask bytes. — the Tin Man
– the Tin Man, Commented Jan 24, 2012 at 7:50

Victor Moroz · Accepted Answer · 2012-01-23 16:30:22Z

6

["%x" % 0x68656c6c6f].pack("H*")

Update: Another crazy idea, which is probably overkill in your case, but this one works right with leading zeros. In fact it's just shift, but can be used with various function like map, inject, each etc.

class S
  include Enumerable

  def initialize(i)
    @i = i
  end

  def each(&block)
    while @i > 0
      @i, b = @i.divmod(256)
      block[b.chr]
    end
  end
end

S.new(0x0168656c6c6f).inject{ |a, c| c + a }

edited Jan 23, 2012 at 16:30

answered Jan 23, 2012 at 14:55

Victor Moroz

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2 Comments

Len Over a year ago

I just noticed something: this only works when there are no leading zeroes!! ["%x" % 0x0168656c6c6f].pack("H*") wouldnt give an expected result ("\001hello")

Len Over a year ago

I wish I could upvote again, great job! The whole construction is indeed a bit overkill in my case and I think it doesn't increase readability in my case. For now, I'll stick with the old-fashioned shift

Tom De Leu · Accepted Answer · 2012-01-23 14:54:19Z

5

["68656c6c6f"].pack("H*") #=> "hello"

Have a look at the docs for Array, specifically the pack and unpack methods.

answered Jan 23, 2012 at 14:54

Tom De Leu

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3 Comments

Victor Moroz Over a year ago

You are almost there, but a was supposed to be a number, not string

Tom De Leu Over a year ago

You're right, I was just pointing him in the right direction though, the pack and unpack methods that are made for this. Your answer with the %x is clever, upvoting it.

Len Over a year ago

I commented on the answer with %x, it doesn't work as I would expect

Adiel Mittmann · Accepted Answer · 2012-01-23 14:47:36Z

3

I think that there's nothing wrong with writing C-like code for the problem that you described. You are dealing with low-level processing, so it's acceptable to use low-level syntax:

n = 0x68656c6c6f
s = ''
while n > 0
  p = n & 0xff
  n = n >> 8
  s = p.chr + s
end
puts s

There must be ways to make the code feel more like Ruby, but, for this problem, I think it's a good alternative. If you had the sequence of characters in an array instead, it would be easier:

puts [0x68, 0x65, 0x6c, 0x6c, 0x6f].map{|n| n.chr}.reduce(:+)

answered Jan 23, 2012 at 14:47

Adiel Mittmann

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3 Comments

Len Over a year ago

Thanks for your answer. For me, the whole bit shifting is more clear than using map+chr+reduce on one line, since I know Ruby is very powerful and has a compact way to do anything, I was wondering how 'Ruby-guys' look at this problem :-). For now, I'll stick with the shifting.

Victor Moroz Over a year ago

Meanwhile n, p = n.divmod(256) will save you one line

Aliaksei Kliuchnikau Over a year ago

To convert array of bytes to string you can also do this: [0x68, 0x65, 0x6c, 0x6c, 0x6f].pack 'c*'

siame · Accepted Answer · 2012-01-23 14:54:39Z

1

a = "0x68656c6c6f"
a = a[2..-1] # get rid of the 0x
a.scan(/../).each { |s| puts s.hex.chr }
H
e
l
l
o

answered Jan 23, 2012 at 14:54

siame

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Comments

Rahul Patel · Accepted Answer · 2017-05-30 13:52:54Z

0

Try this

"0x68656c6c6f"[2..-1].gsub(/../) { |val| val.hex.chr } => "hello"

answered May 30, 2017 at 13:52

Rahul Patel

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