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How to convert base64 encoded string to UUID format

How do I convert a Base64 encoded string to a dash encoded hexadecimal string (mostly uuid)?

For example, if I have

'FWLalpF2T5mmyxS03Q+hNQ0K'

then how can i convert it to:

1562da96-9176-4f99-a6cb-14b4dd0fa135
+3


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2 answers


I was familiar with unpack

, but it prompted me to look into the directive as indicated by flint.

simplest form:

b64 = 'FWLalpF2T5mmyxS03Q+hNQ0K'
b64.unpack("m0").first.unpack("H8H4H4H4H12").join('-')

#=> "1562da96-9176-4f99-a6cb-14b4dd0fa135"

b64.unpack("m0")

give us:

#=> ["\x15b\xDA\x96\x91vO\x99\xA6\xCB\x14\xB4\xDD\x0F\xA15\r\n"]

which is an array, so we use .first

to grab the string and unpack it again using a directive to format it in 8-4-4-4-12 format:



b64.unpack("m0").first.unpack("H8H4H4H4H12")

gives us:

#=> ["1562da96", "9176", "4f99", "a6cb", "14b4dd0fa135"]

an array of strings, so now we just attach it to -

:

b64.unpack("m0").first.unpack("H8H4H4H4H12").join('-')

#=> "1562da96-9176-4f99-a6cb-14b4dd0fa135"
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OOPS

The accepted answer has a flaw:

b64 = 'FWLalpF2T5mmyxS03Q+hNQ0K'
b64.unpack("m0").first.unpack("H8H4H4H4H12").join('-')
# => "1562da96-9176-4f99-a6cb-14b4dd0fa135"

Changing the last char in string b64 results in the same UUID:

b64 = 'FWLalpF2T5mmyxS03Q+hNQ0L'
b64.unpack("m0").first.unpack("H8H4H4H4H12").join('-')
# => "1562da96-9176-4f99-a6cb-14b4dd0fa135"


To prevent this, you might want to write your input (base64 or whatever) to the correct length, eg. with MD5:

require "digest"
b64 = 'FWLalpF2T5mmyxS03Q+hNQ0K'
Digest::MD5.hexdigest(b64).unpack("a8a4a4a4a12").join('-')
# => "df71c785-6552-a977-e0ac-8edb8fd63f6f"

The full input is now relevant, changing the last char results in a different UUID:

require "digest"
b64 = 'FWLalpF2T5mmyxS03Q+hNQ0L'
Digest::MD5.hexdigest(s).unpack("a8a4a4a4a12").join('-')
# => "2625f170-d05a-f65d-38ff-5d9a7a972382"
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