Question

I have a string representation of a MD5 hex digest for a file, that I want to convert to base64 in order to use the Content-MD5 HTTP header when uploading it. Is there a clearer or more efficient mechanism to do than the following?

def hex_to_base64_digest(hexdigest)
  [[hexdigest].pack("H*")].pack("m").strip
end

hex_digest = "65a8e27d8879283831b664bd8b7f0ad4"
expected_base64_digest = "ZajifYh5KDgxtmS9i38K1A=="

raise "Does not match" unless hex_to_base64_digest(hex_digest) === expected_base64_digest

Answer 1

Seems pretty clear and efficient to me. You can save the call to strip by specifying 0 count for the ‘m’ pack format (if count is 0, no line feed are added, see RFC 4648)

def hex_to_base64_digest(hexdigest)
  [[hexdigest].pack("H*")].pack("m0")
end