Generates a v5 non-random UUID (Universally Unique IDentifier).
Using Digest::MD5 generates version 3 UUIDs; Digest::SHA1 generates version
5 UUIDs. uuid_from_hash always
generates the same UUID for a given name and namespace combination.
See RFC 4122 for details of UUID at: www.ietf.org/rfc/rfc4122.txt
# File activesupport/lib/active_support/core_ext/digest/uuid.rb, line 19
def self.uuid_from_hash(hash_class, uuid_namespace, name)
if hash_class == Digest::MD5
version = 3
elsif hash_class == Digest::SHA1
version = 5
else
raise ArgumentError, "Expected Digest::SHA1 or Digest::MD5, got #{hash_class.name}."
end
hash = hash_class.new
hash.update(uuid_namespace)
hash.update(name)
ary = hash.digest.unpack("NnnnnN")
ary[2] = (ary[2] & 0x0FFF) | (version << 12)
ary[3] = (ary[3] & 0x3FFF) | 0x8000
"%08x-%04x-%04x-%04x-%04x%08x" % ary
end