Method: Digest::UUID.uuid_from_hash

Defined in:
activesupport/lib/active_support/core_ext/digest/uuid.rb

.uuid_from_hash(hash_class, namespace, name) ⇒ Object

Generates a v5 non-random UUID (Universally Unique IDentifier).

Using OpenSSL::Digest::MD5 generates version 3 UUIDs; OpenSSL::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



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# File 'activesupport/lib/active_support/core_ext/digest/uuid.rb', line 19

def self.uuid_from_hash(hash_class, namespace, name)
  if hash_class == Digest::MD5 || hash_class == OpenSSL::Digest::MD5
    version = 3
  elsif hash_class == Digest::SHA1 || hash_class == OpenSSL::Digest::SHA1
    version = 5
  else
    raise ArgumentError, "Expected OpenSSL::Digest::SHA1 or OpenSSL::Digest::MD5, got #{hash_class.name}."
  end

  uuid_namespace = pack_uuid_namespace(namespace)

  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