1 files changed, 53 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/digest/uuid.rb b/activesupport/lib/active_support/core_ext/digest/uuid.rb
new file mode 100644
index 0000000000..6e949a2d72
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/digest/uuid.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require "securerandom"
+
+module Digest
+  module UUID
+    DNS_NAMESPACE  = "k\xA7\xB8\x10\x9D\xAD\x11\xD1\x80\xB4\x00\xC0O\xD40\xC8" #:nodoc:
+    URL_NAMESPACE  = "k\xA7\xB8\x11\x9D\xAD\x11\xD1\x80\xB4\x00\xC0O\xD40\xC8" #:nodoc:
+    OID_NAMESPACE  = "k\xA7\xB8\x12\x9D\xAD\x11\xD1\x80\xB4\x00\xC0O\xD40\xC8" #:nodoc:
+    X500_NAMESPACE = "k\xA7\xB8\x14\x9D\xAD\x11\xD1\x80\xB4\x00\xC0O\xD40\xC8" #:nodoc:
+
+    # 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: https://www.ietf.org/rfc/rfc4122.txt
+    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
+
+    # Convenience method for uuid_from_hash using Digest::MD5.
+    def self.uuid_v3(uuid_namespace, name)
+      uuid_from_hash(Digest::MD5, uuid_namespace, name)
+    end
+
+    # Convenience method for uuid_from_hash using Digest::SHA1.
+    def self.uuid_v5(uuid_namespace, name)
+      uuid_from_hash(Digest::SHA1, uuid_namespace, name)
+    end
+
+    # Convenience method for SecureRandom.uuid.
+    def self.uuid_v4
+      SecureRandom.uuid
+    end
+  end
+end