hoon: adds new +mug (as +gum)

pkg/arvo/sys/hoon.hoon

@@ -1081,6 +1081,23 @@
     =+  ham=(mix (rsh 0 31 haz) (end 0 31 haz))
     ?.(=(0 ham) ham $(syd +(syd)))
   --
+++  gum
+  ~/  %gum
+  |=  a=*
+  |^  ?@  a  (mum 0xcafe.babe 0x7fff a)
+      =/  b  (cat 5 $(a -.a) $(a +.a))
+      (mum 0xdead.beef 0xfffe b)
+  ::
+  ++  mum
+    |=  [syd=@uxF fal=@F key=@]
+    =/  wyd  (met 3 key)
+    =|  i=@ud
+    |-  ^-  @F
+    ?:  =(8 i)  fal
+    =/  haz=@F  (muk syd wyd key)
+    =/  ham=@F  (mix (rsh 0 31 haz) (end 0 31 haz))
+    ?.(=(0 ham) ham $(i +(i), syd +(syd)))
+  --
 ::                                                      ::
 ::::  2f: noun ordering                                 ::
   ::                                                    ::

pkg/arvo/tests/sys/hoon/hashes.hoon

@@ -53,6 +53,50 @@
       !>  0x2ad3.9968
       !>  (mug [(dec (bex 128)) 1])
   ==
+::
+++  test-gum
+  ;:  weld
+    %+  expect-eq
+      !>  0x4d44.1035
+      !>  (gum 'Hello, world!')
+    ::
+    %+  expect-eq
+      !>  0x79ff.04e8
+      !>  (gum 0)
+    ::
+    %+  expect-eq
+      !>  0x715c.2a60
+      !>  (gum 1)
+    ::
+    %+  expect-eq
+      !>  0x64df.da5c
+      !>  (gum (crip (reap 28 'x')))
+    ::
+    %+  expect-eq
+      !>  0x192f.5588
+      !>  (gum [0 0])
+    ::
+    %+  expect-eq
+      !>  0x6b32.ec46
+      !>  (gum [1 1])
+    ::
+    %+  expect-eq
+      !>  0x2ef.fe10
+      !>  (gum [2 2])
+    ::
+    %+  expect-eq
+      !>  0x3a81.1aec
+      !>  (gum [1 2 3])
+    ::
+    %+  expect-eq
+      !>  0x7ce.fb7f
+      !>  (gum [0 (bex 32)])
+    ::
+    %+  expect-eq
+      !>  0x2aa0.6bfc
+      !>  (gum [(dec (bex 128)) 1])
+  ==
+::
 ::  SHA tests
 ::  For references see FIPS180-4 and related test vectors
 ::  https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf