to-n-bits works

bippy-scratch.md

@@ -42,12 +42,20 @@ The below requires norsyr's fix to `decompress-point` in order to work.
 =bip173 -build-file %/lib/bip173/hoon
 ```
 
-### BTC pubkey -> address hashing
+### Bech32 Algo
+- hash = hash160(pubkey)
+- words = convert(hash, 8bitTo5bit)
+- encode('bc', [0x00 words])
+
+### BTC pubkey -> address hashing (Hash-160)
 Uses the example data here:
 https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addresses
 
 That one starts with pubkey below. The following runs it through sha256 and ripemd160 to yield the hash:
-`0xf54a.5851.e937.2b87.810a.8e60.cdd2.e7cf.d80b.6e31`
+```
+0xf54a.5851.e937.2b87.810a.8e60.cdd2.e7cf.d80b.6e31
+```
+
 Use `@uc` to make the Hash-160 into a BTC P2PKH address
 ```
 =pubkey 0x2.5086.3ad6.4a87.ae8a.2fe8.3c1a.f1a8.403c.b53f.53e4.86d8.511d.ad8a.0488.7e5b.2352

lib/bip173.hoon

@@ -4,6 +4,29 @@
 ::
 ++  charset  "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
 ::
+++  hash-160
+  |=  pubkey=@ux
+  ^-  @ux
+  =/  sha  (swp 3 (shax (swp 3 pubkey)))
+    %-  ripemd-160:ripemd:crypto
+    [(met 3 sha) sha]
+::  Converts an atom to a list of n-bit numbers, flop to preserve big-endian
+::
+++  to-n-bit
+  |=  [n=@ input=@]
+  ^-  (list @)
+  =/  bits  (flop (rip 0 input))
+  =|  ret=(list @)
+  |-  ?~  bits  ret
+  =/  n-bits  (scag n ((list @) bits))
+  ::  left-shift the "missing" number of bits
+  =/  num=@
+    %:  lsh  0
+        (sub n (lent n-bits))
+        (rep 0 (flop n-bits))
+    ==
+  $(ret (snoc ret num), bits (slag n ((list @) bits)))
+::
 ++  polymod
   |=  values=(list @)
   =/  gen=(list @ux)
@@ -72,13 +95,6 @@
   =/  checksum-pos  (sub (lent data-and-checksum) 6)
   `[hrp (scag checksum-pos data-and-checksum) (slag checksum-pos data-and-checksum)]
 ::
-++  hash-160
-  |=  pubkey=@ux
-  ^-  @ux
-  =/  sha  (swp 3 (shax (swp 3 pubkey)))
-    %-  ripemd-160:ripemd:crypto
-    [(met 3 sha) sha]
-::
 ++  decode-segwit
   |=  segwit=tape
   ^-  (unit [witver=@ witprog=@ux])