cleaner compact-size

lib/bip158.hoon

@@ -172,7 +172,7 @@
 ++  parse-filter
   |=  filter=hexb
   ^-  [n=@ux gcs-set=bits]
-  =+  n=n:(compact-size filter)
+  =+  n=n:(de:csiz filter)
   =/  lead=@  ?:(=(1 wid.n) 1 +(wid.n))
   :-  dat.n
   [(mul 8 (sub wid.filter lead)) `@ub`dat:(drop:byt lead filter)]

lib/btc.hoon

@@ -79,24 +79,37 @@
   :-  20
   %-  ripemd-160
   (sha256 val)
-::  +compact-size: parse compactSize int from head of hex and return result and remainder
-::   - input "h" is little endian, output "n" is big endian
+::  +csiz: handle compact-size integers
+::   - encode: big endian to little endian
+::   - decode: little endian to big endian
 ::
-++  compact-size
-  |=  h=hexb
-  ^-  [n=hexb rest=hexb]
-  =/  s=@ux  dat:(take:byt 1 h)
-  ?:  (lth s 0xfd)  [1^s (drop:byt 1 h)]
-  ~|  "Invalid compact-size at start of {<h>}"
-  =/  len=bloq
+++  csiz
+  |%
+  ++  en
+    |=  a=@
+    ^-  hexb
+    =/  l=@  (met 3 a)
+    ?:  =(l 1)  1^a
+    ?:  =(l 2)  (cat:byt ~[1^0xfd (flip:byt 2^a)])
+    ?:  (lte l 4)  (cat:byt ~[1^0xfe (flip:byt 4^a)])
+    ?:  (lte l 8)  (cat:byt ~[1^0xff (flip:byt 8^a)])
+    ~|("Cannot encode CompactSize longer than 8 bytes" !!)
+  ++  de
+    |=  h=hexb
+    ^-  [n=hexb rest=hexb]
+    =/  s=@ux  dat:(take:byt 1 h)
+    ?:  (lth s 0xfd)  [1^s (drop:byt 1 h)]
+    ~|  "Invalid compact-size at start of {<h>}"
+    =/  len=bloq
     ?+  s  !!
-        %0xfd  1
-        %0xfe  2
-        %0xff  3
+      %0xfd  1
+      %0xfe  2
+      %0xff  3
     ==
   :_  (drop:byt (add 1 len) h)
   %-  flip:byt
   (take:byt (bex len) (drop:byt 1 h))
+  --
 ::
 ++  pubkey-to-address
   |=  [=bipt =network pubkey=hexb]
@@ -161,7 +174,7 @@
         1^0x87
     ==
   ==
-::  +txu: tx utility functions
+::  +txu: transaction utility core3
 ::
 ++  txu
   |%
@@ -259,6 +272,7 @@
   ::
   ++  encode
     |=  =data:tx
+    ::  TODO: below is wrong because it doesn't use compact-size
     ^-  hexb
     %-  cat:byt
     %-  zing

tests/lib/btc.hoon

@@ -4,6 +4,7 @@
 |%
 +$  chyg  ?(%0 %1)
 +$  bits-vector  [bitwidth=@ atoms=(list @) =bits]
++$  compact-size-vector  @ux
 +$  tx-vector  [hex-cord=@t txid=hexb]
 +$  psbt-vector
   $:  =hdkey
@@ -27,6 +28,16 @@
       ==
   ==
 ::
+++  compact-size-vectors
+  ^-  (list compact-size-vector)
+  :~  0x98
+      0x302
+      0xaa.bbcc
+      0xaabb.ccdd
+      0xaa.bbcc.ddee
+      0xaabb.ccdd.eeff.1122 
+  ==
+::
 ++  tx-vectors
   ^-  (list tx-vector)
   :~  :*  '0200000002ab0949a08c5af7c49b8212f417e2f15ab3f5c33dcf153821a8139f877a5b7be40000000000feffffffab0949a08c5af7c49b8212f417e2f15ab3f5c33dcf153821a8139f877a5b7be40100000000feffffff02603bea0b000000001976a914768a40bbd740cbe81d988e71de2a4d5c71396b1d88ac8e240000000000001976a9146f4620b553fa095e721b9ee0efe9fa039cca459788ac00000000'
@@ -156,6 +167,8 @@
   |^  ;:  weld
           %+  category  "bit manipulation"
           (zing (turn bits-vectors check-bits))
+          %+  category  "compact-size en/decoding"
+          (zing (turn compact-size-vectors check-compact-size))
           %+  category  "check PSBT"
           (zing (turn psbt-vectors check-psbt))
           %+  category  "xpub parsing"
@@ -179,6 +192,12 @@
         !>((to-atoms:bit bitwidth.v bits.v))
     ==
   ::
+  ++  check-compact-size
+    |=  v=compact-size-vector
+    %+  expect-eq
+      !>(v)
+      !>(dat:n:(de:csiz (en:csiz v)))
+  ::
   ++  check-psbt
     |=  v=psbt-vector
     =/  key=hexb