From e7f552aeabc693deb5f4db04d2de65e619f3e8b7 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Tue, 30 Mar 2021 09:29:08 -0700
Subject: [PATCH] u3: adds jet and tests for +fein:ob

---
 pkg/urbit/include/jets/q.h  |  2 +
 pkg/urbit/include/jets/w.h  |  2 +
 pkg/urbit/jets/e/fein_ob.c  | 82 +++++++++++++++++++++++++++++++++++++
 pkg/urbit/tests/jet_tests.c | 58 ++++++++++++++++++++++++++
 4 files changed, 144 insertions(+)
 create mode 100644 pkg/urbit/jets/e/fein_ob.c

diff --git a/pkg/urbit/include/jets/q.h b/pkg/urbit/include/jets/q.h
index b952ce700..4cc56f206 100644
--- a/pkg/urbit/include/jets/q.h
+++ b/pkg/urbit/include/jets/q.h
@@ -150,6 +150,8 @@
     u3_noun u3qe_shal(u3_atom, u3_atom);
     u3_noun u3qe_sha1(u3_atom, u3_atom);
 
+    u3_atom u3qe_fein_ob(u3_atom pyn);
+
     u3_noun u3qe_hmac(u3_noun, u3_atom, u3_atom,
                       u3_atom, u3_atom, u3_atom, u3_atom);
 
diff --git a/pkg/urbit/include/jets/w.h b/pkg/urbit/include/jets/w.h
index 8065457fd..d279f3051 100644
--- a/pkg/urbit/include/jets/w.h
+++ b/pkg/urbit/include/jets/w.h
@@ -175,6 +175,8 @@
     u3_noun u3we_shal(u3_noun);
     u3_noun u3we_sha1(u3_noun);
 
+    u3_noun u3we_fein_ob(u3_noun);
+
     u3_noun u3weo_raw(u3_noun);
 
     u3_noun u3wee_puck(u3_noun);
diff --git a/pkg/urbit/jets/e/fein_ob.c b/pkg/urbit/jets/e/fein_ob.c
new file mode 100644
index 000000000..fd9333126
--- /dev/null
+++ b/pkg/urbit/jets/e/fein_ob.c
@@ -0,0 +1,82 @@
+/* j/3/fein.c
+**
+*/
+#include "all.h"
+#include <murmur3.h>
+
+//  +feis:ob constant parameters to +fe:ob
+//
+static const c3_w a_w =     0xffff;
+static const c3_w b_w =    0x10000;
+static const c3_w k_w = 0xffff0000;
+
+//  +raku:ob
+//
+static const c3_w rak_w[4] = { 0xb76d5eed, 0xee281300, 0x85bcae01, 0x4b387af7 };
+
+static c3_w
+_feis_fe(c3_w m_w)
+{
+  c3_w l_w = m_w % a_w;
+  c3_w r_w = m_w / a_w;
+  c3_w f_w, tmp_w;
+  c3_d tmp_d;
+  c3_y k_y[2];
+  c3_y j_y;
+
+  for ( j_y = 0; j_y < 4; j_y++ ) {
+    k_y[0] = r_w & 0xff;
+    k_y[1] = (r_w >> 8) & 0xff;
+
+    MurmurHash3_x86_32(k_y, 2, rak_w[j_y], &f_w);
+
+    tmp_d = (c3_d)f_w + l_w;
+    tmp_w = tmp_d % (!(j_y & 1) ? a_w: b_w);
+    l_w   = r_w;
+    r_w   = tmp_w;
+  }
+
+  return ( a_w == r_w ) ? (r_w * a_w) + l_w : (l_w * a_w) + r_w;
+}
+
+static c3_w
+_feis(c3_w m_w)
+{
+  c3_w c_w = _feis_fe(m_w);
+  return ( c_w < k_w ) ? c_w : _feis_fe(c_w);
+}
+
+u3_atom
+u3qe_fein_ob(u3_atom pyn)
+{
+  c3_w sor_w = u3r_met(4, pyn);
+
+  if ( (sor_w < 2) || (sor_w > 4) ) {
+    return u3k(pyn);
+  }
+
+  if ( 2 == sor_w ) {
+    c3_w pyn_w = u3r_word(0, pyn);
+    c3_w out_w = b_w + _feis(pyn_w - b_w);
+
+    return u3i_word(out_w);
+  }
+  else {
+    c3_w pyn_w[2];
+    u3r_words(0, 2, pyn_w, pyn);
+
+    if ( pyn_w[0] < b_w ) {
+      return u3k(pyn);
+    }
+    else {
+      pyn_w[0] = b_w + _feis(pyn_w[0] - b_w);
+      return u3i_words(2, pyn_w);
+    }
+  }
+}
+
+u3_noun
+u3we_fein_ob(u3_noun cor)
+{
+  return u3qe_fein_ob(u3x_atom(u3x_at(u3x_sam, cor)));
+}
diff --git a/pkg/urbit/tests/jet_tests.c b/pkg/urbit/tests/jet_tests.c
index d88d9f942..1627c2a04 100644
--- a/pkg/urbit/tests/jet_tests.c
+++ b/pkg/urbit/tests/jet_tests.c
@@ -245,6 +245,59 @@ _test_base16(void)
   return ret_i;
 }
 
+static c3_w
+_fein_ob_w(c3_w inp_w)
+{
+  u3_atom inp = u3i_word(inp_w);
+  u3_atom act = u3qe_fein_ob(inp);
+  c3_w  act_w = u3r_word(0, act);
+  u3z(inp); u3z(act);
+  return act_w;
+}
+
+static c3_i
+_expect_fein_ob_w(c3_w inp_w, c3_w exp_w)
+{
+  c3_w act_w = _fein_ob_w(inp_w);
+
+  if ( act_w != exp_w ) {
+    fprintf(stderr, "fein: inp=0x%08x exp=0x%08x act=0x%08x\n",
+                    inp_w, exp_w, act_w);
+    return 0;
+  }
+
+  return 1;
+}
+
+static c3_i
+_test_fein_ob(void)
+{
+  c3_i ret_i = 1;
+
+  ret_i &= _expect_fein_ob_w(0, 0);
+  ret_i &= _expect_fein_ob_w(0xffff, 0xffff);
+  ret_i &= _expect_fein_ob_w(0x1b08f, 0x76b920e5);
+  ret_i &= _expect_fein_ob_w(0x10000, 0x423e60bf);
+  ret_i &= _expect_fein_ob_w(0x10001, 0xd4400acb);
+  ret_i &= _expect_fein_ob_w(0x10002, 0xf429043);
+  ret_i &= _expect_fein_ob_w(0x10000000, 0xa04bc7fa);
+  ret_i &= _expect_fein_ob_w(0x1234abcd, 0x686f6c25);
+  ret_i &= _expect_fein_ob_w(0xabcd1234, 0x4a220c8);
+  ret_i &= _expect_fein_ob_w(0xdeadbeef, 0x909bc4a9);
+  ret_i &= _expect_fein_ob_w(0xfffff, 0x6746b96b);
+  ret_i &= _expect_fein_ob_w(0xffffffff, 0xbba4dcce);
+
+  return ret_i;
+}
+
+static c3_i
+_test_ob(void)
+{
+  c3_i ret_i = 1;
+  ret_i &= _test_fein_ob();
+  return ret_i;
+}
+
 static c3_i
 _test_jets(void)
 {
@@ -255,6 +308,11 @@ _test_jets(void)
     ret_i = 0;
   }
 
+  if ( !_test_ob() ) {
+    fprintf(stderr, "test jets: ob: failed\r\n");
+    ret_i = 0;
+  }
+
   return ret_i;
 }