ripn jet (#1210)

include/jets/w.h

@@ -66,6 +66,7 @@
     u3_noun u3wc_rep(u3_noun);
     u3_noun u3wc_rev(u3_noun);
     u3_noun u3wc_rip(u3_noun);
+    u3_noun u3wc_ripn(u3_noun);
     u3_noun u3wc_rsh(u3_noun);
     u3_noun u3wc_swp(u3_noun);
     u3_noun u3wc_sqt(u3_noun);

jets/c/rip.c

@@ -1,48 +1,47 @@
-/* j/3/rip.c
-**
-*/
 #include "all.h"
 
-
-/* functions
-*/
-  u3_noun
-  u3qc_rip(u3_atom a,
-           u3_atom b)
-  {
-    if ( !_(u3a_is_cat(a)) || (a >= 32) ) {
+u3_noun u3qc_rip(u3_atom bloq, u3_atom b) {
+  if ( !_(u3a_is_cat(bloq)) || (bloq >= 32) ) {
     return u3m_bail(c3__fail);
   }
-    else {
-      u3_noun pir = u3_nul;
-      c3_g a_g = a;
-      c3_w i_w;
 
-      if ( a_g < 5 ) {
-        c3_w met_w = u3r_met(a_g, b);
-        c3_w mek_w = ((1 << (1 << a_g)) - 1);
+  c3_g bloq_g = bloq;
 
-        for ( i_w = 0; i_w < met_w; i_w++ ) {
-          c3_w pat_w = (met_w - (i_w + 1));
-          c3_w bit_w = (pat_w << a_g);
-          c3_w wor_w = (bit_w >> 5);
-          c3_w sif_w = (bit_w & 31);
-          c3_w src_w = u3r_word(wor_w, b);
-          c3_w rip_w = ((src_w >> sif_w) & mek_w);
+  /*
+    This is a fast-path for the case where all the resulting blocks will
+    fit in 31-bit direct atoms.
+  */
+  if ( bloq_g < 5 ) {                                   //  produce direct atoms
+    u3_noun acc     = u3_nul;
 
-          pir = u3nc(rip_w, pir);
+    c3_w met_w   = u3r_met(bloq_g, b);                  //  num blocks in atom
+    c3_w nbits_w = 1 << bloq_g;                         //  block size in bits
+    c3_w bmask_w = (1 << nbits_w) - 1;                  //  result mask
+
+    for ( c3_w i_w = 0; i_w < met_w; i_w++ ) {          //  `i_w` is block index
+      c3_w nex_w = i_w + 1;                             //  next block
+      c3_w pat_w = met_w - nex_w;                       //  blks left after this
+      c3_w bit_w = pat_w << bloq_g;                     //  bits left after this
+      c3_w wor_w = bit_w >> 5;                          //  wrds left after this
+      c3_w sif_w = bit_w & 31;                          //  bits left in word
+      c3_w src_w = u3r_word(wor_w, b);                  //  find word by index
+      c3_w rip_w = (src_w >> sif_w) & bmask_w;          //  get item from word
+
+      acc = u3nc(rip_w, acc);
     }
-        return pir;
+
+    return acc;
   }
-      else {
-        c3_w met_w = u3r_met(a_g, b);
+
+  u3_noun acc   = u3_nul;
+  c3_w    met_w = u3r_met(bloq_g, b);
   c3_w    len_w = u3r_met(5, b);
-        c3_g san_g = (a_g - 5);
+  c3_g    san_g = (bloq_g - 5);
   c3_w    san_w = 1 << san_g;
   c3_w    dif_w = (met_w << san_g) - len_w;
   c3_w    tub_w = ((dif_w == 0) ? san_w : (san_w - dif_w));
 
-        for ( i_w = 0; i_w < met_w; i_w++ ) {
+  for ( c3_w i_w = 0; i_w < met_w; i_w++ ) {
     c3_w  pat_w = (met_w - (i_w + 1));
     c3_w  wut_w = (pat_w << san_g);
     c3_w  sap_w = ((0 == i_w) ? tub_w : san_w);
@@ -50,7 +49,8 @@
 
     if ( 0 == sal_w ) {
       return u3m_bail(c3__fail);
-          } else {
+    }
+
     c3_w    j_w;
     u3_atom rip;
 
@@ -59,34 +59,28 @@
     }
 
     rip = u3a_malt(sal_w);
-            pir = u3nc(rip, pir);
-          }
+    acc = u3nc(rip, acc);
     len_w -= san_w;
   }
-      }
-      return pir;
-    }
-  }
-  u3_noun
-  u3wc_rip(u3_noun cor)
-  {
+
+  return acc;
+}
+
+u3_noun u3wc_rip(u3_noun cor) {
   u3_noun a, b;
 
   if ( (c3n == u3r_mean(cor, u3x_sam_2, &a, u3x_sam_3, &b, 0)) ||
        (c3n == u3ud(a)) ||
-         (c3n == u3ud(b)) )
-    {
+       (c3n == u3ud(b))
+     ) {
     return u3m_bail(c3__exit);
-    } else {
-      return u3qc_rip(a, b);
   }
-  }
-  u3_noun
-  u3kc_rip(u3_atom a,
-           u3_atom b)
-  {
-    u3_noun res = u3qc_rip(a, b);
 
+  return u3qc_rip(a, b);
+}
+
+u3_noun u3kc_rip(u3_atom a, u3_atom b) {
+  u3_noun res = u3qc_rip(a, b);
   u3z(a); u3z(b);
   return res;
-  }
+}

jets/c/ripn.c

@@ -0,0 +1,98 @@
+#include "all.h"
+
+/*
+  Get the lowest `n` bits of a word `w` using a bitmask.
+*/
+#define TAKEBITS(n,w) \
+  ((n)==32) ? (w) :   \
+  ((n)==0)  ? 0   :   \
+  ((w) & ((1 << (n)) - 1))
+
+/*
+  Divide, rounding up.
+*/
+#define DIVCEIL(x,y)  1 + ((x - 1) / y);
+
+/*
+  `ripn` breaks `atom` into a list of blocks, of bit-width `bits`. The
+  resulting list will be least-significant block first.
+
+  XX TODO This only handles cases where the bit-width is <= 32.
+
+  For each block we produce, we need to grab the relevant words inside
+  `atom`, so we first compute their indicies.
+
+  `ins_idx` is the word-index of the least-significant word we
+  care about, and `sig_idx` is the word after that.
+
+  Next we grab those words (`ins_word` and `sig_word`) from the atom
+  using `u3r_word`. Note that `sig_idx` might be out-of-bounds for the
+  underlying array of `atom`, but `u3r_word` returns 0 in that case,
+  which is exatly what we want.
+
+  Now, we need to grab the relevant bits out of both words, and combine
+  them. `bits_rem_in_ins_word` is the number of remaining (insignificant)
+  bits in `ins_word`, `nbits_ins` is the number of bits we want from the
+  less-significant word, and `nbits_sig` from the more-significant one.
+
+  Take the least significant `nbits_sig` bits from `sig_word`, and take
+  the slice we care about from `ins_word`. In order to take that slice,
+  we drop `bits_rem_in_ins_word` insignificant bits, and then take the
+  `nbits_sig` most-significant bits.
+
+  Last, we slice out those bits from the two words, combine them into
+  one word, and cons them onto the front of the result.
+*/
+u3_noun u3qc_ripn(u3_atom bits, u3_atom atom) {
+  if ( !_(u3a_is_cat(bits) || bits==0 || bits>31) ) {
+    return u3m_bail(c3__fail);
+  }
+
+  c3_w bit_width  = u3r_met(0, atom);
+  c3_w num_blocks = DIVCEIL(bit_width, bits);
+
+  u3_noun res = u3_nul;
+
+  for ( c3_w blk = 0; blk < num_blocks; blk++ ) {
+    c3_w next_blk = blk + 1;
+    c3_w blks_rem = num_blocks - next_blk;
+    c3_w bits_rem = blks_rem * bits;
+    c3_w ins_idx  = bits_rem / 32;
+    c3_w sig_idx  = ins_idx + 1;
+
+    c3_w bits_rem_in_ins_word = bits_rem % 32;
+
+    c3_w ins_word  = u3r_word(ins_idx, atom);
+    c3_w sig_word  = u3r_word(sig_idx, atom);
+    c3_w nbits_ins = c3_min(bits, 32 - bits_rem_in_ins_word);
+    c3_w nbits_sig = bits - nbits_ins;
+
+    c3_w ins_word_bits = TAKEBITS(nbits_ins, ins_word >> bits_rem_in_ins_word);
+    c3_w sig_word_bits = TAKEBITS(nbits_sig, sig_word);
+
+    c3_w item = ins_word_bits | (sig_word_bits << nbits_ins);
+
+    res = u3nc(item, res);
+  }
+
+  return res;
+}
+
+u3_noun u3wc_ripn(u3_noun cor) {
+  u3_noun bits, atom;
+
+  if ( (c3n == u3r_mean(cor, u3x_sam_2, &bits, u3x_sam_3, &atom, 0)) ||
+       (c3n == u3ud(bits)) ||
+       (c3n == u3ud(atom)) )
+  {
+    return u3m_bail(c3__exit);
+  }
+
+  return u3qc_ripn(bits, atom);
+}
+
+u3_noun u3kc_ripn(u3_atom bits, u3_atom atom) {
+  u3_noun res = u3qc_ripn(bits, atom);
+  u3z(bits), u3z(atom);
+  return res;
+}

jets/tree.c

@@ -1,5 +1,18 @@
-/* j/tree.c
+/*
+  To generate the hashes, take the sha256 of the jammed battery. For example:
+
+  ```
+  > `@ux`(shax (jam -:ripn))
+  0x2759.a693.1e9e.f9a5.2c8e.ee43.1088.43d9.4d39.32a6.b04f.86cb.6ba1.5553.4329.3a28
+  ```
+
+  Becomes:
+
+  ```
+  2759a6931e9ef9a52c8eee43108843d94d3932a6b04f86cb6ba1555343293a28
+  ```
 */
+
 #include "all.h"
 
 static u3j_harm _141_hex_aes_ecba_en_a[] = {{".2", u3wea_ecba_en}, {}};
@@ -1473,6 +1486,11 @@ static c3_c* _141_two_rip_ha[] = {
   "e8e0b834aded0d2738bcf38a93bf373d412a51e0cee7f274277a6393e634a65e",
   0
 };
+static u3j_harm _141_two_ripn_a[] = {{".2", u3wc_ripn, c3y}, {}};
+static c3_c* _141_two_ripn_ha[] = {
+  "2759a6931e9ef9a52c8eee43108843d94d3932a6b04f86cb6ba1555343293a28",
+  0
+};
 static u3j_harm _141_two_rsh_a[] = {{".2", u3wc_rsh, c3y}, {}};
 static c3_c* _141_two_rsh_ha[] = {
   "a401145b4c11ec8d17a729fe30f06c295865ffed1b970b0a788f0fec1ed0a703",
@@ -1710,6 +1728,7 @@ static u3j_core _141_two_d[] =
   { "rep", 7, _141_two_rep_a, 0, _141_two_rep_ha },
   { "rev", 7, _141_two_rev_a, 0, _141_two_rev_ha },
   { "rip", 7, _141_two_rip_a, 0, _141_two_rip_ha },
+  { "ripn", 7, _141_two_ripn_a, 0, _141_two_ripn_ha },
   { "rsh", 7, _141_two_rsh_a, 0, _141_two_rsh_ha },
   { "swp", 7, _141_two_swp_a, 0, _141_two_swp_ha },
   { "rub", 7, _141_two_rub_a, 0, _141_two_rub_ha },

meson.build

@@ -73,6 +73,7 @@ jets_c_src = [
 'jets/c/rep.c',
 'jets/c/rev.c',
 'jets/c/rip.c',
+'jets/c/ripn.c',
 'jets/c/rsh.c',
 'jets/c/swp.c',
 'jets/c/sqt.c'