added hamdist to the LibTomMath backend

caml_z_tommath.c

@@ -1825,9 +1825,42 @@ CAMLprim value ml_z_popcount(value arg)
   }
 }
 
-CAMLprim value ml_z_hamdist(UNUSED_PARAM value arg1, UNUSED_PARAM value arg2)
+CAMLprim value ml_z_hamdist(value arg1, value arg2)
 {
-  caml_failwith("Z.hamdist: not implemented in LibTomMath backend");
+  if (Z_ISNEG(arg1) != Z_ISNEG(arg2))
+    ml_z_raise_overflow();
+  /* XXX TODO: case where arg1 & arg2 are both negative */
+  if (Z_ISNEG(arg1) || Z_ISNEG(arg2))
+    caml_invalid_argument("Z.hamdist: negative arguments");
+  if (Is_long(arg1) && Is_long(arg2)) {
+    return Val_long(ml_z_count(Long_val(arg1) ^ Long_val(arg2)));
+  }
+  else {
+    Z_DECL(arg1);
+    Z_DECL(arg2);
+    intnat r = 0;
+    mp_digit *a1, *a2;
+    size_t len1, len2;
+    Z_ARG(arg1);
+    Z_ARG(arg2);
+    /* a1 is the shortest one */
+    if (mp_arg1->used <= mp_arg2->used) {
+      a1 = mp_arg1->dp; len1 = mp_arg1->used;
+      a2 = mp_arg2->dp; len2 = mp_arg2->used;
+    }
+    else  {
+      a1 = mp_arg2->dp; len1 = mp_arg2->used;
+      a2 = mp_arg1->dp; len2 = mp_arg1->used;
+    }
+    for (size_t i = 0; i < len1; i++)
+      r += ml_z_count(a1[i] ^ a2[i]);
+    for (size_t i = len1; i < len2; i++)
+      r += ml_z_count(a2[i]);
+    Z_END_ARG(arg1);
+    Z_END_ARG(arg2);
+    if (r < 0 || !Z_FITS_INT(r)) ml_z_raise_overflow();
+    return Val_long(r);
+  }
 }
 
 CAMLprim value ml_z_testbit(value arg, value index)

tests/zq.output-LibTomMath-64-60

@@ -889,7 +889,31 @@ popcount 2^120
  = 1
 popcount (2^120-1)
  = 120
-Failure: Z.hamdist: not implemented in LibTomMath backend
+hamdist 0 0
+ = 0
+hamdist 0 1
+ = 1
+hamdist 0 2^300
+ = 1
+hamdist 2^120 2^120
+ = 0
+hamdist 2^120 (2^120-1)
+ = 121
+hamdist 2^120 2^300
+ = 2
+hamdist (2^120-1) (2^300-1)
+ = 180
+divisible 42 7
+ = true
+divisible 43 7
+ = false
+divisible 0 0
+ = true
+divisible 0 2^120
+ = true
+divisible 2 2^120
+ = false
+Failure: Z.divisible: not implemented in LibTomMath backend
 hash(2^120)
  = 900619431
 hash(2^121)