Simultaneous exponentiation support.

diff --git a/mpmont-mexp.c b/mpmont-mexp.c
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+++ b/mpmont-mexp.c
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+/* -*-c-*-
+ *
+ * $Id: mpmont-mexp.c,v 1.1 1999/11/19 13:19:29 mdw Exp $
+ *
+ * Multiplle simultaneous exponentiations
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * Catacomb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with Catacomb; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: mpmont-mexp.c,v $
+ * Revision 1.1  1999/11/19 13:19:29  mdw
+ * Simultaneous exponentiation support.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "mp.h"
+#include "mpmont.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @mpmont_mexpr@ --- *
+ *
+ * Arguments:  @mpmont *mm@ = pointer to Montgomery reduction context
+ *             @mpmont_factor *f@ = pointer to array of factors
+ *             @size_t n@ = number of factors supplied
+ *
+ * Returns:    If the bases are %$g_0, g_1, \ldots, g_{n-1}$% and the
+ *             exponents are %$e_0, e_1, \ldots, e_{n-1}$% then the result
+ *             is:
+ *
+ *             %$g_0^{e_0} g_1^{e_1} \ldots g_{n-1}^{e_{n-1}} R \bmod m$%
+ */
+
+typedef struct scan {
+  size_t len;
+  mpw w;
+} scan;
+
+mp *mpmont_mexpr(mpmont *mm, mpmont_factor *f, size_t n)
+{
+  size_t vn = 1 << n;
+  mp **v = xmalloc(vn * sizeof(mp *));
+  scan *s;
+  size_t o;
+  unsigned b;
+  mp *a = MP_COPY(mm->r);
+  mp *spare = MP_NEW;
+
+  /* --- Perform the precomputation --- */
+
+  {
+    size_t i, j;
+    size_t mask;
+
+    /* --- Fill in the rest of the array --- *
+     *
+     * Zero never gets used.
+     */
+
+    j = 0;
+    mask = 0;
+    for (i = 1; i < vn; i++) {
+
+      /* --- Check for a new bit entering --- *
+       *
+       * If a bit gets set that wasn't set before, then all the lower bits
+       * are zeroes and I've got to introduce a new base into the array.
+       */
+
+      if ((i & mask) == 0) {
+       v[i] = mpmont_mul(mm, MP_NEW, f[j++].base, mm->r2);
+       mask = i;
+      }
+
+      /* --- Otherwise I can get away with a single multiplication --- *
+       *
+       * In particular, if %$i$% has more than one bit set, then I only need
+       * to calculate %$v_i = v_{\mathit{mask}} v_{i - \mathit{mask}}$%.
+       * Since both are less than %$i$%, they must have already been
+       * computed.
+       */
+
+      else
+       v[i] = mpmont_mul(mm, MP_NEW, v[mask], v[i & ~mask]);
+    }
+  }
+
+  /* --- Set up the bitscanners --- *
+   *
+   * I must scan the exponents from left to right, which is a shame.  It
+   * means that I can't use the standard @mpscan@ stuff, in particular.
+   */
+
+  {
+    size_t i;
+
+    s = xmalloc(n * sizeof(scan));
+    o = 0;
+    for (i = 0; i < n; i++) {
+      s[i].len = MP_LEN(f[i].exp);
+      if (s[i].len > o)
+       o = s[i].len;
+    }
+    b = 0;
+  }
+
+  /* --- Now do the actual calculation --- */
+
+  b = 0;
+  for (;;) {
+    size_t i;
+    size_t j;
+    mp *dd;
+
+    /* --- If no more bits, get some more --- */
+
+    if (!b) {
+      if (!o)
+       break;
+      o--;
+      b = MPW_BITS;
+    }
+
+    /* --- Work out the next index --- */
+
+    j = 0;
+    b--;
+    for (i = 0; i < n; i++) {
+      if (o < s[i].len)
+       j |= (((f[i].exp->v[o] >> b) & 1) << i);
+    }
+
+    /* --- Accumulate the result --- */
+
+    if (spare) {
+      dd = mpmont_mul(mm, spare, a, a);
+      spare = a;
+      a = dd;
+    }
+    
+    if (j) {
+      dd = mpmont_mul(mm, spare, a, v[j]);
+      spare = a;
+      a = dd;
+    }
+  }
+
+  /* --- Tidy up afterwards --- */
+
+  {
+    size_t i;
+    for (i = 1; i < vn; i++)
+      MP_DROP(v[i]);
+    if (spare)
+      MP_DROP(spare);
+    free(v);
+    free(s);
+  }
+
+  return (a);
+}
+
+/* --- @mpmont_mexp@ --- *
+ *
+ * Arguments:  @mpmont *mm@ = pointer to Montgomery reduction context
+ *             @mpmont_factor *f@ = pointer to array of factors
+ *             @size_t n@ = number of factors supplied
+ *
+ * Returns:    Product of bases raised to exponents, all mod @m@.
+ *
+ * Use:                Convenient interface over @mpmont_mexpr@.
+ */
+
+mp *mpmont_mexp(mpmont *mm, mpmont_factor *f, size_t n)
+{
+  mp *d = mpmont_mexpr(mm, f, n);
+  d = mpmont_reduce(mm, d, d);
+  return (d);
+}
+
+/*----- Test rig ----------------------------------------------------------*/
+
+#ifdef TEST_RIG
+
+#include <mLib/testrig.h>
+
+static int verify(size_t n, dstr *v)
+{
+  mp *m = *(mp **)v[0].buf;
+  mpmont_factor *f = xmalloc(n * sizeof(*f));
+  mp *r, *rr;
+  size_t i, j;
+  mpmont mm;
+  int ok = 1;
+
+  j = 1;
+  for (i = 0; i < n; i++) {
+    f[i].base = *(mp **)v[j++].buf;
+    f[i].exp = *(mp **)v[j++].buf;
+  }
+
+  rr = *(mp **)v[j].buf;
+  mpmont_create(&mm, m);
+  r = mpmont_mexp(&mm, f, n);
+  if (MP_CMP(r, !=, rr)) {
+    fputs("\n*** mexp failed\n", stderr);
+    fputs("m = ", stderr); mp_writefile(m, stderr, 10);
+    for (i = 0; i < n; i++) {
+      fprintf(stderr, "\ng_%u = ", i);
+      mp_writefile(f[i].base, stderr, 10);
+      fprintf(stderr, "\ne_%u = ", i);
+      mp_writefile(f[i].exp, stderr, 10);
+    }
+    fputs("\nr = ", stderr); mp_writefile(r, stderr, 10);
+    fputs("\nR = ", stderr); mp_writefile(rr, stderr, 10);
+    fputc('\n', stderr);
+    ok = 0;
+  }
+
+  for (i = 0; i < n; i++) {
+    MP_DROP(f[i].base);
+    MP_DROP(f[i].exp);
+  }
+  MP_DROP(m);
+  MP_DROP(r);
+  MP_DROP(rr);
+  mpmont_destroy(&mm);
+  return (ok);
+}
+
+static int t1(dstr *v) { return verify(1, v); }
+static int t2(dstr *v) { return verify(2, v); }
+static int t3(dstr *v) { return verify(3, v); }
+static int t4(dstr *v) { return verify(4, v); }
+static int t5(dstr *v) { return verify(5, v); }
+
+static test_chunk tests[] = {
+  { "mexp-1", t1, { &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, 0 } },
+  { "mexp-2", t2, { &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, 0 } },
+  { "mexp-3", t3, { &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, 0 } },
+  { "mexp-4", t4, { &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, 0 } },
+  { "mexp-5", t5, { &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, &type_mp,
+                   &type_mp, 0 } },
+  { 0, 0, { 0 } }
+};
+
+int main(int argc, char *argv[])
+{
+  sub_init();
+  test_run(argc, argv, tests, SRCDIR "/tests/mpmont");
+  return (0);
+}   
+
+#endif
+
+/*----- That's all, folks -------------------------------------------------*/