X-Git-Url: https://oss.titaniummirror.com/gitweb?a=blobdiff_plain;f=gmp%2Fmpz%2Fpowm_ui.c;fp=gmp%2Fmpz%2Fpowm_ui.c;h=9e44301d210811b7afbc47903704ebdc18ad7cf9;hb=6fed43773c9b0ce596dca5686f37ac3fc0fa11c0;hp=0000000000000000000000000000000000000000;hpb=27b11d56b743098deb193d510b337ba22dc52e5c;p=msp430-gcc.git

diff --git a/gmp/mpz/powm_ui.c b/gmp/mpz/powm_ui.c
new file mode 100644
index 00000000..9e44301d
--- /dev/null
+++ b/gmp/mpz/powm_ui.c
@@ -0,0 +1,195 @@
+/* mpz_powm_ui(res,base,exp,mod) -- Set RES to (base**exp) mod MOD.
+
+Copyright 1991, 1993, 1994, 1996, 1997, 2000, 2001, 2002, 2005 Free Software
+Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+The GNU MP Library 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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
+
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+/* Compute t = a mod m, a is defined by (ap,an), m is defined by (mp,mn), and
+   t is defined by (tp,mn).  */
+static void
+reduce (mp_ptr tp, mp_srcptr ap, mp_size_t an, mp_srcptr mp, mp_size_t mn)
+{
+  mp_ptr qp;
+  TMP_DECL;
+
+  TMP_MARK;
+  qp = TMP_ALLOC_LIMBS (an - mn + 1);
+
+  mpn_tdiv_qr (qp, tp, 0L, ap, an, mp, mn);
+
+  TMP_FREE;
+}
+
+void
+mpz_powm_ui (mpz_ptr r, mpz_srcptr b, unsigned long int el, mpz_srcptr m)
+{
+  mp_ptr xp, tp, qp, mp, bp;
+  mp_size_t xn, tn, mn, bn;
+  int m_zero_cnt;
+  int c;
+  mp_limb_t e;
+  TMP_DECL;
+
+  mp = PTR(m);
+  mn = ABSIZ(m);
+  if (mn == 0)
+    DIVIDE_BY_ZERO;
+
+  if (el == 0)
+    {
+      /* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0
+	 depending on if MOD equals 1.  */
+      SIZ(r) = (mn == 1 && mp[0] == 1) ? 0 : 1;
+      PTR(r)[0] = 1;
+      return;
+    }
+
+  TMP_MARK;
+
+  /* Normalize m (i.e. make its most significant bit set) as required by
+     division functions below.  */
+  count_leading_zeros (m_zero_cnt, mp[mn - 1]);
+  m_zero_cnt -= GMP_NAIL_BITS;
+  if (m_zero_cnt != 0)
+    {
+      mp_ptr new_mp = TMP_ALLOC_LIMBS (mn);
+      mpn_lshift (new_mp, mp, mn, m_zero_cnt);
+      mp = new_mp;
+    }
+
+  bn = ABSIZ(b);
+  bp = PTR(b);
+  if (bn > mn)
+    {
+      /* Reduce possibly huge base.  Use a function call to reduce, since we
+	 don't want the quotient allocation to live until function return.  */
+      mp_ptr new_bp = TMP_ALLOC_LIMBS (mn);
+      reduce (new_bp, bp, bn, mp, mn);
+      bp = new_bp;
+      bn = mn;
+      /* Canonicalize the base, since we are potentially going to multiply with
+	 it quite a few times.  */
+      MPN_NORMALIZE (bp, bn);
+    }
+
+  if (bn == 0)
+    {
+      SIZ(r) = 0;
+      TMP_FREE;
+      return;
+    }
+
+  tp = TMP_ALLOC_LIMBS (2 * mn + 1);
+  xp = TMP_ALLOC_LIMBS (mn);
+
+  qp = TMP_ALLOC_LIMBS (mn + 1);
+
+  MPN_COPY (xp, bp, bn);
+  xn = bn;
+
+  e = el;
+  count_leading_zeros (c, e);
+  e = (e << c) << 1;		/* shift the exp bits to the left, lose msb */
+  c = BITS_PER_MP_LIMB - 1 - c;
+
+  /* Main loop. */
+
+  /* If m is already normalized (high bit of high limb set), and b is the
+     same size, but a bigger value, and e==1, then there's no modular
+     reductions done and we can end up with a result out of range at the
+     end. */
+  if (c == 0)
+    {
+      if (xn == mn && mpn_cmp (xp, mp, mn) >= 0)
+        mpn_sub_n (xp, xp, mp, mn);
+      goto finishup;
+    }
+
+  while (c != 0)
+    {
+      mpn_sqr_n (tp, xp, xn);
+      tn = 2 * xn; tn -= tp[tn - 1] == 0;
+      if (tn < mn)
+	{
+	  MPN_COPY (xp, tp, tn);
+	  xn = tn;
+	}
+      else
+	{
+	  mpn_tdiv_qr (qp, xp, 0L, tp, tn, mp, mn);
+	  xn = mn;
+	}
+
+      if ((mp_limb_signed_t) e < 0)
+	{
+	  mpn_mul (tp, xp, xn, bp, bn);
+	  tn = xn + bn; tn -= tp[tn - 1] == 0;
+	  if (tn < mn)
+	    {
+	      MPN_COPY (xp, tp, tn);
+	      xn = tn;
+	    }
+	  else
+	    {
+	      mpn_tdiv_qr (qp, xp, 0L, tp, tn, mp, mn);
+	      xn = mn;
+	    }
+	}
+      e <<= 1;
+      c--;
+    }
+
+ finishup:
+  /* We shifted m left m_zero_cnt steps.  Adjust the result by reducing
+     it with the original MOD.  */
+  if (m_zero_cnt != 0)
+    {
+      mp_limb_t cy;
+      cy = mpn_lshift (tp, xp, xn, m_zero_cnt);
+      tp[xn] = cy; xn += cy != 0;
+
+      if (xn < mn)
+	{
+	  MPN_COPY (xp, tp, xn);
+	}
+      else
+	{
+	  mpn_tdiv_qr (qp, xp, 0L, tp, xn, mp, mn);
+	  xn = mn;
+	}
+      mpn_rshift (xp, xp, xn, m_zero_cnt);
+    }
+  MPN_NORMALIZE (xp, xn);
+
+  if ((el & 1) != 0 && SIZ(b) < 0 && xn != 0)
+    {
+      mp = PTR(m);			/* want original, unnormalized m */
+      mpn_sub (xp, mp, mn, xp, xn);
+      xn = mn;
+      MPN_NORMALIZE (xp, xn);
+    }
+  MPZ_REALLOC (r, xn);
+  SIZ (r) = xn;
+  MPN_COPY (PTR(r), xp, xn);
+
+  TMP_FREE;
+}