This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / crypto / mpi / generic_udiv-w-sdiv.c

diff --git a/crypto/mpi/generic_udiv-w-sdiv.c b/crypto/mpi/generic_udiv-w-sdiv.c
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+/* mpihelp_udiv_w_sdiv -- implement udiv_qrnnd on machines with only signed
+ *                       division.
+ * Copyright (C) 1992, 1994, 1996, 1998 Free Software Foundation, Inc.
+ * Contributed by Peter L. Montgomery.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include "mpi-internal.h"
+#include "longlong.h"
+
+
+#if 0  /* not yet ported to MPI */
+
+mpi_limb_t
+mpihelp_udiv_w_sdiv( mpi_limp_t *rp,
+                    mpi_limp_t *a1,
+                    mpi_limp_t *a0,
+                    mpi_limp_t *d   )
+{
+  mp_limb_t q, r;
+  mp_limb_t c0, c1, b1;
+
+  if ((mpi_limb_signed_t) d >= 0)
+    {
+      if (a1 < d - a1 - (a0 >> (BITS_PER_MP_LIMB - 1)))
+       {
+         /* dividend, divisor, and quotient are nonnegative */
+         sdiv_qrnnd (q, r, a1, a0, d);
+       }
+      else
+       {
+         /* Compute c1*2^32 + c0 = a1*2^32 + a0 - 2^31*d */
+         sub_ddmmss (c1, c0, a1, a0, d >> 1, d << (BITS_PER_MP_LIMB - 1));
+         /* Divide (c1*2^32 + c0) by d */
+         sdiv_qrnnd (q, r, c1, c0, d);
+         /* Add 2^31 to quotient */
+         q += (mp_limb_t) 1 << (BITS_PER_MP_LIMB - 1);
+       }
+    }
+  else
+    {
+      b1 = d >> 1;                     /* d/2, between 2^30 and 2^31 - 1 */
+      c1 = a1 >> 1;                    /* A/2 */
+      c0 = (a1 << (BITS_PER_MP_LIMB - 1)) + (a0 >> 1);
+
+      if (a1 < b1)                     /* A < 2^32*b1, so A/2 < 2^31*b1 */
+       {
+         sdiv_qrnnd (q, r, c1, c0, b1); /* (A/2) / (d/2) */
+
+         r = 2*r + (a0 & 1);           /* Remainder from A/(2*b1) */
+         if ((d & 1) != 0)
+           {
+             if (r >= q)
+               r = r - q;
+             else if (q - r <= d)
+               {
+                 r = r - q + d;
+                 q--;
+               }
+             else
+               {
+                 r = r - q + 2*d;
+                 q -= 2;
+               }
+           }
+       }
+      else if (c1 < b1)                /* So 2^31 <= (A/2)/b1 < 2^32 */
+       {
+         c1 = (b1 - 1) - c1;
+         c0 = ~c0;                     /* logical NOT */
+
+         sdiv_qrnnd (q, r, c1, c0, b1); /* (A/2) / (d/2) */
+
+         q = ~q;                       /* (A/2)/b1 */
+         r = (b1 - 1) - r;
+
+         r = 2*r + (a0 & 1);           /* A/(2*b1) */
+
+         if ((d & 1) != 0)
+           {
+             if (r >= q)
+               r = r - q;
+             else if (q - r <= d)
+               {
+                 r = r - q + d;
+                 q--;
+               }
+             else
+               {
+                 r = r - q + 2*d;
+                 q -= 2;
+               }
+           }
+       }
+      else                             /* Implies c1 = b1 */
+       {                               /* Hence a1 = d - 1 = 2*b1 - 1 */
+         if (a0 >= -d)
+           {
+             q = -1;
+             r = a0 + d;
+           }
+         else
+           {
+             q = -2;
+             r = a0 + 2*d;
+           }
+       }
+    }
+
+  *rp = r;
+  return q;
+}
+
+#endif
+