--- /dev/null
+/* gcdext_subdiv_step.c.
+
+ THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY
+ SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
+ GUARANTEED THAT THEY'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 2003, 2004, 2005, 2008 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"
+
+/* Used when mpn_hgcd or mpn_hgcd2 has failed. Then either one of a or
+ b is small, or the difference is small. Perform one subtraction
+ followed by one division. If the gcd is found, stores it in gp and
+ *gn, and returns zero. Otherwise, compute the reduced a and b,
+ return the new size, and cofactors. */
+
+/* Temporary storage: Needs n limbs for the quotient, at qp. tp must
+ point to an area large enough for the resulting cofactor, plus one
+ limb extra. All in all, 2N + 1 if N is a bound for both inputs and
+ outputs. */
+mp_size_t
+mpn_gcdext_subdiv_step (mp_ptr gp, mp_size_t *gn, mp_ptr up, mp_size_t *usizep,
+ mp_ptr ap, mp_ptr bp, mp_size_t n,
+ mp_ptr u0, mp_ptr u1, mp_size_t *unp,
+ mp_ptr qp, mp_ptr tp)
+{
+ mp_size_t an, bn, un;
+ mp_size_t qn;
+ mp_size_t u0n;
+
+ int swapped;
+
+ an = bn = n;
+
+ ASSERT (an > 0);
+ ASSERT (ap[an-1] > 0 || bp[an-1] > 0);
+
+ MPN_NORMALIZE (ap, an);
+ MPN_NORMALIZE (bp, bn);
+
+ un = *unp;
+
+ swapped = 0;
+
+ if (UNLIKELY (an == 0))
+ {
+ return_b:
+ MPN_COPY (gp, bp, bn);
+ *gn = bn;
+
+ MPN_NORMALIZE (u0, un);
+ MPN_COPY (up, u0, un);
+
+ *usizep = swapped ? un : -un;
+
+ return 0;
+ }
+ else if (UNLIKELY (bn == 0))
+ {
+ return_a:
+ MPN_COPY (gp, ap, an);
+ *gn = an;
+
+ MPN_NORMALIZE (u1, un);
+ MPN_COPY (up, u1, un);
+
+ *usizep = swapped ? -un : un;
+
+ return 0;
+ }
+
+ /* Arrange so that a > b, subtract an -= bn, and maintain
+ normalization. */
+ if (an < bn)
+ {
+ MPN_PTR_SWAP (ap, an, bp, bn);
+ MP_PTR_SWAP (u0, u1);
+ swapped ^= 1;
+ }
+ else if (an == bn)
+ {
+ int c;
+ MPN_CMP (c, ap, bp, an);
+ if (UNLIKELY (c == 0))
+ goto return_a;
+ else if (c < 0)
+ {
+ MP_PTR_SWAP (ap, bp);
+ MP_PTR_SWAP (u0, u1);
+ swapped ^= 1;
+ }
+ }
+ /* Reduce a -= b, u1 += u0 */
+ ASSERT_NOCARRY (mpn_sub (ap, ap, an, bp, bn));
+ MPN_NORMALIZE (ap, an);
+ ASSERT (an > 0);
+
+ u1[un] = mpn_add_n (u1, u1, u0, un);
+ un += (u1[un] > 0);
+
+ /* Arrange so that a > b, and divide a = q b + r */
+ if (an < bn)
+ {
+ MPN_PTR_SWAP (ap, an, bp, bn);
+ MP_PTR_SWAP (u0, u1);
+ swapped ^= 1;
+ }
+ else if (an == bn)
+ {
+ int c;
+ MPN_CMP (c, ap, bp, an);
+ if (UNLIKELY (c == 0))
+ goto return_a;
+ else if (c < 0)
+ {
+ MP_PTR_SWAP (ap, bp);
+ MP_PTR_SWAP (u0, u1);
+ swapped ^= 1;
+ }
+ }
+
+ /* Reduce a -= q b, u1 += q u0 */
+ qn = an - bn + 1;
+ mpn_tdiv_qr (qp, ap, 0, ap, an, bp, bn);
+
+ if (mpn_zero_p (ap, bn))
+ goto return_b;
+
+ n = bn;
+
+ /* Update u1 += q u0 */
+ u0n = un;
+ MPN_NORMALIZE (u0, u0n);
+
+ if (u0n > 0)
+ {
+ qn -= (qp[qn - 1] == 0);
+
+ if (qn > u0n)
+ mpn_mul (tp, qp, qn, u0, u0n);
+ else
+ mpn_mul (tp, u0, u0n, qp, qn);
+
+ if (qn + u0n > un)
+ {
+ ASSERT_NOCARRY (mpn_add (u1, tp, qn + u0n, u1, un));
+ un = qn + u0n;
+ un -= (u1[un-1] == 0);
+ }
+ else
+ {
+ u1[un] = mpn_add (u1, u1, un, tp, qn + u0n);
+ un += (u1[un] > 0);
+ }
+ }
+
+ *unp = un;
+ return n;
+}
projects / msp430-gcc.git / blobdiff