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+/* mpi-div.c - MPI functions
+ * Copyright (c) 1997 by Werner Koch (dd9jn)
+ *
+ * This file is part of G10.
+ *
+ * G10 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.
+ *
+ * G10 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 <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "mpi-internal.h"
+#include "longlong.h"
+
+
+
+void
+mpi_fdiv_r( MPI rem, MPI dividend, MPI divisor )
+{
+ int divisor_sign = divisor->sign;
+ MPI temp_divisor = NULL;
+
+ /* We need the original value of the divisor after the remainder has been
+ * preliminary calculated. We have to copy it to temporary space if it's
+ * the same variable as REM. */
+ if( rem == divisor ) {
+ temp_divisor = mpi_copy( divisor );
+ divisor = temp_divisor;
+ }
+
+ mpi_tdiv_r( rem, dividend, divisor );
+
+ if( ((divisor_sign?1:0) ^ (dividend->sign?1:0)) && rem->nlimbs )
+ mpi_add( rem, rem, divisor);
+
+ if( temp_divisor )
+ mpi_free(temp_divisor);
+}
+
+
+
+/****************
+ * Division rounding the quotient towards -infinity.
+ * The remainder gets the same sign as the denominator.
+ * rem is optional
+ */
+
+ulong
+mpi_fdiv_r_ui( MPI rem, MPI dividend, ulong divisor )
+{
+ mpi_limb_t rlimb;
+
+ rlimb = mpihelp_mod_1( dividend->d, dividend->nlimbs, divisor );
+ if( rlimb && dividend->sign )
+ rlimb = divisor - rlimb;
+
+ if( rem ) {
+ rem->d[0] = rlimb;
+ rem->nlimbs = rlimb? 1:0;
+ }
+ return rlimb;
+}
+
+
+void
+mpi_fdiv_q( MPI quot, MPI dividend, MPI divisor )
+{
+ MPI tmp = mpi_alloc( mpi_get_nlimbs(quot) );
+ mpi_fdiv_qr( quot, tmp, dividend, divisor);
+ mpi_free(tmp);
+}
+
+void
+mpi_fdiv_qr( MPI quot, MPI rem, MPI dividend, MPI divisor )
+{
+ int divisor_sign = divisor->sign;
+ MPI temp_divisor = NULL;
+
+ if( quot == divisor || rem == divisor ) {
+ temp_divisor = mpi_copy( divisor );
+ divisor = temp_divisor;
+ }
+
+ mpi_tdiv_qr( quot, rem, dividend, divisor );
+
+ if( (divisor_sign ^ dividend->sign) && rem->nlimbs ) {
+ mpi_sub_ui( quot, quot, 1 );
+ mpi_add( rem, rem, divisor);
+ }
+
+ if( temp_divisor )
+ mpi_free(temp_divisor);
+}
+
+
+/* If den == quot, den needs temporary storage.
+ * If den == rem, den needs temporary storage.
+ * If num == quot, num needs temporary storage.
+ * If den has temporary storage, it can be normalized while being copied,
+ * i.e no extra storage should be allocated.
+ */
+
+void
+mpi_tdiv_r( MPI rem, MPI num, MPI den)
+{
+ mpi_tdiv_qr(NULL, rem, num, den );
+}
+
+void
+mpi_tdiv_qr( MPI quot, MPI rem, MPI num, MPI den)
+{
+ mpi_ptr_t np, dp;
+ mpi_ptr_t qp, rp;
+ mpi_size_t nsize = num->nlimbs;
+ mpi_size_t dsize = den->nlimbs;
+ mpi_size_t qsize, rsize;
+ mpi_size_t sign_remainder = num->sign;
+ mpi_size_t sign_quotient = num->sign ^ den->sign;
+ unsigned normalization_steps;
+ mpi_limb_t q_limb;
+ mpi_ptr_t marker[5];
+ int markidx=0;
+
+ /* Ensure space is enough for quotient and remainder.
+ * We need space for an extra limb in the remainder, because it's
+ * up-shifted (normalized) below. */
+ rsize = nsize + 1;
+ if( rem->alloced < rsize )
+ mpi_resize( rem, rsize);
+
+ qsize = rsize - dsize; /* qsize cannot be bigger than this. */
+ if( qsize <= 0 ) {
+ if( num != rem ) {
+ rem->nlimbs = num->nlimbs;
+ rem->sign = num->sign;
+ MPN_COPY(rem->d, num->d, nsize);
+ }
+ if( quot ) {
+ /* This needs to follow the assignment to rem, in case the
+ * numerator and quotient are the same. */
+ quot->nlimbs = 0;
+ quot->sign = 0;
+ }
+ return;
+ }
+
+ if( quot && quot->alloced < qsize )
+ mpi_resize( quot, qsize);
+
+ /* Read pointers here, when reallocation is finished. */
+ np = num->d;
+ dp = den->d;
+ rp = rem->d;
+
+ /* Optimize division by a single-limb divisor. */
+ if( dsize == 1 ) {
+ mpi_limb_t rlimb;
+ if( quot ) {
+ qp = quot->d;
+ rlimb = mpihelp_divmod_1( qp, np, nsize, dp[0] );
+ qsize -= qp[qsize - 1] == 0;
+ quot->nlimbs = qsize;
+ quot->sign = sign_quotient;
+ }
+ else
+ rlimb = mpihelp_mod_1( np, nsize, dp[0] );
+ rp[0] = rlimb;
+ rsize = rlimb != 0?1:0;
+ rem->nlimbs = rsize;
+ rem->sign = sign_remainder;
+ return;
+ }
+
+
+ if( quot ) {
+ qp = quot->d;
+ /* Make sure QP and NP point to different objects. Otherwise the
+ * numerator would be gradually overwritten by the quotient limbs. */
+ if(qp == np) { /* Copy NP object to temporary space. */
+ np = marker[markidx++] = mpi_alloc_limb_space(nsize);
+ MPN_COPY(np, qp, nsize);
+ }
+ }
+ else /* Put quotient at top of remainder. */
+ qp = rp + dsize;
+
+ count_leading_zeros( normalization_steps, dp[dsize - 1] );
+
+ /* Normalize the denominator, i.e. make its most significant bit set by
+ * shifting it NORMALIZATION_STEPS bits to the left. Also shift the
+ * numerator the same number of steps (to keep the quotient the same!).
+ */
+ if( normalization_steps ) {
+ mpi_ptr_t tp;
+ mpi_limb_t nlimb;
+
+ /* Shift up the denominator setting the most significant bit of
+ * the most significant word. Use temporary storage not to clobber
+ * the original contents of the denominator. */
+ tp = marker[markidx++] = mpi_alloc_limb_space(dsize);
+ mpihelp_lshift( tp, dp, dsize, normalization_steps );
+ dp = tp;
+
+ /* Shift up the numerator, possibly introducing a new most
+ * significant word. Move the shifted numerator in the remainder
+ * meanwhile. */
+ nlimb = mpihelp_lshift(rp, np, nsize, normalization_steps);
+ if( nlimb ) {
+ rp[nsize] = nlimb;
+ rsize = nsize + 1;
+ }
+ else
+ rsize = nsize;
+ }
+ else {
+ /* The denominator is already normalized, as required. Copy it to
+ * temporary space if it overlaps with the quotient or remainder. */
+ if( dp == rp || (quot && (dp == qp))) {
+ mpi_ptr_t tp;
+
+ tp = marker[markidx++] = mpi_alloc_limb_space(dsize);
+ MPN_COPY( tp, dp, dsize );
+ dp = tp;
+ }
+
+ /* Move the numerator to the remainder. */
+ if( rp != np )
+ MPN_COPY(rp, np, nsize);
+
+ rsize = nsize;
+ }
+
+ q_limb = mpihelp_divrem( qp, 0, rp, rsize, dp, dsize );
+
+ if( quot ) {
+ qsize = rsize - dsize;
+ if(q_limb) {
+ qp[qsize] = q_limb;
+ qsize += 1;
+ }
+
+ quot->nlimbs = qsize;
+ quot->sign = sign_quotient;
+ }
+
+ rsize = dsize;
+ MPN_NORMALIZE (rp, rsize);
+
+ if( normalization_steps && rsize ) {
+ mpihelp_rshift(rp, rp, rsize, normalization_steps);
+ rsize -= rp[rsize - 1] == 0?1:0;
+ }
+
+ rem->nlimbs = rsize;
+ rem->sign = sign_remainder;
+ while( markidx )
+ mpi_free_limb_space(marker[--markidx]);
+}
+
+
+/****************
+ * Check wether dividend is divisible by divisor
+ * (note: divisor must fit into a limb)
+ */
+int
+mpi_divisible_ui(MPI dividend, ulong divisor )
+{
+ return !mpihelp_mod_1( dividend->d, dividend->nlimbs, divisor );
+}
+
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