237 lines
5.5 KiB
C
237 lines
5.5 KiB
C
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/* mpi-bit.c - MPI bit level fucntions
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* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include "mpi-internal.h"
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#include "longlong.h"
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const unsigned char __clz_tab[] = {
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0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5,
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6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
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6, 6, 6, 6, 6, 6, 6, 6,
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
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7, 7, 7, 7, 7, 7, 7, 7,
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7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
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7, 7, 7, 7, 7, 7, 7, 7,
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
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8, 8, 8, 8, 8, 8, 8, 8,
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};
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#define A_LIMB_1 ((mpi_limb_t) 1)
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/****************
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* Sometimes we have MSL (most significant limbs) which are 0;
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* this is for some reasons not good, so this function removes them.
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*/
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void mpi_normalize(MPI a)
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{
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for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--)
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;
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}
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/****************
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* Return the number of bits in A.
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*/
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unsigned mpi_get_nbits(MPI a)
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{
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unsigned n;
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mpi_normalize(a);
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if (a->nlimbs) {
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mpi_limb_t alimb = a->d[a->nlimbs - 1];
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if (alimb)
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count_leading_zeros(n, alimb);
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else
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n = BITS_PER_MPI_LIMB;
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n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;
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} else
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n = 0;
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return n;
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}
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EXPORT_SYMBOL_GPL(mpi_get_nbits);
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/****************
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* Test whether bit N is set.
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*/
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int mpi_test_bit(MPI a, unsigned n)
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{
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unsigned limbno, bitno;
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mpi_limb_t limb;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if (limbno >= a->nlimbs)
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return 0; /* too far left: this is a 0 */
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limb = a->d[limbno];
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return (limb & (A_LIMB_1 << bitno)) ? 1 : 0;
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}
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/****************
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* Set bit N of A.
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*/
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int mpi_set_bit(MPI a, unsigned n)
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{
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unsigned limbno, bitno;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if (limbno >= a->nlimbs) { /* resize */
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if (a->alloced >= limbno)
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if (mpi_resize(a, limbno + 1) < 0)
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return -ENOMEM;
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a->nlimbs = limbno + 1;
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}
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a->d[limbno] |= (A_LIMB_1 << bitno);
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return 0;
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}
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/****************
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* Set bit N of A. and clear all bits above
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*/
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int mpi_set_highbit(MPI a, unsigned n)
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{
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unsigned limbno, bitno;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if (limbno >= a->nlimbs) { /* resize */
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if (a->alloced >= limbno)
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if (mpi_resize(a, limbno + 1) < 0)
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return -ENOMEM;
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a->nlimbs = limbno + 1;
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}
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a->d[limbno] |= (A_LIMB_1 << bitno);
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for (bitno++; bitno < BITS_PER_MPI_LIMB; bitno++)
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a->d[limbno] &= ~(A_LIMB_1 << bitno);
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a->nlimbs = limbno + 1;
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return 0;
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}
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/****************
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* clear bit N of A and all bits above
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*/
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void mpi_clear_highbit(MPI a, unsigned n)
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{
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unsigned limbno, bitno;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if (limbno >= a->nlimbs)
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return; /* not allocated, so need to clear bits :-) */
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for (; bitno < BITS_PER_MPI_LIMB; bitno++)
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a->d[limbno] &= ~(A_LIMB_1 << bitno);
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a->nlimbs = limbno + 1;
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}
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/****************
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* Clear bit N of A.
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*/
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void mpi_clear_bit(MPI a, unsigned n)
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{
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unsigned limbno, bitno;
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limbno = n / BITS_PER_MPI_LIMB;
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bitno = n % BITS_PER_MPI_LIMB;
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if (limbno >= a->nlimbs)
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return; /* don't need to clear this bit, it's to far to left */
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a->d[limbno] &= ~(A_LIMB_1 << bitno);
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}
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/****************
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* Shift A by N bits to the right
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* FIXME: should use alloc_limb if X and A are same.
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*/
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int mpi_rshift(MPI x, MPI a, unsigned n)
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{
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mpi_ptr_t xp;
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mpi_size_t xsize;
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xsize = a->nlimbs;
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x->sign = a->sign;
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if (RESIZE_IF_NEEDED(x, (size_t) xsize) < 0)
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return -ENOMEM;
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xp = x->d;
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if (xsize) {
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mpihelp_rshift(xp, a->d, xsize, n);
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MPN_NORMALIZE(xp, xsize);
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}
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x->nlimbs = xsize;
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return 0;
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}
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/****************
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* Shift A by COUNT limbs to the left
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* This is used only within the MPI library
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*/
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int mpi_lshift_limbs(MPI a, unsigned int count)
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{
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mpi_ptr_t ap = a->d;
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int n = a->nlimbs;
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int i;
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if (!count || !n)
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return 0;
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if (RESIZE_IF_NEEDED(a, n + count) < 0)
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return -ENOMEM;
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for (i = n - 1; i >= 0; i--)
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ap[i + count] = ap[i];
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for (i = 0; i < count; i++)
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ap[i] = 0;
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a->nlimbs += count;
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return 0;
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}
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/****************
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* Shift A by COUNT limbs to the right
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* This is used only within the MPI library
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*/
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void mpi_rshift_limbs(MPI a, unsigned int count)
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{
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mpi_ptr_t ap = a->d;
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mpi_size_t n = a->nlimbs;
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unsigned int i;
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if (count >= n) {
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a->nlimbs = 0;
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return;
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}
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for (i = 0; i < n - count; i++)
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ap[i] = ap[i + count];
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ap[i] = 0;
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a->nlimbs -= count;
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}
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