mpi-genesis 1
mpi-genesis 2 * Copyright (C) 1994, 1996, 1998, 1999,
mpi-genesis 3 * 2000, 2001 Free Software Foundation, Inc.
mpi-genesis 4 *
mpi-genesis 5 * This file is part of GNUPG
mpi-genesis 6 *
mpi-genesis 7 * GNUPG is free software; you can redistribute it and/or modify
mpi-genesis 8 * it under the terms of the GNU General Public License as published by
mpi-genesis 9 * the Free Software Foundation; either version 3 of the License, or
mpi-genesis 10 * (at your option) any later version.
mpi-genesis 11 *
mpi-genesis 12 * GNUPG is distributed in the hope that it will be useful,
mpi-genesis 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
mpi-genesis 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
mpi-genesis 15 * GNU General Public License for more details.
mpi-genesis 16 *
mpi-genesis 17 * You should have received a copy of the GNU General Public License
mpi-genesis 18 * along with this program; if not, see <http:
mpi-genesis 19 *
mpi-genesis 20 * Note: This code is heavily based on the GNU MP Library.
mpi-genesis 21 * Actually it's the same code with only minor changes in the
mpi-genesis 22 * way the data is stored; this is to support the abstraction
mpi-genesis 23 * of an optional secure memory allocation which may be used
mpi-genesis 24 * to avoid revealing of sensitive data due to paging etc.
mpi-genesis 25 * The GNU MP Library itself is published under the LGPL;
mpi-genesis 26 * however I decided to publish this code under the plain GPL.
mpi-genesis 27 */
mpi-genesis 28
mpi-genesis 29 #include <config.h>
mpi-genesis 30 #include <stdio.h>
mpi-genesis 31 #include <stdlib.h>
mpi-genesis 32 #include "mpi-internal.h"
mpi-genesis 33
mpi-genesis 34
mpi-genesis 35
mpi-genesis 36 * and store the USIZE least significant limbs of the result at WP.
mpi-genesis 37 * The bits shifted out to the right are returned.
mpi-genesis 38 *
mpi-genesis 39 * Argument constraints:
mpi-genesis 40 * 1. 0 < CNT < BITS_PER_MP_LIMB
mpi-genesis 41 * 2. If the result is to be written over the input, WP must be <= UP.
mpi-genesis 42 */
mpi-genesis 43
mpi-genesis 44 mpi_limb_t
mpi-genesis 45 mpihelp_rshift( mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize, unsigned cnt)
mpi-genesis 46 {
mpi-genesis 47 mpi_limb_t high_limb, low_limb;
mpi-genesis 48 unsigned sh_1, sh_2;
mpi-genesis 49 mpi_size_t i;
mpi-genesis 50 mpi_limb_t retval;
mpi-genesis 51
mpi-genesis 52 sh_1 = cnt;
mpi-genesis 53 wp -= 1;
mpi-genesis 54 sh_2 = BITS_PER_MPI_LIMB - sh_1;
mpi-genesis 55 high_limb = up[0];
mpi-genesis 56 retval = high_limb << sh_2;
mpi-genesis 57 low_limb = high_limb;
mpi-genesis 58 for( i=1; i < usize; i++) {
mpi-genesis 59 high_limb = up[i];
mpi-genesis 60 wp[i] = (low_limb >> sh_1) | (high_limb << sh_2);
mpi-genesis 61 low_limb = high_limb;
mpi-genesis 62 }
mpi-genesis 63 wp[i] = low_limb >> sh_1;
mpi-genesis 64
mpi-genesis 65 return retval;
mpi-genesis 66 }
mpi-genesis 67