mpi-genesis 1
mpi-genesis 2 * Copyright (C) 1994, 1996, 1998, 2001 Free Software Foundation, Inc.
mpi-genesis 3 *
mpi-genesis 4 * This file is part of GnuPG.
mpi-genesis 5 *
mpi-genesis 6 * GnuPG is free software; you can redistribute it and/or modify
mpi-genesis 7 * it under the terms of the GNU General Public License as published by
mpi-genesis 8 * the Free Software Foundation; either version 3 of the License, or
mpi-genesis 9 * (at your option) any later version.
mpi-genesis 10 *
mpi-genesis 11 * GnuPG is distributed in the hope that it will be useful,
mpi-genesis 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
mpi-genesis 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
mpi-genesis 14 * GNU General Public License for more details.
mpi-genesis 15 *
mpi-genesis 16 * You should have received a copy of the GNU General Public License
mpi-genesis 17 * along with this program; if not, see <http:
mpi-genesis 18 *
mpi-genesis 19 * Note: This code is heavily based on the GNU MP Library.
mpi-genesis 20 * Actually it's the same code with only minor changes in the
mpi-genesis 21 * way the data is stored; this is to support the abstraction
mpi-genesis 22 * of an optional secure memory allocation which may be used
mpi-genesis 23 * to avoid revealing of sensitive data due to paging etc.
mpi-genesis 24 * The GNU MP Library itself is published under the LGPL;
mpi-genesis 25 * however I decided to publish this code under the plain GPL.
mpi-genesis 26 */
mpi-genesis 27
mpi-genesis 28 #include <config.h>
mpi-genesis 29 #include <stdio.h>
mpi-genesis 30 #include <stdlib.h>
mpi-genesis 31 #include "mpi-internal.h"
mpi-genesis 32
mpi-genesis 33
mpi-genesis 34 * and store the USIZE least significant digits of the result at WP.
mpi-genesis 35 * Return the bits shifted out from the most significant digit.
mpi-genesis 36 *
mpi-genesis 37 * Argument constraints:
mpi-genesis 38 * 1. 0 < CNT < BITS_PER_MP_LIMB
mpi-genesis 39 * 2. If the result is to be written over the input, WP must be >= UP.
mpi-genesis 40 */
mpi-genesis 41
mpi-genesis 42 mpi_limb_t
mpi-genesis 43 mpihelp_lshift( mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize,
mpi-genesis 44 unsigned int cnt)
mpi-genesis 45 {
mpi-genesis 46 mpi_limb_t high_limb, low_limb;
mpi-genesis 47 unsigned sh_1, sh_2;
mpi-genesis 48 mpi_size_t i;
mpi-genesis 49 mpi_limb_t retval;
mpi-genesis 50
mpi-genesis 51 sh_1 = cnt;
mpi-genesis 52 wp += 1;
mpi-genesis 53 sh_2 = BITS_PER_MPI_LIMB - sh_1;
mpi-genesis 54 i = usize - 1;
mpi-genesis 55 low_limb = up[i];
mpi-genesis 56 retval = low_limb >> sh_2;
mpi-genesis 57 high_limb = low_limb;
mpi-genesis 58 while( --i >= 0 ) {
mpi-genesis 59 low_limb = up[i];
mpi-genesis 60 wp[i] = (high_limb << sh_1) | (low_limb >> sh_2);
mpi-genesis 61 high_limb = low_limb;
mpi-genesis 62 }
mpi-genesis 63 wp[i] = high_limb << sh_1;
mpi-genesis 64
mpi-genesis 65 return retval;
mpi-genesis 66 }
mpi-genesis 67
mpi-genesis 68