]>
git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - lib/mpi/generic_mpih-lshift.c
1 /* mpihelp-lshift.c - MPI helper functions
2 * Copyright (C) 1994, 1996, 1998, 2001 Free Software Foundation, Inc.
4 * This file is part of GnuPG.
6 * GnuPG is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * GnuPG is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
20 * Note: This code is heavily based on the GNU MP Library.
21 * Actually it's the same code with only minor changes in the
22 * way the data is stored; this is to support the abstraction
23 * of an optional secure memory allocation which may be used
24 * to avoid revealing of sensitive data due to paging etc.
25 * The GNU MP Library itself is published under the LGPL;
26 * however I decided to publish this code under the plain GPL.
29 #include "mpi-internal.h"
31 /* Shift U (pointed to by UP and USIZE digits long) CNT bits to the left
32 * and store the USIZE least significant digits of the result at WP.
33 * Return the bits shifted out from the most significant digit.
35 * Argument constraints:
36 * 1. 0 < CNT < BITS_PER_MP_LIMB
37 * 2. If the result is to be written over the input, WP must be >= UP.
41 mpihelp_lshift(mpi_ptr_t wp
, mpi_ptr_t up
, mpi_size_t usize
, unsigned int cnt
)
43 mpi_limb_t high_limb
, low_limb
;
50 sh_2
= BITS_PER_MPI_LIMB
- sh_1
;
53 retval
= low_limb
>> sh_2
;
57 wp
[i
] = (high_limb
<< sh_1
) | (low_limb
>> sh_2
);
60 wp
[i
] = high_limb
<< sh_1
;