mirror of https://gitee.com/openkylin/linux.git
79 lines
2.3 KiB
C
79 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/* mpi-sub-ui.c - Subtract an unsigned integer from an MPI.
|
|
*
|
|
* Copyright 1991, 1993, 1994, 1996, 1999-2002, 2004, 2012, 2013, 2015
|
|
* Free Software Foundation, Inc.
|
|
*
|
|
* This file was based on the GNU MP Library source file:
|
|
* https://gmplib.org/repo/gmp-6.2/file/510b83519d1c/mpz/aors_ui.h
|
|
*
|
|
* The GNU MP Library is free software; you can redistribute it and/or modify
|
|
* it under the terms of either:
|
|
*
|
|
* * the GNU Lesser General Public License as published by the Free
|
|
* Software Foundation; either version 3 of the License, or (at your
|
|
* option) any later version.
|
|
*
|
|
* or
|
|
*
|
|
* * 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.
|
|
*
|
|
* or both in parallel, as here.
|
|
*
|
|
* The GNU MP Library 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 copies of the GNU General Public License and the
|
|
* GNU Lesser General Public License along with the GNU MP Library. If not,
|
|
* see https://www.gnu.org/licenses/.
|
|
*/
|
|
|
|
#include "mpi-internal.h"
|
|
|
|
int mpi_sub_ui(MPI w, MPI u, unsigned long vval)
|
|
{
|
|
if (u->nlimbs == 0) {
|
|
if (mpi_resize(w, 1) < 0)
|
|
return -ENOMEM;
|
|
w->d[0] = vval;
|
|
w->nlimbs = (vval != 0);
|
|
w->sign = (vval != 0);
|
|
return 0;
|
|
}
|
|
|
|
/* If not space for W (and possible carry), increase space. */
|
|
if (mpi_resize(w, u->nlimbs + 1))
|
|
return -ENOMEM;
|
|
|
|
if (u->sign) {
|
|
mpi_limb_t cy;
|
|
|
|
cy = mpihelp_add_1(w->d, u->d, u->nlimbs, (mpi_limb_t) vval);
|
|
w->d[u->nlimbs] = cy;
|
|
w->nlimbs = u->nlimbs + cy;
|
|
w->sign = 1;
|
|
} else {
|
|
/* The signs are different. Need exact comparison to determine
|
|
* which operand to subtract from which.
|
|
*/
|
|
if (u->nlimbs == 1 && u->d[0] < vval) {
|
|
w->d[0] = vval - u->d[0];
|
|
w->nlimbs = 1;
|
|
w->sign = 1;
|
|
} else {
|
|
mpihelp_sub_1(w->d, u->d, u->nlimbs, (mpi_limb_t) vval);
|
|
/* Size can decrease with at most one limb. */
|
|
w->nlimbs = (u->nlimbs - (w->d[u->nlimbs - 1] == 0));
|
|
w->sign = 0;
|
|
}
|
|
}
|
|
|
|
mpi_normalize(w);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(mpi_sub_ui);
|