Commit 4278e9d9 authored by Marcelo Henrique Cerri's avatar Marcelo Henrique Cerri Committed by Herbert Xu
Browse files

lib/mpi: Add mpi_sub_ui() 

Add mpi_sub_ui() based on Gnu MP mpz_sub_ui() function from file
mpz/aors_ui.h[1] from change id 510b83519d1c adapting the code to the
kernel's data structures, helper functions and coding style and also
removing the defines used to produce mpz_sub_ui() and mpz_add_ui()
from the same code.

[1] https://gmplib.org/repo/gmp-6.2/file/510b83519d1c/mpz/aors.h



Signed-off-by: default avatarMarcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: default avatarStephan Mueller <smueller@chronox.de>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent e7d2b41e

include/linux/mpi.h

+3 −0
Original line number Diff line number Diff line
@@ -63,6 +63,9 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod); 
int mpi_cmp_ui(MPI u, ulong v);

int mpi_cmp(MPI u, MPI v);



/*-- mpi-sub-ui.c --*/

int mpi_sub_ui(MPI w, MPI u, unsigned long vval);



/*-- mpi-bit.c --*/

void mpi_normalize(MPI a);

unsigned mpi_get_nbits(MPI a);

lib/mpi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ mpi-y = \ 
	mpicoder.o			\

	mpi-bit.o			\

	mpi-cmp.o			\

	mpi-sub-ui.o			\

	mpih-cmp.o			\

	mpih-div.o			\

	mpih-mul.o			\

lib/mpi/mpi-sub-ui.c

0 → 100644
+78 −0
Original line number Diff line number Diff line 
// 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);

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