cryb-to/lib/mpi/mpi_cmp.c

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/*
* Copyright (c) 2014 Dag-Erling Smørgrav
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "cryb/impl.h"
#include <stdint.h>
#include <stdlib.h>
#include <cryb/mpi.h>
/* n rounded up to nearest multiple of p */
#define RUP(n, p) ((((n) + (p) - 1) / (p)) * (p))
/*
* Compare absolute values
*/
int
mpi_cmp_abs(cryb_mpi *X, cryb_mpi *Y)
{
int i;
/* check width first */
if (X->msb > Y->msb)
return (1);
if (X->msb < Y->msb)
return (-1);
/* no luck, compare word by word */
for (i = X->msb / 32; i >= 0; --i) {
if (X->words[i] > Y->words[i])
return (1);
if (X->words[i] < Y->words[i])
return (-1);
}
return (0);
}
/*
* Compare signed values
*/
int
mpi_cmp(cryb_mpi *X, cryb_mpi *Y)
{
if (X->neg) {
if (Y->neg)
return (-mpi_cmp_abs(X, Y));
else
return (-1);
} else {
if (Y->neg)
return (1);
else
return (mpi_cmp_abs(X, Y));
}
}