mirror of
https://github.com/cryb-to/cryb-to.git
synced 2024-11-15 02:05:40 +00:00
76 lines
2.4 KiB
C
76 lines
2.4 KiB
C
/*
|
|
* Copyright (c) 2014-2016 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 <string.h>
|
|
|
|
#include <cryb/mpi.h>
|
|
|
|
#include "cryb_mpi_impl.h"
|
|
|
|
/*
|
|
* Right-shift X in place by c bits.
|
|
*/
|
|
int
|
|
mpi_rshift(cryb_mpi *X, unsigned int c)
|
|
{
|
|
unsigned int cl, i;
|
|
|
|
/* operands are zero */
|
|
if (c == 0 || X->msb == 0)
|
|
return (0);
|
|
/* shift wider than number, result is zero */
|
|
if (X->msb <= c) {
|
|
mpi_zero(X);
|
|
return (0);
|
|
}
|
|
/* preemptively adjust msb */
|
|
X->msb -= c;
|
|
/* try to move whole words first */
|
|
if (c >= 32) {
|
|
cl = c / 32;
|
|
c = c % 32;
|
|
memmove(X->words, X->words + cl,
|
|
(X->size - cl) * sizeof *X->words);
|
|
memset(X->words + X->size - cl, 0, cl * sizeof *X->words);
|
|
}
|
|
/* done? */
|
|
if (c == 0)
|
|
return (0);
|
|
/* the rest has to be done the hard way */
|
|
for (i = 0; i < X->size - 1; ++i) {
|
|
X->words[i] >>= c;
|
|
X->words[i] |= X->words[i + 1] << (32 - c);
|
|
}
|
|
X->words[X->size - 1] >>= c;
|
|
/* done! */
|
|
return (0);
|
|
}
|