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Implement MPI division.

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This commit is contained in:
Dag-Erling Smørgrav 2017-04-06 17:52:37 +02:00
parent 3c2b134fe4
commit c556bc0aa8
5 changed files with 218 additions and 15 deletions
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4
include/cryb/mpi.h
View file

@ -52,6 +52,8 @@ const char *cryb_mpi_version(void);
#define mpi_dec cryb_mpi_dec
#define mpi_dec_abs cryb_mpi_dec_abs
#define mpi_destroy cryb_mpi_destroy
#define mpi_div cryb_mpi_div
#define mpi_div_abs cryb_mpi_div_abs
#define mpi_eq cryb_mpi_eq
#define mpi_eq_abs cryb_mpi_eq_abs
#define mpi_eq_abs_u32 cryb_mpi_eq_abs_u32
@ -106,6 +108,8 @@ int mpi_copy(cryb_mpi *, const cryb_mpi *);
int mpi_dec(cryb_mpi *);
int mpi_dec_abs(cryb_mpi *);
void mpi_destroy(cryb_mpi *);
int mpi_div(cryb_mpi *, cryb_mpi *, const cryb_mpi *, const cryb_mpi *);
int mpi_div_abs(cryb_mpi *, cryb_mpi *, const cryb_mpi *, const cryb_mpi *);
int mpi_eq(const cryb_mpi *, const cryb_mpi *);
int mpi_eq_abs(const cryb_mpi *, const cryb_mpi *);
int mpi_eq_abs_u32(const cryb_mpi *, uint32_t);

2
lib/mpi/Makefile.am
View file

@ -13,6 +13,8 @@ libcryb_mpi_la_SOURCES = \
cryb_mpi_dec.c \
cryb_mpi_dec_abs.c \
cryb_mpi_destroy.c \
cryb_mpi_div.c \
cryb_mpi_div_abs.c \
cryb_mpi_eq.c \
cryb_mpi_eq_abs.c \
cryb_mpi_eq_i32.c \

54
lib/mpi/cryb_mpi_div.c Normal file
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@ -0,0 +1,54 @@
/*
* Copyright (c) 2017 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 <stddef.h>
#include <stdint.h>
#include <cryb/mpi.h>
#include "cryb_mpi_impl.h"
/*
* Store the quotient and remainder of A divided by B in Q and R.
*/
int
mpi_div(cryb_mpi *Q, cryb_mpi *R, const cryb_mpi *A, const cryb_mpi *B)
{
int neg;
neg = A->neg ^ B->neg;
if (mpi_div_abs(Q, R, A, B) < 0)
return (-1);
if (Q->msb > 0)
Q->neg = neg;
return (0);
}

115
lib/mpi/cryb_mpi_div_abs.c Normal file
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@ -0,0 +1,115 @@
/*
* Copyright (c) 2017 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 <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <strings.h>
#include <cryb/bitwise.h>
#include <cryb/mpi.h>
#include "cryb_mpi_impl.h"
/*
* Store the quotient and remainder of A divided by B in Q and R.
*
* Assumes Q != R, but any combination of {Q,R} == {A,B} is fine. Either
* Q or R or both may be NULL, althought the latter is pointless.
*/
int
mpi_div_abs(cryb_mpi *Q, cryb_mpi *R, const cryb_mpi *A, const cryb_mpi *B)
{
cryb_mpi AA = CRYB_MPI_ZERO, QQ = CRYB_MPI_ZERO;
int cmp;
/* trivial cases */
if (B->msb == 0) {
/* divide something by zero */
errno = EINVAL;
return (-1);
} else if (A->msb == 0) {
/* divide zero by something */
if (Q != NULL)
mpi_zero(Q);
if (R != NULL)
mpi_zero(R);
return (0);
} else if (B->msb == 1) {
/* divide something by one */
if (Q != A && Q != NULL && mpi_copy(Q, A) != 0)
return (-1);
if (R != NULL)
mpi_zero(R);
return (0);
} else if ((cmp = mpi_cmp_abs(A, B)) == 0) {
/* divide something by itself */
if (Q != NULL)
mpi_set(Q, 1);
if (R != NULL)
mpi_zero(R);
return (0);
} else if (cmp < 0) {
/* divide something by something larger */
if (Q != NULL)
mpi_zero(Q);
if (R != A && R != NULL && mpi_copy(R, A) != 0)
return (-1);
return (0);
}
/* division is destructive, so we work on copies */
if (mpi_copy(&AA, A) != 0)
return (-1);
mpi_zero(&QQ);
/*
* Repeatedly subtract B from A until they are the same length,
* then one last time if A is still greater than B.
*/
while (AA.msb > B->msb) {
mpi_sub_abs(&AA, &AA, B);
mpi_inc_abs(&QQ);
}
if (mpi_cmp_abs(&AA, B) >= 0) {
mpi_sub_abs(&AA, &AA, B);
mpi_inc_abs(&QQ);
}
/* store result where requested and clean up */
if (Q != NULL)
mpi_swap(Q, &QQ);
if (R != NULL)
mpi_swap(R, &AA);
mpi_destroy(&AA);
mpi_destroy(&QQ);
return (0);
}

58
t/t_mpi_muldiv.c
View file

@ -145,42 +145,70 @@ static struct t_div_case {
uint8_t b[16];
size_t bmsb;
int bneg:1;
uint8_t e[16];
size_t emsb;
int eneg:1;
uint8_t q[16];
size_t qmsb;
int qneg:1;
uint8_t r[16];
size_t rmsb;
int rneg:1;
} t_div_cases[] = {
{
"0 / 1 == 0",
{ }, 0, 0,
{ 0x01 }, 1, 0,
{ }, 0, 0,
{ }, 0, 0,
},
{
"1 / 1 == 1",
{ 0x01 }, 1, 0,
{ 0x01 }, 1, 0,
{ 0x01 }, 1, 0,
{ }, 0, 0,
},
{
"4 / 2 == 2",
{ 0x04 }, 3, 0,
{ 0x02 }, 2, 0,
{ 0x02 }, 2, 0,
{ }, 0, 0,
},
{
"257 / 127 == 2 rem 3",
{ 0x01, 0x01 }, 9, 0,
{ 0x7f }, 7, 0,
{ 0x02 }, 2, 0,
{ 0x03 }, 2, 0,
},
/* XXX needs lots more tests! */
};
static int
t_mpi_div_tc(char **desc CRYB_UNUSED, void *arg)
{
struct t_div_case *tc = arg;
cryb_mpi a = CRYB_MPI_ZERO, b = CRYB_MPI_ZERO, e = CRYB_MPI_ZERO;
cryb_mpi x = CRYB_MPI_ZERO;
cryb_mpi a = CRYB_MPI_ZERO, b = CRYB_MPI_ZERO;
cryb_mpi q = CRYB_MPI_ZERO, r = CRYB_MPI_ZERO;
cryb_mpi eq = CRYB_MPI_ZERO, er = CRYB_MPI_ZERO;
int ret = 1;
mpi_load(&a, tc->a, (tc->amsb + 7) / 8);
a.neg = tc->aneg;
mpi_load(&b, tc->b, (tc->bmsb + 7) / 8);
b.neg = tc->bneg;
mpi_load(&e, tc->e, (tc->emsb + 7) / 8);
e.neg = tc->eneg;
#if 0
ret &= t_compare_i(0, mpi_div_abs(&x, &a, &b));
#else
mpi_load(&x, tc->e, (tc->emsb + 7) / 8);
#endif
ret &= t_compare_mpi(&e, &x);
mpi_load(&eq, tc->q, (tc->qmsb + 7) / 8);
eq.neg = tc->qneg;
mpi_load(&er, tc->r, (tc->rmsb + 7) / 8);
er.neg = tc->rneg;
ret &= t_compare_i(0, mpi_div_abs(&q, &r, &a, &b));
ret &= t_compare_mpi(&eq, &q);
ret &= t_compare_mpi(&er, &r);
mpi_destroy(&a);
mpi_destroy(&b);
mpi_destroy(&e);
mpi_destroy(&x);
mpi_destroy(&q);
mpi_destroy(&r);
mpi_destroy(&eq);
mpi_destroy(&er);
return (ret);
}