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godot/thirdparty/openssl/crypto/bn/bn_sqr.c

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/* crypto/bn/bn_sqr.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* 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 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
#include <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"
/* r must not be a */
/*
* I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96
*/
int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
{
int ret = bn_sqr_fixed_top(r, a, ctx);
bn_correct_top(r);
bn_check_top(r);
return ret;
}
int bn_sqr_fixed_top(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
{
int max, al;
int ret = 0;
BIGNUM *tmp, *rr;
#ifdef BN_COUNT
fprintf(stderr, "BN_sqr %d * %d\n", a->top, a->top);
#endif
bn_check_top(a);
al = a->top;
if (al <= 0) {
r->top = 0;
r->neg = 0;
return 1;
}
BN_CTX_start(ctx);
rr = (a != r) ? r : BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
if (!rr || !tmp)
goto err;
max = 2 * al; /* Non-zero (from above) */
if (bn_wexpand(rr, max) == NULL)
goto err;
if (al == 4) {
#ifndef BN_SQR_COMBA
BN_ULONG t[8];
bn_sqr_normal(rr->d, a->d, 4, t);
#else
bn_sqr_comba4(rr->d, a->d);
#endif
} else if (al == 8) {
#ifndef BN_SQR_COMBA
BN_ULONG t[16];
bn_sqr_normal(rr->d, a->d, 8, t);
#else
bn_sqr_comba8(rr->d, a->d);
#endif
} else {
#if defined(BN_RECURSION)
if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) {
BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL * 2];
bn_sqr_normal(rr->d, a->d, al, t);
} else {
int j, k;
j = BN_num_bits_word((BN_ULONG)al);
j = 1 << (j - 1);
k = j + j;
if (al == j) {
if (bn_wexpand(tmp, k * 2) == NULL)
goto err;
bn_sqr_recursive(rr->d, a->d, al, tmp->d);
} else {
if (bn_wexpand(tmp, max) == NULL)
goto err;
bn_sqr_normal(rr->d, a->d, al, tmp->d);
}
}
#else
if (bn_wexpand(tmp, max) == NULL)
goto err;
bn_sqr_normal(rr->d, a->d, al, tmp->d);
#endif
}
rr->neg = 0;
rr->top = max;
rr->flags |= BN_FLG_FIXED_TOP;
if (r != rr && BN_copy(r, rr) == NULL)
goto err;
ret = 1;
err:
bn_check_top(rr);
bn_check_top(tmp);
BN_CTX_end(ctx);
return (ret);
}
/* tmp must have 2*n words */
void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)
{
int i, j, max;
const BN_ULONG *ap;
BN_ULONG *rp;
max = n * 2;
ap = a;
rp = r;
rp[0] = rp[max - 1] = 0;
rp++;
j = n;
if (--j > 0) {
ap++;
rp[j] = bn_mul_words(rp, ap, j, ap[-1]);
rp += 2;
}
for (i = n - 2; i > 0; i--) {
j--;
ap++;
rp[j] = bn_mul_add_words(rp, ap, j, ap[-1]);
rp += 2;
}
bn_add_words(r, r, r, max);
/* There will not be a carry */
bn_sqr_words(tmp, a, n);
bn_add_words(r, r, tmp, max);
}
#ifdef BN_RECURSION
/*-
* r is 2*n words in size,
* a and b are both n words in size. (There's not actually a 'b' here ...)
* n must be a power of 2.
* We multiply and return the result.
* t must be 2*n words in size
* We calculate
* a[0]*b[0]
* a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
* a[1]*b[1]
*/
void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)
{
int n = n2 / 2;
int zero, c1;
BN_ULONG ln, lo, *p;
# ifdef BN_COUNT
fprintf(stderr, " bn_sqr_recursive %d * %d\n", n2, n2);
# endif
if (n2 == 4) {
# ifndef BN_SQR_COMBA
bn_sqr_normal(r, a, 4, t);
# else
bn_sqr_comba4(r, a);
# endif
return;
} else if (n2 == 8) {
# ifndef BN_SQR_COMBA
bn_sqr_normal(r, a, 8, t);
# else
bn_sqr_comba8(r, a);
# endif
return;
}
if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) {
bn_sqr_normal(r, a, n2, t);
return;
}
/* r=(a[0]-a[1])*(a[1]-a[0]) */
c1 = bn_cmp_words(a, &(a[n]), n);
zero = 0;
if (c1 > 0)
bn_sub_words(t, a, &(a[n]), n);
else if (c1 < 0)
bn_sub_words(t, &(a[n]), a, n);
else
zero = 1;
/* The result will always be negative unless it is zero */
p = &(t[n2 * 2]);
if (!zero)
bn_sqr_recursive(&(t[n2]), t, n, p);
else
memset(&(t[n2]), 0, n2 * sizeof(BN_ULONG));
bn_sqr_recursive(r, a, n, p);
bn_sqr_recursive(&(r[n2]), &(a[n]), n, p);
/*-
* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
* r[10] holds (a[0]*b[0])
* r[32] holds (b[1]*b[1])
*/
c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
/* t[32] is negative */
c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
/*-
* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
* r[10] holds (a[0]*a[0])
* r[32] holds (a[1]*a[1])
* c1 holds the carry bits
*/
c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
if (c1) {
p = &(r[n + n2]);
lo = *p;
ln = (lo + c1) & BN_MASK2;
*p = ln;
/*
* The overflow will stop before we over write words we should not
* overwrite
*/
if (ln < (BN_ULONG)c1) {
do {
p++;
lo = *p;
ln = (lo + 1) & BN_MASK2;
*p = ln;
} while (ln == 0);
}
}
}
#endif
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