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+/* 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 <openssl/bn.h>
+
+#include <openssl/err.h>
+#include <openssl/mem.h>
+
+#include "internal.h"
+
+
+int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
+ const BIGNUM *tmp;
+ int a_neg = a->neg, ret;
+
+ /* a + b a+b
+ * a + -b a-b
+ * -a + b b-a
+ * -a + -b -(a+b)
+ */
+ if (a_neg ^ b->neg) {
+ /* only one is negative */
+ if (a_neg) {
+ tmp = a;
+ a = b;
+ b = tmp;
+ }
+
+ /* we are now a - b */
+ if (BN_ucmp(a, b) < 0) {
+ if (!BN_usub(r, b, a)) {
+ return 0;
+ }
+ r->neg = 1;
+ } else {
+ if (!BN_usub(r, a, b)) {
+ return 0;
+ }
+ r->neg = 0;
+ }
+ return 1;
+ }
+
+ ret = BN_uadd(r, a, b);
+ r->neg = a_neg;
+ return ret;
+}
+
+int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
+ int max, min, dif;
+ BN_ULONG *ap, *bp, *rp, carry, t1, t2;
+ const BIGNUM *tmp;
+
+ if (a->top < b->top) {
+ tmp = a;
+ a = b;
+ b = tmp;
+ }
+ max = a->top;
+ min = b->top;
+ dif = max - min;
+
+ if (bn_wexpand(r, max + 1) == NULL) {
+ return 0;
+ }
+
+ r->top = max;
+
+ ap = a->d;
+ bp = b->d;
+ rp = r->d;
+
+ carry = bn_add_words(rp, ap, bp, min);
+ rp += min;
+ ap += min;
+ bp += min;
+
+ if (carry) {
+ while (dif) {
+ dif--;
+ t1 = *(ap++);
+ t2 = (t1 + 1) & BN_MASK2;
+ *(rp++) = t2;
+ if (t2) {
+ carry = 0;
+ break;
+ }
+ }
+ if (carry) {
+ /* carry != 0 => dif == 0 */
+ *rp = 1;
+ r->top++;
+ }
+ }
+
+ if (dif && rp != ap) {
+ while (dif--) {
+ /* copy remaining words if ap != rp */
+ *(rp++) = *(ap++);
+ }
+ }
+
+ r->neg = 0;
+ return 1;
+}
+
+int BN_add_word(BIGNUM *a, BN_ULONG w) {
+ BN_ULONG l;
+ int i;
+
+ w &= BN_MASK2;
+
+ /* degenerate case: w is zero */
+ if (!w) {
+ return 1;
+ }
+
+ /* degenerate case: a is zero */
+ if (BN_is_zero(a)) {
+ return BN_set_word(a, w);
+ }
+
+ /* handle 'a' when negative */
+ if (a->neg) {
+ a->neg = 0;
+ i = BN_sub_word(a, w);
+ if (!BN_is_zero(a)) {
+ a->neg = !(a->neg);
+ }
+ return i;
+ }
+
+ for (i = 0; w != 0 && i < a->top; i++) {
+ a->d[i] = l = (a->d[i] + w) & BN_MASK2;
+ w = (w > l) ? 1 : 0;
+ }
+
+ if (w && i == a->top) {
+ if (bn_wexpand(a, a->top + 1) == NULL) {
+ return 0;
+ }
+ a->top++;
+ a->d[i] = w;
+ }
+
+ return 1;
+}
+
+int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
+ int max;
+ int add = 0, neg = 0;
+ const BIGNUM *tmp;
+
+ /* a - b a-b
+ * a - -b a+b
+ * -a - b -(a+b)
+ * -a - -b b-a
+ */
+ if (a->neg) {
+ if (b->neg) {
+ tmp = a;
+ a = b;
+ b = tmp;
+ } else {
+ add = 1;
+ neg = 1;
+ }
+ } else {
+ if (b->neg) {
+ add = 1;
+ neg = 0;
+ }
+ }
+
+ if (add) {
+ if (!BN_uadd(r, a, b)) {
+ return 0;
+ }
+
+ r->neg = neg;
+ return 1;
+ }
+
+ /* We are actually doing a - b :-) */
+
+ max = (a->top > b->top) ? a->top : b->top;
+ if (bn_wexpand(r, max) == NULL) {
+ return 0;
+ }
+
+ if (BN_ucmp(a, b) < 0) {
+ if (!BN_usub(r, b, a)) {
+ return 0;
+ }
+ r->neg = 1;
+ } else {
+ if (!BN_usub(r, a, b)) {
+ return 0;
+ }
+ r->neg = 0;
+ }
+
+ return 1;
+}
+
+int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) {
+ int max, min, dif;
+ register BN_ULONG t1, t2, *ap, *bp, *rp;
+ int i, carry;
+
+ max = a->top;
+ min = b->top;
+ dif = max - min;
+
+ if (dif < 0) /* hmm... should not be happening */
+ {
+ OPENSSL_PUT_ERROR(BN, BN_usub, BN_R_ARG2_LT_ARG3);
+ return 0;
+ }
+
+ if (bn_wexpand(r, max) == NULL) {
+ return 0;
+ }
+
+ ap = a->d;
+ bp = b->d;
+ rp = r->d;
+
+ carry = 0;
+ for (i = min; i != 0; i--) {
+ t1 = *(ap++);
+ t2 = *(bp++);
+ if (carry) {
+ carry = (t1 <= t2);
+ t1 = (t1 - t2 - 1) & BN_MASK2;
+ } else {
+ carry = (t1 < t2);
+ t1 = (t1 - t2) & BN_MASK2;
+ }
+ *(rp++) = t1 & BN_MASK2;
+ }
+
+ if (carry) /* subtracted */
+ {
+ if (!dif) {
+ /* error: a < b */
+ return 0;
+ }
+
+ while (dif) {
+ dif--;
+ t1 = *(ap++);
+ t2 = (t1 - 1) & BN_MASK2;
+ *(rp++) = t2;
+ if (t1) {
+ break;
+ }
+ }
+ }
+
+ if (rp != ap) {
+ for (;;) {
+ if (!dif--) {
+ break;
+ }
+ rp[0] = ap[0];
+ if (!dif--) {
+ break;
+ }
+ rp[1] = ap[1];
+ if (!dif--) {
+ break;
+ }
+ rp[2] = ap[2];
+ if (!dif--) {
+ break;
+ }
+ rp[3] = ap[3];
+ rp += 4;
+ ap += 4;
+ }
+ }
+
+ r->top = max;
+ r->neg = 0;
+ bn_correct_top(r);
+
+ return 1;
+}
+
+int BN_sub_word(BIGNUM *a, BN_ULONG w) {
+ int i;
+
+ w &= BN_MASK2;
+
+ /* degenerate case: w is zero */
+ if (!w) {
+ return 1;
+ }
+
+ /* degenerate case: a is zero */
+ if (BN_is_zero(a)) {
+ i = BN_set_word(a, w);
+ if (i != 0) {
+ BN_set_negative(a, 1);
+ }
+ return i;
+ }
+
+ /* handle 'a' when negative */
+ if (a->neg) {
+ a->neg = 0;
+ i = BN_add_word(a, w);
+ a->neg = 1;
+ return i;
+ }
+
+ if ((a->top == 1) && (a->d[0] < w)) {
+ a->d[0] = w - a->d[0];
+ a->neg = 1;
+ return 1;
+ }
+
+ i = 0;
+ for (;;) {
+ if (a->d[i] >= w) {
+ a->d[i] -= w;
+ break;
+ } else {
+ a->d[i] = (a->d[i] - w) & BN_MASK2;
+ i++;
+ w = 1;
+ }
+ }
+
+ if ((a->d[i] == 0) && (i == (a->top - 1))) {
+ a->top--;
+ }
+
+ return 1;
+}
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