release/src/router/openssl/crypto/bn/bn_add.c

   1 /* crypto/bn/bn_add.c */
   2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58
  59 #include <stdio.h>
  60 #include "cryptlib.h"
  61 #include "bn_lcl.h"
  62
  63 /* r can == a or b */
  64 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
  65 {
  66     const BIGNUM *tmp;
  67     int a_neg = a->neg, ret;
  68
  69     bn_check_top(a);
  70     bn_check_top(b);
  71
  72     /*-
  73      *  a +  b      a+b
  74      *  a + -b      a-b
  75      * -a +  b      b-a
  76      * -a + -b      -(a+b)
  77      */
  78     if (a_neg ^ b->neg) {
  79         /* only one is negative */
  80         if (a_neg) {
  81             tmp = a;
  82             a = b;
  83             b = tmp;
  84         }
  85
  86         /* we are now a - b */
  87
  88         if (BN_ucmp(a, b) < 0) {
  89             if (!BN_usub(r, b, a))
  90                 return (0);
  91             r->neg = 1;
  92         } else {
  93             if (!BN_usub(r, a, b))
  94                 return (0);
  95             r->neg = 0;
  96         }
  97         return (1);
  98     }
  99
 100     ret = BN_uadd(r, a, b);
 101     r->neg = a_neg;
 102     bn_check_top(r);
 103     return ret;
 104 }
 105
 106 /* unsigned add of b to a */
 107 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 108 {
 109     int max, min, dif;
 110     BN_ULONG *ap, *bp, *rp, carry, t1, t2;
 111     const BIGNUM *tmp;
 112
 113     bn_check_top(a);
 114     bn_check_top(b);
 115
 116     if (a->top < b->top) {
 117         tmp = a;
 118         a = b;
 119         b = tmp;
 120     }
 121     max = a->top;
 122     min = b->top;
 123     dif = max - min;
 124
 125     if (bn_wexpand(r, max + 1) == NULL)
 126         return 0;
 127
 128     r->top = max;
 129
 130     ap = a->d;
 131     bp = b->d;
 132     rp = r->d;
 133
 134     carry = bn_add_words(rp, ap, bp, min);
 135     rp += min;
 136     ap += min;
 137     bp += min;
 138
 139     if (carry) {
 140         while (dif) {
 141             dif--;
 142             t1 = *(ap++);
 143             t2 = (t1 + 1) & BN_MASK2;
 144             *(rp++) = t2;
 145             if (t2) {
 146                 carry = 0;
 147                 break;
 148             }
 149         }
 150         if (carry) {
 151             /* carry != 0 => dif == 0 */
 152             *rp = 1;
 153             r->top++;
 154         }
 155     }
 156     if (dif && rp != ap)
 157         while (dif--)
 158             /* copy remaining words if ap != rp */
 159             *(rp++) = *(ap++);
 160     r->neg = 0;
 161     bn_check_top(r);
 162     return 1;
 163 }
 164
 165 /* unsigned subtraction of b from a, a must be larger than b. */
 166 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 167 {
 168     int max, min, dif;
 169     register BN_ULONG t1, t2, *ap, *bp, *rp;
 170     int i, carry;
 171 #if defined(IRIX_CC_BUG) && !defined(LINT)
 172     int dummy;
 173 #endif
 174
 175     bn_check_top(a);
 176     bn_check_top(b);
 177
 178     max = a->top;
 179     min = b->top;
 180     dif = max - min;
 181
 182     if (dif < 0) {              /* hmm... should not be happening */
 183         BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);
 184         return (0);
 185     }
 186
 187     if (bn_wexpand(r, max) == NULL)
 188         return (0);
 189
 190     ap = a->d;
 191     bp = b->d;
 192     rp = r->d;
 193
 194 #if 1
 195     carry = 0;
 196     for (i = min; i != 0; i--) {
 197         t1 = *(ap++);
 198         t2 = *(bp++);
 199         if (carry) {
 200             carry = (t1 <= t2);
 201             t1 = (t1 - t2 - 1) & BN_MASK2;
 202         } else {
 203             carry = (t1 < t2);
 204             t1 = (t1 - t2) & BN_MASK2;
 205         }
 206 # if defined(IRIX_CC_BUG) && !defined(LINT)
 207         dummy = t1;
 208 # endif
 209         *(rp++) = t1 & BN_MASK2;
 210     }
 211 #else
 212     carry = bn_sub_words(rp, ap, bp, min);
 213     ap += min;
 214     bp += min;
 215     rp += min;
 216 #endif
 217     if (carry) {                /* subtracted */
 218         if (!dif)
 219             /* error: a < b */
 220             return 0;
 221         while (dif) {
 222             dif--;
 223             t1 = *(ap++);
 224             t2 = (t1 - 1) & BN_MASK2;
 225             *(rp++) = t2;
 226             if (t1)
 227                 break;
 228         }
 229     }
 230 #if 0
 231     memcpy(rp, ap, sizeof(*rp) * (max - i));
 232 #else
 233     if (rp != ap) {
 234         for (;;) {
 235             if (!dif--)
 236                 break;
 237             rp[0] = ap[0];
 238             if (!dif--)
 239                 break;
 240             rp[1] = ap[1];
 241             if (!dif--)
 242                 break;
 243             rp[2] = ap[2];
 244             if (!dif--)
 245                 break;
 246             rp[3] = ap[3];
 247             rp += 4;
 248             ap += 4;
 249         }
 250     }
 251 #endif
 252
 253     r->top = max;
 254     r->neg = 0;
 255     bn_correct_top(r);
 256     return (1);
 257 }
 258
 259 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 260 {
 261     int max;
 262     int add = 0, neg = 0;
 263     const BIGNUM *tmp;
 264
 265     bn_check_top(a);
 266     bn_check_top(b);
 267
 268     /*-
 269      *  a -  b      a-b
 270      *  a - -b      a+b
 271      * -a -  b      -(a+b)
 272      * -a - -b      b-a
 273      */
 274     if (a->neg) {
 275         if (b->neg) {
 276             tmp = a;
 277             a = b;
 278             b = tmp;
 279         } else {
 280             add = 1;
 281             neg = 1;
 282         }
 283     } else {
 284         if (b->neg) {
 285             add = 1;
 286             neg = 0;
 287         }
 288     }
 289
 290     if (add) {
 291         if (!BN_uadd(r, a, b))
 292             return (0);
 293         r->neg = neg;
 294         return (1);
 295     }
 296
 297     /* We are actually doing a - b :-) */
 298
 299     max = (a->top > b->top) ? a->top : b->top;
 300     if (bn_wexpand(r, max) == NULL)
 301         return (0);
 302     if (BN_ucmp(a, b) < 0) {
 303         if (!BN_usub(r, b, a))
 304             return (0);
 305         r->neg = 1;
 306     } else {
 307         if (!BN_usub(r, a, b))
 308             return (0);
 309         r->neg = 0;
 310     }
 311     bn_check_top(r);
 312     return (1);
 313 }